Catalyst- and Additive-Free Trifluoromethylselenolation with [Me4N

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Catalyst- and Additive-Free Trifluoromethylselenolation with [Me4N][SeCF3] Tao Dong, Jian He, Zhi-Han Li, and Cheng-Pan Zhang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b03673 • Publication Date (Web): 15 Nov 2017 Downloaded from http://pubs.acs.org on November 17, 2017

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ACS Sustainable Chemistry & Engineering

Catalyst- and Additive-Free Trifluoromethylselenolation with [Me4N][SeCF3] Tao Donga, Jian He*,b, Zhi-Han Lia, Cheng-Pan Zhang*,a,b a

School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, 205 Luoshi Road, Wuhan, 430070, China Email: [email protected], [email protected] b

College of Pharmacy, Army Medical University, Shapingba, Chongqing 400038, China Email: [email protected]

Abstract Environment-benign trifluoromethylselenolation of alkyl halides, electron-deficient aryl halides, diaryliodonium triflates, aryldiazonium tetrafluoroborates, and α-diazo carbonyls with the readily accessible [Me4N][SeCF3] salt is described. A large number of structurally diversified substrates, previously trifluoromethylselenolated by metal-SeCF3 complex or under metal-mediated catalysis at elevated temperatures, were smoothly converted in this reaction at room temperature or -40 oC to room temperature without using any catalyst or additive. Yields of the reactions were comparative to or even higher than those of the early reports employing transition metal catalysts. Compared to the known means, advantages of this method include simplicity, sustainability, high speed, low reaction temperatures, mild reaction conditions, a wide range of substrates, and good functional group tolerance. This catalyst- and additive-free protocol allows a mild and straightforward synthesis of various

trifluoromethyl

selenoethers,

and

demonstrates

the

possibility

of

trifluoromethylselenolation with [Me4N][SeCF3] under greener conditions. Keywords:

halides;

diaryliodonium;

aryldiazonium;

α-diazo

carbonyls;

environment-benign; trifluoromethylselenolation

Introduction The strategic incorporation of XCF3 (X = O, S, Se, CH2) groups into organic molecules has attracted great attention in the recent years.1-8 Such functionalities can significantly change the physicochemical and biological properties of a molecule, including the electrosteric nature, pKa values, lipophilicity, and the thermal and chemical stability.1-8 Since none of natural XCF3-containing molecules have been

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found so far, these compounds have to be manually synthesized.9-11 Amongst all XCF3-bonded molecules, trifluoromethyl selenoethers are the least studied, probably due to the common fear that selenium substances are often highly toxic, air sensitive, and with penetrating odor.12-17 In spite of their unpleasant features, organoselenium compounds have shown very useful biological activities at a lower dosage.12-17 The SeCF3 functionalities can endow molecules with higher lipophilicity and membrane permeability than the CF3 groups, which are important factors in modulating the potency of agrochemicals and pharmaceuticals.5-11 In view of their potential applications, the development of efficient and convenient methods to synthesize trifluoromethyl selenoethers is of great interest. The traditional methods to import SeCF3 moieties into organic scaffolds mainly focused on the nucleophilic trifluoromethylation of diselenides or selenocyanates by ‒

CF3 anions.18-26 However, these conversions suffer from harsh reaction conditions

and/or a narrow range of substrates. To overcome these disadvantages, the direct nucleophilic and electrophilic trifluoromethylselenolation was developed by using MSeCF3 or XSeCF3 reagents (M = 1/2Hg, Cu, [Me4N]; or X = Cl, SeCF3) (Scheme 1).5,27-45 In 1980’s, Yagupolskii and his group reported that CuSeCF3 complex derived from CF3SeSeCF3 and copper powder reacted with aryl iodide to provide aryl trifluoromethyl selenoethers in good yields.27 Haas and coworkers found that reaction of

1-

or

2-iodo-adamantane

with

Hg(SeCF3)2

yielded

1-

or

2-trifluoromethylselenolated adamantane.28 Complex [LCu(SeCF3)]2 prepared by Weng and coworkers proved to be an efficient trifluoromethylselenolation reagent for a wide range of substrates including aryl, vinyl, allylic, propargylic, and alkyl halides, α- or β-bromo-α,β-unsaturated carbonyls, and terminal alkynes.29-39 Goossen and Rueping disclosed the Cu-catalyzed/mediated trifluoromethylselenolation of aryl diazonium salts, α-diazo esters, boronic acids or acid esters, and terminal alkynes by [Me4N][SeCF3] at room temperature, affording a series of trifluoromethylselenolated arenes, esters, and alkynes under mild conditions.40-42 Recently, Schoenebeck’s and our groups revealed that reactions of aryl halides with [Me4N][SeCF3] in the presence of Pd- or Ni-catalyst provided the corresponding trifluoromethyl selenoethers in good to quantitative yields.43-44 At this stage, one may be aware that all these direct trifluoromethylselenolation reactions required transition metals, ligands, additives, and/or high reaction temperatures (Scheme 1).


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Scheme

Previous

1.

Transition

Metal-Mediated/Catalyzed

Trifluoromethylselenolation Previous work X

[CuSeCF3] or LCuSeCF3

or R X

R

95-130 oC

SeCF3 or R SeCF3

R

X = I, Br, or Cl O

N2 R

R

BF4

1 or R

OR

This work

or

R

SeCF3 R

I

1 R X or Ar

R

O

SeCF3

N2

X [NMe ][SeCF ] 4 3 conditions

N2

[NMe4][SeCF3] [Cu], rt

Ar2 OTf

[Me4N][SeCF3]

N2

BF4 or R1

CH3CN COR2

R1

OR SeCF3

when X = I; condition A: [Pd], 40-60 oC when X = I, Br, Cl; condition B: [Ni], rt or 50 oC

R SeCF3 or Ar1 SeCF3 + Ar2 SeCF3

SeCF3 R or SeCF3

R1 COR2 catalyst- and additive-free up to > 99% yield

On the other hand, in comparison with trifluoromethylthiolation,3,4,46-58 the direct trifluoromethylselenolation was much less investigated owing to the lack of diverse SeCF3 reagents.5,6,27-45 [Me4N][SeCF3] is by far the most convenient and easily accessed trifluoromethylselenolation reagent among all the known SeCF3 transfer sources.59 However, it is much poorly exploited compared to [Me4N][SCF3].60 It was found that the ‒SeCF3 anion is thermally stable,59 and has good nucleophilicity.45 We imagined that the readily accessible [Me4N][SeCF3] would sustainably achieve various nucleophilic reactions without using transition metals and/or additives at low reaction temperatures (Scheme 1).

Experimental Section General Information All reactions were carried out under a nitrogen atmosphere. Unless otherwise specified, NMR spectra were recorded in CDCl3 on a 600, 500 or 400 MHz (for 1H), 471 or 376 MHz (for 19F), and 126 or 100 MHz (for 13C) spectrometer. All chemical shifts were reported in ppm relative to TMS for 1H NMR (0 ppm) and PhCF3 for 19F NMR (-63.0 ppm) as an internal or external standard. The coupling constants were



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reported in Hertz (Hz). The following abbreviations were used to explain the multiplicities: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, br = broad. Melting points were measured and uncorrected. MS experiments were performed on a TOF-Q ESI or EI instrument. [Me4N][SeCF3] was synthesized according to the literature.59 Solvents were dried before use according to the literature.61 Substrates 1q,62 1r,63 4a-c,64 4d,65 4e-g,66 4h,65 4i,66 4j,65 4k,67 6a-i,68,69 7a-e,70 7f,71 7g-h,41 7i-j,72 7k,73 and 7l,74 were synthesized according to the literatures. Other reagents and substrates used in the reactions were all purchased from the commercial sources and used without further purification.

