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

This paper aimed at investigating the reaction of some acyl hydrazides with different terminal dibromoalkanes. This investigation revealed that acyl hydrazide by reacting with 1,4 and 1,5- dibromoalkanes in the presence of DABCO (1,4-diazabicyclo[2.2.2]octane) and TBAB (tetrabutylammonium bromide) underwent 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 a 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. The product yield was found to be 60- 85% in 6-12 h.