Collective Synthesis of 3-Acylindoles, Indole-3-carboxylic Esters, Indole-3-sulfinic Acids, and 3-(Methylsulfonyl)indoles from Free (N–H) Indoles via Common N-Indolyl Triethylborate

Abstract

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.

Palladium-Catalyzed Direct C2-Biarylation of Indoles

“…The title compound was prepared as described in the reported procedure with indole (4.268 mmol, 1 equiv) as starting material. Yield: 350 mg, 42%, off-white solid.…”

“…IR (CH 2 Cl 2 , cm −1 ): 3126,3052,2873,1536,1356,1156,746 3-(Methylsulfonyl)-1H-indole (1o-Int-2). The title compound was prepared as described in the reported procedure 24 with indole (4.268 mmol, 1 equiv) as starting material. Yield: 350 mg, 42%, off-white solid.…”

Sophalines E–I, Five Quinolizidine-Based Alkaloids with Antiviral Activities against the Hepatitis B Virus from the Seeds of Sophora alopecuroides

“…Compound 2 was constructed from sophoridine 4 and 3acetylindole. 18 The key biogenetic intermediate B2 was derived from sophoridine through oxidation, dehydration, and hydrogenation reactions. Then, intermediate B2 was further oxidized to yield B3, 19 which was combined with 3acetylindole to obtain B4.…”

“…Finally, 1 was formed readily by dehydration and subsequent hydrogenation reactions. Compound 2 was constructed from sophoridine and 3-acetylindole . The key biogenetic intermediate B2 was derived from sophoridine through oxidation, dehydration, and hydrogenation reactions.…”

Copper-Catalyzed Synthesis of Indol-3-yl α-(Difluoromethyl)-α-(trifluoromethyl)carbinols: Construction of Difluoromethylated sp3 Carbon Centers

“…3-Substituted indoles are very important structural motifs in biologically active natural products and drug molecules because they are capable of binding many receptors with high affinity. − Direct functionalization of indoles at the C3 position is an effective strategy for synthesis of this class of compounds. For example, numerous elegant methods have been developed for their synthesis, which include alkylation, − arylation, acylation, − sulfonylation, and trifluoromethylthiolation , of indoles.…”