Subscriber access provided by READING UNIV
Letter
Enantioselective Aza-Friedel-Crafts Reaction of Indoles with Ketimines Catalyzed by Chiral Potassium Binaphthyldisulfonates Manabu Hatano, Takuya Mochizuki, Keisuke Nishikawa, and Kazuaki Ishihara ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.7b03708 • Publication Date (Web): 04 Dec 2017 Downloaded from http://pubs.acs.org on December 4, 2017
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Catalysis 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.
Page 1 of 6
Enantioselective Aza-Friedel–Crafts Reaction of Indoles with Ketimines Catalyzed by Chiral Potassium Binaphthyldisulfonates Manabu Hatano, Takuya Mochizuki, Keisuke Nishikawa, Kazuaki Ishihara* Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan ABSTRACT: The enantioselective aza-Friedel–Crafts reaction of indoles with low-reactive ketimines has been developed in the presence of a chiral mono-potassium binaphthyldisulfonate as a strong Brønsted acid catalyst. A broad substrate scope was achieved, and the corresponding 3-indolylmethanamines with a chiral quaternary carbon center were obtained in high yields with high enantioselectivities. The addition of a catalytic amount of acetic acid considerably promoted the reaction, and a gram-scale reaction could be achieved with reduced catalyst loading. KEYWORDS: chiral Brønsted acid, aza-Friedel–Crafts reaction, indole, ketimine, sulfonic acid
A functionalized indole scaffold is one of the most important heterocycles in bioactive compounds in nature, as well as in material science, pharmaceuticals, and agrochemicals.1 In particular, the synthesis of optically active 3-indolylmethanamines has been widely investigated due to the ubiquity of their biological properties. Indeed, for the catalytic enantioselective azaFriedel–Crafts (aza-FC) reaction of indoles with reactive aldimines to provide optically active 3-indolylmethanamines, several chiral metal salt catalysts2 and chiral organocatalysts3 have been developed over the last decade (Figure 1a).4,5 In contrast, to the best of our knowledge, simple and low-reactive ketimines have not been used in the catalytic enantioselective aza-FC reaction, although Zhou used ketimine-tautomerized aryl enamides6 and some research groups used electron-withdrawing groupfunctionalized reactive ketimines,7 such as α-ketimino esters, CF3-substituted ketimines, and cyclic ketimines (Figure 1b). Interestingly, for these activated ketimines and enamides in Figure 1b, chiral phosphoric acid catalysts 18 were exclusively used, except for a recent example with N,N’-dioxide-Zn(II) catalyst by Feng.7j Accordingly, to overcome the low reactivity and strong basicity of simple ketimines (i.e., deactivation of catalysts by neutralization),9 we envisioned that stronger chiral Brønsted acid catalysts might be favored. In this regard, we recently developed chiral 3,3’-Ar2-BINSA (1,1’-binaphthalene-2,2’-disulfonic acid) 2 with strong Brønsted acidity,10 which was highly effective for the catalytic asymmetric cycloaddition of low-reactive styrenes with aldimines by taking advantage of the serendipitous discovery of a 3:1:3 (R)-2/Mg/K cluster catalyst.11 Here, we tried to develop a catalytic enantioselective aza-FC reaction of indoles with simple ketimines, for the first time, in the presence of chiral mono-alkali metal salts of 3,3’-Ar2-BINSA (R)-2 (Figure 1c). We initially examined the reaction of N-Bn-indole 5a with NTs-ketimine 4a in dichloromethane at –78 °C as a probe reaction, since the N-Bn moiety would inherently increase the nucleophilicity of indole and the N-Ts moiety would reliably increase the electrophilicity of the imino-carbon (Table 1, also see the Supporting Information (SI) for the optimization of
(a) Previous works: Aldimines N
Chiral metal salt catalysts R2HN H or Chiral organocatalysts R1 *
R2
+ N R3
H R1 Reactive
Many examples
N R3
(b) Previous works: Activated ketimines or their precursors N R1
R2
N
CO2R N
R1
R2
Ar
R2
O CONR2
HN
Ac
R R1
CF3
N R1
Ts R2
R1
= aryl, alkyl R2 = alkyl Low-reactive
P O
OH
OH
Ar (R)-1
Ar
(c) This work: Simple ketimines
O
O
NH
Ar
O H S O O M Stronger Brønsted acid O by BBA or LBA system S O O Ar (R)-2 (M = H, Li, Na, K, Cs)
E
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
ACS Catalysis
Figure 1. Enantioselective aza-Friedel–Crafts reaction and chiral catalysts.
