1-(3,4-Dihydro-4-oxoquinazolin-3-yl)aziridines (Q-substituted aziridines): ring-opening reactions with C–N bond cleavage and preparation of Q-free chirons

The presence of the Q group in ring-opening reactions of N-(Q)-aziridines 3, 4, 5 and 6 has been found to be advantageous in the following ways, (i) nucleophilic ring-opening by cuprate or by azide with inversion of configuration is assisted by the electron-withdrawing character of the Q group, (ii) ring-opening of aziridines 5 or 6 to the corresponding alcohols 36 and 23 with retention of configuration can be accomplished by participation of the Q group: the Q carbonyl oxygen becomes the hydroxy oxygen in the alcohol product, (iii) the combined effects of the electron-withdrawing Q group and ring strain allow preparation of individual aziridine N-invertomers 3 and 4 whose ring-opening with hydrogen chloride in dichloromethane proceeds with complementary stereochemistry. The Q group is also believed to be involved in ring-opening of aziridines 5 and 6 mediated by samarium(III) nitrate hexahydrate with predominant retention of configuration. Reductive removal of the Q group from these ring-opened products gave chirons 12, 19 and 21.