Applications of ortho-quinone methides in the synthesis of natural products

Abstract

ortho-Methylene cyclohexadienones, which are collectivelly referred to as ortho-quinone methides (o-QMs), were first suggested by Fries in 1907. o-QMs are a kind of short-lived and highly reactive versatile intermediates in organic synthesis. The unstability nature of o-QMs is due to their propensity to undergo rapid rearomatisation either by Michael addition of nucleophiles or, often more usefully, by cycloaddition with 2π partners or via oxa-6π-electrocyclisation to give benzopyrans. ortho-Quinone methides were always used in the synthesis of natural products through Michael addition and cycloaddition. As a new member of the family of inherently reactive species, ortho-quinone methides are similar with radicals, carbocations, carbenes, etc. And now using o-QMs to form skeletons of natural products has become a very useful stratergy. This review contains the major application in the synthesis of natural products during 2009 to 2014.