Numerical analysis of the stereoselectivity of photoreduction of cyclohexanones and of its variations. Confirmation of the involvement of a pyramidal radical

A general method of numerical analysis of the experimental data was applied to the study of the stereoselectivity of photoreduction of cyclohexanones. The two assumptions, which were previously, put forward to account for the stereoselectivity variations, namely:

(1) the involvement of a more or less solvated planar radical, (2) the involvement of two diastereoisomeric pyramidal radicals which carry the stereochemical information could thus be separated with a high degree of reliability; the second assumption only is to be retained. The ratio of the spontaneous inversion rates of the two pyramidal radicals could be calculated and compared with the experimental value which was obtained independently from the selective deuteriation of the diastereoisomeric cyclohexanols.