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Photochemical Approach for the Preparation of N-Alkyl/Aryl Substituted Fulleropyrrolidines: Photoaddition Reactions of Silyl Group Containing #-Aminonitriles with Fullerene C 60

Suk Hyun Lim, Jiin Oh, Keepyung Nahm, Sunguk Noh, Jun Ho Shim, Cheolhee Kim, Eunae Kim, and Dae Won Cho J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b02804 • Publication Date (Web): 09 Jan 2019 Downloaded from http://pubs.acs.org on January 12, 2019

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is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

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The Journal of Organic Chemistry

Photochemical Approach for the Preparation of N-Alkyl/Aryl Substituted Fulleropyrrolidines: Photoaddition Reactions of Silyl Group Containing -Aminonitriles with Fullerene C60

Suk Hyun Lim,1 Jiin Oh,1 Keepyung Nahm,1 Sunguk Noh,2 Jun Ho Shim,2 Cheolhee Kim,3 Eunae Kim,3 Dae Won Cho,1*

1Department

of Chemistry, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea ([email protected])

2Department

3College

of Chemistry, Daegu Univeristy, Gyeongsan, 38453, Republic of Korea

of Pharmacy, Chosun University, Gwangju 61452, Republic of Korea

1 ACS Paragon Plus Environment

The Journal of Organic Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Graphical Abstract R Me3Si

N

CN

hv / C60 SET

R Me3Si

N

CN

R = alkyl, aryl

R E

N

CN R

C60 E

N

CN

dipolar cycloaddition E = H or SiMe3


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Abstract The photochemical reactions of C60 with N-(trimethylsilyl)methyl- and N-alkyl/aryl substituted -aminonitriles were explored to evaluate the scope and reaction efficiency depending on structural nature of amine substrates. The results showed that photoreactions of C60 with trimethylsilyl group containing N-alkyl amines produced predominantly both trimethylsilyl- and cyano group containing trans-pyrrolidine ring fused fulleropyrrolidines in a chemo- and stereoselective manner. Interestingly, photoreactions of C60 with N-branched alkyl substituted amines led to exclusive formation of non-silyl containing cycloadducts. In contrast to those of N-alkyl substituted -aminonitriles, photoreactions of N-(trimethylsilyl)methyl- and N-aryl substituted -aminonitriles gave rise to formation of both transand cis-isomeric fulleropyrrolidines with an inefficient and non-stereoselective manner. The feasible mechanistic pathways leading to generation of fulleropyrrolidines are 1,3-dipolar cycloaddition of the azomethine ylides, generated by either SET (in N2-purged condition) or H-atom abstraction (in O2purged condition) process, to fullerene C60. The stereoselectivities of photoproducts depending on the nature of amines are likely to be associated with conformational stabilities of in situ generated azoemthine ylides.



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Introduction Chemical functionalization of spherical fullerene surface by introducing a wide variety of organic moieties have received intense interest in the material1-4 and biological science fields.5-8 due to the useful photochemical/photophysical characteristics of functionalized fullerenes, in which the intrinsic properties of fullerene itself (i.e., high electron affinity,9 small reorganization energy,10 electron transporting ability,11,12 and their interesting physical properties) are maintained while possessing the turned processability such as solubility, HOMO-LUMO energy level, molecular interactions and surface energy.13 Among a number of functionalized fullerene derivatives, N-heterocyclic pyrrolidine ring fused fullerenes, or fulleropyrrolidines, are one of the most extensively explored fullerene families after the pioneering study of Prato and co-workers,14 who have developed 1,3-dipolar cycloaddition reactions of thermally generated azomethine ylides from aldehyde-induced decarboxylation of secondary amino acids to electron deficient fullerene C60 across the [6,6]-juncture position of pristine fullerene C60. Since then, several types of ylide intermediates have been successfully applied to the synthesis of fulleropyrrolidines. The commonly employed synthetic approaches involve the ring opening reactions of aziridine or oxazolines,15 the Prato type thermal and photochemical decarboxylation of iminium carboxylates that are derived from either arylmethylamines16 or -amino acids/esters,17 and deprotonation of imines bearing electron withdrawing group at the position -carbon to nitrogen atom.18 (Scheme 1) In particular, in the presence of metal ions such as Cu(II), Ag(I) or Fe(III), the


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ylides arisen by 1,2-prototropic shift of imines (e.g., migration of proton from -carbon to nitrogen atom) undergo cycloaddition with fullerene C60 to produce N-unsubstiuted pyrrolidine fused fullerene derivatives in a stereoselective manner.18b-18d Owing to the facility of constructing five-membered cyclic amine via a pathway involving 1,3-dipolar cycloaddition reactions of azomethine ylides19 and the growing importance of functionalized fullerenes, lots of synthetic efforts are still underway to develop diverse ylide precusors that are ready applicable to the preparation of fulleropyrrolidines. Scheme 1. R1CHO

RNHCH2R2

+

R N

hv or R2

R1

aziridine

R1

R N

R2

R1

R N

R2

C60

3

2

R R

1

R

OR =C

R=H

N O

oxazoline

R3

1,2-prototropic shift R1

N

fulleropyrrolidine

R2

imine

In recent studies exploring photoaddition reactions occurring between C60 and amine substrates,20 we observed that while photoaddition reactions of C60 with tertiary N-alkyl glycinates 1 (ArCH2NMeCH2CO2Et) in the presence of molecular oxygen (O2) take place to form fulleropyrrolidines 5 through a 1,3-dipolar cycloaddition of in situ generated azomethine ylides 3 that possess both ethoxycarbonyl- and aryl substituents to C60, the photoreactions of oxygenated solutions of C60 and N-(trimethylsilyl)methyl substituted glycinates 2 (ArCH2N(CH2SiMe3)CH2CO2Et) lead to 5 ACS Paragon Plus Environment


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the formation of fulleropyrrolidines 6 through a pathway involving cycloaddition reaction of the azomethine ylides 4 possessing both ethoxycarbonyl- and trimethylsilyl group to C60 with a much efficient manner. (Scheme 2) Based on the mechanistic analysis, we recognized that singlet oxygen (1O2)21-22 would be responsible for the generation of azomethine ylide intermediates and, in addition, trimethylsilyl group in the glycinate substrates play an important role in governing the reaction efficiencies as well as the reaction pathways followed in the photochemical processes. Scheme 2. Ar E

N

1 (E = H) 2 (E = SiMe3)

CO2Et

hv / C60 / O2

Ar

Ar H

N

Me3Si

CO2Et

N

CO2Et

3 (from 1)

4 (from 2)

C60

C60

H Ar

N

Ar CO2Et

Me3Si

N

CO2Et

6 (from 4)

5 (from 3)

More recently, we designed a novel type of N-(trimethylsilyl)methyl- and N-arylmethyl substituted tertiary -aminonitriles (ArCH2N(CH2SiMe3)CH2CN, Ar = substituted phenyl) that serve


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as chemical equivalents of tertiary glycinates, and explored photochemical reactions of designed aminonitriles with C60.23 Observation made in the study showed that photoirradiation of solutions containing -aminonitriles and C60 gave rise to the stereoselective formation of trans-isomeric fulleropyrrolidines through a pathway involving [3+2]-cycloaddition of azomethine ylides generated from -aminonitirles to C60 under the both oxygenated (O2-purged) and deoxygenated (N2-saturated) conditions. The in situ generated ylide intermediates would be formed either by single electron transfer (SET) from -aminonitriles to triplet excited state of C60 (in N2-purged condition)24-25 followed by desilylation or deprotonation, or by H-atom abstraction by singlet oxygen (in O2-purged condition).21 More important observation was that the efficiencies of these photoreactions are highly dependent on solvent polarity, presence/absence of silyl group, and electronic nature of -aminonitriles. As continuing research programs aimed at exploring the scope and efficiency of the photochemical reactions occurring between fullerene C60 and amine substances, in current study, we newly designed and prepared -aminonitrile substrates, which have both a trimethylsilylmethyl (Me3SiCH2) group and a variety of alkyl or aryl substituents at a nitrogen atom, and then carried out photochemical reactions of them with C60. The results, described below, show that the photoreactions of both N-alkyl/aryl and N-(trimethylsilyl)methyl substituted -aminonitriles take place to form fulleropyrrolidines and, importantly, the efficiency and chemoselectivity of photoreactions are varied depending on the structural nature of N-alkyl/aryl substituents of -aminonitirles. Especially, steric hindrance provided by N-alkyl/aryl substituents of -aminonitirles plays an important role in



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governing reaction efficiency as well as chemoselectivity.

