On the stereochemistry of Grignard addition to bicyclo[3.3.1]nonan-2-one. Preferential axial attack on a cyclohexanone system by a bulky nucleophile

Abstract

Bicyclo[3.3.1]nonan-2-one (1) reacts with methylmagnesium iodide to give, in a high overall yield, a 19:1 mixture of exo-2-methylbicyclo[3.3.1]nonan-2-ol (2) and the endo-epimer (3), respectively. The high propensity of compound (1) for axial attack by a bulky reagent, such as a Grignard reagent, is atypical of bridged cyclohexanones. Possibly, flattening of the bicyclo[3.3.1]nonan-2-one skeleton favours axial attack. Results of the oxymercuriation–demercuriation of related olefins is in accordance with this view.