Stereoselective Aza-Diels-Alder Reactions

The Diels-Alder reaction is one of the most useful and often studied transformations in organic chemistry. The reaction has been employed, often as the key step, in the total synthesis of a wide range of biologically-active natural products. The utility of the reaction is based upon its ability to form six-membered cyclic systems with up to four contiguous stereocenters as well as the reactions ability to incorporate heteroatoms into the cycloadduct. The use of imines as the dienophile has been studied in great detail over the last fifteen years. The development of stereoselective variants of the reaction has been at the forefront of these studies. The use of chiral auxiliaries and chiral catalyst to control the stereochemistry of the product has seen much success over this period of time. The purpose of this review is to give a detailed discussion of the recent advances in Diels-Alder methodology involving a carbon-nitrogen double bond. The review is divided into two major sections. The first discusses the development of Diastereoselective aza-Diels-Alder reactions, while the second part discusses Enantioselective variants of the reaction.