Hetarylnitrenes V. Reactions of Tetrazolopyrazine Ring Contraction of Nitrenodiazines in Solution. Preliminary communication

Thermolysis of tetrazolopyrazine ( 1 ) in organic solvents gives pyrazinylnitrene ( 2 ) which undergoes ring contraction to 1‐cyanoimidazole ( 3 ). 7‐Methyl‐5‐methylthio‐tetrazolo[1,5‐ c ]pyrimidine ( 4 ) likewise gives 1‐cyano‐2‐methylthio‐4‐methyl‐imidazole ( 6 ). The two tetrazoles also undergo ring contraction to 1‐cyanoimidazoles by gas chromatography, and 1 gives a low yield of 3 by photolysis. Thermolysis of 1 and 4 in cyclohexane gives aminopyrazine ( 7 ) and 6‐amino‐4‐methyl‐2‐methylthio‐pyrimidine ( 8 ), respectively. Tetrazolo[1,5‐ a ]pyrimidines ( 9 ) give only 2‐aminopyrimidines ( 10 ). 1‐Cyanoimidazole, formed by thermolysis of 1 in acetic acid, reacts further to give 1‐acetylimidazole, which with more acetic acid gives imidazole and acetic anhydride. An earlier report [2] of ring expansion of pyrazinylnitrene in acetic acid is discredited. In protic deuteriated solvents (D 3 O, CH 3 OD), tetrazolopyrazine reacts as an enamine, specifically exchanging HC(6) for deuterium.