General

Procedures

for

Trifluoromethylselenolation

of

the

Catalyst-

Various

Organic

and

Additive-Free

Electrophiles

with

[Me4N][SeCF3]. Procedure A (for Scheme 2): Under a N2 atmosphere, an oven-dried tube was charged with alkyl or aryl halide 1 (0.2 mmol) and a solution of [Me4N][SeCF3] (54 mg, 0.24 mmol) in CH3CN (2 mL) with stirring. The mixture was reacted at room temperature till the starting halide was completely transformed (monitored by TLC). The resulting mixture was quenched by water and extracted with diethyl ether (3 × 5 mL). The combined organic layers were washed with brine, dried over anhydrous Na2SO4, and concentrated to dryness. The residue was purified by flash column chromatography on silica gel using petroleum ether or a mixture of petroleum ether and ethyl acetate as eluents to give the trifluoromethylselenolated product. Benzyl(trifluoromethyl)selane (3a).24 Light yellow oil (40.6 mg from benzyl 4-methylbenzenesulfonate (1c, 0.2 mmol), 85% yield), petroleum ether as eluent for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.37-7.33 (m, 4H), 7.31-7.28 (m, 1H), 4.27 (s, 2H);

19

F NMR (376 MHz, CDCl3) δ -34.5 (s, 3F);

13

C NMR (126

MHz, CDCl3) δ 136.1, 129.0, 128.9, 127.8, 122.9 (q, J = 332.0 Hz), 29.2 (q, J = 1.8 Hz). 2-(((Trifluoromethyl)selanyl)methyl)benzonitrile (3b).30 Colorless oil (51.8 mg from 2-(bromomethyl)benzonitrile (1d, 0.2 mmol), 98% yield), petroleum ether/ethyl acetate = 5:1 (v/v) as eluents for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.67 (d, J = 7.5 Hz, 1H), 7.57 (t, J = 7.5 Hz, 1H), 7.49 (d, J = 7.9 Hz, 1H), 7.40 (t, J = 7.2 Hz, 1H), 4.38 (s, 2H);

19

F NMR (471 MHz, CDCl3) δ -34.1 (s, 3F); 13C NMR

(126 MHz, CDCl3) δ 140.9, 133.3, 133.1, 130.2, 128.3, 122.7 (q, J = 332.1 Hz), 117.0,


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112.5, 26.6. (4-Nitrobenzyl)(trifluoromethyl)selane

(3c).

Yellow

oil

(53.9

mg

from

1-(chloromethyl)-4-nitrobenzene (1e, 0.2 mmol), 95% yield), petroleum ether/ethyl acetate = 10:1 (v/v) as eluents for column chromatography. 1H NMR (500 MHz, CDCl3) δ 8.19 (d, J = 7.8 Hz, 2H), 7.51 (d, J = 7.9 Hz, 2H), 4.28 (s, 2H); 19F NMR (471 MHz, CDCl3) δ -34.1 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 147.4, 144.3, 129.9, 124.1, 122.4 (q, J = 332.1 Hz), 28.0. IR (KBr): 3063, 3031, 2959, 2948, 2871, 1775, 1702, 1613, 1466, 1444, 1435, 1401, 1370, 1317, 1227, 1208, 1101, 1006, 897, 884, 877, 737, 716 cm−1. HRMS-EI (m/z) calcd. for C8H6F3NO274Se: 278.9575, found: 278.9571. (4-Methylbenzyl)(trifluoromethyl)selane (3d).30 Colorless oil (43.5 mg from 1-(bromomethyl)-4-methylbenzene (1f, 0.2 mmol), 86% yield; 1.063 g from 1-(bromomethyl)-4-methylbenzene (1f, 5.0 mmol), 84% yield), petroleum ether as eluent for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.24 (d, J = 7.5 Hz, 2H), 7.14 (d, J = 7.5 Hz, 2H), 4.24 (s, 2H), 2.35 (s, 3H); 19F NMR (471 MHz, CDCl3) δ -34.5 (s, 3F); 13C NMR (100 MHz, CDCl3) δ 137.6, 132.9, 129.6, 128.9, 122.9 (q, J = 331.0 Hz), 29.0 (q, J = 1.8 Hz), 21.2. (3-Methoxybenzyl)(trifluoromethyl)selane

(3e).30 Yellow oil (50.7 mg

from

1-(bromomethyl)-3-methoxybenzene (1g, 0.2 mmol), 94% yield), petroleum ether as eluent for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.27 (t, J = 7.9 Hz, 1H), 6.95 (d, J = 7.5 Hz, 1H), 6.91 (s, 1H), 6.85 (d, J = 8.2 Hz, 1H), 4.25 (s, 2H), 3.84 (s, 3H); 19F NMR (471 MHz, CDCl3) δ -34.5 (s, 3F); 13C NMR (100 MHz, CDCl3) δ 159.9, 137.5, 129.9, 122.9 (q, J = 331.5 Hz), 121.3, 114.5, 113.4, 55.3, 29.1 (q, J = 1.7 Hz). 1-Phenyl-2-((trifluoromethyl)selanyl)ethan-1-one (3f).39 Light yellow solid (52.1 mg from 2-bromo-1-phenylethan-1-one (1h, 0.2 mmol), 98% yield; 380.4 mg from 2-bromo-1-phenylethan-1-one (1h, 1.5 mmol), 95% yield; 39.5 mg from 2-diazo-1-phenylethan-1-one (7j, 0.2 mmol), 74% yield), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for column chromatography. M.p.: 36-38 oC. 1H NMR (500 MHz, CDCl3) δ 7.97 (d, J = 7.5 Hz, 2H), 7.64 (t, J = 7.7 Hz, 1H), 7.51 (t, J = 7.3 Hz, 2H), 4.63 (s, 2H);

19

F NMR (471 MHz, CDCl3) δ -34.2 (s, 3F);

13

C NMR (126

MHz, CDCl3) δ 193.6, 134.8, 134.2, 129.0, 128.6, 122.8 (q, J = 331.3 Hz), 33.1. IR (KBr): 3071, 3039, 2987, 2929, 1672, 1592, 1579, 1450, 1387, 1320, 1288, 1185, 1170, 1100, 1074, 1000, 984, 867, 757, 737, 689, 619 cm−1. HRMS-ESI (m/z) calcd.



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for [C9H8F3O74Se]+ ([M + H]+): 262.9747, found: 262.9749. N-Benzyl-2-((trifluoromethyl)selanyl)acetamide (3g). White solid (55.6 mg from N-benzyl-2-bromoacetamide (1i, 0.2 mmol), 94% yield), petroleum ether/ethyl acetate = 10:1 (v/v) as eluents for column chromatography. M.p.: 44-46 oC. 1H NMR (400 MHz, CDCl3) δ 7.28-7.21 (m, 3H), 7.17 (d, J = 7.3 Hz, 2H), 6.67 (brs, 1H), 4.34 (d, J = 5.7 Hz, 2H), 3.56 (s, 2H);

