Catalytic fate of structurally characterized manganese(iii)–salen complexes towards efficient transformation of primary amides to amines or nitriles using hydrosilane

Abstract

A convenient and selective hydrosilylative transformation of chemically inert primary amides (26 examples) into the corresponding primary amines with key functional group tolerance has been developed by using simple well-defined O,N,N,O donor salen-based earth abundant manganese(III) complexes under mild conditions. On a slight modification of the reaction condition by adding the blocking agent secondary amide, the transformation of primary amides to amines stops in the intermediate nitrile state (9 examples). The same catalyst also has the capability to reduce nitriles to amines (15 examples) using inexpensive silanes such as polymethylhydrosiloxane (PMHS). Mechanistic studies and DFT calculations are also carried out to understand the reaction mechanism and chemoselectivity. In this catalytic transformation, the manganese catalyst activates the primary amides and the overall reduction proceeds via the dehydration of the primary amides into the corresponding nitriles, which are then reduced into the corresponding primary amines.