Results and Discussion Photoreactions of C60 with N-alkyl substituted -aminonitriles 8a-8i. For the photochemical reactions, a variety of -aminonitriles bearing both (trimethylsilyl)methyl and alkyl group at a nitrogen atom were initially synthesized by well-established base-promoted cyanomethylation of respective secondary N-(trimethylsilyl)methyl substituted amines26 with bromoacetonitrile (BrCH2CN). These synthetic sequences gave rise to production of the target -aminonitriles possessing both silyl- and cyano group successfully in modest to high yields (64-91%). (Scheme 3) Scheme 3. Me3Si

R4 NH

K2CO3 / MeCN BrCH2CN

7a (R4 = benzyl) 7b (R4 = hexyl) 7c (R4 = propyl) 7d (R4 = CH2CH2OCH3) 7e (R4 = allyl) 7f (R4 = iso-propyl) 7g (R4 = tert-butyl) 7h (R4 = cyclohexyl) 7i (R4 = iso-butyl)

Me3Si

R4 N

CN

8a (R4 = benzyl, 91%) 8b (R4 = hexyl, 81%) 8c (R4 = propyl, 72%) 8d (R4 = CH2CH2OCH3, 81%) 8e (R4 = allyl, 83%) 8f (R4 = iso-propyl, 64%) 8g (R4 = tert-butyl, 74%) 8h (R4 = cyclohexyl, 66%) 8i (R4 = iso-butyl, 85%l)

Next, photochemical reactions were performed by irradiation (450W Hanovia medium pressure mercury lamp equipped with flint glass filter (> 310 nm)) of 10% EtOH-toluene (v/v) solutions containing C60 (0.28 mmol) and the -aminonitrile (0.56 mmol) under the either deoxygenated (N2purged) or oxygenated (O2- purged) condition. The photolysates were then subjected to column


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chromatography to determine photoproducts and their yields. Scheme 4. R4

R4 N

Me3Si

R4 N

Me3Si

CN

N

CN

hv / C60 CN

+

10% EtOH-toluene/



10a (R4 = benzyl) 10b (R4 = hexyl) 10c (R4 = propyl) 10d (R4 = CH2CH2OCH3) 10e (R4 = allyl) 10i (R4 = iso-butyl)

Table 1. Products and yields of photoreactions of -aminonitriles 8a-8i with C60 in 10% EtOH-toluene solutions. entry

amine

reaction condition

irradiation time (h)

conversion (%)a

product (%)b

1

8a

N2

1

71

9a (6), 10a (30)

2

8a

N2

2

85

9a (11), 10a (42)

3

8a

O2

1

94

9a (4), 10a (42)

4

8b

N2

1

78

9b (10), 10b (28)

5

8b

N2

2

100

9b (16), 10b (41)

6

8b

O2

1

95

9b (5), 10b (37)

7

8c

N2

1

80

9c (11), 10c (26)

8

8c

N2

2

100

9c (18), 10c (39)

9

8c

O2

1

96

9c (7), 10c (36)

10

8d

N2

1

72

9d (2), 10d (31)



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11

8d

N2

2

94

9d (3), 10d (48)

12

8d

O2

1

92

9d (8), 10d (55)

13

8e

N2

2

92

9e (9), 10e (34)

14

8e

O2

1

95

9e (8), 10e (40)

15

8f

N2

2

91

9f (45)

16

8f

O2

1

95

9f (48)

17

8g

N2

2

86

9g (46)

18

8g

O2

1

95

9g (49)

19

8h

N2

2

89

9h (42)

20

8h

O2

1

93

9h (53)

21

8i

N2

2

98

9i (20), 10i (35)

22

8i

O2

1

100

9i (17), 10i (40)

aConversion

was determined by recovered C60. bIsolation yields.

Firstly, we carried out photoreactions of C60 with -aminonitriles 8a-8i. As the results displayed in Scheme 4 and Table 1 show, the photoirradiation of N2-purged 10% EtOH-toluene solution containing C60 and -aminonitriles 8a-8d for 1 h led to production of the silyl group containing fulleropyrrolidines 10a-10d (trans isomers) as a major product, along with lesser amount of non-silyl group containing adducts 9a-9d. (entries 1, 4, 7 and 10 in Table 1) Under the same reaction condition, a much longer irradiation (2 h) of solutions containing 8a-8d and C60 brought about much higher conversion of the starting C60 and, as a result, high photoproduct yields. (entries 2, 5, 8 and 11 in Table 1) In the O2-purged reaction condition, photoreactions of C60 with 8a-8d took place more efficiently than those in N2-purged condition to produce trans-fulleropyrroldine adducts dominantly. (entries 3, 10 ACS Paragon Plus Environment

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6, 9 and 12 in Table 1). Similar photoreaction patterns were also found in the photoreactions of C60 with 8e, resulting in production of silyl- (major) and non-silyl (minor) substituted fulleropyrrolidines under the both N2- and O2-purged conditions. (entries 13-14 in Table 1) The product distribution patterns arisen from photoreactions of C60 with α-aminonitrile 8f-8h were comparable to those observed from the reaction of 8a-8e. In particular, the reactions of C60 with -aminonitriles 8f-8h, which contain additional alkyl substituent at -carbon position to the nitrogen atom, took place to produce the non-silyl substituted fulleropyrrolidines 9f-9h exclusively in both N2and O2-purged conditions. (entries 15-20 in Table 1) However, the photoreaction of -aminonitrile 8i that possesses extra alkyl moiety at -carbon position to the nitrogen atom gave rise to formation of a silyl group containing fulleropyrrolidine 10i as a major adduct, along with a non-silyl fulleropyrrolidine 9i as a minor one. These product distribution changes seem to indicate that steric bulkiness offered by a proximal alkyl substituent to the nitrogen center is responsible for chemoselectivity of photoaddition reactions taking place between C60 and -aminonitriles. To gain more information related to steric hindrance effects, -aminonitriles 8j-8k that have additional phenyl (8j) or -methyl (8k) substituent at benzyl position were designed, prepared and then, their photochemical reaction patterns were examined under the same reaction condition used in above reactions. (Scheme 5 and Table 2) Scheme 5.



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R5

Ph N Ph Me3Si

R NH

5

K2CO3 / MeCN ICH2CN

R5

Ph Me3Si

7j (R5 = Ph) 7k (R5 = Me)

N

CN

hv / C60 CN

10% EtOHtoluene

8j (R5 = Ph, 65%) 8k (R5 = Me, 85%) 9j (R5 = Ph) 9k + 9l (R5 = Me,diastereomer)

Table 2. Products and yields of photoreactions of -aminonitriles 8j-8k with C60 in 10% EtOH-toluene solutions. entry

amine

reaction condition


conversion (%)a

product (%)b

1

8j

N2

6

-c

-c

2

8j

O2

6

19

9i (11)

3

8k

N2

2

76

9k (24), 9l (24)

4

8k

O2

1

84

9k (33), 9l (33)

aConversion

was determined by recovered C60. cIsolation yields. cNo reaction

As the results depicted in Scheme 5 and Table 2 show, the photoreactions of C60 with bulky phenyl (R5 = Ph) containing amine 8j did not occur under the N2-purged condition, even by much longer photoirradiation . (entry 1 in Table 2) Albeit low conversion and photoproduct yields, however, the reaction of 8j took place to produce the non-silyl containing fulleropyrrolidine 9i under the O2purged condition. (entry 2 in Table 2) In case of relatively less bulky group (i.e., -methyl) containing amine substrate 8k (R5 = Me), only the non-silyl group containing fulleropyrrolidines (9k and 9l) were produced as an inseparable diastereomeric mixture due to the two stereogenic centers. Based on observation summarized in Table 1 and 2, it is noteworthy to mention that steric hindrance near the


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nitrogen atom plays a crucial factor influencing not only reaction efficiencies but chemoselectivities. Specifically, the photoreactions of N-alkyl substituted -aminonitriles, possessing no extra substituent, lead to formation of both silyl- and non-silyl group containing fulleropyrroldines, in which the former adducts would be predominant. In contrast, the reactions using -aminonitriles that have no extra -substitutent (i.e., iso-propyl (8f), tert-butyl (8g), cyclohexyl (8h), (-phenyl)benzyl (8j) and (-methyl)benzyl (8k)), give rise to generation of non-silyl group containing fulleropyrrolidines chemoselectively. Structural assignments of silyl- and non-silyl group containing fulleropyrrolidines formed in these reactions were determined by using NMR, IR and UV-visible spectroscopic methods, and HRMS analysis as well as by comparison of the data to those of previously characterized analogs.16,18,20,23 In the NMR spectra of the non-silyl fulleropyrrolidines 9a-9i, owing the one chiral carbon center, 1H NMR of 9a-9i show that their methylene protons (CH2) near to fullerene core appear as AB quartets in at ca. 4.5-4.8 ppm and methine protons (CH) at chiral carbon bearing a cyano group appear at ca. 5.7 as a singlet. In addition, the 13C NMR spectra of 9a-9i contain peaks that correspond to two sp3 carbons of the fullerene core (ca. 68-70 ppm), methylene carbons and one chiral carbon at ca. 65-72 ppm. As for silyl group containing fulleropyrrolidines 10a-10e and 10i, two methine protons on chiral carbons which have both trimethylsilyl and cyano groups appear as a singlet peak at ca. 4.3-4.4 and 5.7-5.8 ppm region, respectively. The 13C NMR spectra of 10a-10e and 10i comprise resonances for the two quaternary sp3 carbons of the fullerene core as well as two chiral carbons in downfield region.



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(ca. 66-74 ppm) Importantly, the presence of cyano group in fulleropyrrolidines is readily confirmed by both 13C NMR spectra, which show cyano carbon resonate at ca. 114-115 ppm in all substances and FT-IR spectra, which show characteristic stretching vibration peak at ca. 2260 cm-1. In addition, the UV-visible absorption spectra of all of photoadducts, which contain characteristic maxima peak ca. 431-433 nm, show that all of products are 1,2-adducts formed by addition across the [6,6]-juncture of C60.16,18,20,27 Assignment of stereochemistry of silyl group containing fulleropyrrolidines 10a-10e and 10i (i.e., trans vs cis) is also important issue to be explored. Although X-ray crystallographic analysis is highly useful, but, due to the difficulty in crystallizing photoproducts, we took advantage of nuclear Overhauser enhancement spectroscopy (NOESY) technique to determine stereochemistry. Based on the theoretical assumption of NOESY technique where the correlation peaks in NOESY spectra (i.e., NOE signal) arise when the protons are interacting each other within spatially proximal distance,16d,23,28 we expected that while the two methine protons in the trans isomeric fulleropyrrolidines would have no correlation peaks in NOESY spectra due to their great spatial separation, however, clear correlation peaks between the two methine protons in the cis isomeric fulleropyrrolidines would arise. Because the two methine proton signals in all of fulleropyrroldines (10a-10e and 10i) are observed at nearly equal chemical shift (ca. 4.3 and 5.8 ppm respectively), we chose two representative fulleropyrroldines (10a-10b) and their NOESY data were analyzed. The NOESY spectral data of 10a-10b showed that no NOE signals between two methine protons arise.