19

F NMR (376 MHz, CDCl3) δ -34.8 (s, 3F); 13C NMR

(126 MHz, CDCl3) δ 166.8, 137.3, 128.8, 127.8, 127.8, 122.2 (q, J = 331.9 Hz), 44.4, 27.6 (q, J = 1.5 Hz). IR (KBr): 3297, 3069, 3032, 2990, 2926, 2877, 1641, 1550, 1499, 1454, 1407, 1361, 1328, 1317, 1301, 1209, 1140, 1107, 1078, 1029, 1006, 748, 741, 694 cm−1. HRMS-ESI (m/z) calcd. for [C10H11F3NO74Se]+ ([M + H]+): 292.0012, found: 292.0015. Benzyl 2-((trifluoromethyl)selanyl)acetate (3h). Colorless oil (56.7 mg from benzyl 2-bromoacetate (1j, 0.2 mmol), 95% yield), petroleum ether/ethyl acetate = 10:1 (v/v) as eluents for column chromatography. 1H NMR (400 MHz, CDCl3) δ 7.41-7.35 (m, 5H), 5.20 (s, 2H), 3.73 (s, 2H); 19F NMR (376 MHz, CDCl3) δ -34.9 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 168.6, 135.0, 128.7, 128.6, 128.4, 122.1 (q, J = 331.8 Hz), 68.0, 24.9 (q, J = 1.9 Hz). IR (KBr): 3068, 3036, 2958, 2894, 1737, 1499, 1456, 1408, 1377, 1276, 1119, 1097, 1076, 971, 739, 698 cm−1. HRMS-ESI (m/z) calcd. for [C10H9F3NaO274Se]+ ([M + Na]+): 314.9672, found: 314.9675. 2-((Trifluoromethyl)selanyl)-2,3-dihydro-1H-inden-1-one (3i). Yellow oil (51.2 mg from 2-bromo-2,3-dihydro-1H-inden-1-one (1k, 0.2 mmol), 92% yield), petroleum ether/ethyl acetate = 5:1 (v/v) as eluents for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.82 (d, J = 7.7 Hz, 1H), 7.67 (td, J = 7.7, 0.88 Hz, 1H), 7.48 (d, J = 7.7 Hz, 1H), 7.44 (t, J = 7.6 Hz, 1H), 4.51 (dd, J = 8.0, 3.9 Hz, 1H), 3.83 (dd, J = 17.8, 7.8 Hz, 1H), 3.48 (dd, J = 17.9, 3.8 Hz, 1H); 19F NMR (471 MHz, CDCl3) δ -32.3 (s, 3F);

13

C NMR (126 MHz, CDCl3) δ 200.7, 152.2, 135.9, 134.7, 128.2, 126.4, 124.7,

122.6 (q, J = 332.0 Hz), 43.2, 36.2. IR (KBr): 3074, 3038, 2929, 2855, 1721, 1717, 1609, 1588, 1474, 1466, 1436, 1325, 1299, 1275, 1209, 1122, 1097, 1076, 1023, 1008, 840, 792, 739, 677 cm−1. HRMS-EI (m/z) calcd. for C10H7F3O74Se: 273.9674, found: 273.9679. Cinnamyl(trifluoromethyl)selane

(3j).31

Light

yellow

oil

(45.7

mg

from

(E)-(3-bromoprop-1-en-1-yl)benzene (1l, 0.2 mmol), 86% yield), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.36 (d, J = 6.8 Hz, 2H), 7.31 (t, J = 6.5 Hz, 2H), 7.24 (m, 1H), 6.57


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(d, J = 15.7 Hz, 1H), 6.32 (m, 1H), 3.83 (d, J = 7.1 Hz, 2H); CDCl3) δ -33.8 (s, 3F);

19

F NMR (471 MHz,

13

C NMR (126 MHz, CDCl3) δ 136.2, 134.0, 128.7, 128.1,

126.5, 124.0, 122.8 (q, J = 332.0 Hz), 27.9. (3-Phenylprop-2-yn-1-yl)(trifluoromethyl)selane (3k).31 Light yellow oil (47.4 mg from (3-chloroprop-1-yn-1-yl)benzene (1m, 0.2 mmol), 90% yield), petroleum ether as eluent for column chromatography. 1H NMR (400 MHz, CDCl3) δ 7.43 (m, 2H), 7.33-7.31 (m, 3H), 3.91 (s, 2H);

19

F NMR (376 MHz, CDCl3) δ -34.6 (s, 3F);

13

C

NMR (126 MHz, CDCl3) δ 131.8, 128.6, 128.3, 122.5 (q, J = 331.3 Hz), 122.5, 84.9, 83.4, 11.6 (q, J = 2.7 Hz). Phenethyl(trifluoromethyl)selane

(3l).30

Light

yellow

oil

(47.6

mg

from

(2-bromoethyl)benzene (1n, 0.2 mmol), 94% yield; 45.1 mg from phenethyl 4-methylbenzenesulfonate (1o, 0.2 mmol), 89% yield), petroleum ether as eluent for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.37 (t, J = 6.9 Hz, 2H), 7.30 (t, J = 6.9 Hz, 1H), 7.25 (d, J = 6.6 Hz, 2H), 3.26 (t, J = 6.7 Hz, 2H), 3.15 (t, J = 6.7 Hz, 2H); 19F NMR (471 MHz, CDCl3) δ -34.0 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 140.0, 128.9, 128.6, 127.1, 123.0 (q, J = 331.1 Hz), 36.9, 26.9. 2-(3-((Trifluoromethyl)selanyl)propyl)isoindoline-1,3-dione (3m).30 Colorless solid (64.5 mg from 2-(3-bromopropyl)isoindoline-1,3-dione (1p, 0.2 mmol), 96% yield), petroleum ether/ethyl acetate = 5:1 (v/v) as eluents for column chromatography. 1H NMR (400 MHz, CDCl3) δ 7.84 (m, 2H), 7.72 (m, 2H), 3.82 (t, J = 6.5 Hz, 2H), 2.97 (t, J = 7.2 Hz, 2H), 2.18 (m, 2H);

19

F NMR (376 MHz, CDCl3) δ -34.3 (s, 3F);

13

C

NMR (126 MHz, CDCl3) δ 168.6, 134.4, 132.2, 123.6, 122.8 (q, J = 331.3 Hz), 37.5, 29.8, 22.9 (q, J = 1.8 Hz). (4-Phenylbutan-2-yl)(trifluoromethyl)selane (3n).30 Light yellow oil (46.7 mg from (3-bromobutyl)benzene (1q, 0.2 mmol) and [Me4N][SeCF3] (0.4 mmol), 83% yield; 53.4 mg from (3-iodobutyl)benzene (1r, 0.2 mmol) and [Me4N][SeCF3] (0.4 mmol), 95% yield), petroleum ether as eluent for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.32 (t, J = 7.4 Hz, 2H), 7.24-7.20 (m, 3H), 3.54 (m, 1H), 2.78 (m, 2H), 2.10 (m, 1H), 2.02 (m, 1H), 1.65 (d, J = 6.9 Hz, 3H); CDCl3) δ -32.0 (s, 3F);

19

F NMR (471 MHz,

13

C NMR (126 MHz, CDCl3) δ 140.9, 128.6, 128.4, 126.2,

123.2 (q, J = 330.4 Hz), 39.4, 39.2, 33.7, 23.0. (2,4-Dinitrophenyl)(trifluoromethyl)selane (3o). Yellow solid (36.5 mg from 1-fluoro-2,4-dinitrobenzene (1s, 0.3 mmol) and [Me4N][SeCF3] (0.2 mmol), 58% yield; 62.0 mg from 1-chloro-2,4-dinitrobenzene (1t, 0.2 mmol), 98% yield; 61.2 mg



