10.1002/cctc.202000309
ChemCatChem
COMMUNICATION
[4]
a) P. Saravanan, R. V. Anand, V. K. Singh, Tetrahedron Lett. 1998, 39,
3823-3824; b) N. Khan, S. Agrawal, R. I. Kureshy, H. R. Sayed, S. S.
Singh, R. V. Jasra, J. Organomet. Chem. 2007, 692, 4361-4366; c) B.
Karimi, L. Ma’Man, Org. Lett. 2004, 6, 4813-4815; d) M. L. Kantam, P.
Sreekanth, P. L. Santhi, Green. Chem. 2000, 2, 47-48; e) K. Iwanami, J.
C. Choi, T. Sakakura, H. Yasuda, Chem. Commun. 2008, 1002-1004; f)
M. Bandini, P. G. Cozzi, A. Garelli, Eur. J. Org. Chem. 2002, 3243-
3249; g) Y. Suzuki, A. MD. Bakar, K. Muramatsu, M. Sato, Tetrahedron
2006, 62, 4227-4231; h) G. Strappaveccia, D. Lanari, D. Gelman, F.
Pizzo, O. Rosati, M. Curini, L. Vaccaro, Green Chem. 2013, 15, 199-
204.
(for 1) to 22.2 ppm also corroborates with the proposed adduct
Int1. In the 1H NMR spectrum of the Int1, two septets (3.04 and
3.73 ppm) and four doublets (1.18, 0.87, 0.66 and 0.46 ppm) for
the 2,6-iPr2C6H3 moieties of the ligand were observed that are
similar to our previous observations for an unsymmetrical tetra
coordinated cationic Al center[17] whereas, the planar
arrangement around Al center of cation 1 gave one septet and
two doublets.[17] We believe that this adduct formation leads to
the activation of Si-CN bond of Me3SiCN. At this stage, after the
addition of benzaldehyde, nucleophilic attack of the carbonyl
oxygen at the Si center of the activated Me3SiCN occurred
leading to the transfer of cyanide moiety from Si center to the
electrophilic carbonyl carbon involving sigma bond metathesis
possibly via a cyclic four membered transition state TS1.
Simultaneous regeneration of the catalyst 1 was evident by
reappearance of the signal at 23.7 ppm in the 31P{1H} NMR
spectrum of the reaction mixture. Further, in 29Si NMR spectrum
of reaction mixture the appearance of signal at 24.3 ppm
indicates elimination of product 2a from Int2. Probably due to
the steric reasons it forms a very labile adduct with the cationic
Al center and thus enabling the catalyst to be available for the
next reaction cycle.
In summary, we have developed a new efficient and
sustainable catalyst for the chemoselective cyanosilylation of
aldehydes and ketones. The current procedure employed a
methyl aluminum cation [LAlMe]+[MeAl(C6F5)3]– as the catalyst
and Me3SiCN as a cyanide precursor to prepare cyanohydrin
trimethylsilylethers in a homogeneous process. Solvent-free,
room temperature conditions, very low catalyst loadings, atom-
economical process, and short reaction duration are attractive
features of this catalyst. The pronounced Lewis acidity of the
cationic aluminum center facilitates this reaction and opens up
new avenues in the area of main group catalysis compared to
expensive heavier transition elements. The reaction conditions
optimized here can also be extended for scaled up synthesis
making the whole process adoptable.
[5]
a) Y. Fu, B. Hou, X. Zhao, Z. Du, Y. Hu, Chin. J. Org. Chem. 2015, 35,
2507-2521; b) J. Li, Y. Ren, C. Qi, H. Jiang, Chem. Commun. 2017, 53,
8223-8226. c) F. Wang, Y. Wei, S. Wang, X. Zhu, S. Zhou, G. Yang, X.
Gu, G. Zhang,; X. Mu, Organometallics 2015, 34, 86-93; d) Y.
Kikukawa, K. Suzuki, M. Sugawa, T. Hirano, K. Kamata, K. Yamaguchi,
N. Mizuno, Angew. Chem., Int. Ed., 2012, 51, 3686-3690; e) S. S. Kim,
G. Rajagopal, S. C. George, Appl. Organometal. Chem. 2007, 21, 368
– 372.
[6]
[7]
[8]
a) M. K. Bisai, T. Das, K. Vanka, S. S. Sen, Chem. Commun. 2018, 54,
6843– 6846; b) N. Kurono, K. Suzuki, T. Ohkuma, Lett. Org. Chem.
2006, 3, 275-277.
a) W. Wang, M. Luo, J. Li, S. A. Pullarkat, M. Ma, Chem. Commun.
2018, 54, 3042-3044; b) Y. Wang, M. Feng, Y. Liu, X. Zhang, J. Chem.
Res. 2012, 566-567.
S. Yadav, R. Dixit, K. Vanka, S. S. Sen, Chem.–Eur. J. 2018, 24, 1269-
1273.
[9]
S. T. Kadam, S. S. Kim, Appl. Organomet. Chem. 2009, 23, 119-123.
a) Z. Yang, M. Zhong, X. Ma, S. De, C. Anusha, P. Parameswaran, H.
