Temperature-controlled S vs N selective alkylation of 1-phenyl tetrazole-5-thione with α,β-unsaturated systems in solvent-free organic salt media

Abstract

In this work, a novel series of N and S-alkylated derivatives of 1-phenyl tetrazole-5-thione were synthesized by Michael addition in organic salt media TBAB (Tetrabutylammonium bromide) using inorganic base K₂CO₃ under solvent-free conditions. The new and conveniently synthesized products showed unusual regioselectivity during the reaction. S-Michael adducts via reaction between 1-phenyl tetrazole-5-thione and acrylic esters as well as acrylonitrile were afforded at room temperature and N-Michael adducts obtained at 70°C. Both reactions occurred within 24 h. Surprisingly, using fumarate esters as Michael acceptor proceeded a S_N2 reaction at 100°C due to steric effects. The structures of products all were confirmed by ¹H and ¹³C NMR spectra and target compound yields were good to excellent.

GRAPHICAL ABSTRACT

KEYWORDS:

• 1-phenyl tetrazole-5-thione
• Michael addition
• regioselective reaction
• α,β-unsaturated systems
• tetrabutylammonium bromide
• solvent-free conditions

Acknowledgments

Authors are thankful of the laboratories of Tehran and Tabriz University as well as University of Mohaghegh Ardabili for the products analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).