Three-Component Synthesis of 1-Substituted 5-Aminotetrazoles Promoted by Bismuth Nitrate.

A nontoxic bismuth-promoted multicomponent synthesis of 5-aminotetrazoles and bistetrazoles is reported. The reaction of phenyl isothiocyanate, NaN 3 , and amine (primary aliphatic, aromatic, and aliphatic diamine) promoted by Bi(NO 3 ) 3 ·5H 2 O under microwave heating affords good yields, short reaction times, simple workup, and purification without column chromatography. A set of diagnostic 1 H NMR signals was identified as a guide for quickly elucidating the exclusive (or main) regioisomer formed, with the stronger electron donor group located at heterocyclic nitrogen 1. This regioselectivity is strongly dependent on the electronic density of the amine. It is opposite to that obtained by several thiourea desulfurization methods promoted by thiophilic metals and metal-free protocols.