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Page 8 of 29

from 1-bromo-2,4-dinitrobenzene (1u, 0.2 mmol), 97% yield; 56.1 mg from 1-iodo-2,4-dinitrobenzene (1v, 0.2 mmol), 89% yield), petroleum ether/ethyl acetate = 10:1 (v/v) as eluents for column chromatography. M.p.: 72-74 oC. 1H NMR (500 MHz, CDCl3) δ 9.19 (s, 1H), 8.49 (d, J = 8.8 Hz, 1H), 8.09 (d, J = 8.8 Hz, 1H); 19F NMR (471 MHz, CDCl3) δ -36.8 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 146.8, 145.7, 136.2, 131.2 (q, J = 2.7 Hz), 128.3, 123.0 (q, J = 336.5 Hz), 121.7. IR (KBr): 3141, 3105, 3087, 3044, 1595, 1528, 1459, 1348, 1337, 1305, 1260, 1162, 1128, 1100, 1078, 1033, 984, 915, 834, 735, 666 cm−1. HRMS-EI (m/z) calcd. for C7H3F3N2O474Se: 309.9270, found: 309.9267. 3-Nitro-4-((trifluoromethyl)selanyl)pyridine (3p). Light yellow solid (48.8 mg from 4-chloro-3-nitropyridine (1w, 0.2 mmol), 90% yield), petroleum ether/ethyl acetate = 5:1 (v/v) as eluents for column chromatography. M.p.: 38-40 oC. 1H NMR (400 MHz, CDCl3) δ 9.50 (s, 1H), 8.72 (d, J = 5.5 Hz, 1H), 7.80 (d, J = 5.5 Hz, 1H); 19F NMR (376 MHz, CDCl3) δ -36.8 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 153.4, 147.7, 141.7, 139.6, 123.8 (q, J = 2.30 Hz), 122.9 (q, J = 335.6 Hz). IR (KBr): 3092, 3069, 3036, 2957, 1736, 1499, 1456, 1408, 1377, 1276, 1097, 1075, 1030, 972, 909, 863, 825, 739, 698 cm−1. HRMS-ESI (m/z) calcd. for [C6H4F3N2O274Se]+ ([M + H]+): 266.9444, found, 266.9448.

Procedure B (for Scheme 3): Under a nitrogen atmosphere, a solution of diaryliodonium salt 4 (0.2 mmol) in CH3CN (1 mL) was added dropwise via a syringe within several minutes to a solution of [Me4N][SeCF3] (67 mg, 0.3 mmol) in CH3CN (1 mL). The mixture was reacted at room temperature or 60 oC till the stating diaryliodonium salt was consumed. The resulting mixture was quenched by water and the yields of the trifluoromethylselenolated products were determined by

19

F NMR

−

using OTf anion (from 4) as an internal standard.

Procedure C (for Scheme 4): Under a N2 atmosphere, a solution of aryldiazonium tetrafluoroborate 6 (0.2 mmol) in CH3CN (1 mL) was added dropwise to a solution of [Me4N][SeCF3] (89 mg, 0.4 mmol) in CH3CN (1 mL) at -20 or -40 oC via an automatic syringe pump over a period of 1 hour. The mixture was warmed to room temperature for 3 hours. Then solvent was removed under reduced pressure. The residue was purified by flash column chromatography on silica gel using petroleum ether or a mixture of petroleum ether and ethyl acetate as eluents to give the


Page 9 of 29

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trifluoromethylselenolated product. (4-Methoxyphenyl)(trifluoromethyl)selane (3q).26 Colorless oil (44.9 mg from 4-methoxybenzenediazonium tetrafluoroborate (6a, 0.2 mmol), 88%), petroleum ether as eluent for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.66 (d, J = 8.5 Hz, 2H), 6.91 (d, J = 8.5 Hz, 2H), 3.84 (s, 3H); 19F NMR (471 MHz, CDCl3) δ -37.2 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 161.5, 138.9, 122.5 (q, J = 333.8 Hz), 115.2, 113.0, 55.4. (4-Nitrophenyl)(trifluoromethyl)selane

(3s).26

White

solid

(44.3

mg

from

mesityl(4-nitrophenyl)iodonium triflate (4c, 0.2 mmol), 82%; 40.5 mg from 4-nitrobenzenediazonium tetrafluoroborate (6g, 0.2 mmol), 75%), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for column chromatography. 1H NMR (500 MHz, CDCl3) δ 8.24 (d, J = 8.5 Hz, 2H), 7.92 (d, J = 8.5 Hz, 2H); MHz, CDCl3) δ -34.7 (s, 3F);

13

19

F NMR (471

C NMR (126 MHz, CDCl3) δ 149.0, 137.1, 130.5,

124.4, 122.2 (q, J = 333.3 Hz). (2,4-Dimethylphenyl)(trifluoromethyl)selane (3y). Light yellow oil (26.1 mg from 2,4-dimethylbenzenediazonium tetrafluoroborate (6b, 0.2 mmol), 52%), purified by preparative TLC plate (GF 254 silica gel, 0.5 mm thickness) using petroleum ether as eluent. 1H NMR (500 MHz, CDCl3) δ 7.65 (d, J = 7.8 Hz, 1H), 7.17 (s, 1H), 7.01 (d, J = 7.7 Hz, 1H), 2.53 (s, 3H), 2.36 (s, 3H); 19F NMR (471 MHz, CDCl3) δ -36.0 (s, 3F); 13

C NMR (126 MHz, CDCl3) δ 143.3, 141.4, 139.1, 131.5, 127.8, 122.7 (q, J = 333.6

Hz), 120.3, 23.3, 21.2. IR (KBr): 3007, 2955, 2922, 2850, 1725, 1646, 1469, 1420, 1384, 1273, 1123, 1102, 1029, 986, 876, 811, 737, 712, 646 cm-1. HRMS-EI (m/z) calcd. for C9H9F374Se: 247.9881, found: 247.9884. [1,1'-Biphenyl]-4-yl(trifluoromethyl)selane. (3z).26 White solid (37.3 mg from [1,1'-biphenyl]-4-diazonium tetrafluoroborate (6d, 0.2 mmol), 62%), petroleum ether as eluent for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.82 (d, J = 8.0 Hz, 2H), 7.63-7.60 (m, 4H), 7.48 (t, J = 7.6 Hz, 2H), 7.41 (t, J = 7.3 Hz, 1H);

19

F

NMR (376 MHz, CDCl3) δ -36.0 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 143.4, 139.8, 137.5, 129.0, 128.3, 128.1, 127.2, 122.6 (q, J = 333.0 Hz), 121.3 (q, J = 1.7 Hz). Ethyl 4-((trifluoromethyl)selanyl)benzoate (3aa).44 Yellow oil (47.9 mg from 4-(ethoxycarbonyl)benzenediazonium tetrafluoroborate (6e, 0.2 mmol), 81%), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for column chromatography. 1H NMR (500 MHz, CDCl3) δ 8.05 (d, J = 8.2 Hz, 2H), 7.80 (d, J = 8.2 Hz, 2H), 4.40 (q, J = 7.1 Hz, 2H), 1.40 (t, J = 7.1 Hz, 3H); 19F NMR (471 MHz, CDCl3) δ -35.3 (s, 3F);



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Page 10 of 29

13

C NMR (126 MHz, CDCl3) δ 165.7, 136.4, 132.2, 130.5, 127.9, 122.4 (q, J = 332.6

Hz), 61.4, 14.3. 4-((Trifluoromethyl)selanyl)benzonitrile (3ab).26 White solid (40.8 mg from 4-cyanobenzenediazonium tetrafluoroborate (6f, 0.2 mmol), 82%), petroleum ether/ethyl acetate = 40:1 (v/v) as eluents for column chromatography. 1H NMR (500 MHz, CDCl3) δ 7.86 (d, J = 8.1 Hz, 2H), 7.68 (d, J = 8.3 Hz, 2H);

