A modified Bischler-Napieralski procedure for the synthesis of 3-aryl-3,4-dihydroisoquinolines
Robert D. Larsen*, Robert A. Reamer, Edward G. Corley, Paul Davis, Edward J. J. Grabowski, Paul J. Reider, Ichiro Shinkai
*Department of Process Research, Merck Research Laboratories, P.O. Box 2000, R80Y-245, Rahway, NJ, 07065-0900, USA
R. D. Larsen, R. A. Reamer, E. G. Corley, P. Davis, E. J. J. Grabowski, P. J. Reider, I. Shinkai, J. Org. Chem., 1991, 56, 6034-6038.
Elimination of the amide group as the nitrile via retro-Ritter reaction is avoided in a modified Bischler-Napieralski procedure by its conversion to an N-acyliminium intermediate with oxalyl chloride-FeCl3. Removal of the oxalyl group in refluxing MeOH-sulfuric acid provides 3,4-dihydroisoquinolines in good yields.
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proposed reaction pathway