Modifications to the Vilsmeier-Haack formylation of 1, 4-dimethylcarbazole and its application to the synthesis of ellipticines

Figure represented. An improved method for the preparation of 3-formyl-1,4-dimethylcarbazole, a key intermediate in the synthesis of ellipticine, is presented. Conditions of the Vilsmeier-Haack reaction have been modified to facilitate the production of 3-formyl-1,4-dimethylcarbazole as a major product leading to an overall improvement in yield of ellipticine from 3% to 14%. This approach was also applied to the synthesis of 6-methylellipticine and 9-methoxyellipticine.