A Facile Synthesis of 4‐, 6‐ and 7‐Formyl‐1H‐indole‐2‐carboxylates: The CH₂SO₃H Functionality as a Masked Formyl Group.

Abstract

A Facile Synthesis of 4-, 6-and 7-Formyl-1H-indole-2-carboxylates: The CH 2 SO 3 H Functionality as a Masked Formyl Group. -This procedure offers a new synthetic entry for formylindoles (IV) and (VII) carrying base-sensitive functionalities. The transformation of the sulfomethyl group to the formyl function is accomplished by elimination of SO2 followed by hydrolysis and oxidation providing a regioselective method for the direct synthesis of formylindoles (IV) and (VII). The advantages of this procedure are the absence of side reactions, good yields and experimental simplicity. Protection of the indole nitrogen is not necessary. Noteworthy, a marked increase in the rate of hydrolysis of 7-chloromethyl-indoles compared to that of (II) and (V) is observed. -(PETE*, B.; SZOELLOESY, A.; SZOKOL, B.; J. Heterocycl. Chem. 43 (2006) 5, 1331-1335; Dep. Org. Chem. Technol., Budapest Univ. Technol. Econ., H-1521 Budapest, Hung.; Eng.) -H. Hoennerscheid 08-116