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

Nitrogen Lewis acids (NLAs) are emerging as a powerful tool in strong bond activation and catalysis. Till now, NN-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.

Automated summary

Nitrogen Lewis acids (NLAs) have emerged as a powerful tool in strong bond activation and catalysis. This article presents the synthesis and characterization of a new generation of nitrenium-based Lewis acids and demonstrates their efficiency in gram-scale hydrosilylation reactions. Experimental and theoretical studies provide insights into the mechanistic action of nitrenium Lewis acids in reduction-type reactions.