Reductive cleavage of N-substituted aromatic amides as tert-butyl acylcarbamates

Abstract

Synthetic and spectroscopic details related to a set of heteroaromatic N-benzyl carboxamides and especially the corresponding tert-butyl acylcarbamates are reported. These compounds were required to study the postulated effect of various heterocycles (pyridine and pyrazine with and without condensed benzene rings) on the cleavage of acyl-N bonds by reduction. All compounds were initially characterized by cyclic voltammetry which indicated various degrees of facilitated reduction, reflecting a direct influence of the heterocyclic component. Selected acylcarbamates were studied with respect to acyl-N bond cleavage by mild reducing agents and selectively deacylated by activated aluminium and sodium borohydride. Conversion to acylcarbamates followed by reduction might therefore be a mild, efficient two-step procedure to effect cleavage of amides, allowing isolation of carbamates and with sodium borohydride also the corresponding alcohols.