Friedel-Crafts Type Allyfation of Anisole with (Substituted Allyl) germanes

Abstract

The Friedel-Crafts type reaction of (substituted allyl) triethylgermanes (1) with anisole was studied. When allylgermanes (1) were treated with two equimolar amounts of copper (II) chloride in an isole at room temperature, the allylated products (2) were obtained in good yields.
The regioselectivity of the reaction is largely affected by substituents on allylgermanes (1); a methoxyphenyl group is selectively introduced to the less substituted side of an allylic system. In the case of the reactions of regioisomeric (1, 3disubstituted allyl) germanes (1c and d), the allylated compounds (2)with almost the same product distribution were obtained regardless of the original location of triethylgermyl group. These results suggest that the present reaction proceeds via the allylic carbocation intermediate (4).
It was found that the Friedel-Crafts type reaction of 1 was effected also with tin (IV) chloride, and the allylated products (2) were obtained with the similar regioselectivity observed in the copper (II) chloridepromoted reactions. On the basis of the fact that allyltriphenylstannane (6) was formed by the successive treatments of allyltriethylgermane with tin (IV) chloride and phenylmagnesium bromide, it is assumed that the tin (IV) chloride promoted reaction may proceed through the allyltrichlorostannane intermediate (5).