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(see Supporting Information) Photoreactions of C60 with N-aryl substituted -aminonitriles 13a-13f. The scope of amine substrate were expanded to N-aryl substituted -aminonitriles 13a-13f, in which aryl group contains un-substituted (H), electron-donating (Me), and electron withdrawing (F) substituent at ortho and/or para position. Similarly to above amine substrates, both silyl- and cyano groups were readily introduced by sequential N-alkylation reactions from primary aniline derivatives 11a-11f. (Scheme 6) Scheme 6. X

X

X K2CO3 ICH2SiMe3

NH2 11a (X = H) 11b (X = p-Me) 11c (X = p-F) 11d (X = o-Me) 11e (X = o,p-diMe) 11f (X = o,o,p-triMe)

K2CO3 Me3Si

BrCH2CN

NH

12a (X = H, 78%) 12b (X = p-Me, 81%) 12c (X = p-F, 81%) 12d (X = o-Me, 66%) 12e (X = o,p-diMe, 70%) 12f (X = o,o,p-triMe, 70%)

Me3Si

N

CN

13a (X = H, 67%) 13b (X = p-Me, 66%) 13c (X = p-F, 85%) 13d (X = o-Me, 79%) 13e (X = o,p-diMe, 58%) 13f (X = o,o,p-triMe, 85%)

The photochemical reactions of C60 with prepared N-aryl substituted -aminonitriles 13a-13f were then performed under the same reaction conditions used above. The photoproducts and their yields are depicted in Scheme 7 and Table 3. Scheme 7.



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X

Me3Si

X

N

X

Me3Si

CN

hv / C60 Me3Si

N

CN

CN

+

10% EtOHtoluene

13a (X = H) 13b (X = p-Me) 13c (X = p-F) 13d (X = o-Me) 13e (X = o,p-diMe) 13f (X = o,o,p-triMe)

N

14a (X = p-H) 14b (X = p-Me) 14c (X = p-F)

15a (X = p-H) 15b (X = p-Me) 15c (X = p-F)

Table 3. Products and yields of photoreactions of -aminonitriles 13a-13f with C60 in 10% EtOHtoluene solutions. entry

amine

reaction condition


conversion (%)a

product (%)b

1

13a

N2

2

55

14a (16), 15a (13)

2

13a

O2

1

51

14a (14), 15a (11)

3

13b

N2

2

61

14b (18), 15b (12)

4

13b

O2

1

58

14b (17), 15b (15)

5

13c

N2

2

34

14c (11), 15c (5)

6

13c

O2

1

35

14c (9), 15c (9)

7

13d

N2 or O2

5

-c

-c

8

13e

N2 or O2

5

-c

-c

9

13f

N2 or O2

5

-c

-c

aConversion

was determined by recovered C60. bIsolation yields. cNo reaction

The results of photoreactions of C60 with N-aryl substituted -aminonitriles were quite comparable to those obtained from the photoreactions using N-alkyl substituted -aminonitriles in terms of both reaction efficiency and product distribution patterns. For instance, under the same


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irradiation time period, the photoreactions of N-aryl amines 13a-13c brought about much lower conversion of C60 and product yields compared to those of N-alkyl substituted amines. (entries 1-6 in Table 3) Noticeably, no photoreaction took place when the ortho-Me substituted phenyl ring containing amines 13d-13f were used in the reaction. (entries 7-9 in Table 3) Another interesting observation was that while the reactions of C60 with N-alkyl amines 8a-8e and 8i give rise to transisomeric fulleropyrrolidines selectively (Table 1), those with N-aryl amines 13a-13c produced ca. ranging from 2.2: 1 to 1: 1 ratios of trans- to cis-isomeric mixture of fulleropyrrolidines. (Table 3) Stereochemistry of photoproducts were unambiguously determined based on NOESY spectral data of representative photoproducts 14a and 15a. The NOESY data analysis showed that while trans-isomer 14a did not show any NOE correlation peaks, however, cis-isomer 15a clearly showed NOE correlation peaks. (see Supporting Information) It should be also noted that electronic nature of amine substrates play a key role to control the reaction efficiency. Specifically, while the photoreaction of para-electron donating group (p-Me) substituted arene ring containing amine 13b occurred more efficiently than that arising from analogous un-substituted arylamine 13a, the reactions of paraelectron withdrawing group (p-F) substituted arene ring containing amine 13c took place less efficiently than that of 13a.23,29 Considering these electronic effect influencing reaction efficiency, it is unlikely that extremely low reaction efficiency of amines 13d-13f is a consequence of electronic effect of amine. Mechanistic pathways leading to formation of fulleropyrrolidines. Based on analysis of



Page 18 of 53

photoproducts resulting from the photoreactions of C60 and -aminonitriles as well as the results of earlier studies,20a,23 it is possible to suggest the plausible mechanistic pathways leading to formation of silyl- and non-silyl group containing fulleropyrrolidines. The route followed in the photoreactions of C60 with silyl group containing -aminonitriles under the N2-purged solution is initiated by SET from the N-alkyl/aryl substituted -aminonitriles 16 to the triplet excited states of C60 (3C60*), which are generated by rapid and efficient intersystem crossing process from 1C60* (kISC = ~ 2 x 109 s-1, ISC = 1).22 As a result, the SET step in the pathway forms radical ion pairs comprised of aminium radicals 17 and the C60 radical anions of C60 (C60-). The generated aminium radicals 17 undergo competitive -CH deprotonation by C60- (pKa of H-C60 is 4 in ODCB and 9 in DMSO)30 vs solvent-promoted desilylation (~SiR3+) to give the respective silyl (19) and non-silyl (18) containing -amino radicals, along with the hydrofullerene radicals (H-C60). Although -silyl substituted aminium radicals 17 are known to undergo silophilic solvent-promoted desilylation with exceptionally large rates that exceed those of -CH deprotonation,31,32 the results of current study show that -CH deprotonation process takes place more preferentially than desilylation route when the -CH acidity of the aminium radicals is enhanced by -substituent like electron withdrawing cyano group. Then, the -amino radicals 1819, generated by either -CH deprotonation or desilylation, are oxidized by SET to either H-C60 or C60 to form the respective iminium ions 20 and 21, along with the hydrofullerene anion (H-C60-). Deprotonation of 20 and 21 then produces the respective 1,3-dipolar azomethine ylides 22 and 23, which are finally trapped by fullerene C60 to give N-heterocycle fused fulleropyrrolidines 24.


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Scheme 8. R Me3Si

N

R

1. hv/ C60

CN

Me3Si

2. SET

N

C60

CN Ha

(R = alkyl, aryl) 17

16 EtOH ~ SiMe3+

~ H a+

R N

R CN

+ H C60

Me3Si

N

18

19 SET to C60 or H-C60

SET to C60 or H-C60

R N

R CN + H C60

Me3Si

N

CN

+ H C60

CN

+

21

20

R

R N

H C60

CN

CN +

Me3Si

H2C60

N

H2C60

23

22 C60

C60 R E

N

CN

24 (E =SiMe3 or H)

It is worthy to mention about unique chemoselectivity observed in the photoreactions of N-alkyl substituted -aminonitriles that contain additional alkyl substituent at -carbon position, 8f-8h and 8i8j, in which non-silyl substituted fulleropyrrolidines were produced exclusively. The presence of extra -substituent placed proximally on the nitrogen atom within N-alkyl group might lead to a change in the chemoselectivity that typically favor silyl- containing fulleropyrrolidines. These exceptional 19 ACS Paragon Plus Environment


Page 20 of 53

chemoselectivity would be largely related to steric hindrance of formed aminium radicals 17. (Scheme 8) Specifically, because both bulky alkyl and trimethylsilyl groups in generated aminium radicals block the access of C60- to -CH proton (i.e., Ha) of aminium radicals, less sterically hindered solvent, such as EtOH, is readily eligible to approach to Si center to facilitate desilylation to generate non-silyl containing -amino radicals 18. In addition, another important observation was that ortho-Me substituted phenyl containing Naryl amines are unreactive in the photoreactions with C60. To probe possible origin of the effect of ortho-substituent on the phenyl rings, cyclic voltammetry measurements were performed to evaluate the electron donating propensities of the amines. As the results, summarized in Table 4, show that, the N-aryl substituted amines were oxidized irreversibly and did not show significant differing in oxidation potential values (Eox) although the Eox value of amine 13e is relatively lower than other amines. These results represent that the extremely low reaction efficiencies of ortho-Me substituted phenyl containing amines are not likely to be a consequence of varying SET rates occurring from the amines to 3C60* (3Ered* = 1.14 V vs SCE)33 because the free energy changes for the electron transfer process (GSET) is negative, ensuring that SET step is thermodynamically favorable with a diffusion-controlled rates. Although little information has been accumulated to explain the source of reaction efficiency diminishing effects, we postulate that a potentially interesting relationship may exist between the reaction efficiencies and steric hindrance. Further study to explore how steric factors influence the reaction efficiencies in these SET-promoted photochemical reactions is underway.


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Table 4. Oxidation potentials (Eox) of N-aryl amines 13a-13f and free energy changes (GSET). substrate

Eox (V)a (vs SCE)

GSET (V)b

13a

0.88

-0.26

13b

0.88

-0.26

13c

0.96

-0.18

13d

1.07

-0.07

13e

0.72

-0.42

13f

0.98

-0.16

aE ox

of amines were determined by potential of onset of oxidation. bDetermined by using eq. GSET = Eox (amine) - *Ered (C60), Eox (amine) is oxidation potential of amine and *Ered (C60) is excited state of reduction potential of C60 (1.14V vs SCE).

