NEW (4+2)-CYCLOADDITIONS OF IN SITU GENERATED INDOLYL ENOL ETHERS AS HETEROCYCLIC DONOR-ACTIVATED 1,3-DIENES TO CARBAZOLE DERIVATIVES

Article abstract of DOI:10.1016/S0040-4039(00)96290-7

The ambident alkoxy-indolyl-methylcarbenium ions 1a-c are deprotonated by NaH to give in situ generated enol ethers which can be easily trapped by a dienophile such as, a.g., dimethyl acetylenedicarboxylate to form the carbazole derivatives 3, 4, and I.On reaction with the ethoxy-2-methylindolylcarbenium ion 1 d under the same conditions, a stereoselective Michael-type addition with formation of 6 takes place.