A general and direct C3 functionalization of free (N-H) indoles with readily available electrophiles such as acid chlorides, chloroformates, thionyl chloride, and methylsulfonyl chloride via a common N-indolyl triethylborate intermediate is reported. The reaction proceeds smoothly under mild conditions in up to 93% yield. Indoles with substituents at the C2, C4, C5, C6, and C7 positions are well tolerated. The easy accessibility of a variety of important 3-acylindoles, indole-3-carboxylic esters, indole-3-sulfinic acids, and 3-(methylsulfonyl)indoles demonstrates the high degree of compatibility and practicability of this method.
There are two molecules in the asymmetric unit of the title compound, C17H20O4S2. There are slight differences in the twist of the two rings relative to the S–C–S chain [dihedral angles of 48.41 (18) and 87.58 (16)° in the first molecule and 45.98 (18) and 87.02 (18)° in the second] and the difference in the C—S—C—S torsion angles [176.68 (17) and −77.6 (2)° for the two independent molecules].
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