Other six-and seven-membered rings

Under reducing regimes some 1,3,5- and 1,2,4-triazines ring contract to imidazoles [84-86], but there is no obvious synthetic importance. When a-halogenooximes react with amidines, they appear to form AH- 

5- oxadiazines, which are deoxygenated by iron carbonyls to give 2,4-disubstituted imidazoles in good yields [87 j. Thermal rearrangement of l//-l,4-diazepine-7(6W)-thiones occurs on brief heating at 120°C in DMSO to give l-vinylimidazole-2(3f/)-thiones in 92-95% yields [88]. 

Jackson, H. Marky, H. J. Hansen and H. Schmidt, Helv. Chim. Acta SS, 919 (1972). 

Ticfenthaler, W. Ddrscheln, H. Goth and H. Schmid, Helv. Chim. Acta 50, 2244 (1967). 

Fieser and M. Fieser, in Reagents for Organic Synthesis. Wiley, New York, 1967, p. 637. 

---