substrates). Conventional chiral phosphoric acids,8 such as (R)1a, could not promote the reaction due to insufficient Brønsted acidity (entry 1, also see the SI). In contrast, when we used a much stronger Brønsted acid, (R)-3,3’-(3,5-Ph2C6H3)2-BINSA ((R)-2a)10 (see the SI for the initial screening of catalysts as well as our previous (R)-2/Mg/K cluster catalyst11a with much weaker Brønsted acidity than (R)-2 alone), 6a was obtained with 95% ee, although the yield was low (51%) due to some byproducts that mainly consisted of 7a (37%) (entry 2). To prevent serious side reactions, we must ensure that the catalysts are not too strongly Brønsted acidic, since one Brønsted acid moiety in (R)-2a might be activated by the other Brønsted acid moiety according to Yamamoto’s Brønsted acid-activated chiral Brønsted acid (BBA) theory.12 Therefore, we used (R)-2a-derived mono-alkali metal salts, either of which might have an adequately ‘weaker’ Brønsted acidity than (R)-2a, based on the Lewis acid-activated chiral Brønsted acid (LBA) theory.12,13 As a result, (R)-2b–e with mono-Li(I), Na(I), K(I), and Cs(I) gave 6a with 95–96% ee and
ACS Paragon Plus Environment
ACS Catalysis 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
greatly reduced side reactions (entries 3–6). In particular, (R)-2d showed good chemoselectivity, and the yield of 6a (96%) was better than with the other catalysts (entry 5).14 Notably, ketimine 4a was stable under our reaction conditions, and we did not observe the tautomerization of 4a to the corresponding enamide during the reaction (see the SI). Interestingly, dipotassium salt (R)-2f did not promote the reaction (entry 7), and thus a Brønsted acid (i.e., SO3H) catalysis should be necessary (see the SI for control experiments with Lewis acid catalysts (CF3SO3)nM). We also examined disulfonimide (R)-3a as a chiral Brønsted acid catalyst.15 However, (R)-3a and its potassium salt (R)-3b showed no catalytic activity (entries 8 and 9). Moreover, N-unprotected-indole 5b was useless in our catalysis (entry 11), since (R)-2d would have weak basicity on the S=O moieties, and chiral phosphoric acid catalyst (R)-1a was also useless (entry 10), although its strong base moiety (P=O) might interact with the N-H portion of 5b.
Page 2 of 6
products 6l and 6m were obtained with 93% ee and 87% ee, respectively.
N Ar
Catalyst (10 mol%)
Ts + N Me R
Ph
4a
TsHN Me
4a–m
CH2Cl2, MS 3Å –78 ºC, 20 h
5a (R = Bn) 5b (R = H) Ar O
O P O
OH
Ar (R)-1a
Ar
Ar
SO3M SO3M
SO3M SO3H
SO2 NM SO2
Ar (R)-2a (M = H) (R)-2f (M = K)
Ar = 3,5-Ph2C6H3
Ar (R)-2b (M = Li) (R)-2c (M = Na) (R)-2d (M = K) (R)-2e (M = Cs)
entry
catalyst
6/7
conversion of 4a (%)
1 2 3 4 5 6 7 8 9 10 11
(R)-1a (R)-2a (R)-2b (R)-2c (R)-2d (R)-2e (R)-2f (R)-3a (R)-3b (R)-1a (R)-2d
6a/7a 6a/7a 6a/7a 6a/7a 6a/7a 6a/7a 6a/7a 6a/7a 6a/7a 6b/7b 6b/7b
0 >99 >99 96 96 90 0 0 0 0 0
Ar (R)-3a (M = H) (R)-3b (M = K)
6, yield (%)
6, ee (%)
7, yield (%)
0 51 76 73 92 80 0 0 0 0 4
– 95 95 95 96 96 – – – – 70
0 37 6 6 4 4 0 0 0 0 0
aThe
reaction was carried out with 4a (0.20 mmol), 5a or 5b (0.26 mmol), catalyst (10 mol%), and MS 3Å in dichloromethane at –78 °C for 20 h.