In the photoreactions of C60 with N-alkyl/aryl substituted -aminonitriles under the O2-purged solutions, fulleropyrrolidine formation takes place through a pathway involving singlet oxygenmediated formation of azomethine ylides. (Scheme 9) As suggested by Foote and co-workers,21 triplet excited states of C60 (3C60*) anticipate in energy transfer process in the presence of molecular oxygen to form singlet oxygen (1O2),22 which abstracts -CH hydrogen atom from -aminonitriles to generate -amino radical intermediates 25 along with the hydroperoxy radical (HOO). Then, either subsequent -hydrogen atom abstraction or consecutive SET-deprotonation process finally form the key fulleropyrrolidine precusors 28 that cycloadd to C60. In some case, -amino radicals 25 may undergo sequential SET-desilylation processes to form the precusors of non-silyl fulleropyrrolidines 28. Scheme 9.



R

R Me3Si

N

Me3Si

CN 1

(R = alkyl, aryl)

O2

N

CN

25

SET

16

HOO

energy transfer 3

C60*

+

Me3Si

3

HOO

O2 R N

Page 22 of 53

HOO CN

C60

N

N

CN

26

~H+

R Me3Si

R Me3Si

CN

28

27

Stereochemistry of fulleropyrrolidines. The lack of stereoselectivity observed in photoreactions of C60 with N-aryl substituted -aminonitriles appears to be largely associated with conformational stabilities of in situ formed 1,3-dipolar azomethine ylides. As suggested by earlier studies,19 the azomethine ylides have four possible conformations with two S-shaped geometries leading to transisomeric products and the W- and U-shaped geometries leading to cis-isomeric products. (Scheme 10) Although these conformations isomerize each other, one of the ylide comformations with greater extent of stability than others would preferentially participate in cycloaddition reaction with C60 to produce photoproducts. Scheme 10.


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R Me3Si

N

CN

(R = alkyl, aryl)

ylide forming process

R

R Me3Si

N

N

R

R

CN

Me3Si

N

N

CN

SiMe3

SiMe3

CN

CN

S2

S1

W-shape

S-shape

U-shape

C60

C60

trans-fulleropyrrolidine

cis-fulleropyrrolidine

To explore the origin that govern the stereochemistry of fulleropyrrolidines in the photochemical reactions of C60 with -aminonitriles, both N-propyl (8c) and N-phenyl (13a) substituted aminonitriles were chosen as representative substances and their conformational stabilities were calculated by using DFT calculations with B3LYP/6-31+G(d) basis set. (Figure 1) In the DFT calculation for N-propyl amine 8c, one form of S-shaped conformations was calculated to be the most stable than the other geometries, with U-shaped conformation being the least stable. (Figure 1) However, in the case of N-phenyl amine 13a, one of S-shaped conformations was estimated to be slightly more stable than the different form of S- and U-shaped conformations, with W-shaped conformation being much less stable. Thus, due to the relatively small differences in energies, the azomethine ylide originated from 13a, having not only S-shaped but W-shaped conformation, would participate in cycloaddition reaction with C60 to produce trans- and cis-isomeric photoproducts.



Page 24 of 53

Figure 1. Relative energy profiles depending on azomethine ylide conformations generated from (a) N-propyl (8c) and (b) N-phenyl (13a) substituted -aminonitriles.

Conclusion In current study described above, photochemical reactions of C60 with N-(trimethylsilyl)methyland N-alkyl/aryl substituted -aminonitriles were explored to evaluate the scope and reaction efficiency depending on structural nature of amine substrates. The results showed that photoreactions of C60 with trimethylsilyl group containing N-alkyl amines produced predominantly silyl- and cyano group containing trans-pyrrolidine ring fused fulleropyrrolidines in a chemo- and stereoselective manner. Importantly, photoreactions of C60 with branched alkyl substituted amines led to exclusive formation of non-silyl containing cycloadducts. In contrast to those of N-alkyl substituted aminonitriles, photoreaction of N-aryl substituted -aminonitriles gave rise to formation of both transand cis-isomeric fulleropyrrolidines with an inefficient and non-stereoselective manner. When the ortho-Me substituted phenyl containing amines were used in the photoreaction with C60, no 24 ACS Paragon Plus Environment

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photoproducts were observed probably due to the steric hindrance of amine substrates. The mechanistic routes leading to generation of fulleropyrrolidines would be cycloaddition of azomethine ylides, generated by either SET (in N2-purged condition) or H-atom abstraction (in O2-purged condition) process, to fullerene C60. Finally, the observation that the photoaddition reactions of C60 with trimethylsilyl and cyano group substituted amines take place efficiently under the mild condition show that these photochemical strategy could serve as a highly useful way for the preparation of a variety of fulleropyrrolidine derivatives.

Experimental General. The 1H (300 MHz) and

13C

NMR (75 MHz) spectra were recorded on CDCl3, and

chemical shifts were reported in parts per million (, ppm) relative to CHCl3 (7.24 ppm for 1H and 77.0 ppm for

13C)

as an internal standard. High resolution (HRMS) mass spectra were obtained by

using an either ESI or MALDI-TOF. All starting materials used in the synthetic routes came from commercial sources. Photochemical reactions were conducted by using an immersion-well photochemical apparatus, consisting of a 450 W Hanovia medium pressure mercury vapor UV lamp (aceglass cat. # 7825-34), a power supply (aceglass cat. # 7830-61), a water-cooled quartz immersion well (aceglass cat # 7874-27), a borosilicate reaction vessel (agceglass cat. # 7841-03) and a flint glass filter (> 310 nm). Detail information about UV lamps used in this study are provided on Supporting



Page 26 of 53

Information. Synthesis of -aminonitriles 8a-8k. Individual acetonitrile solutions (100 mL) containing secondary N-alkyl amines 7a-7k26 (5 mmol), K2CO3 (10 mmol) and 2-bromoacetonitrile (5.5 mmol) were stirred for 12 h at room temperature. Then, the reaction solutions were concentrated in vacuo to give residues that were partitioned between water and CH2Cl2. The CH2Cl2 layers were dried and concentrated in vacuo to afford residues that were subjected to silica gel column chromatography (EtOAc/hexane = 1: 15 - 1: 30) to yield corresponding -aminonitiriles 8a23 (1.06 g, 91%), 8b (1.0 g, 81%), 8c (0.66 g, 72%), 8d (0.81 g, 81%), 8e (0.76 g, 83%), 8f (0.59 g, 64%), 8g (0.73 g, 74%), 8h (0.74 g, 66%), 8i (0.84 g, 85%).8j (1.0 g, 65%) and 8k (1.05 g, 85%). 8a: 1H-NMR 0.12 (s, 9H), 2.18 (s, 2H), 3.40 (s, 2H), 3.62 (s, 2H), 7.27-7.34 (m, 5H). 8b: 1H-NMR 0.01 (s, 9H), 0.82 (t, 3H, J = 6.6 Hz), 1.22-1.24 (m, 6H), 1.30-1.35 (m, 2H), 1.97 (s, 2H), 2.36 (t, 2H, J = 7.2 Hz), 3.46 (s, 2H); 13C-NMR -1.8, 13.9, 22.4, 26.5, 27.4, 31.5, 45.3, 46.0, 57.1, 114.7; HRMS (ESI) m/z: [M+Na]+ Calcd for C12H26N2SiNa 249.1763; Found 249.1769. 8c: 1H-NMR 0.04 (s, 9H), 0.87 (t, 3H, J = 7.5 Hz), 1.36-1.48 (m, 2H), 2.01 (s, 2H), 2.38 (t, 2H, J = 7.5 Hz), 3.50 (s, 2H); 13C-NMR -2.0, 11.1, 20.4, 45.1, 45.8, 58.6, 114.5; HRMS (ESI) m/z: [M+Na]+ Calcd for C9H20N2SiNa 207.1293; Found 207.1299. 8d: 1H-NMR 0.05 (s, 9H), 2.08 (s, 2H), 2.65 (t, 2H, J = 5.1 Hz), 3.31 (s, 3H), 3.45 (t, 2H, J = 5.1 Hz), 3.61 (s, 2H); 13C-NMR -2.2, 45.9, 46.4, 55.7, 58.2, 70.6, 114.7; HRMS (ESI) m/z: [M+Na]+ Calcd for C9H20N2OSiNa 223.1243; Found 223.1244.


