Electron‐impact induced fragmentation of 3‐hydroxy quinazoline‐2,4(1H,3H) dione, pyridopyrimidine‐2,4(1H,3H)diones, lumazine and alloxazine

Abstract

Electron‐bombardment of the N‐3‐hydroxy derivatives of the above‐mentioned condensed uracils revealed that the major fragmentations involved the heterocyclic ring. The most intense ion proved to be the M‐32 ion which was created by the loss of the NHOH radical from the molecular ion. Mechanisms for this transition are presented. Other fragmentations common to these systems are discussed and compared with those reported for the corresponding N‐3 deoxy analogs of the title compounds. The mass spectral fragmentations of the O‐methyl‐, N‐methyl‐ and O,N‐dimethyl derivatives of 3‐hydroxyquinazoline‐2,4(1H,3H)dione were analyzed and were consistent with those expected from these structures. Electron bombardment of the 3‐benzenesulfonyloxy derivatives of the title compounds resulted primarily in the scission of the sulfonate group in preference to that of the heterocyclic dione ring. These sulfonates also showed ions which indicated that a Lossen rearrangement had taken place in the mass spectrometer.