19

F NMR (471

MHz, CDCl3) δ -34.9 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 136.9, 132.9, 128.5 (q, J = 1.4 Hz), 122.2 (q, J = 333.5 Hz), 117.8, 114.3. 2-((Trifluoromethyl)selanyl)benzo[d]thiazole (3ac).36 Light yellow oil (30.5 mg from benzo[d]thiazole-2-diazonium tetrafluoroborate (6h, 0.3 mmol) and [Me4N][SeCF3] (0.2 mmol), 54%), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for column chromatography. 1H NMR (500 MHz, CDCl3) δ 8.15 (d, J = 8.2 Hz, 1H), 7.93 (d, J = 8.0 Hz, 1H), 7.55 (t, J = 7.5 Hz, 1H), 7.48 (t, J = 7.7 Hz, 1H); 19F NMR (471 MHz, CDCl3) δ -33.3 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 153.7, 147.5 (q, J = 1.8 Hz), 138.4, 126.8, 126.4, 123.9, 122.1 (q, J = 334.5 Hz), 121.2. N-(2,6-dimethoxypyrimidin-4-yl)-4-((trifluoromethyl)selanyl)benzenesulfonamide (3ad).

Light

yellow

solid

(55.7

4-(N-(2,6-dimethoxypyrimidin-4-yl)sulfamoyl)benzenediazonium

mg

from

tetrafluoroborate

(6i, 0.3 mmol) and [Me4N][SeCF3] (0.2 mmol), 63%), petroleum ether/ethyl acetate = 2:1 (v/v) as eluents for column chromatography. M.p.: 147-149 oC. 1H NMR (500 MHz, CDCl3) δ 8.53 (brs, 1H), 7.98 (d, J = 8.4 Hz, 2H), 7.87 (d, J = 8.2 Hz, 2H), 6.23 (s, 1H), 3.93 (s, 3H), 3.89 (s, 3H);

19

F NMR (471 MHz, CDCl3) δ -34.7 (s, 3F); 13C

NMR (126 MHz, CDCl3) δ 172.8, 164.3, 158.5, 141.3, 136.9, 128.2, 127.4, 122.3 (q, J = 332.8 Hz), 86.0, 55.0, 54.3. IR (KBr): 3446, 3220, 3048, 2999, 2957, 2900, 1744, 1601, 1575, 1477, 1458, 1439, 1388, 1361, 1327, 1276, 1258, 1208, 1181, 1151, 1126, 1098, 1085, 1061, 1010, 998, 983, 882, 851, 826, 786, 744, 738, 657, 623, 600 cm-1. HRMS-ESI (m/z) calcd. for [C13H13F3N3O4SSe]+ ([M + H]+): 443.9739; found: 443.9726.

Procedure D (for Scheme 5): Under a N2 atmosphere, an oven-dried tube (20 mL) was charged with α-diazo carbonyl 7 (0.2 mmol), [Me4N][SeCF3] (54 mg, 0.24 mmol), and CH3CN (1 mL) with stirring. At -20 oC, a solution of TfOH (30 mg, 0.2 mmol) in CH3CN (1 mL) was added dropwise via a syringe within several minutes. The mixture was warmed to room temperature for 3 hours. The reaction mixture was concentrated


Page 11 of 29

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and purified by preparative TLC plate (GF 254 silica gel, 0.5 mm thickness) using a mixture

of

petroleum ether and

ethyl acetate

as eluents

to

give

the

trifluoromethylselenolated product. Ethyl 2-(4-methoxyphenyl)-2-((trifluoromethyl)selanyl)acetate (3ae). Light yellow oil (57.3 mg from ethyl 2-diazo-2-(4-methoxyphenyl)acetate (7a, 0.2 mmol), 84%), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for preparative TLC. 1H NMR (500 MHz, CDCl3) δ 7.40 (d, J = 8.7 Hz, 2H), 6.88 (d, J = 8.7 Hz, 2H), 5.20 (s, 1H), 4.29-4.15 (m, 2H), 3.81 (s, 3H), 1.27 (t, J = 7.2 Hz, 3H); 19F NMR (471 MHz, CDCl3) δ -34.3 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 169.9, 159.9, 129.7, 126.4, 122.8 (q, J = 332.9 Hz), 114.4, 62.5, 55.3, 46.5 (q, J = 1.8 Hz), 13.9. IR (KBr): 2984, 2938, 2909, 2840, 1740, 1610, 1584, 1513, 1465, 1444, 1426, 1393, 1370, 1330, 1306, 1289, 1255, 1213, 1179, 1141, 1096, 1073, 1031, 835, 809, 794, 738 cm-1. HRMS-ESI (m/z) calcd. for [C12H13F3O3SeNa]+ ([M + Na]+): 364.9874; found: 364.9862. Ethyl 2-phenyl-2-((trifluoromethyl)selanyl)acetate (3af). Light yellow oil (45.3 mg from ethyl 2-diazo-2-phenylacetate (7b, 0.2 mmol), 73%), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for preparative TLC. 1H NMR (500 MHz, CDCl3) δ 7.48 (dm, J = 8.1 Hz, 2H), 7.39-7.32 (m, 3H), 5.21 (s, 1H), 4.29-4.16 (m, 2H), 1.27 (t, J = 7.5 Hz, 3H); 19F NMR (471 MHz, CDCl3) δ -34.3 (s, 3F);

13

C NMR (126 MHz,

CDCl3) δ 169.7, 134.8, 129.0, 128.8, 128.4, 122.8 (q, J = 332.5 Hz), 62.6, 46.9 (q, J = 1.8 Hz), 13.9. IR (KBr): 3067, 3033, 2985, 2939, 1741, 1601, 1586, 1497, 1455, 1394, 1370, 1342, 1304, 1280, 1211, 1141, 1097, 1074, 1024, 869, 739, 696, 673 cm-1. HRMS-ESI (m/z) calcd. for [C11H11F3O2SeNa]+ ([M + Na]+): 334.9769; found: 334.9762. Ethyl 2-(naphthalen-2-yl)-2-((trifluoromethyl)selanyl)acetate (3ag). White solid (57.8 mg from ethyl 2-diazo-2-(naphthalen-2-yl)acetate (7c, 0.2 mmol), 80%), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for preparative TLC. M.p.: 48-50 oC. 1H NMR (500 MHz, CDCl3) δ 7.94 (s, 1H), 7.87-7.83 (m, 3H), 7.60 (dd, J = 8.5, 1.7 Hz, 1H), 7.53-7.51 (m, 2H), 5.41 (s, 1H), 4.32-4.18 (m, 2H), 1.28 (t, J = 7.1 Hz, 3H); 19F NMR (471 MHz, CDCl3) δ -34.2 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 169.7, 133.2, 133.2, 132.0, 129.1, 128.1, 127.9, 127.7, 126.8, 126.7, 125.6, 122.8 (q, J = 332.8 Hz), 62.7, 47.4 (q, J = 1.5 Hz), 13.9. IR (KBr): 3057, 2988, 2942, 2905, 2872, 1737, 1596, 1508, 1468, 1449, 1373, 1305, 1275, 1252, 1189, 1140, 1094, 1073, 1019, 956, 903, 869, 833, 812, 752, 739, 655 cm-1. HRMS-ESI (m/z) calcd. for [C15H13F3O2SeNa]+ ([M + Na]+): 384.9925; found: 384.9920.



