LIGHT-POWERED AND RADICAL MEDIATED γ-BENZYLATION OF 2-SILYLOXYFURANS VIA VINYLOGOUS C(sp2)-H ACTIVATION

2-Silyloxyfurans are widely recognized as Mukaiyama-type vinylogous nucleophiles,1 enabling access to a diverse array of bioactive γ-butenolides and butyrolactones. While their use in polar transformations is well established, their potential in radical chemistry remains largely unexplored. In a recent work,2 we succeeded in developing two complementary vinylogous benzylation strategies of 2-silyloxyfurans 1, mediated by visible light and suitable photoredox catalysts (Figure 1).3 Central to both processes is the generation of a benzyl radical 2• via photoreduction of a redox-active ester 2. This intermediate then follows one of two distinct pathways: in the first one, photoinduced oxidation of the silyloxyfuran yields a novel silyl radical cation 1•+, which captures the nucleophilic benzyl radical 2•; in the second one, with electron-rich substrates, the benzyl radical undergoes a net-neutral radical-polar crossover to form a benzyl carbocation 2+, allowing for a polar-type vinylogous benzylation. These strategies provide the streamlined access to a broad scope of chiral γ-benzyl butenolides 3, some of which serving as key intermediates in the synthesis of bioactive phenyl-γ-valerolactone metabolites.