W. Roesky, Angew. Chem. Int. Ed. 2015, 54, 10225-10229; b) Z. Yang,
Y. Yi, M. Zhong, S. De, T. Mondal, D. Koley, X. Ma, D. Zhang, H. W.
Roesky, Chem.–Eur. J., 2016, 22, 6932-6938; c) M. K. Sharma, S.
Sinhababu, G. Mukherjee, G. Rajaraman, S. Nagendran, Dalton Trans.
2017, 46, 7672-7676.
[10]
[11] a) L. Martin, L. A, R. G. Bergman, T. D. Tilley, J. Am. Chem. Soc. 2015,
137, 5328-5331; b) V. S. V. S. N. Swamy, M. K. Bisai, T. Das, S. S.
Sen, Chem. Commun. 2017, 53, 6910-6913.
[12] a) R. Dasgupts, S. Das, S. Hiwase, S. K. Pati, S. Khan, Organometallics.
2019, 38, 1429-1435; b) R. K. Sitwatch, S. Nagendran, Chem.–Eur. J.
2014, 20, 13551-13556.
[13]
Y. Li, J. Wang, Y. Wu, H. Zhu, P. P. Samuel, H. W. Roesky, Dalton
Trans. 2013, 42, 13715-13722.
[14] a) D. H. Ryu, E. J. Corey, J. Am. Chem. Soc. 2004, 126, 8106-8107; b)
X.-P. Zeng, Z.-Y. Cao, X. Wang, L. Chen, F. Zhou, F. Zhu, C.-H. Wang,
J. Zhou, J. Am. Chem. Soc. 2016, 138, 416−425.
Acknowledgements
[15] Structurally characterized three coordinated cationic organoaluminum
species are rare, the known examples are published in: a) E. Ihara, V.
G. Jr. Young, R. F. Jordan, J. Am. Chem. Soc. 1998, 120, 8277–8278;
b) C. E. Radzewich, I. A. Guzei, R. F. Jordan, C. E. Radzewich, I. A.
Guzei, R. F. Jordan, J. Am. Chem. Soc. 1999, 121, 8673–8674; c) A. V.
Korolev, E. Ihara, I. A. Guzei, V. G. Jr. Young, R. F. Jordan, J. Am.
Chem. Soc. 2001, 123, 8291–8309; d) O. Stanga, C. L. Lund, H. Liang,
J. W. Quail, J. Müller, Organometallics 2005, 24, 6120-6125; e) G. I.
Nikonov, ACS Catal. 2017, 7, 7257-7266.
We acknowledge IISER Mohali for NMR central facility and for
all other infrastructural support. The authors thank Dr. S.
Venkataramani and Dr. S. A. Babu for useful discussions. S. R.
and M. B. acknowledge IISER Mohali for PhD fellowships.
Conflict of Interest
[16] a) D. Atwood, Coord. Chem. Rev. 1998, 176, 407-430; b) D. Franz, S.
Inoue, Chem. Eur. J. 2019, 25, 2898-2926.
The authors declare no conflict of interest.
[17]
B. Prashanth, M. Bhandari, S. Ravi, K. R. Shamasundar, S. Singh,
Chem. Eur. J. 2018, 24, 4794-4799.
Keywords: cyanosilylation • organoaluminum catalyst • carbonyl
[18] a) V. Gutmann, Coord. Chem. Rev. 1976, 18, 225–255; b) M. A.
Beckett, D. S. Brassington, M. E. Light, M. B. Hursthouse, J. Chem.
Soc., Dalton Trans. 2001, 1768–1772; c) M. A. Beckett, G. C.
Strickland, J. R. Holland, K. S. Varma, Polymer 1996, 37, 4629-4631;
d) M. A. Beckett, D. S. Brassington, S. J. Coles, M. B. Hursthouse,
Inorg. Chem. Commun. 2000, 3, 530–533.
• chemoselecetivity • cationic aluminum complex
[1]
[2]
M. North, D. L. Usanov, C. Young, Chem. Rev. 2008, 108, 5146-5226.
a) H. Groger, Chem. Rev. 2003, 103, 2795-2828; b) S. Kobayashi, H.
Ishitani, Chem. Rev. 1999, 99, 1069-1094.
[19]
a) P. I. Dalko, L. Moisan, Angew. Chem., Int. Ed. 2004, 43, 5138-5175;
b) J. O. Metzger, Angew. Chem., Int. Ed. 1998, 37, 2975-2978; c) K.
Tanaka, F. Toda, Chem. Rev. 2000, 100, 1025-1074.
[3]
a) G. K. Surya Prakash, H. Vaghoo, C. Panja, V. Surampudi, R.
Kultyshev, T. Mathew, G. A. Olah, Proc. Natl. Acad. Sci. U.S.A. 2007,
104, 3026−3030; b) W. Wang, M. Luo, W. Yao, M. Ma, S. A. Pullarkat,
L. Xu, P.-H. Leung, ACS Sustainable Chem. Eng. 2019, 7, 1718-1722.
4
This article is protected by copyright. All rights reserved.