Nitrile Ylides and Azirines: Gas‐Phase Generation from 2,3‐Dihydro‐1,4,λ5‐oxazaphospholes and Matrix Isolation

A thermally generated nitrile ylide has been directly observed for the first time: Pyrolysis of 1 at 700°C leads to the nitrile ylide 2 (sharp IR band at v = 2250 cm). The flash pyrolysis of 1 at 400°C, on the other hand, furnishes the azirine 3, the ring of which opens upon irradiation to give 2 (R = tBu). (Figure Presented.