Palladium(0)-catalyzed allylation of 2,2?-dihydroxybiphenyl by 1-ethenylcyclopropyl sulfonates: Preparation of 2,2?-bis(cyclopropylideneethoxy) biphenyls

Dipotassium salts of 2,2?-dihydroxybiphenyl derivatives underwent palladium(0) catalyzed regioselective allylation by sulfonic esters (mesylates, tosylates) of 1-ethenylcyclopropanol to produce, in good yields, 2,2?-bis(cyclopropylideneethoxy)biphenyls, which are of biological interest. Whilst the tetrapotassium salt of 2,2?,6,6?-tetrahydroxybiphenyl, formed the triadduct 2,2?-tris(cyclopropylideneethoxy)hydroxybiphenyl as its main product. An unexpected palladium-induced rearrangement of the monoadducts 2-(2-cyclopropylideneethoxy)-2?-hydroxybiphenyl derivatives into the 2-[2-(1-ethenylcyclopropyloxy)]-2?-hydroxybiphenyl derivatives occurred; while the minor diastereomer of the monoadduct 2-[(2-cyclopropylidene-1-trimethylsilyl)ethoxy]-6,6-dimethoxy-2?- hydroxybiphenyl upon standing in CDCl, underwent Claisen rearrangement into the 2,2?-dihydroxy-6,6?-dimethoxy-3-(2-trimethylsilylethenyl) cyclopropylbiphenyl.