Palladium(0)-catalyzed Allylation of 2, 2-dihydroxybiphenyl by 1-ethenyl-cyclopropyl sulphonates:preparation of 2, 2-bis(cyclopropylidenethoxy)biphenyl

The dipotassium salts of 2,2'-dihydroxybiphenyl derivatives underwent palladium(0) catalyzed regioselective allylation by the sulfonic esters (mesylates, tosylates) of 1-ethenyl cyclopropanol to provide in good yields the 2,2'-bis(cyclopropylideneethoxy)biphenyls of biological interest; while the tetrapotassium salt of 2,2',6,6'-tetrahydroxybiphenyl, led mainly to the triadduct. An unexpected palladium-induced rearrangement of the mono cyclopropylideneethoxy adducts into the 2-[2-(1-ethenyl cyclopropyloxy)]-2'-hydroxybiphenyl derivatives was evidenced. Claisen rearrangement into the 2,2'-dihydroxy-6,6'-dimethoxy-3-(2- trimethylsilylethenyl)cyclopropylbiphenyl was observed at room temperature in CDCl3.