摘要:
Efficient transfer-epimetalations of simple olefins and acetylenes by R2TiL2 reagents (R = Bu-n, Bu-t; L = X) are readily achieved in THF at - 78 degreesC to generate titanacyclopropa(e)ne intermediates, readily capable of inserting various unsaturated addends (olefin, acetylene, nitrile). Analogous epimetalations conducted in hydrocarbons lead to the stereoselective polymerization of 1-alkenes and the cyclotrimerizations of acetylenes. The 2-substituted-1-halotitanacyclopropyl cation is proposed as the active site for stereoselective olefin polymerization.