With the optimized reaction conditions in hand, we next examined the scope of N-Ts-ketimines 4 (Scheme 1). As a result, p-Br 6c, m-Br 6d, p-Me 6e, and m-Me 6f were obtained with 94– 98% ee.16 Highly electron-donating p-MeO 6g showed high enantioselectively (92% ee), but the yield was low (37%) even with the use of 20 mol% of catalyst.17 Another substrate with the 2-naphthyl moiety could also be used, and desired 6h was obtained with 92% ee. Moreover, substrates with heteroaromatic structures were tolerable in the presence of 10–20 mol% of (R)-2d, and the corresponding products 6i–k were obtained with high enantioselectivities (84–98% ee). Remarkably, not only methyl ketimines but also ethyl and n-propyl ketimines could be used without serious problems, and the corresponding
5a
6a–m
TsHN Me
N Bn
TsHN Me Br
Ph N 6a Bn 92%, 96% ee
Br
N 6c Bn 93%, 98% ee
TsHN Me
N 6d Bn 85%, 98% ee
TsHN Me
TsHN Me
Me Me
N 6e Bn 74%, 96% eeb TsHN Me
N Bn 6h 82%, 92% ee
N N R R 7a (R = Bn) 7b (R = H)
Ar
Ar
CH2Cl2, MS 3Å –78 ºC, 20 h
TsHN Me
+
N R 6a (R = Bn) 6b (R = H)
N Bn
Product 6, yield, and enantioselectivity:a
Me Ph
Ph
TsHN R
(R)-2d (10 mol%) +
R
Table 1. Optimization of the Reaction Conditionsa N
Ts
TsHN Me S N 6k Bn 82%, 90% ee
N N MeO 6f 6g Bn Bn 80%, 94% ee 37%, 92% eeb TsHN Me O N Bn 6i 82%, 84% eeb TsHN Et
TsHN Me S N Bn 6j 52%, 98% eeb TsHN n-Pr
Ph
Ph
N 6l Bn 88%, 93% ee
N 6m Bn 78%, 87% ee
aThe reaction was carried out with 4 (0.20 mmol), 5a (0.26 mmol), (R)-2d (10 mol%), and MS 3Å in dichloromethane at –78 °C for 20 h unless otherwise noted. b20 mol% of (R)-2d was used.
Scheme 1. Substrate scope in the catalytic enantioselective aza-FC reaction of indole 5a with ketimines 4. Next, we investigated the substituent effects of N-Bn-indoles 8 (Scheme 2). As a result, 4-MeO-substituted indole gave 9a with 90% ee but in low yield (20% within 20 h), probably due to steric hindrance. In contrast, the electron-donating MeOsubstituent at the 5-, 6-, or 7-position of N-Bn-indole significantly promoted the reaction with 91–97% ee, and the reaction was almost complete within 3 h (see 9b–d). Since 5-hydroxyindole derivatives are synthetically important,18 we used N-Bn-5-BnOindole 8e in place of N-Bn-5-MeO-indole 8b. As a result, the yield and enantioselectivity were improved, and 9e was obtained in 96% yield with 94% ee within 3 h. By taking advantage of the great reactivity of 8e, we next examined the reaction of 8e with particularly low-reactive ketimines. As a result, 8e could be used with low-reactive p-Me- and p-MeO-ketimines, and the corresponding products 9g and 9h were obtained with improved yields (cf. 5a-derived 6e and 6g with 20 mol% of (R)2d in Scheme 1). Moreover, heteroaromatic ketimines also showed improved yields, and 9i and 9j were obtained in 74% and 68% yields, respectively, with the use of 10 mol% of (R)-2d (cf. 6j with 20 mol% of (R)-2d in Scheme 1). Ethyl and n-propyl ketimines gave the corresponding products 9k and 9l in high yields with 95% ee and 87% ee, respectively (cf. 6l and 6m in Scheme 1). In contrast to such low-reactive ketimines, relatively reactive p-F-, p-Br-, and p-I-ketimines could provide 9m–o in 92–99% yields with 96–97% ee within 2–4 h. To date, aliphatic ketimines were not generally suitable in our catalyst system. However, when we used 10a, 11a was ob-
ACS Paragon Plus Environment
Page 3 of 6 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
