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-a]pyrimidinones

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(3H)-ones instead of the expected tetrazolopyrimidinone due to azide tetrazole tautomerism. Nevertheless it has been discovered that substituted tetrazolo[1,5-a]pyrimidin-7(4H)-ones could be isolated in pure form from a methanolic solution of the respective 2-azidopyrimidin-4(3H)-ones through crystallization. The structure of tetrazolo[1,5-a]pyrimidin-7(4H)-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.