Cp2TiCl2-CATALYZED GRIGNARD EXCHANGE REACTIONS WITH ACETYLENES. A CONVENIENT METHOD FOR PREPARATION OF E-ALKENYL GRIGNARD REAGENTS

Article abstract of DOI:10.1016/0040-4039(81)80047-0

Disubstituted acetylenes react with isobutylmagnesium halide in the presence of a catalytic amount of Cp2TiCl2 in ether to afford E-alkenyl Grignard reagents selectively and in almost quantitative yields.The regiochemistry of this hydromagnesation reaction is high for alkylarylacetylenes and silylacetylenes giving E-ArC(MgBr)=CHR from alkylarylacetylenes, E-ArC(MgBr)=CH(SiMe3) from arylsilylacetylenes, and E-CHR=C(MgBr)(SiMe3) from alkylsilylacetylenes, respectively.Thanks to the high reactivity of the Grignard reagent, the present reaction offers a novel, selective and operationally simple route for preparation of trisubstituted olefins.