Simple, Stable, and Versatile Double-Allylation Reagents for the Stereoselective Preparation of Skeletally Diverse Compounds

摘要

We have disclosed a new family of simple and efficient double-allylation reagents: the α-trimethylsilylmethyl allylboronate 1 and the crotylboronates 12. These stable bimetallic reagents add onto a wide range of aldehydes to afford a direct access to hydroxyl-functionalized allylic silanes in very high E/Z selectivity and excellent enantioselectivity. The use of the Lewis acid-catalyzed allylboration manifold was key to the overall selectivity of this process. Through the hydroxyl-functionalized allylsilane products, reagents 1 and 12 can be exploited in chemodivergent syntheses of various compound classes such as propionate units, polysubsti-tuted furans, vinylcyclopropanes, and larger carbocycles. Other transformations of allylic silanes such as oxidations and Pd-catalyzed reactions can be envisaged. Thus, reagents 1 and 12 are expected to find multiple applications in natural product synthesis and diversity-oriented synthesis.