4.6 Article

Transition Metal-Free Synthesis of Halobenzo[b]furans from O-Aryl Carbamates via o-Lithiation Reactions

Journal

MOLECULES
Volume 27, Issue 2, Pages -

Publisher

MDPI
DOI: 10.3390/molecules27020525

Keywords

o-lithiation; carbamates; alkynylation; benzo[b]furans; cyclization

Funding

  1. Ministerio de Ciencia e Innovacion
  2. FEDER [PID2020115789GB-C21, BU049P20]
  3. Junta de Castilla y Leon
  4. la Caixa Foundation [LCF/PR/PR18/51130007 > (CAIXA-UBU001)]

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A straightforward and transition metal-free one-pot protocol for synthesizing halobenzo[b]furans has been developed using easily available starting materials. The researchers fine-tuned the different steps involved to achieve a successful one-pot procedure and synthesized a wide variety of new halobenzo[b]furans.
A straightforward and transition metal-free one-pot protocol to synthesize halobenzo[b]furans has been developed employing simple and easily available starting materials such as O-aryl carbamates and alkynylsulfones. The fine-tuning of the different steps involved was key to achieving a successful one-pot procedure. Initially, a directed ortho-lithiation process, which uses the carbamate as the directed metalation group, was crucial in providing access to O-2-alkynylaryl N,N-diethyl carbamates by a direct alkynylation of the o-lithiated carbamate, with arylsulfonylalkynes as electrophilic reagents. Cyclization of the generated o-alkynylaryl carbamates was successfully accomplished through a strategy involving in situ carbamate alkaline hydrolysis under conventional heating or microwave irradiation, coupled with a subsequent heterocyclization step delivering the desired benzo[b]furans. A wide variety of new halobenzo[b]furans has been synthesized and their utility has been demonstrated by their further transformation.

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