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Page 12 of 29

Ethyl 2-(4-acetamidophenyl)-2-((trifluoromethyl)selanyl)acetate (3ah). White solid (67.4 mg from ethyl 2-(4-acetamidophenyl)-2-diazoacetate (7d, 0.2 mmol), 92%), petroleum ether/ethyl acetate = 2:1 (v/v) as eluents for preparative TLC. M.p.: 98-100 o

C. 1H NMR (500 MHz, CDCl3) δ 7.51 (d, J = 8.4 Hz, 2H), 7.42 (d, J = 8.4 Hz, 2H),

7.37 (brs, 1H), 5.19 (s, 1H), 4.28-4.15 (m, 2H), 2.17 (s, 3H), 1.26 (t, J = 7.1 Hz, 3H); 19

F NMR (471 MHz, CDCl3) δ -34.2 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 169.7,

168.4, 138.4, 130.3, 129.2, 122.8 (q, J = 332.6 Hz), 120.1, 62.6, 46.5, 24.6, 13.9. IR (KBr): 3295, 3255, 3190, 3122, 3067, 2992, 2962, 2946, 1732, 1665, 1608, 1554, 1513, 1463, 1447, 1412, 1371, 1324, 1296, 1266, 1214, 1137, 1097, 1072, 1015, 967, 878, 847, 816, 773, 741 cm-1. HRMS-ESI (m/z) calcd. for [C13H14F3NO3SeNa]+ ([M + Na]+): 391.9983; found: 391.9975. Ethyl 2-(4-chlorophenyl)-2-((trifluoromethyl)selanyl)acetate (3ai). Light yellow oil (57.4 mg from ethyl 2-(4-chlorophenyl)-2-diazoacetate (7e, 0.2 mmol), 83%), petroleum ether/ethyl acetate = 40:1 (v/v) as eluents for preparative TLC. 1H NMR (500 MHz, CDCl3) δ 7.42 (d, J = 8.5 Hz, 2H), 7.34 (d, J = 8.5 Hz, 2H), 5.18 (s, 1H), 4.29-4.16 (m, 2H), 1.26 (t, J = 7.2 Hz, 3H); 19F NMR (471 MHz, CDCl3) δ -34.1 (s, 3F);

13

C NMR (126 MHz, CDCl3) δ 169.3, 134.9, 133.5, 129.8, 129.3, 122.7 (q, J =

332.8 Hz), 62.8, 46.2 (q, J = 1.4 Hz), 13.9. IR (KBr): 2986, 2940, 2908, 1739, 1595, 1492, 1466, 1447, 1412, 1394, 1370, 1322, 1299, 1272, 1212, 1143, 1095, 1016, 960, 830, 768, 739, 678 cm-1. HRMS-EI (m/z) calcd. for C11H10ClF3O274Se: 339.9546; found: 339.9541. Ethyl 2-(3,4-dichlorophenyl)-2-((trifluoromethyl)selanyl)acetate (3aj). Light yellow oil (51.8 mg from ethyl 2-diazo-2-(3,4-dichlorophenyl)acetate (7f, 0.2 mmol), 68%), petroleum ether/ethyl acetate = 40:1 (v/v) as eluents for preparative TLC. 1H NMR (600 MHz, CDCl3) δ 7.63 (s, 1H), 7.47 (m, 1H), 7.36 (m, 1H), 5.17 (s, 1H), 4.30-4.23 (m, 2H), 1.31 (t, J = 6.8 Hz, 3H);

19

F NMR (471 MHz, CDCl3) δ -34.0 (s, 3F);

13

C

NMR (126 MHz, CDCl3) δ 168.9, 135.2, 133.2, 133.2, 131.0, 130.4, 127.8, 122.5 (q, J = 332.8 Hz), 63.0, 45.6, 13.9. IR (KBr): 2985, 2930, 2856, 1736, 1591, 1561, 1473, 1447, 1404, 1369, 1311, 1268, 1212, 1134, 1096, 1033, 957, 909, 879, 861, 828, 789, 739, 713, 672 cm-1. HRMS-EI (m/z) calcd. for C11H9Cl2F3O274Se: 373.9156; found: 373.9165. Ethyl 3-phenyl-2-((trifluoromethyl)selanyl)propanoate (3ak).41 Light yellow oil (39.4 mg from ethyl 2-diazo-3-phenylpropanoate (7g, 0.2 mmol), 61%), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for preparative TLC. 1H NMR (500 MHz,


Page 13 of 29

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CDCl3) δ 7.33 (m, 2H), 7.29 (m, 1H), 7.22 (d, J = 6.9 Hz, 2H), 4.19-4.11 (m, 3H), 3.38 (dd, J = 14.0, 10.1 Hz, 1H), 3.27 (dd, J = 14.1, 6.0 Hz, 1H), 1.20 (t, J = 7.1 Hz, 3H);

19

F NMR (471 MHz, CDCl3) δ -33.4 (s, 3F);

13

C NMR (126 MHz, CDCl3) δ

171.0, 137.2, 129.0, 128.7, 127.3, 122.5 (q, J = 332.3 Hz), 61.9, 43.1, 38.6, 13.8. Methyl 3-(4-hydroxyphenyl)-2-((trifluoromethyl)selanyl)propanoate (3al).41 Colorless oil (42.7 mg from methyl 2-diazo-3-(4-hydroxyphenyl)propanoate (7h, 0.2 mmol), 65%), petroleum ether/ethyl acetate = 3:1 (v/v) as eluents for preparative TLC. 1H NMR (500 MHz, CDCl3) δ 7.06 (d, J = 8.3 Hz, 2H), 6.76 (d, J = 8.4 Hz, 2H), 5.06 (s, 1H), 4.07 (dd, J = 9.6, 5.9 Hz, 1H), 3.69 (s, 3H), 3.27 (dd, J = 14.0, 10.6 Hz, 1H); 3.17 (dd, J = 14.1, 6.0 Hz, 1H);

19

F NMR (471 MHz, CDCl3) δ -33.5 (s, 3F);

13

C

NMR (126 MHz, CDCl3) δ 171.7, 154.9, 130.2, 129.0, 122.5 (q, J = 332.1 Hz), 115.6, 52.8, 43.1, 37.8. 1-(Thiophen-2-yl)-2-((trifluoromethyl)selanyl)ethan-1-one (3am). Light yellow solid (39.6 mg from 2-diazo-1-(thiophen-2-yl)ethan-1-one (7i, 0.2 mmol), 73%), petroleum ether/ethyl acetate = 10:1 (v/v) as eluents for preparative TLC. M.p.: 56-58 oC. 1H NMR (500 MHz, CDCl3) δ 7.78 (dd, J = 3.7, 0.94 Hz, 1H), 7.74 (dd, J = 4.9, 0.89 Hz, 1H), 7.18 (dd, J = 4.8, 3.9 Hz, 1H), 4.45 (s, 2H); 19F NMR (471 MHz, CDCl3) δ -34.3 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 186.2, 141.5, 135.4, 133.4, 128.5, 122.6 (q, J = 330.2 Hz), 31.9 (d, J = 1.3 Hz). IR (KBr): 2922, 2851, 1654, 1610, 1575, 1470, 1413,

1348,

1098, 1033,

858,

723 cm-1.

