Triphenylphosphine/1,2-Diiodoethane-Promoted Formylation of Indoles with N,N-Dimethylformamide

Abstract

Despite intensive studies on the synthesis of 3-formylindoles, it is still highly desirable to develop efficient methods for the formylation of indoles, due to the shortcomings of the reported methods, such as inconvenient operations and/or harsh reaction conditions. Here, we describe a Ph₃P/ICH₂CH₂I-promoted formylation of indoles with DMF under mild conditions. A Vilsmeier-type intermediate is readily formed from DMF promoted by the Ph₃P/ICH₂CH₂I system. A one-step formylation process can be applied to various electron-rich indoles, but a hydrolysis needs to be carried out as a second step in the case of electron-deficient indoles. Convenient operations make this protocol attractive.

Key words

formylation - indoles - aldehydes - Vilsmeier-type intermediate - dimethylformamide

Publication History

Received: 09 September 2021

Accepted after revision: 20 October 2021

Accepted Manuscript online:
20 October 2021

Article published online:
10 November 2021

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