Halogenation of Indoles with Copper(II) Halides: Selective Synthesis of 2-Halo-, 3-Halo-, and 2,3-Dibromoindoles

Abstract

A simple and selective protocol for the halogenation of indoles with copper(II) bromide or chloride to synthesize 2-halo-, 3-halo-, and 2,3-dibromoindoles was developed. It was found that both base and water could be used as switches for the selectivity of the halogenation reactions. In the presence of copper(II) halide and sodium hydroxide, 3-haloindoles were obtained as the major products, whereas the selectivity was shifted toward 2,3-dihaloindoles when water was added instead of sodium hydroxide. Moreover, 2-halogenations of 3-substituted indoles were also performed successfully in moderate to good yields under the standard conditions.

Photo-induced 1,2-alkylarylation/cyclization of alkenes, alkyl halides and N-alkylindoles via an EDA-complex

“…Firstly, product 4a contains a quaternary carbon center and different C–C bonds, selective cleavage of C–C bonds by Cu(OAc) 2 and H 2 O to obtain prop-1-ene-1,1,3-triyltribenzene 10 in 86% yield. 23 Subsequently, photocatalytic sulfonylation of 4a with aryl sulfonyl chlorides to selectively construct C–S bonds and obtained the product 11 . 24 Finally, product 4a underwent bromination with N -bromosuccinimide (NBS) in chloroform (CHCl 3 ) and dimethyl sulfoxide (DMSO) at room temperature to afford 2-bromo indoles 12 , 25 which could further introduce other important functional groups.…”