The Cdouble bondN double bond of certain cis- or trans-cycloalkane and
diexo- or diendo-norbornane-condensed pyridazinones was reduced with
NaBH3CN. The cis- or trans nature of the starting cycloalkane
derivatives was always retained in the saturated products, with a high
degree of diastereoselectivity: the hydrogen on the new stereocenter
and the annelational hydrogen next to the carbonyl always exhibited the
same steric orientation. The stereostructures were determined by means
of nmr measurements and confirmed by molecular modelling.