A reinvestigation of 4-hydroxyindole-6-carboxylate synthesis from pyrrole-2-carboxaldehyde: a facile synthesis of indoles and indolizines.
Cyclization of the Stobbe product 3 under the literature conditions (acetic anhydride/sodium acetate) affords both the indole 6 and the indolizine 8. The presence of base promotes the formation of indolizine products, and using acetic anhydride/triethylamine leads to indolizine products in good yield. Improved conditions for conversion to indoles 2, 5, and 6 are reported, and inconsistencies in some of the literature structure assignments and characterization data are noted.
Kim
Musong
M
Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, USA.
Vedejs
Edwin
E
D002264:Carboxylic Acids / Q000737:chemistry*; D007211:Indoles / Q000138:chemical synthesis*; D007212:Indolizines / Q000138:chemical synthesis*; D008956:Models, Chemical; D015394:Molecular Structure; D011758:Pyrroles / Q000737:chemistry*
D002264:Carboxylic Acids; D007211:Indoles; D007212:Indolizines; D011758:Pyrroles