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New Generation of Nitrenium Salts: Catalytic Hydrosilylation of Imines and a Mechanism of Action of Nitrogen Lewis Acids

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posted on 25.05.2022, 17:40 authored by Kuldeep Singh, Idan Avigdori, Alexander Kaushansky, Natalia Fridman, Dor Toledano, Mark Gandelman
Nitrogen Lewis acids (NLAs) are emerging as a powerful tool in strong bond activation and catalysis. Till now, N,N-dialkyl-nitrenium salts were known and utilized in chemical transformations. In this article, we report on the synthesis and characterization of the next generation of nitrenium-based Lewis acidsN,N-diaryl-substituted naphthotriazinium salts,which opens the door to libraries of stereoelectronically modifiable catalysts. We exemplify the potency of these Lewis acidic catalysts in a gram-scale hydrosilylation of various ketimines and aldimines in yields up to 99% and a catalyst loading as low as 0.1 mol %. Notably, dialkyl-nitrenium salts proved inefficient in this reaction. Based on our experimental and theoretical studies, we elucidated the mechanistic action of nitrenium Lewis acids in such reduction-type reactions, demonstrating a unique hydridic behavior of N–H bonds in triazanes.

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