Tetrazole synthesis via the palladium-catalyzed three component coupling reaction.

Abstract

The synthesis of tetrazoles was achieved via the palladium-catalyzed three component coupling (TCC) reaction; The TCC reaction of malononitrile derivatives, allyl acetate and trimethylsilyl azide proceeds very smoothly under a catalytic amount of Pd(PPh3)4 to give 2-allyltetrazoles, and further the TCC reaction of various activated cyano compounds, allyl methyl carbonate and trimethylsilyl azide proceeds readily under a catalytic amount of Pd2(dba)3 x CHCl3 and (2-furyl)3P to give 2-allyltetrazoles. pi-Allylpalladium azide complex is proposed as a key intermediate in the catalytic cycle and the [3 + 2] cycloaddition between the pi-allylpalladium azide complex and cyano compounds most probably gives the tetrazole frameworks. The deallylation of the derived allyltetrazoles was attained via the two-step procedure; the ruthenium-catalyzed isomerization and ozonolysis.