Advances in Catalytic Asymmetric Reactions Involving o-Hydroxybenzyl Alcohols

Ortho-quinone methides (o-QMs) belong to a class of highly reactive organic intermediates, which play an important role in catalytic asymmetric formations of carbon-carbon bond and carbon-heteroatom bond. However, o-QMs are highly unstable, which led to the underdevelopment of catalytic asymmetric reactions involving o-QMs. The utilization of some precursors for in situ generating o-QMs is a solution to address this challenging issue. Therefore, the development of catalytic asymmetric reactions involving in situ generated o-QMs has absorbed great attention from the chemists. The key to develop such reactions is to exploit easily available and stable precursors of o-QMs. Ortho-hydroxybenzyl alcohols are a kind of o-QM precursors with unique advantages. Hence, the catalytic asymmetric [4+n] cycloadditions, tandem cyclizations and nucleophilic additions of o-hydroxybenzyl alcohols have developed very rapidly in recent years, which have become efficient strategies for the synthesis of chiral oxygen-containing heterocycles and arylmethane derivatives. The catalytic asymmetric reactions involving o-hydroxybenzyl alcohols are summarized, which will open a new window for the design of new type of o-hydroxybenzyl alcohols and their involved catalytic asymmetric reactions.