ACS Catalysis tained in 80% yield with 82% ee (Eq. (1)). Fortunately, recrystallization of 11a increased the enantio-purity to 99% ee without any serious loss of yield. Moreover, a reaction of ketimine 10b with cyclohexyl moiety as a sec-alkyl group was slugguish, and 11b was obtained in 15% yield, although the enantioselectivity was good (81% ee) (Eq. (2)).19 Ts
N
+
Ar
R 4
N Bn
Ar
CH2Cl2, MS 3Å –78 ºC, 2–20 h
8a–f
OR'
TsHN R
(R)-2d (10 mol%)
OR’
N Bn
9a–o
Product 9, yield, and enantioselectivity:a OMe
MeO TsHN Me
TsHN Me
Ph
TsHN Me
Ph
N Bn 9a 20%, 90% ee (20 h)
OMe
Ph N
N
Bn 9b 96%, 91% ee (20 h) 86%, 91% ee (3 h)
9c Bn 99%, 95% ee (20 h) 85%, 95% ee (3 h)
OBn TsHN Me
TsHN Me
TsHN Me
Ph
Ph
OMe N N Bn 9d 9e Bn 87%, 97% ee (20 h) 96%, 94% ee (3 h) 79%, 97% ee (3 h) OBn TsHN Me
9g
90%, 94% ee (12 h)
9h
OBn
TsHN Me S
N Bn
Ph (3) CH2Cl2, MS 3Å N 12 13 –78 ºC Bn 12 h, 87% (1.01 g), 94% ee (R)-2d (1 mol%) / AcOH (0 mol%) [2.5 mmol of 12]: (R)-2d (1 mol%) / AcOH (10 mol%) [2.5 mmol of 12]: 0.5 h, >99% (1.17 g), 92% ee (R)-2d (0.3 mol%) / AcOH (10 mol%) [25 mmol of 12]: 8 h, 92% (10.73 g), 97% ee
+ 5a
N Bn 9l 90%, 87% ee (15 h)
OBn TsHN Me
OBn TsHN Me
Figure 2. 10 gram scale synthesis of 13.
reaction was carried out with 4 (0.20 mmol), 8 (0.26 mmol), (R)-2d (10 mol%), and MS 3Å in dichloromethane at –78 °C for 2–20 h.
OBn
Ts
(Ar = Mesityl)
CH2Cl2, MS 3Å –78 ºC, 1 h
recrystallization
N Bn 80%, 82% ee 62%, 99% ee
Ts (R)-2d (10 mol%)
Me
+ 8e
OBn
TsHN Me (2)
CH2Cl2, MS 3Å –78 ºC, 20 h
10b
(1)
Ar 11a
10a
N
TsHN Me
(R)-2d (10 mol%) + 8e
N 11b Bn 15%, 81% ee
N
OBn
Ts
Me + 8e Br
Scheme 2. Substitution effect of indoles 8.
Me
H
Ph
N 9k Bn 97%, 95% ee (6 h)
aThe
Ar
TsHN H
OBn
N N N Br I Bn Bn Bn 9m 9o 9n 92%, 96% ee (2 h) 99%, 97% ee (2 h) 95%, 97% ee (4 h)
N
(R)-2d (0.3–1 mol%) AcOH (0–10 mol%)
TsHN n-Pr
OBn TsHN Me
Ts
74%, 98% ee (20 h)
Ph
9j 68%, 95% ee (20 h)
N
Ph
N Bn
9i
OBn TsHN Et
N Bn
OBn TsHN Me S
74%, 95% ee (20 h) OBn
F
N 9f Bn 92%, 95% ee (3 h)
TsHN Me
N MeO Bn
Me
OBn
Ph
Our powerful catalyst (R)-2d could reduce the amount of catalyst required to 1 mol% for aldimine 12 in place of ketimines, and product 13 was obtained in 87% yield (1.01 g) with 94% ee within 12 h (Eq. (3)). In particular, we found that the addition of acetic acid (10 mol%) could greatly shorten the reaction time (also see the SI), and 13 was obtained in >99% yield (1.17 g) with 92% ee within 30 min. Ultimately, we could reduce the amount of catalyst (R)-2d to 0.3 mol% (68.1 mg) in the presence of acetic acid (10 mol%), and 13 was obtained in 92% yield (10.73 g) with 97% ee after a single recrystallization without routine purification by silica gel column chromatography (Figure 2). To the best of our knowledge, this is one of the best reported performances in the catalytic enantioselective aza-FC reaction of indoles with aldimines. Next, we confirmed the effect of acetic acid by the scale-up of ketimine 4b (5 mmol) (Eq. (4)). As expected, with the use of a reduced amount of (R)-2d (5 mol%) in the presence of acetic acid, the corresponding product 9n was obtained in 92% yield (3.07 g) with 97% ee within 3 h. While the role of acetic acid in promoting the reaction is not clear at this preliminary stage,20 it could coordinate to the K+center leading to a possible monomeric active catalyst (vide infra)21 and/or act as a H+-carrier22 between release of the product and regeneration of (R)-2d.
