Benzylmagnesium chloride, reaction with rearrangement

Dimethyl and diethyl sulfates have been widely employed in the synthesis of alkylbenzenes and alkylnaphthalenes from aryl- and benzyl-type organometallic reagents. The final methyl groups of isodu-rene and pseudocumene are introduced in this manner. The reaction is superior to the Wurtz synthesis (method 9) for the preparation of o- and -diethylbenzenes. n-Propylbenzene obtained from benzylmagnesium chloride and diethyl sulfate ° is contaminated with a "rearranged product, f -ethyltoluene. ... 

The formation of pyrylium salts from methyl(ene) ketones and 1,3-diketones, e.g., of 2,4,6-triphenylpyrylium from acetophenone and dibenzoylmethane, has an interesting counterpart in several reactions of pyrylium salts. With nucleophiles like phenylhydrazine,353 hydroxylamine,353 or benzylmagnesium chloride,178-180 2,4,6-triphenylpyrylium forms unstable 2,4-dien-l-ones or 4 -pyrans, which rearrange easily to more stable pyrazolines, isoxazolines, or 2H-pyrans on treatment with strong acids, both types of product split off acetophenone, yielding 1,3,5-triphenylpyrazole, 3,5-diphenyl-isoxazole, and 1,3-diphenylnaphthalene, respectively. These same products can be obtained directly from the above nucleophiles and dibenzoylmethane.63,354-357 The condensation of methyl(ene) ketones with 1,3-diketones yielding pyrylium salts can, therefore, be considered reversible in a certain sense. 

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