Novel syntheses of hexahydro-1H-pyrrolo[1,2-a]imidazoles and octahydroimidazo[1,2-a]pyridines

1-Phenyl-5-(benzotriazol-1-yl)hexahydro-1H-pyrrolo[1,2-a]imidazole (18) and 1-phenyl-5-benzotriazolyloctahydroimidazo[1,2-a]pyridine (27) were readily prepared from succindialdehyde or glutaraldehyde, benzotriazole, and N-phe nylethylenediamine. Synthons 18 and 27 reacted with Grignard reagents, ally lsilanes, silyl ethers, and triethyl phosphite to produce 1-phenyl-5-substi tuted-hexahydro-1H-pyrrolo[1,2-a]imidazoles 20a-f, 22, 24a,b, and 25 and 1- phenyl-5-substituted-octahydroimidazo[1,2-a]pyridines 28a-e, 32, 33a,b, and 34 in good to excellent yields. The configurations of 20, 22, 24, and 25 w ere determined to be cis isomers by NOE experiment, while the configuration s and conformations of 28a-e, 32, 33a,b, and 34 were elucidated by H-1-H-1 COSY and H-1-C-13 COSY.