4b 1.76 g (5 mmol)
TsHN Me
(R)-2d (5 mol%) AcOH (10 mol%) CH2Cl2, MS 3Å –78 ºC, 3 h
Br
N 9n Bn 92% (3.07 g), 97% ee
(4)
Next, we turned to mechanistic aspects. In the ESI-MS analysis of (R)-2d, monomeric species were exclusively observed (see the SI), unlike with our previous BINSA/Mg/K clusters based on BINSA-trimers.11a Moreover, in the probe reaction of 5a with 4a, a non-linear effect between (R)-2d and (R)-6a was not observed (see the SI). Therefore, a chiral LBA-postulated monomeric structure might be considered, as shown in Figure 1c. Indeed, based on the near-constant enantioselectivity (95–96% ee) for (R)-2a–e catalysts with proton and alkali metals in Table 1, proton would act as an active center solely. However, we cannot deny, at this preliminary stage, the cooperative activation of imino-nitogen by the proton (Brønsted acid) and Ts-oxygen by the alkali metal center (Lewis acid), respectively. Therefore,
ACS Paragon Plus Environment
ACS Catalysis 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
two possible transition states, such as monodentate TS-14 and bidentate TS-15, are shown in Figure 3 as working models,23 and both transition states might explain the si-face preference through carbon–carbon bond formation without significant steric constraints.
Page 4 of 6
Corresponding Author *E-mail:
[email protected] ORCID Manabu Hatano: 0000-0002-5595-9206 Kazuaki Ishihara: 0000-0003-4191-3845
Notes The authors declare no competing financial interest.
■ ACKNOWLEDGMENT Financial support was partially provided by JSPS KAKENHI Grant Numbers JP17H03054 and JP15H05810 in Precisely Designed Catalysts with Customized Scaffolding.
■ REFERENCES
Figure 3. Possible transition states.
Finally, we removed the N-protecting groups of representative product 6a under Birch reduction conditions. The use of Na/naphthalene in THF at –78 °C provided N-Ts-removed 16 in >99% yield (Eq. (5)). On the other hand, the use of Na/ammonia in THF at –78 °C followed by re-protection of the NH2 moiety with (Boc)2O provided N-Bn-removed 17 in 95% yield (Eq. (6)). H2N Me
TsHN Me Na/naphthalene
Ph N Bn 6a, 96% ee
Ph
THF, –78 ºC to 0 ºC 15 min
(5)
N 16 Bn >99%, 96% ee BocHN Me
1) Na/NH3, THF, –78 ºC, 2 h 2) Boc2O, Et3N, DMAP, rt, 8 h
Ph
(6)
N 17 H 95% (2 steps), 96% ee
In summary, we have developed an enantioselective azaFriedel–Crafts reaction of indoles with simple and low-reactive ketimines, for the first time, in the presence of chiral monopotassium binaphthyldisulfonate as a strong Brønsted acid catalyst. A broad substrate scope was observed, and the corresponding 3-indolylmethanamines with a quaternary chiral carbon center were obtained in high yields and with high enantioselectivities. The addition of acetic acid considerably promoted the reaction, and a gram-scale reaction could be achieved with reduced catalyst loading.
■ ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acscatal.xxxxxxxxx. Experimental procedure, characterization data, control experiments, copies of 1H NMR and 13C NMR spectra of all new compounds (PDF) X-ray data of 6a and S9 (CIF)
■ AUTHOR INFORMATION
(1) (a) Sundberg, R. J. Indoles, Academic, New York, 1996. (b) Saxton, J. E. Nat. Prod. Rep. 1997, 14, 559–590. (c) Sharma, V.; Kumar, P.; Pathak, D. J. Heterocyclic Chem. 2010, 47, 491–502. (d) Kochanowska-Karamyan, A. J.; Hamann, M. T. Chem. Rev. 2010, 110, 4489– 4497. (e) Schmidt, A. W.; Reddy, K. R.; Knölker, H.-J. Chem. Rev. 2012, 112, 3193–3328. (f) Zhang, M.-Z.; Chen, Q.; Yang, G.-F. Eur. J. Med. Chem. 2015, 89, 421–441. (2) (a) Jia, Y.-X.; Xie, J.-H.; Duan, H.-F.; Wang, L.-X.; Zhou, Q.-L. Org. Lett. 2006, 8, 1621–1624. (b) Liu, Z.; Shi, M. Tetrahedron: Asymmetry 2009, 20, 119–123. (c) Wang, B.-L.; Li, N.-K.; Zhang, J.-X.; Liu, G.-G.; Liu, T.; Shen, Q.; Wang, X.-W. Org. Biomol. Chem. 2011, 9, 2614–2617. (d) Liu, L.; Zhao, Q.; Du, F.; Chen, H.; Qin, Z.; Fu, B. Tetrahedron: Asymmetry 2011, 22, 1874–1878. (e) Takizawa, S.; Arteaga, F. A.; Yoshida, Y.; Kodera, J.; Nagata, Y.; Sasai, H. Dalton Trans. 2013, 42, 11787–11790. (f) Kumari, P.; Bera, P. K.; Khan, N.-u. H.; Kureshy, R. I.; Abdi, S. H. R.; Bajaj, H. C. Catal. Sci. Technol. 2014, 4, 563–568. (g) Zou, K.; Ye, J.; Wu, X.-Y. Tetrahedron 2015, 71, 7869– 7873. (h) Arai, T.; Kakino, J. Angew. Chem. Int. Ed. 2016, 55, 15263– 15267. (i) Kim, M. J.; Xue, L.; Liu, Y.; Paladhi, S.; Park, S. J.; Yan, H.; Song, C. E. Adv. Synth. Catal. 2017, 359, 811–823. (3) Cinchona alkaloid with thiourea group catalysts: (a) Wang, Y.Q.; Song, J.; Hong, R.; Li, H.; Deng, L. J. Am. Chem. Soc. 2006, 128, 8156–8157. Chiral phosphoric acid catalysts: (b) Terada, M.; Sorimachi, K. J. Am. Chem. Soc. 2007, 129, 292–293. (c) Kang, Q.; Zhao, Z.-A.; You, S.-L. J. Am. Chem. Soc. 2007, 129, 1484–1485. (d) Rowland, G. B.; Rowland, E. B.; Liang, Y.; Perman, J. A.; Antilla, J. C. Org. Lett. 2007, 9, 2609–2611. (e) Terada, M.; Yokoyama, S.; Sorimachi, K.; Uraguchi, D. Adv. Synth. Catal. 2007, 349, 1863–1867. (f) Zhang, G.-W.; Wang, L.; Nie, J.; Ma, J.-A. Adv. Synth. Catal. 2008, 350, 1457–1463. (g) Qiu, H.; Li, M.; Jiang, L.-Q.; Lv, F.-P.; Zan, L.; Zhai, C.-W.; Doyle, M. P.; Hu, W.-H. Nature Chem. 2012, 4, 733–738. (4) Synthesis of 3-indolylmethanamines by rhodium-catalyzed asymmetric arylation: (a) Yang, H.-Y.; Xu, M.-H. Chem. Commun. 2010, 46, 9223–9225. (b) Li, Y.; Xu, M.-H. Chem. Commun. 2014, 50, 3771–3782. (c) Jiang, T.; Wang, Z.; Xu, M.-H. Org. Lett. 2015, 17, 528–531. (d) Liu, M.-Q.; Jiang, T.; Chen, W.-W.; Xu, M.-H. Org. Chem. Front. 2017, 4, 2159–2162. For reviews: (e) Tian, P.; Dong, H.Q.; Lin, G.-Q. ACS Catal. 