Expedient Construction Of Tetrahydroindoles Via Organocatalyzed "4+2" Cycloadditions Between Vinyl Pyrroles And Enals

The [4+2] cycloaddition reaction is a powerful strategy for the formation of carbon-carbon bonds in organic synthesis, which allows facile, stereospecific entry into six-membered ring systems. Many different versions of the Diels-Alder reaction were elaborated, including intramolecular [4+2]cycloadditions, hetero Diels-Alder reactions, pressure-accelerated Diels-Alder reactions, Lewis acid accelerated Diels-Alder reactions, and organocatalyzed asymmetric Diels-Alder reaction. The recent progress in [4+2] cycloaddition reaction, especially in organocatalyzed [4+2] cycloaddition reactions will be reviewed in this chapter.The second chapter has developed the first example of construction the tetrahydroindoles via organocatalyzed [4+2] cycloaddition between 2-vinyl pyrroles andα,β-unsaturated aldehydes. Under the catalysis ofα,α-diphenylprolinol trimethylsilyl ether, the reaction proceeded smoothly with moderate yields and high enantiostereoselectivities. Sinces the resulting functionalized tetrahydroindoles skeleton are versatile synthetic intermediates, this chemistry hold potential applications in nature products and biological molecules synthesis.