Efficient syntheses of a novel 5-thia-1-azacycl[3.3.2]azine ring system and 3H-1,4-diazacycl[3.3.2]azine derivatives

Novel 5-thia-1-azacycl[3.3.2]azine derivatives 1, 5-thia-1,8b-diazaacenaphthylenes, have successfully been prepared. An X-ray crystallographic analysis of 1c revealed that the 5-thia-1-azacycl[3.3.2]azine ring system adopts a planar structure as to the internal ring nitrogen atom. The 1H NMR spectrum for unsubstituted ring system 1d implies contribution of a paramagnetic ring current in the peripheral 12π-electron ring system. Also, 3H-1,4-diazacycl[3.3.2]azine derivatives, 4-benzyl-4,5-dihydro-3H-1,4,8b-triazaacenaphthylen(e)-3-ones 2 and -3,5-diones 3 were synthesized with high efficiency via 3-(trichloroacetyl)imidazo[1,2-a]pyridine derivatives as new useful synthetic intermediates.