3- Vinylindole, cycloaddition reactions asymmetric Diels-Alder reaction

Enantiomerically pure tetrahydrocarbazoles have been obtained by asymmetric Diels-Alder reactions [89] of 2- vinyl- and 3-vinylindoles with Oppolzer s acryloylsultam. The results of the [4+2] cycloadditions of 3-vinylindoles (Scheme 2.37) show that the exo-addition is preferred. 

The reaction of 2- and 3-vinylindoles with dienophile 214 constitutes the first example of an asymmetric Diels-Alder reaction of vinyl heterocycles. From 3-vinylindoles, enantiomerically pure carbazoles 215a-c were obtained, whereas from the vinylindole 197 together with 215d, diastereomer 216 was obtained as a minor product. Conversely, 2-vinylindoles provided inseparable mixtures of diasteromeric carbazoles. On the other hand, the cycloaddition reactions of 3-vinylindoles with 217 furnish the tetrahy-drocarbazoles 218 with endo-diastereoselectivity (93T2863). 

First asymmetric Diels-Alder reactions in the vinylhetarene series cycloaddition with vinylindoles to enantiomerically pure carbazole derivatives [133]... 

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