CYCLIZATION OF THE GRIGNARD-REAGENT FROM 5-CHLORO-3-METHYL-1-HEXENE - REVERSIBLE ORGANOMAGNESIUM REARRANGEMENT

The Grignard reagent from 5-chloro-3-methyl-1-hexene cyclized reversibly to form an equilibrium mixture with two stereoisomers of the 2,4-dimethylcyclobutylmethyl-Grignard reagent. Equilibrium and rate constants for the opposing reactions have been evaluated at 80-100 and 100-120°C, respectively. Over this range, the equilibrium mixture favors the cyclic reagent by a ratio of about 3 1. Comparison with results for related compounds indicates that methyl substitution influences the equilibrium both by destabilization of the organomagnesium function and by stabilization of the strained ring. Additional comparisons of rate and equilibrium constants are discussed. © 1979.