ortho-Quinone methides as key intermediates in cascade heterocyclizations

Development of new methods of heterocyclic synthesis is still a topical issue. In this connection, the trend related to the use of highly reactive o-quinone methides for the synthesis and functionalization of heterocycles appears rather promising. Since most of o-quinone methides are unstable, the choice of precursors and generation conditions is highly important for subsequent transformations involving them. Various methods of generation of o-quinone methides and cascade hetero-cyclizations in which the formation of these compounds is a key step are surveyed in the review. The trends of using o-quinone methides in the synthesis of various heterocycles are analyzed and the heterocyclization reactions involving these compounds are classified.