Stereoselective Synthesis of Dihydropyrans by Hetero Diels-Alder Reactions

摘要

Over the last 20 years the stereoselective HDA cycloadditon reactions in general, and those leading to the formation of dihydropyrans in particular, have found widespread application in organic synthesis. Notwithstanding this tremendous amount of work, there is still plenty of room for further development in many directions. While the use of chiral reagents seems now well established in its scope and limitations, the hunting season for efficient chiral LA has just opened. However, a deeper understanding of the origin of stereocontrol of the processes promoted by chiral catalyst is needed in order to extend to the HDA reactions the spectacular successes witnessed by its all-carbon counterpart. In addition to these rather obvious goals, it can be safely anticipated that application of these methodologies to combinatorial chemistry will be soon looked after.101 The multicomponent nature of some of the HDA cycloadditons described above and the recent availability of methods for anchoring on a polymeric matrix the reaction partners make this prediction an unrisky bet.