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Zinc Hydride Catalyzed Chemoselective Hydroboration of Isocyanates: Amide Bond Formation and C=O Bond Cleavage
Author(s) -
Sahoo Rajata Kumar,
Sarkar Nabin,
Nembenna Sharanappa
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202100375
Subject(s) - chemistry , hydroboration , deoxygenation , medicinal chemistry , amide , hydride , alkene , bond cleavage , hemiaminal , catalysis , organic chemistry , hydrogen
Herein, a remarkable conjugated bis‐guanidinate (CBG) supported zinc hydride, [{LZnH} 2 ; L={(ArHN)(ArN)−C=N−C=(NAr)(NHAr); Ar=2,6‐Et 2 ‐C 6 H 3 }] ( I ) catalyzed partial reduction of heteroallenes via hydroboration is reported. A large number of aryl and alkyl isocyanates, including electron‐donating and withdrawing groups, undergo reduction to obtain selectively N‐boryl formamide, bis(boryl) hemiaminal and N‐boryl methyl amine products. The compound I effectively catalyzes the chemoselective reduction of various isocyanates, in which the construction of the amide bond occurs. Isocyanates undergo a deoxygenation hydroboration reaction, in which the C=O bond cleaves, leading to N‐boryl methyl amines. Several functionalities such as nitro, cyano, halide, and alkene groups are well‐tolerated. Furthermore, a series of kinetic, control experiments and structurally characterized intermediates suggest that the zinc hydride species are responsible for all reduction steps and breaking the C=O bond.