Stereochemistry of 1,4-Addition of Nucleophiles to Ethyl Cyclohexylidenecyanoacetates

Article abstract of DOI:10.1021/jo00136a004

The stereochemistry of 1,4-addition of several nucleophiles such as cyanide, sodium borohydride, and methylmagnesium iodide to three substituted ethyl cyclohexylidenecyanoacetates (1-3) has been determined.A higher preference for equatorial attack is observed in these compounds than in related cyclohexanones, which is considerably diminished by the use of aprotic polar solvents.The results do not show any appreciable contribution of product stability control, recently shown to be important for hydride reduction of cyclohexanones, and have been rationalized on thebasis of a six-center cyclic transition state in which steric factors play a dominant role.These compounds have also been reduced by catalytic hydrogenation (Pd/C), and, interestingly, with unhindered systems (1, 2) hydrogenation takes place more from the axial side (40-60percent) as compared to cyclohexanones.