Stereoretentive Decarboxylative C-3 Func-tionalization of Chromone-3-carboxylic Acids via Visible Light Irradiation

ABSTRACT: Herein, we report a stereoretentive and decar-boxylative C-3 functionalization of chromone-3-carboxylic acids with optically active aziridines via visible light irradia-tion. This metal-free and operationally simple protocol utilizes a simple combination of stable and inexpensive tetrabu-tylammonium iodide and visible light irradiation. It enables a facile and direct access to chiral 3-substituted chromenones with maintaining the optical purity of starting aziri-dines.Cross-coupling reactions allowing for efficient carbon–carbon as well as carbon–heteroatom bond formations are of crucial importance in the modern organic chemistry.1 Among them transition-metal-catalyzed decarboxylative cross-couplings utilizing carboxylic acids as substrates occupy a prominent position.2 They offer several distinctive advantages related to availability and price of carboxylic acid derivatives, their stability and handling as well as generation of less-toxic carbon dioxide as the by-product that reduces the waste treatment costs. While these methods have proven particularly useful for C(sp2)-C(sp2) bond formations and were applied for the synthesis of numerous relevant products ranging from pharmaceuticals to organic materials, their application in the C(sp2)-C(sp3) remains limited. Consequently, there is a need for the development of alternative, transition-metal-free cross-coupling reactions allowing for C(sp2)-C(sp3) bond formations.