Functionalization of Styrenes by Copper-Catalyzed Borylation/ ortho-Cyanation and Silver-Catalyzed Annulation Processes

An efficient two‐step method for the assembly of indanone derivatives starting from a simple vinyl arene has been developed. The sequence first involves addition of bis(pinacolato)diboron (B2pin2) and N‐cyano‐N‐phenyl‐p‐methylbenzenesulfonamide (NCTS) to a broad range of styrenes by utilizing IMesCuCl as catalyst. This step simultaneously accomplishes hydroboration of the alkene and ortho cyanation of the benzene unit. The products thus obtained are further functionalized by a AgNO3/Selectfluor‐mediated coupling of the BPin and cyano functionalities to annulate a new five‐membered ring. This combined two‐step sequence provides a versatile method for the site‐selective derivatization of a broad range of vinyl arene substrates. A Cu and Ag sequence: The bis‐functionalization of styrenes is accomplished through a copper‐catalyzed process that enables hydroboration of the alkene and regioselective ortho cyanation of the arene. The resulting adducts are converted, by a radical cyclization process, into a cyclopentanone unit fused to the original aromatic ring. Together, these methods allow efficient cyclopentannulation of a broad range of styrene derivatives.