2012, 2, 95–119. (5) For reviews on catalytic asymmetric functionalization of indoles: (a) Friestad, G. K. Mathies, A. K. Tetrahedron 2007, 63, 2541–2569. (b) You, S.-L.; Cai, Q.; Zeng, M. Chem. Soc. Rev. 2009, 38, 2190–2201. (c) Bandini, M.; Eichholzer, A. Angew. Chem. Int. Ed. 2009, 48, 9608– 9644. (d) Bartoli, G.; Bencivenni, G.; Dalpozzo, R. Chem. Soc. Rev. 2010, 39, 4449–4465. (e) Wu, H.; He, Y.-P.; Shi, F. Synthesis 2015, 47, 1990–2016. (f) Sandtorv, A. H. Adv. Synth. Catal. 2015, 357, 2403– 2435. (g) Dalpozzo, R. Chem. Soc. Rev. 2015, 44, 742–778. (h) Chen, J.B.; Jia, Y.-X. Org. Biomol. Chem. 2017, 15, 3550–3567. (6) (a) Jia, Y.-X.; Zhong, J.; Zhu, S.-F.; Zhang, C.-M.; Zhou, Q.-L. Angew. Chem. Int. Ed. 2007, 46, 5565–5567. (b) Hermeke, J.; Toy, P. H. Tetrahedron 2011, 67, 4103–4109. (7) (a) Husmann, R.; Sugiono, E.; Mersmann, S.; Raabe, G.; Rueping, M.; Bolm, C. Org. Lett. 2011, 13, 1044–1047. (b) Rueping,
ACS Paragon Plus Environment
Page 5 of 6 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
ACS Catalysis M.; Raja, S.; Núñez, A. Adv. Synth. Catal. 2011, 353, 563–568. (c) Yu, X.; Wang, Y.; Wu, G.; Song, H.; Zhou, Z.; Tang, C. Eur. J. Org. Chem. 2011, 3060–3066. (d) Qian, Y.; Jing, C.; Zhai, C.; Hu, W.-h. Adv. Synth. Catal. 2012, 354, 301–307. (e) Aranzamendi, E.; Sotomayor, N.; Lete, E. J. Org. Chem. 2012, 77, 2986–2991. (f) Feng, J.; Yan, W.; Wang, D.; Li, P.; Sun, Q.; Wang, R. Chem. Commun. 2012, 48, 8003– 8005. (g) Zhang, K.-F.; Nie, J.; Guo, R.; Zheng, Y.; Ma, J.-A. Adv. Synth. Catal. 2013, 355, 3497–3502. (h) Kano, T.; Takechi, R.; Kobayashi, R.; Maruoka, K. Org. Biomol. Chem. 2014, 12, 724–727. (i) Wu, L.; Liu, R.-R.; Zhang, G.; Wang, D.-J.; Wu, H.; Gao, J.; Jia, Y.-X. Adv. Synth. Catal. 2015, 357, 709–713. (j) Zhang, X.; Zhang, J.; Lin, L.; Zheng, H.; Wu, W.; Liu, X.; Feng, X. Adv. Synth. Catal. 2016, 358, 3021–3026. (k) Zhao, Y.; Wang, L.; Zhao, J. Tetrahedron Lett. 2017, 58, 213–217. (8) For reviews on chiral phosphoric acid catalysts: (a) Akiyama, T. Chem. Rev. 2007, 107, 5744–5768. (b) Terada, M. Synthesis 2010, 2010, 1929–1982. (c) Kampen, D.; Reisinger, C. M.; List, B. Top. Curr. Chem. 2010, 291, 395–456. (d) Parmar, D.; Sugiono, E.; Raja, S.; Rueping, M. Chem. Rev. 2014, 114, 9047–9153. (e) Akiyama, T.; Mori, K. Chem. Rev. 2015, 115, 9277–9306. (9) Shibasaki pioneeringly developed the catalytic asymmetric reaction of simple ketimines. See reviews. (a) Shibasaki, M.; Kanai. M. Chem. Rev. 2008, 108, 2853–2873. (b) Kumagai, N.; Shibasaki, M. Bull. Chem. Soc. Jpn. 2015, 88, 503–517. Also see the recent selected papers. (c) Trost, B. M.; Silverman, S. M. J. Am. Chem. Soc. 2010, 132, 8238– 8240. (d) Shintani, R.; Takeda, M.; Tsuji, T.; Hayashi, T. J. Am. Chem. Soc. 2010, 132, 13168–13169. (e) Shintani, R.; Takeda, M.; Soh, Y.T.; Ito, T.; Hayashi, T. Org. Lett. 