Steric and kinetic effects of changing solvent and reagent in grignard reactions on some 4-substituted cyclohexanones

Abstract

The stereochemistry and relative rates of Grignard reactions on some 4R-substituted cyclohexanones (R=tBu, Me, OMe. CO 2Me, OCOPh and Cl) have been determined under two separate reaction conditions (MeMgI in C 6H 6 and MeMgCl in THF). The results of our studies indicate that substrates containing an ester group have a higher reaction order in Grignard rcactant than other groups when reactions were carried out in the aromatic solvent. The same is not true for reactions carried out in THF. Both stereochemical product ratios and relative reaction rates are better understood assuming that compounds containing a polar group (OMe and Cl at least) react via a transition state possessing that group in the axial conformation.