MINO(IMINO)]PERHYDROPYRIDO[1,2-D][1,3,4]OXADIAZINE AND INO(IMINO)]PERHYDROPYRROLO[1,2-D][1,3,4]OXADIAZINE - HETEROCYCLIC RING-SYSTEMS INVOLVING A BRIDGE-HEAD NITROGEN

Hydrazino alcohols (1-4) were converted with phenyl or 4-chlorophenyl isothiocyanate into their thiourea derivatives (5a,b, 6a,b, 9a,b and 1 0a,b) which then were cyclized by treatment with methyl iodide and alk ali to furnish ino(imino)]perhydropyrido[1,2-d][1,3,4]oxadiazines (7a, b) and perhydropyrrolo[1,2-d][1,3,4]oxadiazines (12a,b) and their 2-ar ylimino-3N-methyl derivatives (8a,b and 13b). The nmr spectra and X-ra y crystallographic analysis indicated that the 1,3,4-oxadiazines adopt rigid cis- or trans-fused ring conformations, depending on the parent ring size and the 3N-substituent. It was found that in the unsubstitu ted 1,3,4-oxadiazines (7a,b and 12a,b) involving a potential tautomeri c equilibrium, the amino form is most likely to predominate.