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8e: 1H-NMR 0.02 (s, 9H), 2.01 (s, 2H), 3.01 (d, 2H, J = 6.6 Hz), 3.45 (s, 2H), 5.11-5.15 (m, 1H), 5.18-5.25 (m, 1H), 5.62-5.75 (m, 1H); 13C-NMR -1.9, 44.8, 45.8, 60.1, 114.5, 118.8, 134.3; HRMS (ESI) m/z: [M+Na]+ Calcd for C9H18N2SiNa 205.1137; Found 205.1133. 8f: 1H-NMR 0.01 (s, 9H), 0.97 (d, 1H, J = 6.3 Hz), 2.02 (s, 2H), 2.73 (quintet, 1H, J = 6.6 Hz), 3.42 (s, 2H);

13C-NMR

-2.1, 18.8, 40.8, 41.3, 54.6, 116.7; HRMS (ESI) m/z: [M+Na]+ Calcd for

C9H20N2SiNa 207.1293; Found 207.1290. 8g: 1H-NMR 0.00 (s, 9H), 1.05 (s, 9H), 2.09 (s, 2H), 3.52 (s, 2H); 13C-NMR -2.0, 26.5, 37.8, 39.2, 55.5, 117.9; HRMS (ESI) m/z: [M+Na]+ Calcd for C10H22N2SiNa 221.1450; Found 221.1451. 8h: 1H-NMR 0.00 (s, 9H), 1.01-1.20 (m, 6H), 1.71-1.82 (m, 4H), 2.10 (s, 2H), 2.26-2.33 (m, 1H), 3.47 (s, 2H);

13C-NMR

-1.9, 25.4, 25.8, 29.4, 41.5, 41.6, 63.3, 116.9; HRMS (ESI) m/z: [M+Na]+

Calcd for C12H24N2SiNa 247.1606; Found 247.1604. 8i: 1H-NMR 0.05 (s, 9H), 0.86 (d, 6H, J = 6.6 Hz), 1.56-1.70 (m, 1H), 2.0 (s, 2H), 2.18 (d, 2H, J = 6.6 Hz); 13C-NMR -1.9, 20.1, 25.8, 45.4, 46.1, 65.2, 114.5; HRMS (ESI) m/z: [M+Na]+ Calcd for C10H22N2SiNa 221.1450; Found 221.1453. 8j: 1H-NMR 0.08 (s, 9H), 2.11 (s, 2H), 3.51 (s, 2H), 4.47 (s, 1H), 7.16-7.21 (m, 2H), 7.25-7.30 (m, 4H), 7.41-7.44 (m, 4H); 13C-NMR -1.8, 43.0, 43.2, 75.8, 114.3, 127.2, 127.4, 128.5, 141.7; HRMS (ESI) m/z: [M+Na]+ Calcd for C19H24N2SiNa 331.1606; Found 331.1600. 8k: 1H-NMR 0.04 (s, 9H), 1.35 (d, 3H, J = 6.6 Hz), 2.10 (dd, 2H, J = 46.4 Hz, 14.7 Hz), 3.48 (dd, 2H, J = 50.4 Hz, 17.4 Hz), 3.57 (q, 3H, J = 6.6 Hz), 7.30-7.31 (m, 5H); 13C-NMR -1.9, 20.2, 42.3,



Page 28 of 53

64.2, 77.2, 115.1, 127.0, 127.1, 128.3, 143.7; HRMS (ESI) m/z: [M+Na]+ Calcd for C14H22N2SiNa 269.1450; Found 269.1455. Synthesis of -aminonitriles 13a-13f. Step 1. Individual toluene (100 mL for 11a) or DMF solutions (100 mL for 11b-11f) containing N-aryl amines 11a-11f (20 mmol) and iodomethyltrimethylsilane (ICH2SiMe3, 10 mmol) were stirred for 12 h at 130 oC. Then, the reaction solutions were concentrated in vacuo to give residues that were subjected to silica gel column chromatography (EtOAc/hexane = 1: 30 - 1: 40) to yield corresponding secondary N-aryl amines 12a (2.8 g, 78%),34 12b (3.1 g, 81%),34 12c (3.2 g, 81%),34 12d (2.76 g, 66%),34 12e (2.9 g, 70%) and 12f (3.1 g, 70%). 12e: 1H-NMR 0.23 (s, 9H), 2.19 (s, 3H), 2.32 (s, 3H), 2.58 (s, 2H), 6.72 (d, 1H, J = 8.1 Hz), 6.95 (s, 1H), 7.04 (d, 1H, J = 8.1 Hz); 13C-NMR -2.7, 17.1, 20.3, 33.5, 109.5, 121.6, 125.5, 127.3, 130.6, 146.0; HRMS (ESI) m/z: [M+Na]+ Calcd for C12H21NSiNa 230.1341; Found 230.1344. 12f: 1H-NMR 0.17 (s, 9H), 2.25 (s, 3H), 2.27 (s, 6H), 2.41 (s, 2H), 6.83 (s, 2H); 13C-NMR -2.8, 18.0, 20.5, 39.3, 129.4, 131.0, 146.3; HRMS (ESI) m/z: [M+Na]+ Calcd for C13H23NSiNa 244.1497; Found 244.1496. Step 2. Each N-aryl amines (12a-12f, 7 mmol) were dissolved in toluene solvent (100 mL). After adding K2CO3 (15 mmol) and 2-bromoacetonitrile (8.5 mmol) to the toluene solutions, the each reaction mixtures were allowed to stir at room temperature for 12 h. Then, the reaction solutions were concentrated in vacuo to give residues that were subjected to silica gel column chromatography


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(EtOAc/hexane = 1: 20 - 1: 30) to yield corresponding -aminonitiriles 13a (1.02 g, 67%), 13b (1.07 g, 66%), 13c (1.41 g, 85%), 13d (1.37 g, 79%), 13e (1.0 g, 58%) and 13f (1.55 g, 85%). 13a: 1H-NMR 0.1 (s, 9H), 2.84 (s, 2H), 4.09 (s, 2H), 6.85-6.91 (m, 3H), 7.25-7.30 (m, 2H); 13CNMR -1.7, 43.0, 43.1, 115.4, 115.7, 119.7, 129.1, 148.8; HRMS (ESI) m/z: [M+Na]+ Calcd for C12H18N2SiNa 241.1137; Found 241.1139. 13b: 1H-NMR 0.07 (s, 9H), 2.26 (s, 3H), 2.77 (s, 2H), 4.04 (s, 2H), 6.81 (d, 2H, J = 8.7 Hz), 7.08 (d, 2H, J = 8.7 Hz); 13C-NMR -1.6, 20.4, 43.6, 44.4, 115.8, 116.9, 129.8, 130.2, 147.1; HRMS (ESI) m/z: [M+Na]+ Calcd for C13H20N2SiNa 255.1293; Found 255.1290. 13c: 1H-NMR 0.04 (s, 9H), 2.74 (s, 2H), 4.0 (s, 2H), 6.88-7.0 (m, 4H); 13C-NMR -1.7, 44.0, 45.5, 115.5, 115.8 (d, JC-F = 22.3 Hz), 119.4 (d, JC-F = 7.8 Hz), 145.9 (d, JC-F = 2.3 Hz), 157.9 (d, JC-F = 239.2 Hz); HRMS (ESI) m/z: [M+Na]+ Calcd for C12H17FN2SiNa 259.1043; Found 259.1046. 13d: 1H-NMR -0.08 (s, 9H), 2.28 (s, 3H), 2.71 (s, 2H), 3.75 (s, 2H), 7.04-7.09 (m, 1H), 7.16-7.21 (m, 2H), 7.32-7.35 (m, 1H); 13C-NMR -1.8, 17.4, 44.6, 47.8, 115.5, 122.9, 125.4, 126.6, 131.0, 133.7, 149.0; HRMS (ESI) m/z: [M+Na]+ Calcd for C13H20N2SiNa 255.1293; Found 255.1295. 13e: 1H-NMR -0.05 (s, 9H), 2.27 (s, 3H), 2.30 (s, 3H), 2.71 (s, 2H), 3.76 (s, 2H), 7.02 (s, 2H), 7.27 (s, 1H); 13C-NMR -1.7, 17.3, 20.8, 44.7, 48.1, 115.7, 122.8, 127.2, 131.6, 133.4, 135.0, 146.5; HRMS (ESI) m/z: [M+Na]+ Calcd for C14H22N2SiNa 269.1450; Found 269.1449. 13f: 1H-NMR -0.06 (s, 9H), 2.24 (s, 3H), 2.32 (s, 6H), 2.86 (s, 2H), 3.88 (s, 2H), 6.82 (s, 2H); 13C-NMR

-1.8, 19.3, 20.6, 44.8, 45.8, 117.7, 129.8, 135.7, 136.9, 144.3; HRMS (ESI) m/z: [M+Na]+



Page 30 of 53

Calcd for C15H24N2SiNa 283.1606; Found 283.1602. General procedure of photoreactions of C60 with -aminonitriles 8a-8k and 13a-13f. The 10% EtOH-toluene (v/v) solutions (220 mL) containing C60 (0.28 mmol) and the α-aminonitriles (0.56 mmol) that were purged with nitrogen or oxygen before and during irradiations, were irradiated with a 450 W Hanovia medium vapor pressure mercury lamp surrounded by a flint glass filter (> 310 nm) in a water-cooled quartz immersion well for time periods given below. The photolysates were concentrated in vacuo and the unreacted C60 was recovered by filtration using CHCl3 to determine conversion yields. Photoproducts were separated by using silica gel column chromatography (CS2) of crude photolysates. Photoreaction of C60 with 8a. In N2-purged, 10% EtOH-toluene solution: 1h irradiation (71%), column chromatography (CS2) to yield 9a23 (10 mg, 6%) and 10a23 (56 mg, 30%); 2 h irradiation (85% conversion), column chromatography (CS2) to yield 9a (23 mg, 11%) and 10a (94 mg, 42%). In O2purged, 10% EtOH-toluene solution: 1 h irradiation (94% conversion), column chromatography (CS2) to yield 9a (8 mg, 4%) and 10a (107 mg, 42%). Photoreaction of C60 with 8b. In N2-purged, 10% EtOH-toluene solution: 1 h irradiation (78% conversion), column chromatography (CS2) to yield 9b (24 mg, 10%) and 10b (74 mg, 28%); 2 h irradiation (100% conversion), column chromatography (CS2) to yield 9b (38 mg, 16%) and 10b (107 mg, 41%). In O2-purged, 10% EtOH-toluene solution: 1 h irradiation (95% conversion), column chromatography (CS2) to yield 9b (13 mg, 5%) and 10b (96 mg, 37%).


