Bifunctional chiral catalyst for the Diels-Alder reaction and pseudopericyclic reactions and the reactivity of formylketene with acetylene
The Diels-Alder reaction (DAR) has become an important method for the synthesis of a six-membered ring, especially since it allows for the formation of four contiguous asymmetric centers with control of relative stereochemistry. The regioselectivity and stereoselectivity of the reaction is predictable. The preferred orientations in the reaction of a monosubstituted diene and a monosubstituted dienophile is shown in Scheme 2.1. This preference can be rationalized by the formation of intermediates 1 and 2, since these intermediates show the stabilization of the charges and they somewhat reflect charge redistribution in the actual transition state for the reaction.