MECHANISM OF ORGANOCALCIUM REAGENT FORMATION

The stereochemistry of the reaction of (S)-(+)-1-bromo- and (S)-(+)-1-chloro-1-methyl-2,2-diphenylcyclopropane and (S)-(+)-1-bromo-1-(methoxymethyl)-2,2-diphenylcyclopropane with calcium-aromatic complexes is reported as is its reaction with a radical clock, 6-chloro-6-methyl-1-heptene. Evidence is presented which indicates that these reactions occur by a single electron transfer to yield free radicals as intermediates. The reduction of a number of these substrates with solutions of calcium dissolved in liquid ammonia is also reported. Metallic bronze Ca(NH3)6 in THF at -30-degrees-C behaves as a solid surface in its reaction with alkyl halides.