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9b: 1H-NMR 0.97 (t, 3H, J = 6.9 Hz), 1.38-1.56 (m, 4H), 1.62-1.68 (m, 2H), 1.90-2.00 (m, 2H), 3.11-3.19 (m, 1H), 3.27-3.36 (m, 1H), 4.56 (dd, 2H, J = 50.1 Hz, 9.6 Hz), 5.55 (s, 1H);

13C-NMR

(CDCl3 + CS2) 14.2, 22.9, 27.1, 28.2, 31.7, 51.4, 64.2, 66.0, 68.4, 71.8, 114.1, 135.4, 136.1, 136.7, 137.6, 139.6, 139.7, 139.9, 140.0, 141.3, 141.4, 141.5, 141.6, 141.7, 141.8 (2C), 142.2, 142.3, 142.7, 144.0, 144.2, 144.6, 144.8, 144.9, 145.0, 145.2, 145.4, 145.5, 145.7, 145.9, 146.0, 146.9, 147.0, 149.3, 151.6, 152.0, 154.0; HRMS (MALDI-TOF) m/z: M+ Calcd for C69H16N2 872.1313; Found 872.1317. 10b: 1H-NMR 0.49 (s, 9H), 1.00 (t, 3H, J = 6.9 Hz), 1.42-1.52 (m, 2H), 1.62-1.72 (m, 2H), 1.902.01 (m, 2H), 3.07-3.16 (m, 1H), 3.54-3.63 (m, 1H), 4.256 (s, 1H), 5.77 (s, 1H); 13C-NMR (CDCl3 + CS2) 0.62, 14.3, 22.9, 27.0, 29.0, 31.9, 51.6, 66.5, 67.7, 73.6, 73.9, 114.7, 136.3, 136.5, 138.7 (2C), 139.8, 139.9, 141.3 (2C), 141.5, 141.6, 141.8, 141.9, 142.0 (2C), 142.4, 142.5 (3C), 142.8 (2C), 144.1 (2C), 144.3 (2C), 144.4, 144.9, 145.0, 145.1, 145.2, 145.3 (3C), 145.4 (2C), 145.7 (2C), 145.8, 146.1, 146.6, 147.0, 150.6, 152.5, 153.2, 153.5); HRMS (MALDI-TOF) m/z: M+ Calcd for C72H24N2Si 944.1709; Found 944.1710. Photoreaction of C60 with 8c. In N2-purged, 10% EtOH-toluene solution: 1 h irradiation (80% conversion), column chromatography (CS2) to yield 9c (25 mg, 11%) and 10c (65 mg, 26%); 2 h irradiation (100% conversion), column chromatography (CS2) to yield 9c (41 mg, 18%) and 10c (97 mg, 39%). In O2-purged, 10% EtOH-toluene solution: 1 h irradiation (96% conversion), column chromatography (CS2) to yield 9c (17 mg, 7%) and 10c (91 mg, 36%). 9c: 1H-NMR 1.29 (t, 3H, J = 7.2 Hz), 1.95-2.07 (m, 2H), 3.11-3.20 (m, 1H), 3.26-3.36 (m, 1H),



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4.58 (dd, 2H, J = 48.8 Hz, 9.9 Hz), 5.55 (s, 1H); 13C-NMR (CDCl3 + CS2) 12.0, 21.8, 53.2, 64.3, 66.2, 68.5, 71.9, 114.4, 135.5, 136.3, 136.9, 137.8, 139.8, 139.9, 140.0 (2C), 141.5, 141.6 (2C), 141.7 (2C), 141.8 (2C), 141.9, 142.0, 142.4, 142.5, 142.8, 144.2, 144.4, 144.8, 144.9, 145.1, 145.2, 145.3, 145.4, 145.5, 145.6, 145.7, 145.9 (2C), 146.1 (2C), 147.1, 147.2, 149.4, 151.7, 152.1, 154.1; HRMS (MALDITOF) m/z: M+ Calcd for C66H10N2 830.0844; Found 830.0849. 10c: 1H-NMR 0.50 (s, 9H), 1.29 (d, 3H, J = 7.2 Hz),1.94-2.02 (m, 2H), 3.12-3.18 (m, 1H), 3.493.58 (m, 1H), 4.26 (s, 1H), 5.75 (s, 1H); 13C-NMR (CDCl3 + CS2) 0.5, 11.8, 22.3, 53.0, 66.1, 67.5, 73.5, 73.9, 114.5, 136.2, 136.3, 136.4, 137.2, 138.6, 138.7 (2C), 139.8, 141.2, 141.3, 141.5 (2C), 141.6, 141.7 (2C), 141.9 (2C), 142.0, 142.3, 142.4, 142.7, 142.8, 144.0, 144.1, 144.2, 144.3 (2C), 144.8, 144.9, 145.0, 145.2, 145.3 (2C), 145.4, 145.6, 145.7 (2C), 146.0, 146.9, 150.5, 152.4, 153.1, 153.4; HRMS (MALDI-TOF) m/z: M+ Calcd for C69H18N2Si 902.1239; Found 902.1233. Photoreaction of C60 with 8d. In N2-purged, 10% EtOH-toluene solution: 1 h irradiation (72% conversion), column chromatography (CS2) to yield 9d (4 mg, 2%) and 10d (78 mg, 31%); 2 h irradiation (94% conversion), column chromatography (CS2) to yield 9d (7 mg, 3%) and 10d (122 mg, 48%). In O2-purged, 10% EtOH-toluene solution: 1 h irradiation (92% conversion), column chromatography (CS2) to yield 9d (17 mg, 8%) and 10d (129 mg, 55%). 9d: 1H-NMR 3.45-3.46 (m, 2H), 3.54 (s, 3H), 3.85-3.91 (m, 1H), 4.00-4.07 (m, 1H), 4.65 (dd, 2H, J = 38.9 Hz, 9.9 Hz), 5.76 (s, 1H); 13C-NMR (CDCl3 + CS2) 50.9, 58.8, 65.6, 66.9, 68.4, 71.8, 72.2, 114.8, 135.6, 136.3, 137.0, 137.8 (2C), 139.8, 139.9, 140.1 (2C), 141.5, 141.6, 141.7 (3C), 141.7,


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141.8, 142.0 (2C), 142.4, 142.5, 142.8, 144.2, 144.4, 144.9 (2C), 145.0, 145.1 (2C), 145.2, 145.3 (2C), 145.4, 145.6, 145.7 (2C), 145.9 (2C), 146.1 (2C), 146.2, 147.1, 147.2, 149.7, 151.8, 152.2, 154.2; HRMS (MALDI-TOF) m/z: M+ Calcd for C66H10N2O 846.0793; Found 846.0799. 10d: 1H-NMR 0.49 (s, 9H), 3.36-3.44 (m, 1H), 3.53 (s, 3H), 3.80-3.90 (m, 2H), 3.93-4.00 (m, 1H), 4.38 (s, 1H), 6.04 (s, 1H); 13C-NMR (CDCl3 + CS2) 0.4, 50.7, 58.6, 67.9, 68.3, 72.3, 73.9, 74.4, 115.4, 136.0, 136.2, 137.0, 138.7, 139.6, 139.7, 141.2 (3C), 141.4, 141.5, 141.6 (3C), 141.8 (2C), 142.2, 142.3 (3C), 142.6, 143.9, 144.0, 144.1, 144.4, 144.8, 144.9 (2C), 145.0, 145.1 (2C), 145.2, 145.3, 145.5 (2C), 145.6 (2C), 145.9 (2C), 146.3, 146.7, 146.8, 150.7, 153.2, 153.4; HRMS (MALDITOF) m/z: M+ Calcd for C69H18N2OSi 918.1188; Found 918.1190. Photoreaction of C60 with 8e. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (92% conversion), column chromatography (CS2) to yield 9e (21 mg, 9%) and 10e (86 mg, 34%). In O2purged, 10% EtOH-toluene solution: 1 h irradiation (95% conversion), column chromatography (CS2) to yield 9e (19 mg, 8%) and 10e (99 mg, 40%). 9e: 1H-NMR 3.75-3.82 (m, 1H), 3.99-4.05 (m, 1H), 4.60 (dd, 2H, J = 50.9 Hz, 9.6 Hz), 5.50 (d, 1H, J = 10.2 Hz), 5.56 (s, 1H), 5.72 (d, 1H, J = 17.1 Hz), 6.20-6.33 (m, 1H); 13C-NMR (CDCl3 + CS2) 54.2, 64.2, 65.6, 68.4, 71.8, 114.1, 119.8, 132.8, 135.4, 136.2, 136.8, 137.7, 139.7, 139.8, 140.0 (2C), 141.4 (2C), 141.5, 141.6, 141.7 (2C), 141.9, 142.3, 142.4, 142.7, 144.1, 144.3, 144.6, 144.8, 145.0, 145.1 (2C), 145.3, 145.4 (2C), 145.5, 145.6, 145.8, 146.0 (2C), 147.0, 147.1, 149.3, 151.5, 151.9, 153.9; HRMS (MALDI-TOF) m/z: M+ Calcd for C66H8N2 828.0687; Found 828.0686.