2011, 13, 2977–2979. (f) Lu, G.; Yoshino, T.; Morimoto, H.; Matsunaga, S.; Shibasaki, M. Angew. Chem. Int. Ed. 2011, 50, 4382–4385. (g) Tran, D. N.; Cramer, N. Angew. Chem. Int. Ed. 2011, 50, 11098–11102. (h) Trost, B. M.; Silverman, S. M. J. Am. Chem. Soc. 2012, 134, 4941–4954. (i) Yin, L.; Otsuka, Y.; Takada, H.; Mouri, S.; Yazaki, R.; Kumagai, N.; Shibasaki, M. Org. Lett. 2013, 15, 698–701. (j) Hayashi, M.; Sano, M.; Funahashi, Y.; Nakamura, S. Angew. Chem. Int. Ed. 2013, 52, 5557–5560. (k) Yin, L.; Takada, H.; Kumagai, N.; Shibasaki, M. Angew. Chem. Int. Ed. 2013, 52, 7310–7313. (l) Hirner, S.; Kolb, A.; Westmeier, J.; Gebhardt, S.; Middel, S.; Harms, K.; von Zezschwitz, P. Org. Lett. 2014, 16, 3162–3165. (m) Ortín, I.; Dixon, D. J. Angew. Chem. Int. Ed. 2014, 53, 3462–3465. (n) Hayashi, M.; Iwanaga, M.; Shiomi, N.; Nakane, D.; Masuda, H.; Nakamura, S. Angew. Chem. Int. Ed. 2014, 53, 8411–8415. (o) Lin, S.; Kawato, Y.; Kumagai, N.; Shibasaki, M.; Angew. Chem. Int. Ed. 2015, 54, 5183–5186. (10) pKa (DMSO) of (R)-3,3’-unsubstituted BINSA is –9.06, while pKa (DMSO) of p-TsOH is 0.9. Yang, C.; Xue, X.-S.; Li, X.; Cheng, J.-P. J. Org. Chem. 2014, 79, 4340–4351. (11) (a) Hatano, M.; Nishikawa, K.; Ishihara, K. J. Am. Chem. Soc. 2017, 139, 8424–8427. Also see our original papers of BINSA chem-
istry: (b) Hatano, M.; Maki, T.; Moriyama, K.; Arinobe, M.; Ishihara, K. J. Am. Chem. Soc. 2008, 130, 16858–16860. (c) Hatano, M.; Hattori, Y.; Furuya, Y.; Ishihara, K. Org. Lett. 2009, 11, 2321–2324. (d) Hatano, M.; Sugiura, Y.; Ishihara, K. Tetrahedron: Asymmetry 2010, 21, 1311–1314. (e) Hatano, M.; Sugiura, Y.; Akakura, M.; Ishihara, K. Synlett 2011, 2011, 1247–1250. (f) Hatano, M.; Ozaki, T.; Sugiura, Y.; Ishihara, K. Chem. Commun. 2012, 48, 4986–4988. (g) Hatano, M.; Ozaki, T.; Nishikawa, K.; Ishihara, K. J. Org. Chem. 2013, 78, 10405– 10413. (h) Hatano, M.; Ishihara, K. Asian J. Org. Chem. 2014, 3, 352– 365. (12) (a) Ishibashi, H.; Ishihara, K.; Yamamoto, H. Chem. Rec. 2002, 2, 177–188. (b) Yamamoto, H.; Futatsugi, K. Angew. Chem. Int. Ed. 2005, 44, 1924–1942. (13) The electronegativity on the Pauling scale is in the order H (2.0) > Li (0.98) > Na (0.93) > K (0.82) > Cs (0.79). The corresponding Brønsted acidity for (R)-2a–e as BBA or LBA might have the same order. (14) Under the standard reaction conditions at –78 °C, (R)-2d did not cause ion-exchange from MS 3Å. See the SI for details. (15) (a) García-García, P.; Lay, F.; García-García, P.; Rabalakos, C.; List, B. Angew. Chem. Int. Ed. 2009, 48, 4363–4366. See a review, (b) van Gemmeren, M.; Lay, F.; List, B. Aldrichimica Acta 2014, 47, 3– 13. (16) Reaction of ketimines with an ortho-substituent on the aryl moiety, such as 2-Me-C6H4 and 1-naphthyl, did not almost proceed (
