Carbometallation of conjugated enynes

Generation of stereo- and regio-defined alkenylmetals via hydrometallation or carbometallation of alkynes followed by cross-coupling (Scheme 1-11) is a synthetically attractive notion for preparing arylated alkenes, conjugated dienes, and conjugated enynes. Its feasibility was demonstrated in 1976 [14,15] in the prototypical examples shown in Schemes 1-4 and 1-5. In these processes, hydroalumination was employed for generating the required alkenylmetals. 

This intramolecular carbolithiation of silylated conjugated enynes was then successfully applied to the construction of small carbocycles such as cyclopropanes and cyclobutanes [35]. Due to the stabilization of the propargylic organolithium after carbocyclization, the reversibility of the intramolecular carbometallation of strained carbocycles was impeded (Scheme 7-37), e.g., for the cyclobutane synthesis. 

---