MPHT-Promoted Bromocyclization of ortho-Substituted Arylalkynes: Application to the Synthesis of 2-Substituted 3-Bromobenzofurans and -Benzo[b]thiophenes

✍ Scribed by Maud Jacubert; Abdellatif Tikad; Olivier Provot; Abdallah Hamze; Jean-Daniel Brion; Mouâd Alami

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 558 KB
• Volume: 2010
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.201000529

✦ Synopsis

Abstract

A convenient and general approach to the synthesis of 2‐substituted 3‐bromobenzofurans and ‐benzothiophenes was developed. The procedure is based on the cyclization of ortho‐substituted arylalkynes in the presence of N‐methylpyrrolidin‐2‐one hydrotribromide (MPHT) as a soft and easy‐to‐handle electrophilic brominating reagent. Under mild reaction conditions, MPHT promoted the bromocyclization of various enynes and diynes as well as arylalkynes to give 2‐substituted 3‐bromobenzofurans and ‐benzothiophenes in high to excellent yields. Subsequent functionalization by palladium‐catalyzed coupling reactions at the C–Br bond afforded general access to 2,3‐disubstituted benzofurans and benzothiophenes of biological interest.