An approach to functionalized carbazoles from Z -enoate propargylic alcohols. A unified total synthesis of N -Me-carazostatin, N -Me-carbazoquinocin C and N -Me-lipocarbazole A4.

Development of an acid catalyzed, intramolecular benzannulation of indoles for the synthesis of functionalized carbazoles has been reported. The indole appended Z -enoate propargylic alcohols have been employed. The N -EDG-indoles involve the 5- exo-dig cyclization followed by 1,2-migration to give the carbazole-butenoates, whereas the N -EWG-indoles undergo the Z -enoate assisted Meyer-Schuster rearrangement to give the dihydrocarbazole-4- oxo -butanoates. Utilizing one of the 2-methyl-carbazole-butyraldehyde (obtained from the corresponding carbazole-butanoate) as the key intermediate, we have developed a simple approach for an efficient synthesis of N -Me-carazostatin, N -Me-carbazoquinocin C and N -Me-lipocarbazole A4.