THE BROOK REARRANGEMENT

摘要

The Brook rearrangement describes the intramolecular silyl group migration from a carbon to an oxygen atom.1-15 It constitutes a well-known and powerful approach for the functionalization of organosilanes. The research on this rearrangement dates back to the 1950s, wherein Gilman and co-workers unexpectedly observed an "abnormal" product from the addition of triphenylsilyl potassium to benzophenone (Scheme l). A more complete and accurate understanding of the mechanism of this process was not established until a few years later when Brook and co-workers discovered that the abnormal product arose from a normal addition followed by an intramolecular anionic carbon to oxygen silyl group migration. The migratory aptitude of silyl groups in this context was found to be more general when treating various silylcarbinols with base (Scheme 2). The fascination with this rearrangement has resulted in many significant contributions which comprise a family of intramolecular carbon-to-oxygen silyl group migrations now widely recognized as the Brook rearrangement. The notation "[1,n]-" is used as a prefix to the term "Brook rearrangement" in which "n" refers to the number of chemical bonds between the migrating silicon and the terminal oxygen atom (Scheme 3). The reverse of this process constitutes the intramolecular oxygen to carbon silyl migration, which was first reported by Speier24 and was later systematically studied by West.25 These types of reverse silyl migrations only occur under specific circumstances and are typically referred to as retro-Brook (or West) rearrangements.