Thermal reaction of 2H-azirines, bearing a methoxy or methylthio group at the neighboring position to azirine ring, was studied. In thermolysis of ethyl 2-(2-methoxynaphth-1-yl)-2H-azirine-3-carboxylate, attack of the vinyl nitrene at the peri position to form a 1-azaphenalene ring was observed. In thermal reaction of its thio analogue, 1-azaphenalene was also formed, but a naphthothiazine formed by the attack of vinyl nitrene at the sulfur atom was the major product. Mechanisms and differences of the reactions depending on O and S are discussed.

Das thermische Verhalten der 2H‐Azirine (I) und (II) wird untersucht.

New types of cyclization reaction to form 1,2-thiazine and 1-azaphenalene, found in thermal rearrangement of 2H-aeirine~ having 0-and Sfunotions, are disoussed with