HRMS-ESI (m/z)

calcd. for

[C7H5F3OSSeNa]+ ([M + Na]+): 296.9071; found: 296.9065. 1,3-Diphenyl-2-((trifluoromethyl)selanyl)propan-1-one (3an). Light yellow oil (45.2 mg from 2-diazo-1,3-diphenylpropan-1-one (7k, 0.2 mmol), 63%), petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for preparative TLC. 1H NMR (500 MHz, CDCl3) δ 7.81 (d, J = 7.5 Hz, 2H), 7.56 (t, J = 7.5 Hz, 1H), 7.42 (t, J = 7.9 Hz, 2H), 7.24 (t, J = 7.2 Hz, 2H), 7.18 (m, 3H), 5.12 (dd, J = 9.8, 5.1 Hz, 1H), 3.70 (dd, J = 14.0, 10.1 Hz, 1H), 3.42 (dd, J = 13.9, 5.1 Hz, 1H);

19

F NMR (471 MHz, CDCl3) δ

-33.2 (s, 3F); 13C NMR (126 MHz, CDCl3) δ 196.4, 137.8, 135.1, 133.8, 129.2, 128.8, 128.7, 128.5, 127.1, 122.8 (q, J = 332.6 Hz), 45.9, 39.7. IR (KBr): 3088, 3064, 3030, 2928, 2855, 1679, 1597, 1581, 1496, 1448, 1385, 1348, 1328, 1305, 1284, 1234, 1184, 1122, 1097, 1075, 1030, 1002, 975, 940, 940, 739, 724, 699, 686 cm-1. HRMS-ESI (m/z) calcd. for [C16H13F3OSeNa]+ ([M + Na]+): 380.9976; found: 380.9969. Ethyl (E)-5-phenyl-2-((trifluoromethyl)selanyl)pent-4-enoate (3ao).41 Colorless oil (51.4 mg from ethyl (E)-2-diazo-5-phenylpent-4-enoate (7l, 0.2 mmol), 73%),



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Page 14 of 29

petroleum ether/ethyl acetate = 20:1 (v/v) as eluents for preparative TLC. 1H NMR (500 MHz, CDCl3) δ 7.36-7.30 (m, 4H), 7.25 (t, J = 6.9 Hz, 1H), 6.52 (d, J = 15.7 Hz, 1H), 6.17 (dt, J = 15.8, 7.3 Hz, 1H), 4.23 (m, 2H), 4.04 (dd, J = 8.2, 6.3 Hz, 1H), 2.91 (m, 2H), 1.28 (t, J = 7.2, 3H); 19F NMR (471 MHz, CDCl3): δ -33.3 (s, 3F); 13C NMR (126 MHz, CDCl3): δ 171.1, 136.7, 134.1, 128.6, 127.7, 126.3, 124.5, 122.6 (q, J = 332.1 Hz), 62.0, 42.0, 35.8, 14.0.

Results and Discussion Indeed, reaction of benzyl chloride or bromide (1a or 1b) with [Me4N][SeCF3] (1.2 equiv) in CH3CN at room temperature under a N2 atmosphere for 0.5 h gave benzyl(trifluoromethyl)selane (3a) in 89% or 88% yield (Scheme 2). The reaction proceeded very fast without any catalyst or additive. In a similar manner, treatment of benzyl

4-methylbenzenesulfonate

(1c),

1-(chloromethyl)-4-nitrobenzene (1e),

2-(bromomethyl)benzonitrile

(1d),

1-(bromomethyl)-4-methylbenzene (1f), and

1-(bromomethyl)-3-methoxybenzene (1g) with [Me4N][SeCF3] at room temperature provided 85% of 3a, 98% of 3b, 95% of 3c, 86% of 3d, and 94% of 3e, respectively. The yields of 3b, 3d, and 3e are a little higher than those obtained in the previous report using [(bpy)Cu(SeCF3)]2 at 110 oC for 16 h.30 2-Bromo-1-phenylethan-1-one (1h),

N-benzyl-2-bromoacetamide

(1i),

benzyl

2-bromoacetate

(1j),

and

2-bromo-2,3-dihydro-1H-inden-1-one (1k) reacted with [Me4N][SeCF3] under the same conditions afforded 3f-i in high yields, where the starting materials were completely

transformed

within

a

few

minutes.

Reactions

of

(E)-(3-bromoprop-1-en-1-yl)benzene (1l) and (3-chloroprop-1-yn-1-yl)benzene (1m) with [Me4N][SeCF3] at room temperature for 0.5 or 3 h furnished 3j and 3k in 86-90% yields, which are slightly better than those using [(bpy)Cu(SeCF3)]2 as a SeCF3 reagent at 70 oC for 16 h.31 (2-Bromoethyl)benzene (1n) or phenethyl 4-methylbenzenesulfonate

(1o),

2-(3-bromopropyl)isoindoline-1,3-dione

(1p),

(3-bromobutyl)benzene (1q) or (3-iodobutyl)benzene (1r) reacted with [Me4N][SeCF3] to yield 83-96% of 3l-n. These conversions are superior to the known reaction systems that employed [(bpy)Cu(SeCF3)]2 at 110 TMSCF3/Se8/KF/CuI/phen/Ag2CO3 at 80 aromatic

halides

such

as

o

C or an assembly of

o

C.29,30 Moreover, electron-deficient

1-halo-2,4-dinitrobenzenes

(1s-v)

and

4-chloro-3-nitropyridine (1w) were all smoothly converted at room temperature in this reaction, affording trifluoromethylselenolated products (3o and 3p) in 58-98% yields.


Page 15 of 29

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Scheme 2. Catalyst- and Additive-Free Trifluoromethylselenolation of Organic Halides by [Me4N][SeCF3] a

a

Reaction conditions: Organic halide 1 (0.2 mmol) was added to a solution of

[Me4N][SeCF3] (0.24 mmol) in CH3CN (2 mL) and reacted at room temperature for 0.5 h. Isolated yields. internal standard. f

24 h.

g

c

b

Yields were determined by

19

F NMR using PhCF3 as an

The reaction was run on a 5.0 mmol scale.

[Me4N][SeCF3] (0.4 mmol).

h

d

3 h.

e

48 h.

1s (0.3 mmol) and [Me4N][SeCF3] (0.2

mmol).

Next,

transition

metal-

and

additive-free

trifluoromethylselenolation

of

diaryliodonium triflates with [Me4N][SeCF3] was examined (Scheme 3).45 Mesityl(4-methoxyphenyl)- or (4-chlorophenyl)(mesityl)iodonium triflate (4a or 4b) reacted with [Me4N][SeCF3] (1.5 equiv) at 60 oC or room temperature for 10 h to afford a mixture of (4-methoxyphenyl)(trifluoromethyl)selane (3q, 12%) and mesityl(trifluoromethyl)selane

(5,

49%)

or

a

mixture

of

(4-chlorophenyl)(trifluoromethyl)selane (3r, 47%) and 5 (7%). The reaction happened



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Page 16 of 29

preferentially at the aryl group bearing relatively electron-deficient functionality. This is different from the results that only alkynyl moieties were attacked when [Me4N][SeCF3]

reacted

Trifluoromethylselenolation [Me4N][SeCF3]

at

with of room

alkynyl(phenyl)iodonium

mesityl(4-nitrophenyl)iodonium temperature

yielded

tosylates.45 triflate

with

82%

of

(4-nitrophenyl)(trifluoromethyl)selane (3s), and compound 5 was formed only in a trace amount. Symmetric diaryliodonium triflates (4d-j) reacted under similar conditions to provide the corresponding aryl(trifluoromethyl)selanes in 33% to >99% yields. The electron-donating groups on the phenyl rings of 4d and 4f slowed down the transformations (60 oC/10 h), while the electron-withdrawing groups on the phenyl rings of 4h-j facilitated the reactions (rt/3 h), leading to much higher yields of the products. The steric hindrance of 4e is a benefit for the reaction, which rendered easier trifluoromethylselenolation of 4e than 4g, even though it possesses electron-donating methyl groups. Furthermore, this transition metal- and additive-free reaction was applicable to phenyl(thiophen-2-yl)iodonium triflate (4k), which was chosen as a representative of heteroaryl iodonium systems.