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10e: 1H-NMR 0.51 (s, 9H), 3.62-3.69 (m, 1H), 4.29 (s, 1H), 4.34-4.39 (m, 1H), 5.50 (d, 1H, J = 9.9 Hz), 5.73 (d, 1H, J = 9.9 Hz), 5.77 (s, 1H), 6.15-6.29 (m, 1H); 13C-NMR (CDCl3 + CS2) 0.3, 54.5, 66.6, 67.0, 73.3, 74.2, 114.5, 120.0, 133.5, 136.2, 136.3 (2C), 137.1, 138.6, 138.7, 139.7, 139.8, 141.2 (3C), 141.4, 141.5, 141.6 (2C), 141.8, 141.9 (2C), 142.3 (3C), 142.4, 142.6, 142.7, 143.9, 144.0, 144.2, 144.3, 144.7, 144.8, 144.9 (2C), 145.1, 145.2, 145.3, 145.5, 145.6 (2C), 145.7 (2C), 145.9, 146.4, 146.8 (2C), 150.4, 152.2, 153.0, 153.3; HRMS (MALDI-TOF) m/z: M+ Calcd for C69H16N2Si 900.1083; Found 900.1088. Photoreaction of C60 with 8f. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (91% conversion), column chromatography (CS2) to yield 9f (105 mg, 45%). In O2-purged, 10% EtOHtoluene solution: 1 h irradiation (95% conversion), column chromatography (CS2) to yield 9f (121 mg, 48%). 1H-NMR 1.60-1.65 (m, 6H), 3.44 (septet, 1H, J = 6.3 Hz), 4.65 (dd, 2H, J = 133.8 Hz, 9.6 Hz), 5.73 (s, 1H); 13C-NMR (CDCl3 + CS2) 21.2, 22.0, 50.8, 62.1, 64.6, 68.3, 71.7, 114.5, 135.5, 136.2, 137.0, 137.7, 139.6, 139.7, 139.9, 140.0, 141.4, 141.5 (3C), 141.6 (2C), 141.7, 141.8, 141.9, 142.2, 142.3, 142.4, 142.7, 144.0, 144.1, 144.3, 144.6, 144.8, 144.9, 145.0 (2C), 145.1 (2C), 145.2, 145.3, 145.4 (2C), 145.5, 145.6, 145.7, 145.8, 145.9, 146.0, 147.0, 147.1, 149.4, 151.8, 152.0, 154.4; HRMS (MALDI-TOF) m/z: M+ Calcd for C66H10N2 830.0844; Found 830.0845. Photoreaction of C60 with 8g. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (86% conversion), column chromatography (CS2) to yield 9g (109 mg, 46%). In O2-purged, 10% EtOHtoluene solution: 1 h irradiation (95% conversion), column chromatography (CS2) to yield 9g (115 mg,


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49%). 1H-NMR 1.71 (s, 9H), 4.77 (dd, 2H, J = 23.9 Hz, 9.6 Hz), 5.73 (s, 1H); 13C-NMR (CDCl3 + CS2) 27.4, 53.3, 58.0, 60.8, 68.3, 72.6, 117.5, 135.5, 136.6, 137.1, 138.1, 139.9, 141.5 (3C), 141.6 (2C), 141.9 (3C), 142.0, 142.3, 142.7 (2C), 144.0, 144.1 (2C), 144.4, 144.6 (2C), 144.8, 145.0 (3C), 145.1, 145.2, 145.3, 145.4, 145.5, 145.7, 145.8 (2C), 145.9, 146.0 (4C), 147.0, 147.1, 149.3, 151.9, 152.2, 154.8; HRMS (MALDI-TOF) m/z: M+ Calcd for C67H12N2 844.1000; Found 844.1006. Photoreaction of C60 with 8h. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (89% conversion), column chromatography (CS2) to yield 9h (102 mg, 42%). In O2-purged, 10% EtOHtoluene solution: 1 h irradiation (93% conversion), column chromatography (CS2) to yield 9h (129 mg, 53%). 1H-NMR 1.44-1.67 (m, 3H), 1.74-1.86 (m, 3H), 2.00-2.10 (m, 2H), 2.23-2.38 (m, 2H), 3.103.16 (m, 1H), 4.43 (d, 1H, J = 9.6 Hz), 4.82 (d, 1H, J = 9.6 Hz), 5.75 (s, 1H); 13C-NMR (CDCl3 + CS2) 24.2, 26.1, 31.1, 31.7, 57.5, 61.5, 63.9, 68.2, 71.5, 114.5, 135.5, 136.3, 137.0, 137.8, 139.7, 139.8, 140.0 (2C), 141.4, 141.5 (2C), 141.6 (2C), 141.8, 141.9 (3C), 142.2, 142.3, 142.4, 142.7 (2C), 144.0, 144.1 (2C), 144.4, 144.6, 144.8, 145.0 (3C), 145.1 (2C), 145.2, 145.3, 145.4 (2C), 145.5, 145.7 (2C), 145.8, 146.0 (2C), 147.0, 147.1, 149.4, 151.9, 152.0, 154.6; HRMS (MALDI-TOF) m/z: M+ Calcd for C69H14N2 870.1157; Found 870.1159. Photoreaction of C60 with 8i. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (98% conversion), column chromatography (CS2) to yield 9i (46 mg, 20%) and 10i (90 mg, 35%). In O2purged, 10% EtOH-toluene solution: 1 h irradiation (95% conversion), column chromatography (CS2) to yield 9i (39 mg, 17%) and 10i (102 mg, 40%).



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9i: 1H-NMR 1.26-1.28 (m, 6H), 2.17-2.26 (m, 1H), 2.97-3.12 (m, 2H), 4.58 (dd, 2H, J = 44.6 Hz, 9.9 Hz), 5.55 (s, 1H); 13C-NMR (CDCl3 + CS2) 20.7, 20.9, 59.0, 64.3, 66.4, 68.6, 72.0, 114.6, 135.4, 136.3, 136.9, 137.8, 139.8, 139.9, 140.1, 140.2, 141.5, 141.6 (2C), 141.7 (2C), 141.8, 141.9, 142.0 (2C), 142.4, 142.5, 142.8, 144.2, 144.4, 144.8 (2C), 145.0, 145.1, 145.2 (3C), 145.3, 145.4, 145.5, 145.7 (2C), 145.8, 145.9, 146.1 (3C), 146.2, 147.1, 147.2, 149.4, 151.8, 152.1, 154.2; HRMS (MALDITOF) m/z: M+ Calcd for C67H12N2 844.1000; Found 844.1004. 10i: 1H-NMR 0.47 (s, 9H), 1.21 (d, 3H, J = 6.3 Hz), 1.29 (d, 3H, J = 6.6 Hz), 2.15-2.22 (m, 1H), 3.01-3.06 (m, 1H), 3.14-3.21 (m, 1H), 4.24 (s, 1H), 5.71 (s, 1H); 13C-NMR (CDCl3 + CS2) 0.7, 20.0, 21.1, 27.6, 59.0, 66.4, 67.6, 73.5, 73.8, 114.7, 136.2, 136.4 (2C), 137.3, 138.7, 139.8, 139.9, 141.2, 141.3, 141.4, 141.5, 141.6, 141.9, 142.0 (2C), 142.4, 142.5, 142.8 (2C), 144.1 (2C), 144.3 (2C), 144.4, 144.8, 144.9, 145.0, 145.2, 145.3 (2C), 145.4, 145.7 (2C), 145.8, 146.1, 146.7, 147.0, 150.5, 152.3, 153.2, 153.5; HRMS (MALDI-TOF) m/z: M+ Calcd for C70H20N2Si 916.1396; Found 916.1399. Photoreaction of C60 with 8j. In N2-purged, 10% EtOH-toluene solution: no reaction. In O2purged, 10% EtOH-toluene solution: 6 h irradiation (19% conversion), column chromatography (CS2) to yield 9j (28 mg, 11%). 1H-NMR 4.60 (dd, 2H, J = 89.6 Hz, 9.9 Hz), 5.24 (s, 1H), 5.50 (s, 1H), 7.297.36 (m, 2H), 7.41-7.47 (m, 4H), 7.82-7.85 (m, 4H); 13C-NMR (CDCl3 + CS2) 62.8, 65.3, 68.5, 70.3, 71.7, 114.4, 125.1, 127.0, 127.4, 127.9, 128.0, 128.2, 128.7, 129.1, 129.2, 135.4, 136.4, 137.0, 1396.7, 139.9, 140.0, 140.2, 140.4, 140.9, 141.6 (2C), 141.7 (2C), 142.0, 142.3, 142.4, 142.5, 142.7, 142.8, 144.1 (2C), 144.2, 144.5, 144.6, 144.7, 145.1 (2C), 145.2, 145.4 (2C), 145.6, 145.8 (2C), 145.9 (2C),


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146.1, 151.5, 151.9, 154.5; HRMS (MALDI-TOF) m/z: M+ Calcd for C76H14N2 954.1157; Found 954.1155. Photoreaction of C60 with 8k. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (76% conversion), column chromatography (CS2) to yield diastereomeric mixture 9k (70 mg, 24%) and 9l (71 mg, 24%). In O2-purged, 10% EtOH-toluene solution: 1 h irradiation (84% conversion), column chromatography (CS2) to yield 9k (80 mg, 33%) and 9l (81 mg, 33%). 9k: 1H-NMR 1.88 (d, 3H, J = 6.6 Hz), 4.20-4.27 (m, 1H), 4.79 (dd, 2H, J = 143 Hz, 9.6 Hz), 5.92 (s, 1H), 7.32-7.41 (m, 1H), 7.42-7.50 (m, 2H), 7.69-7.73 (m, 2H); 13C-NMR (CDCl3 + CS2) 23.0, 60.4, 63.4, 65.5, 68.5, 71.3, 114.3, 125.4, 126.9, 127.8, 128.1, 128.7, 129.1, 135.3, 136.4, 136.8, 137.7, 139.6, 139.7, 139.9, 140.0, 141.4, 141.5 (3C), 141.6 (2C), 141.7, 141.8, 141.9, 142.0, 142.2, 142.3, 142.4, 142.7 (2C), 142.8, 144.0 (2C), 144.1 (2C), 144.4, 144.6, 144.8, 145.0 (2C), 145.1, 145.2, 145.3, 145.4, 145.56, 145.8, 146.0 (4C), 147.0 (2C), 149.2, 151.7, 151.8, 154.4; HRMS (MALDI-TOF) m/z: M+ Calcd for C71H12N2 892.1000; Found 892.1005. 9l: 1H-NMR 1.89 (d, 3H, J = 6.6 Hz), 4.27-4.33 (m, 1H), 4.23 (dd, 2H, J = 53.9 Hz, 10.2 Hz), 5.21 (s, 1H), 7.32-7.41 (m, 1H), 7.42-7.50 (m, 2H), 7.69-7.73 (m, 2H); 13C-NMR (CDCl3 + CS2) 22.3, 60.7, 61.7, 64.2, 68.2, 71.9, 114.1, 125.4, 126.6, 127.9, 128.1, 128.7, 129.0, 135.3, 136.1, 137.0, 137.8, 139.7, 139.8, 140.0 (2C), 141.4, 141.5 (3C), 141.6 (2C), 141.7, 141.8, 141.9, 142.0, 142.2, 142.3, 142.4, 142.7 (2C), 142.8, 144.0 (2C), 144.1 (2C), 144.4, 144.6, 144.8, 145.0 (2C), 145.1, 145.2, 145.3, 145.4, 145.56, 145.8, 146.0 (4C), 147.0, 147.1, 149.1, 151.7, 151.9, 154.4; HRMS (MALDI-TOF) m/z:



