Reactions of Organomagnesates and Aryl Halides:  Metalation and Nucleophilic Substitution

Reactions with aryl halides (ArX) of preparations obtained in diethyl ether from an R 2 Mg compound and a cryptand, an alkali-metal alkoxide, or tetrabutylammonium bromide lead to ArH and ArR. ArH results from magnesium−halogen exchange, and ArR results from aryne formation. Reactions of similar preparations with pyridine lead to formation of larger amounts of substitution product, and those with 2-cyclohexen-1-one to larger amounts of 1,4-addition product, than do reactions of R 2 Mg alone.