A Convenient Method for the Generation of Allylic Dihaloboranes and Diallyl(chloro)borane and Their Application in the Allylboration of Alkenes and Acetylenes

Abstract

Abstract A convenient approach to the highly reactive allylic dihaloboranes and diallyl(chloro)borane based on exchange reactions between BHal 3 (Hal = Cl, Br) and allylic triorganoboranes (allyl, cinnamyl and 2‐methylenecyclobutane derivatives) has been developed. The compounds thus generated readily react with terminal alkenes and acetylenes to form the corresponding cis ‐1,2‐allylboration products. These products were isolated by standard techniques and transformed into boronates (boron amides). Deboronation of these products led to 1,4‐pentadiene derivatives or unsaturated alcohols. 2‐Substituted 1,4‐pentadienyl(dichloro)boranes obtained from acetylenes underwent intramolecular chloroboration at a moderate temperature to form 5‐chloro‐2‐borinene derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)