Unusual Regio- and Chemoselectivity in Oxidation of Pyrroles and Indoles Enabled by a Thianthrenium Salt Intermediate.
Angew Chem Int Ed Engl
; 63(33): e202405057, 2024 Aug 12.
Article
em En
| MEDLINE
| ID: mdl-38830180
ABSTRACT
A dearomative oxidation of pyrroles to Δ3-pyrrol-2-ones is described, which employs a sulfoxide as oxidant, in conjunction with a carboxylic acid anhydride and a Brønsted acid additive. 3-substituted pyrroles undergo regioselective oxidation to give the product isomer in which oxygen has been introduced at the more hindered position. Regioselectivity is rationalized by a proposed mechanism that proceeds by initial thianthrenium introduction at the less-hindered pyrrole α-position, followed by distal attack of an oxygen nucleophile and subsequent elimination of thianthrene. The same reaction conditions are also able to effect a chemoselective oxidation of indoles to indolin-3-ones and additionally of indolin-3-ones to 2-hydroxyindolin-3-ones. Here again, the regio- and chemoselectivities are rationalized through the intermediacy of a thianthrenium salt.
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MEDLINE
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En
Ano de publicação:
2024
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Article