Conversion of tetrazoles into hydrazonoyl chlorides. Novel donor–dithiazolium interactions

Abstract

5-Substituted tetrazoles 13, readily prepared from RCN and aluminium azide, react rapidly with Appel salt 1 at room temperature to give hydrazonoyl chlorides 16 in high yield. 5-Aminotetrazole 4 reacts further to give the extended bis(iminodithiazole) 6 and a minor product 7. Mechanisms are proposed for these reactions (except for the formation of 7) which are supported by the smooth conversion of 5-amino-2-substituted tetrazoles 11, but not 5-amino-1-substituted tetrazoles, into the normal iminodithiazoles 12. The red bis(imine) 6 rearranges to the yellow 1,3,4-thiadiazole 19 in warm DMSO. The structures of 1, 6, 7 and 19 are proved by X-ray crystallography which also reveals the presence in each case of a strong intermolecular 3-centre interaction between the adjacent dithiazole ring sulfur atoms and either oxygen, nitrogen or chlorine donors.