A Facile Synthesis of 4-Substituted 3-Formylindoles

Abstract

A new synthetic method for 3-formylindoles having a carbon side chain at the 4-position was elaborated by means of thallation-palladation method.Although the preparation of (3-formylindol-4-y1)thallium his-trifluoroacetate (5) from 3-formylindole ( 2 ) was reported,2 no attempt has been made to introduce carbon side chains into the C-T1 bond because of the lack of suitable method.Our interest in the synthesis of 4-substituted indoles prompted us to develop such method.3 Recently, Spencer and Thorpe reported the reaction of arylthallium compounds with 'H-NMR (CDC13) c : 3.73 (3H, s), 6.46 (lH, d, J=16 Hz), 6.68 (lH, br d, J=3.2 Hz), m), 7.96 LlH, d, J=16 Hz), 8.33 LlH, br s, NH).