Application of High Pressure in Cycloaddition Reactions

摘要

Cycloaddition reactions can be a straightforward and stereoselective entrance to homo cyclic and hetero cyclic compounds. Therefore they are often applied in the synthesis of cyclic natural products. Generally cycloadditions proceed well when one reaction partner is electron-rich and the other is electron-poor. For that reason the scope is often determined by the degree of electron-richness and/or electron-poorness of the used reaction partners. For example moderate electron-rich enol ethers need strong electron-poor reaction partners such as tetracyanoethylene to undergo polar [2+2] cyloaddition reactions. In several cases it has been shown that the scope of these cycloadditions can be extended by the use of Lewis acid catalysts. These catalysts usually complex with the electron-withdrawing substituent making the concomittant reaction partner more electron-poor.