Compounds with bridgehead nitrogen. Part. 69. The NMR spectra and stereochemistry of perhydrocyclopenta[f]pyrido[1,2,-c][1,3]oxazepines
Abstract
The positions of conformational equilibria in a series of perhydrocyclopenta[f]pyrido[1,2-c][1,3]oxazepines have been determined by 1H and 13C NMR spectroscopy. In contrast with syn- and anti-perhydropyrido[1,2-c][1,3]benzoaxepine which favour the trans-fused conformers the equilibria for the cyclopenta analogues show marked shifts towards the O-inside cis-fused conformers (71%cis conformer for the syn isomer, 78%cis conformer for the anti isomer).