Direct C(sp³)–H acyloxylation of indolin-3-ones with carboxylic acids catalysed by KI

Abstract

The first KI-catalyzed direct acyloxylation of indolin-3-ones with carboxylic acids has been developed using 30% aq. H2O2 as a green oxidant at room temperature. Moreover, mechanism studies indicated that a radical oxidation process may be involved for this transformation.

Anodic C(sp3)–H Acyloxylation of Indolin-3-ones Enabled by Oxidant-Free Cross-Dehydrogenative C(sp3)–O Coupling

“…When 1-acetylindoline-3-one and probenecid were used as substrates for electrolysis on an 8 mmol scale, the acyloxylation product (8) was obtained after 14 h of reaction with a good yield of 84% (Scheme 2a). Subsequently, the acyloxylation product 8 could be converted into product 8-a via a Witting reaction 7 with an isolated yield of 58% (Scheme 2b). The reaction of 8 and quinoline 1-oxide under acetic anhydride provided a quaternary carbon product (8-b) with a 57% yield (Scheme 2c).…”

“…N-Substituted indolin-3-one substrates (35a−40a, 42a−44a, 46a, and 48a) were prepared according to the reported procedures. 7,19 General Procedure A1 for the Synthesis of 1-Acetyl-1Hbenzo [g]indol-3(2H)-one (41a). 19b To a solution of KOH (3.839 g, 68.4 mmol) and K 2 CO 3 (4.149 g, 30.0 mmol) in H 2 O (60 mL) were added glycine (45 mmol, 1.5 equiv) and 1-bromo-2-naphthoic acid (30 mmol, 1 equiv).…”

“…In addition, a metal-free strategy for direct C(sp 3 )−H acyloxylation of indolin-3-ones with carboxylic acid (3 equiv) by using 30% aq H 2 O 2 as a mild oxidant has also been realized, where the C2 positions of substrates need to be unsubstituted (Scheme 1a). 7 In the trend toward green chemistry, 8 researchers are turning to a greener and sustainable metal-free catalytic system that uses mild reaction conditions, readily available reaction materials, and no stoichiometric oxidant addition for constructing indoline-like motifs with a C(sp 3 )−O bond, which is still desirable but challenging.…”

“…Some strategies have been implemented, including the oxidation of indole, the bromination/nucleophilic reaction of indolin-3-ones with allyl alcohol, and the hydroxylation of indolin-3-ones, usually requiring a metal catalyst, Schmidt rearrangement conditions (NaN 3 /H 2 SO 4 ), or stoichiometric oxidants such as Br 2 , m -CPBA, or PhI­(OAc) 2 . In addition, a metal-free strategy for direct C­(sp 3 )–H acyloxylation of indolin-3-ones with carboxylic acid (3 equiv) by using 30% aq H 2 O 2 as a mild oxidant has also been realized, where the C2 positions of substrates need to be unsubstituted (Scheme a) . In the trend toward green chemistry, researchers are turning to a greener and sustainable metal-free catalytic system that uses mild reaction conditions, readily available reaction materials, and no stoichiometric oxidant addition for constructing indoline-like motifs with a C­(sp 3 )–O bond, which is still desirable but challenging.…”

“…5, 152.9, 138.3, 133.5, 132.2, 130.9, 125.1, 124.5, 122.9, 118.4, 117.9, 116.9, 81.6, 24 192.3,169.9,163.3,152.9,151.3,138.3,133.6,131.8,125.2,124.6,124.5,122.8,117.9,81.6,24.1. HRMS (ESI) 1-Acetyl-3-oxoindolin-2-yl 4-Fluorobenzoate (7). The title compound was prepared following general procedure B and purified by using silica gel chromatography (2:1 petroleum ether/ethyl acetate).…”