Ring closures from eneearbamoyl azides. Syntheses of tetrahydro‐3‐indazolinones and 4‐imidazolin‐2‐ones

Abstract

AbstractReaction of phosgene with cyclohexylidene amines gives good yields of (1‐eyclohexen‐l‐yl)‐carbamoyl chlorides (1). Compound 1 can be converted to the corresponding eneearbamoyl azide (2), which on pyrolysis gives an improved synthesis of 1‐substituted‐4,5,6,7‐tetrahydro‐3‐indazolinones (7). When 1 is substituted by an allylic rather than alkyl or aryl group, the major products are 4‐imidazolin‐2‐ones (8) accompanied by only minor amounts of 7. The thermolysis reaction has been extended to N‐allylcarbamoyl azides in general, thus providing a new and facile synthesis for 1,4‐disubstituted 4‐imidazolin‐2‐ones (9). A tentative mechanism is advanced, involving intermediate azide addition to the allylic double bond.