Photochemical Generation and Spectroscopic Characterization of Parent 3‐Iminooxetane and 3‐Oxazoline From 3‐Azidooxetane

ABSTRACT Simple heterocyclic imines are of potential prebiotic and astrochemical relevance, yet many parent representatives remain uncharacterized. Here, we report the photochemical formation of two C 3 H 5 NO isomers, namely 3‐iminooxetane and 3‐oxazoline, by irradiation of matrix‐isolated 3‐azidooxetane in argon at 3 K. Photolysis at 308 nm leads to efficient azide depletion and formation of both imines, which were assigned by infrared spectroscopy in combination with anharmonic quantum‐chemical calculations. Deuterium‐labeling experiments further support the assignments and reveal isotope shifts consistent with the proposed structures. Subsequent irradiation at 222 nm consumes both heterocycles, leading to a complex product mixture including methoxyacetonitrile, ketenimine, and formaldehyde, as well as spectral features tentatively assigned to 2‐(methyleneamino)acetaldehyde. Multireference calculations support facile N 2 extrusion and reveal pronounced singlet‐state near‐degeneracy together with a substantially stabilized lowest triplet state upon N 2 separation. The comparable formation of both heterocycles, despite their different thermodynamic stabilities, indicates that product selectivity is not governed by thermodynamic stability alone.