Synthesis of Nitrogen Heterocycles through 1,3-Dipolar Cycloaddition Reactions

摘要

Nitrogen heterocycles represent an extremely vast class of compounds and their importance matches their numbers. From the examples reported in this short review it is clear that the 1,3-DC reaction is one of the most important methods for the construction of nitrogen containing heterocycles. The use of chiral starting material or of chiral auxiliaries has often made it possible to control regioselectivity, endo/exo selectivity, and diastereofacial selectivity in 1,3-DC reactions where one to four new chiral centers are formed. Some examples have been shown of the successful application of these reactions as the key step in the synthesis of optically active target molecules, particularly important in the case of products formed from dipoles, such as nitrones, nitrile oxides, and azomethine ylides. With the increased demand for optically active compounds in the future and with the improvement of asymmetric metal catalysis, the development of new approaches to asymmetric 1,3-DC reactions are to be expected. The development of such reactions might appear as a difficult enough endeavour, but it is by no means an impossible task and it definitely seems worth the effort.