John Joseph Partridge

The Synthesis and stereochemistry of 5-substituted 2-methylcyclo-heptanones.

The cis and trans isomers of 5-methyl(2b), 5-isopropyl(2c), 5-t-butyl(2d), 5-isopropylol(2e), and 5-carbethoxy-2-methylcycloheptanone (2f) were prepared in 80-90% yield via treatment of the appropriate 4-substituted cyclohexanone with diazoethane in 20% ethanol-ether. The initial (kinetic) distribution of the isomeric pairs was approximately 1: 1. Equilibration of 2b-e in methanolic sodium carbonate afforded isomer distributions of 2.5: 1 (2b), 2: 1 (2c), 3: 1 (2d), and 3: 1 (2e), respectively, favoring the trans isomer in each case. Stereorational syntheses of trans-2,5-dimethylcycloheptanone and trans-2-methyl-5-isopropylolcycloheptanone were carried out to determine the stereochemistry of the products derived from the ring-expansion reactions.