Halogen-Bonding-Promoted C–H Malonylation of Indoles under Visible-Light Irradiation

Abstract

Herein, we report a halogen-bonding-based electron donor−acceptor (EDA) complex-promoted photoreaction for the synthesis of C2-malonylated indoles. The protocol provides access to a broad range of functionalized indoles in good yields through the coupling reaction of indoles with diethyl bromomalonate under visible-light irradiation without the need for any transition-metal catalyst or photocatalyst.

Photochemical [2 + 2 + 1] annulation of 2-vinyloxy arylalkynes with bromomalonates via energy transfer

“…1 Visible light catalyzed radical cleavage of bromomalonates has been developed well by the groups of Stephenson, 2 Zhu, 3 Melchiorre 4 and others. 5 However, these methods depend on the use of expensive and nonrecyclable photocatalysts. Accordingly, the development of photocatalyst- and additive-free photochemical strategies has emerged as a promising new direction.…”

Halogen-bond-promoted direct cross-coupling of ethyl 3-bromo-3-alkyl-2,2-difluoropropanoates with coumarins/quinolinones

“…To the best of our knowledge, to date, only limited examples of C–Br bond transformations promoted by halogen bonding have been realized. 13…”