Rhodium(I)‐Catalyzed C2‐Selective Decarbonylative C−H Alkylation of Indoles with Alkyl Carboxylic Acids and Anhydrides. Issue 4 (17th March 2021)

• Record Type: Journal Article
• Authors: Yu, Haiyang; Zhao, Haoqiang; Xu, Xin; Zhang, Xin; Yu, Zexin; Li, Lingchao; Wang, Peng; Shi, Qian; Xu, Lijin
• Is Part Of: Asian journal of organic chemistry. Volume 10:Issue 4(2021)
• Page Start: 879
• Page End: 885
• Publication Date: 2021-03-17
• Subjects: Indole -- C−H activation -- alkylation -- rhodium -- carboxylic acids -- decarbonylation -- directing group; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; 547.005
• DOI: 10.1002/ajoc.202000712
• Languages: English
• ISSNs: 2193-5807

Abstract

Abstract: A Rh(I)‐catalyzed chelation‐assisted C2‐selective C−H decarbonylative alkylation of indoles with readily available, cheap, safe and structurally diverse alkyl carboxylic acids or anhydrides has been developed. A wide variety of primary and secondary alkyl carboxylic acids and differently substituted indoles are compatible with this transformation, allowing facile synthesis of various C2‐alkylated indoles with high efficiency and broad tolerance of diverse functional groups. The reaction proceeds in the absence of any external oxidant, and the presence of readily installable and removable N ‐pyrimidyl directing group is critical for catalysis. The process is convenient and scalable, and avoids the use of a dried solvent and an inert atmosphere. Moreover, selective C7‐alkylation and C2, C7‐dialkylation have also been achieved by slightly modifying the reaction conditions. Abstract : N‐(2‐pyrimidyl)‐indoles undergo highly regioselective C2‐H alkylation with alkyl carboxylic acids or anhydrides in the presence of [Rh(CO)2 Cl]2 catalyst under oxidant‐free conditions to exclusively afford the C2‐alkylated indoles in good to excellent yields. Moreover, selective C7‐alkylation and C2, C7‐dialkylation of indoles have also been achieved by slightly modifying the reaction conditions.