Abstract
Based upon the analysis of 1H NMR data, along with molecular modeling, it was shown that the reduction of 3,7-dihetera(N,N-; N,O-; N,S-)bicyclo[3.3.1]nonan-9-ones by LiAlH4 led to a mixture of two stereoisomeric secondary alcohols with different orientations of the hydroxyl groups in one of the ring systems. Diaza derivatives in deuterochloroform exist in predominant chair-boat conformations. However, the replacement of nitrogen in one of the heterocycles by oxygen or sulfur led to stereoisomers one of which existed in chair-boat conformation and another in a chair–chair conformation. In all cases the boat conformation is stabilized by formation of an intramolecular hydrogen bond (IMHB) between a lone electron pair of the nitrogen atom and a proton on the pseudo axial hydroxyl group of the other ring.