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M+ Calcd for C71H12N2 892.1000; Found 892.1005. Photoreaction of C60 with 13a. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (55% conversion), column chromatography (CS2) to yield 14a (42 mg, 16%) and 15a (34 mg, 13%). In O2purged, 10% EtOH-toluene solution: 1 h irradiation (51% conversion), column chromatography (CS2) to yield 14a (36 mg, 14%) and 15a (29 mg, 11%). 14a: 1H-NMR 1.15 (s, 9H), 5.11 (s, 1H), 5.85 (s, 1H), 7.41-7.46 (m, 1H), 7.52-7.57 (m, 2H), 7.9 (d, 2H, J = 7.8 Hz); 13C-NMR (CDCl3 + CS2) 0.57, 66.0, 69.7, 73.7, 116.6, 127.6, 127.7, 129.3, 136.2, 136.6, 136.7, 137.4, 138.8, 139.7, 139.9, 141.3, 141.4, 141.5, 141.6 (2C), 141.7 (2C), 141.9, 142.0, 142.5, 142.7, 142.8, 144.0, 144.2 (2C), 144.4, 144.5, 144.8, 144.9, 145.1, 145.2, 145.3, 145.4, 145.7, 145.8, 146.1, 146.5, 147.0 (2C), 150.5, 152.6, 152.7, 153.4; HRMS (MALDI-TOF) m/z: M+ Calcd for C72H16N2Si 936.1083; Found 936.1085. 15a: 1H-NMR 0.22 (s, 9H), 4.94 (s, 1H), 5.84 (s, 1H), 7.31-7.36 (m, 1H), 7.52-7.58 (m, 2H), 7.63 (d, 2H, J = 8.1 Hz); 13C-NMR (CDCl3 + CS2) 0.3, 68.3, 68.9, 72.8, 72.9, 116.6, 123.6, 125.2, 126.1, 129.7 (2C), 134.7, 135.5, 137.2, 137.6, 139.0, 139.9, 140.0, 141.4, 141.5, 141.6 (2C), 141.7, 141.9, 142.0 (2C), 142.5, 142.8, 142.9, 144.1, 144.2, 144.3, 144.4, 145.0 (2C), 145.1, 145.3, 145.5, 145.6, 145.7, 145.8 (2C), 145.9, 146.0, 146.1, 146.2, 147.1 (2C), 150.6, 151.6, 152.4, 153.5; HRMS (MALDITOF) m/z: M+ Calcd for C72H16N2Si 936.1083; Found 936.1088. Photoreaction of C60 with 13b. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (61% conversion), column chromatography (CS2) to yield 14b (47 mg, 18%) and 15b (32 mg, 12%). In O2-


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purged, 10% EtOH-toluene solution: 1 h irradiation (58% conversion), column chromatography (CS2) to yield 14b (44 mg, 17%) and 15b (40 mg, 15%). 14b: 1H-NMR 0.14 (s, 9H), 2.50 (s, 3H), 5.06 (s, 1H), 5.78 (s, 1H), 7.32 (d, 2H, J = 8.1 Hz), 7.78 (d, 2H, J = 8.1 Hz); 13C-NMR (CDCl3 + CS2) 0.6, 21.2, 65.8, 70.0, 73.7, 73.8, 116.8, 127.8, 129.9, 136.2, 136.7 (2C), 137.4, 137.5, 138.7, 138.8, 139.7, 139.9, 141.3, 141.5 (2C), 141.6 (2C), 141.7 (2C), 141.9, 142.0, 142.3, 142.4, 142.5 (2C), 142.7, 142.8, 144.0, 144.2, 144.3, 144.4, 144.5, 144.8, 144.9, 145.1, 145.2, 145.3, 145.4, 145.5, 145.7 (2C), 145.8, 146.1, 146.6, 147.0 (2C), 150.6, 152.6, 152.9, 153.6; HRMS (MALDI-TOF) m/z: M+ Calcd for C73H18N2Si 950.1239; Found 950.1236. 15b: 1H-NMR 1.13 (s, 9H), 2.48 (s, 3H), 4.73 (s, 1H), 5.70 (s, 1H), 7.34 (d, 2H, J = 7.8 Hz), 7.58 (d, 2H, J = 7.8 Hz); 13C-NMR (CDCl3 + CS2) 0.2, 21.1, 69.0, 70.1, 72.6, 73.2, 116.2, 124.9, 130.3, 135.1, 135.5, 136.7, 137.1, 137.5, 138.8, 139.0, 139.8, 140.0, 141.2, 141.3, 141.4, 141.5, 141.8, 141.9, 142.0, 142.5, 142.6, 142.7, 142.9, 144.0, 144.3, 144.4, 145.0 (3C), 145.1, 145.2 (2C), 145.3, 145.5 (2C), 145.7, 145.8, 145.9, 146.0, 146.1, 146.2, 147.0, 147.1, 150.9, 151.5, 152.8, 153.0; HRMS (MALDI-TOF) m/z: M+ Calcd for C73H18N2Si 950.1239; Found 950.1240. Photoreaction of C60 with 13c. In N2-purged, 10% EtOH-toluene solution: 2 h irradiation (34% conversion), column chromatography (CS2) to yield diastereomeric mixture 14c (29 mg, 11%) and 15c (14 mg, 5%). In O2-purged, 10% EtOH-toluene solution: 1 h irradiation (35% conversion), column chromatography (CS2) to yield 14c (23 mg, 9%) and 15c (22 mg, 9%). 14c: 1H-NMR 0.13 (s, 9H), 5.03 (s, 1H), 5.79 (s, 1H), 7.19-7.24 (m, 2H), 7.89-7.93 (m, 2H); 13C-



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NMR (CDCl3 + CS2) 0.5, 65.8, 70.1, 73.5, 73.7, 116.1 (d, JC-F = 22 Hz), 116.5, 129.8, 129.9, 136.1, 136.7, 137.4, 138.7, 138.8, 139.7, 139.9, 140.0, 141.3, 141.4, 141.5 (2C), 141.6 (2C), 141.7, 141.9, 142.0, 142.3, 142.5 (2C), 142.7, 142.8, 144.0, 144.2 (2C), 144.4, 144.8, 144.9, 145.1, 145.3 (2C), 145.4, 145.7, 145.8, 146.1, 146.6, 147.0 (2C), 150.3, 152.2, 152.7, 153.4, 161.7 (d, JC-F = 248.2 Hz); HRMS (MALDI-TOF) m/z: M+ Calcd for C72H15N2FSi 954.0989; Found 954.0988. 15c: 1H-NMR 0.08 (s, 9H), 4.61 (s, 1H), 5.57 (s, 1H), 7.19 (d, 2H, J = 8.7 Hz), 7.65-7.70 (m, 2H);

13C-NMR

(CDCl3 + CS2) 0.0, 69.3, 70.5, 72.3, 73.0, 115.7, 116.4 (d, JC-F = 22.2 Hz), 127.1,

127.3, 135.1, 135.3, 136.8, 137.3, 138.7, 138.9, 139.7, 139.9, 141.0 (3C), 141.1, 141.2 (2C), 141.4, 141.6, 141.7, 141.8, 142.4, 142.6, 142.8, 143.9, 144.0, 144.2, 144.3, 144.8, 144.9 (2C), 145.0, 145.1, 145.2 (2C), 145.3, 145.5, 145.6, 145.7 (2C), 145.8, 145.9, 146.0 (2C), 146.1, 146.9, 150.7, 151.0, 152.4, 152.5, 161.2 (d, JC-F = 246.4 Hz); HRMS (MALDI-TOF) m/z: M+ Calcd for C72H15N2FSi 954.0989; Found 954.0991. Cyclic voltammetry. Oxidation potentials of amine substrates were determined by cyclic voltammetry (CV) using a platinum working electrode, platinum-wire counter electrode, and Ag/Ag+ reference electrode. Measurements were performed under Ar gas; a dichloromethane solution containing tetrabutylammonium tetrafluoroborate (0.1 M) was used as a supporting electrolyte, and the scan rate was 50 mVs-1 at room temperature.


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Calculation Method. All calculations were performed with Gaussian 09.35 B3LYP/6-31+G(d) was used for the structural optimization for conformation of azomethine ylides derived from 8c and 13a. All optimized structures are confirmed by a vibrational analysis.

Supporting information The Supporting Information is available free of charge on the ACS Publication website at DOI: Information about light source (450 W Hanovia medium pressure mercury vapor UV lamp), 1H and 13C

NMR spectra of all previously unidentified compounds, UV-visible spectra of new fullerene

derivatives, B3LYP/6-31+G(d) calculated total energies (Hartree) and optimized Cartesian coordinates of the azomethine ylides formed from 8c and 13a

Author information Corresponding authors *E-mail: [email protected]

Notes The authors declare no competing financial interest.

Acknowledgements



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This investigation was financially supported from National Research Foundation of Korea (NRF2018R1D1A3B07049687).

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