Conversion of Cyclohexanone to Spiro[3,4-cyclohexano-4-hydroxybicyclo[3.3.1]nonan-9-one-2,l'-cyclohexane]

The course of cyclohexanone self-condensation, under a variety of reaction conditions, has been a classic problem for over 80 years. Self-condensation of cyclohexanone catalyzed by sodium methoxide-dimethylformamide has been shown to afford the title substance (10, mp 186.5-187 °C) in 40% yield. Structural elucidation of ketol 10 was undertaken by degradative methods and provided the interesting series of products illustrated by structures 11-14,16-21, and 23. Unequivocal confirmation for the skeletal arrangement of ketol 10 and the stereochemical assignments was obtained by solving the X-ray crystal structure.