An Unusual Ring Contraction in the Formation of N‐Nitrosohexamethyleneimine and N‐Nitrosopiperidine from Tolazamide

The previously reported reaction of tolazamide with nitrite, under physiological conditions, to form N‐nitrosohexamethyleneimine and surprisingly, N‐nitrosopiperidine was confirmed. By using the six‐membered ring analogue of tolazamide, 1‐(piperidyl)‐3‐(p‐tolylsulfonyl)urea, which yields the corresponding N‐nitrosopiperidine and N‐nitrosopyrrolidine, the present study shows that an unusual ring contraction occurs, excising the carbon alpha to the nitrogen.