Application of Primary Allylamines from Morita–Baylis–Hillman Adducts: Cyanogen Azide Mediated Synthesis of Substituted 5‐Aminotetrazoles and Their Attempted Transformation into Tetrazolo[1,5‐<i>a</i>]pyrimidinones

Abstract

Abstract A general protocol for the synthesis of substituted 5‐aminotetrazoles by treating cyanogen azide with primary allylamines afforded either by S N 2 or S N 2′ reactions of Morita–Baylis–Hillman acetates of acrylate has been developed. The base‐promoted intramolecular cyclizations of these tetrazoles afford highly substituted 2‐azidopyrimidin‐4(3 H )‐ones instead of the expected tetrazolopyrimidinone due to azide–tetrazole tautomerism. Nevertheless it has been discovered that substituted tetrazolo[1,5‐ a ]pyrimidin‐7(4 H )‐ones could be isolated in pure form from a methanolic solution of the respective 2‐azidopyrimidin‐4(3 H )‐ones through crystallization. The structure of tetrazolo[1,5‐ a ]pyrimidin‐7(4 H )‐one was unambiguously assigned by X‐ray crystallography. The existence of azide–tetrazole tautomerism in this class of compounds has been supported through NMR spectroscopic studies.