Preparation of polyfunctional olefins and allenes using 1,1-bimetallics of zinc and zirconium
摘要:
The hydrozirconation of various alkenylzinc halides with Cp2Zr(H)Cl in dry dichloromethane provides 1,1-dimetalloalkanes of zinc and zirconium which react with aldehydes, providing (E)-alkenes with good to excellent stereoselectivity (up to 98% E). The reaction tolerates the presence of a wide range of functionalities in the dimetallic species as well as in the aldehyde, allowing the preparation of functionalized olefins. Ketones can also be olefinated by these reagents. However, only a moderate stereoselectivity is observed. The hydrozirconation of alkynylzinc halides with CP2Zr(H)Cl gives 1,1-dimetalloalkenes of zinc and zirconium which react with aldehydes, affording allenes. The olefination of alpha,beta-unsaturated aldehydes provides a short access of 1,2,4-trienes.