A Synthesis Of Novel Dienes And A Application In Organocatalytic Asymmetric Diels-Alder Reaction

The asymmetric Diels-Alder reaction is a powerful method to synthesize functionalized six-membered carbocycles and heterocycles, containing multiple contiguous stereocenters. It also can construct important polycyclic frameworks via special diene-dienophile combinations. These cyclic compounds are a key structural motif present in many active natural products and pharmaceuticals. Therefore, the catalytic asymmetric Diels-Alder reaction plays a major role in organic synthesis, and organic chemists are paying increasingly attention in this field. The asymmetric catalytic methods have been developped from the quite toxic organometallic catalysis to the metal-free organocatalysis which is simple, green and environmentally benign. Design and synthesis of effective catalysts is important for Diels-Alder reaction. At the same time, the suitable dienes which could match with dienophile in accordance with the electronic orbital theory is also much more important. Consequently, the synthesis of appropriate and effective dienes is very important to the realisation of Diels-Alder reaction. We report herein a new PPh3-catalyzed synthesis of novel dicyano-2-methylenebut-3-enoates by the reaction of propiolates withα,α-dicyanoolefins. And first time take it as efficient dienes with aliphatic aldehydes to realize an unprecedented all-carbon-based asymmetric inverse-electron-demand Diels-Alder reaction (IEDDAR) via organocatalysis.