Green Synthesis of Acylhydrazides Involving a Heterocyclic Moiety using Terminal Dihaloalkanes in Organic Salt Media under Solvent-Free Conditions

Abstract

In this paper, the reaction of some acyl hydrazides with different terminal dibromoalkanes is investigated. This investigation revealed that acyl hydrazide in the reaction with 1,4 and 1,5-dibromoalkanes in the presence of DABCO (1,4-diazabicyclo[2.2.2]octane) and TBAB (tetrabutylammonium bromide) undergo a facile intramolecular N2-double-alkylation to form pyrrolidine and piperidine ring derivatives under solvent-free conditions. Moreover, the alkylation of acyl hydrazide with 1,6-dibromohexane as substrate produced the related N2-mono-alkylated derivatives under the same conditions. Interestingly, using K2CO3 as the base in this reaction for 1,6-dibromohexane led to acyl hydrazide containing an azepane ring. Surprisingly, direct alkylation of 4-nitrobenzohydrazide with 1,2-dibromoethane led to an oxadiazine ring derivative. Yields of products were 60-85% in 6-12h.