Functionalized Alkenylzinc Reagents Bearing Carbonyl Groups: Preparation by Direct Metal Insertion and Reaction with Electrophiles

摘要

Functionalized alkenes bearing aldehyde, keto, or ester functions are found in a plethora of natural products as well as in pharmaceutically active substances. Consequently, functionalized alkenyl organometallic compounds bearing such sensitive carbonyl groups are important intermediates in organic synthesis. In particular, alkenylzinc halides would be useful targets due to their high functional-group tolerance and their excellent reactivity in the presence of an appropriate catalyst. Functionalized alkenyl organometallic compounds are mostly prepared by halogen-metal exchange reactions of the corresponding iodoalkenes. The major drawbacks of this method are the low reaction temperatures required and the use of expensive alkenyl iodides as the starting material. Furthermore, only a few direct insertion reactions for the synthesis of unfunctionalized alkenyl organometailics have been reported. For instance, Rieke et al. described the use of highly active zinc (Zn*), which was prepared by reduction of ZnCl2 with lithium naphthalide, for the synthesis of styrylzinc bromide.