Scheme

3.

Catalyst-

and

Additive-free

Diaryliodonium Triflate by [Me4N][SeCF3]

Trifluoromethylselenolation

a


of

Page 17 of 29

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


Ar1

I

Ar2 + [Me4N][SeCF3] OTf 2 4 (1.5 equiv)

CH3CN N2, rt, 10 h

I

I

O

O2N

I

3s, 82% isolated yield 5, trace

I

I

O

OTf 4d (1.5 equiv 4d) 3q, 33%b

t-Bu OTf 4e 5, 72% I

I OTf 4g 3u, 63 %c

OTf 4c

OTf 4b 3r, 47% 5, 7%

3q, 12%b 5, 49%b

a

I

Cl OTf 4a

O

Ar1 SeCF3 + Ar2 SeCF3 5 3

X

X

OTf

t-Bu

OTf 4f 3t, 40 %b

4h (X = F) 4i (X = Br) 4j (X = NO2)

X = F, 3v, 75 %d X = Br, 3w, 85 %d X = NO2, 3s, > 99%d

S

I OTf 4k 3x, 27% 3u, 17%

Reaction conditions: To a solution of [Me4N][SeCF3] (0.3 mmol) in CH3CN (1 mL)

was added a solution of diaryliodonium salt 4 (0.2 mmol) in CH3CN (1 mL). Yields were determined by 19F NMR using –OTf anion (from 4) as an internal standard. 60 oC.

c

[Me4N][SeCF3] (0.4 mmol).

d

b

3 h.

Trifluoromethylselenolation of aryldiazonium tetrafluoroborates by [Me4N][SeCF3] in the absence of transition-metal catalysts and additives was also explored (Scheme 4). We were pleased to find that by simply mixing [Me4N][SeCF3] and aryldiazonium tetrafluoroborates in CH3CN at -40 or -20 oC to room temperature for 4 h, the expected aryl trifluoromethyl selenoethers were formed in good yields. In contrast to the previous report that the Sandmeyer trifluoromethylthiolation with [Me4N][SCF3] required copper catalysis,40 this trifluoromethylselenolation using [Me4N][SeCF3] occurred smoothly without transition metal or additive, allowing for an efficient and green access to various aryl trifluoromethyl selenoethers. The yields of 3q and 3s are comparable to those from CuSCN-catalyzed trifluoromethylthiolation in the previous literature.40 The scope of the reaction variant was demonstrated by the examples given in Scheme 4, including functionalized arenes, heteroarene, and an analogue of



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Page 18 of 29

Sulfadimethoxine (a long-lasting sulfonamide antimicrobial). These findings are significant because it amended the assumption that the Sandmeyer protocols usually need transition-metal catalysts or other initiators.

Scheme 4. Catalyst- and Additive-Free Trifluoromethylselenolation of Aryldiazonium Tetrafluoroborates by [Me4N][SeCF3] a

a

Reaction conditions: A solution of 6 (0.2 mmol) in CH3CN (1 mL) was added

dropwise to a solution of [Me4N][SeCF3] (0.4 mmol) in CH3CN (1 mL) at -20 oC over a period of 1 h and the mixture was warmed to room temperature for another 3 h. Isolated yields.

b

c 19

Room temperature.

PhOCF3 as an internal standard.

d

F NMR yield was determined by using

o

-40 C to room temperature.

e

6 (0.3 mmol)

and [Me4N][SeCF3] (0.2 mmol). In addition, reaction of α-diazo carbonyl compounds with [Me4N][SeCF3] in the presence

of

trifluoromethanesulfonic

acid

afforded

the

corresponding

α-trifluoromethylselenolated carbonyls in excellent yields (Scheme 5). Both α-diazo esters and α-diazo ketones were readily converted at -40 or -20 oC to room temperature to form the desired products. A survey of the reaction conditions for this transition metal-free trifluoromethylselenolation revealed that the choice of a suitable acid was essential for the reaction and that its absence led to none of the desired product (see Tables S1 and S2 in the Supporting Information). CF3SO3H appears to be a better choice, which may behave as a source of α-hydrogen atom for the product (see the control experiments in the Supporting Information). CF3SO3H may first protonate

the

α-diazo

carbonyls

at

the

α-carbon


sites,

and

subsequent

Page 19 of 29

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trifluoromethylselenolation of the resulting α-protonated α-diazonium intermediates by −SeCF3 anion yields the final products. Nevertheless, the exact mechanism still remains unknown. It should be noted that the ‒SeCF3 anion successfully survived with CF3SO3H in CH3CN in the presence of 4 equiv of D2O, indicating good chemical stability (see SI). Remarkably, the yield of 3ao obtained in this reaction was identical to that using CuSCN as the catalyst, and tetramethylammonium ion and/or residual moisture (in the reaction mixture) as the proton source in the previous report.41

Scheme 5. Catalyst- and Additive-Free Trifluoromethylselenolation of α-Diazo Carbonyls by [Me4N][SeCF3]a

a

Reaction conditions: To a solution of α-diazo carbonyl 7 (0.2 mmol) and

[Me4N][SeCF3] (0.24 mmol) in CH3CN (1 mL) was added a solution of TfOH (0.2 mmol) in CH3CN (1 mL) at -20 oC and the mixture was warmed to room temperature for 3 h. Isolated yields.

b

-40 oC to room temperature.

c

Room temperature.

Conclusion In summary, we have verified that [Me4N][SeCF3] can react with different types of organic electrophiles under environmental friendly, catalyst- and additive-free conditions. Various alkyl halides, electron-deficient aryl halides, diaryliodonium triflates, aryldiazonium tetrafluoroborates, and α-diazo carbonyls were readily trifluoromethylselenolated at room temperature, 60 oC, or -40 oC to room temperature



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Page 20 of 29

in the reaction to give the corresponding trifluoromethyl selenoethers in good to high yields. Notably, the yields of the reaction were similar to or even better than those of the transition metal-mediated trifluoromethylselenolation at elevated temperatures in the literatures.29-42 In comparison with the known methods, the present reaction has featured several advantages such as simplicity, speediness, friendly to the environment, low reaction temperatures, a wide range of substrates, good functional group tolerance, and without use of transition metals and additives. This protocol provides a mild and straightforward access to a large number of trifluoromethyl selenoethers

and

demonstrates

a

greener


with

[Me4N][SeCF3].

Associated Content Supporting Information The Supporting Information is available free of charge on the ACS Publications website. A survey of the reaction conditions, control experiments, NMR data (PDF).

Author Information Corresponding Authors *E-mail: [email protected], [email protected] (C.-P.Z.) *E-mail: [email protected] (J.H.) ORCID Cheng-Pan Zhang: 0000-0002-2803-4611

Notes The authors declare no competing financial interest. This work is dedicated to Prof. István T. Horváth at the City University of Hong Kong on the occasion of his 65th birthday.

Acknowledgements We thank the Wuhan University of Technology, the Army Medical University, the Fundamental Research Funds for the Central Universities, the National Natural Science Foundation of China (21602165), the “Chutian Scholar” Program from Department of Education of Hubei Province (China), the “Hundred Talent” Program of Hubei Province, and the Wuhan Youth Chen-Guang Project (2016070204010113)


Page 21 of 29

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for financial support.

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10.1021/ol303217s.


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Table of Contents (TOC) Graphic

Structurally diversified organic electrophiles were readily trifluoromethylselenolated by [Me4N][SeCF3] at low reaction temperatures under catalyst- and additive-free conditions.


Catalyst- and Additive-Free Trifluoromethylselenolation with [Me4N

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