PHOTOINDUCED, RADICAL-MEDIATED γ-ALKYLATIONS OF 2-SILYLOXYFURANS

2-Silyloxyfurans 1 are highly versatile vinylogous nucleophiles[1] widely employed in polar Mukaiyama-type reactions, yet their potential in radical chemistry remains largely untapped. In our recent works,[2,3] we disclosed complementary photochemical strategies that uncover the reactivity of 2-silyloxyfurans as either traps electrophilic radicals 2• and carbocations 3+, or as precursors of electrophilic radical species 1•+ capable of capturing nucleophilic radicals 3• (Figure 1). In one approach, the use of 2-bromoacetophenones[3] or electron-rich N-acyloxy-phthalimmide substrates[2] enables the formation of electrophilic radicals 2• (Figure 1A) or benzyl carbocations 3+ (Figure 1B) under net-neutral radical–polar crossover conditions, which are regio- and chemoselectively intercepted by the vinylogous nucleophile. Alternatively,[2] visible light-induced oxidation of silyloxyfuran 1 generates an unprecedented silyl-stabilized radical cation 1•+, which efficiently couples with nucleophilic benzyl radicals 3• formed through photoredox reduction of suitable redox-active esters (Figure 1C). These methodologies provide direct γ-functionalization pathways to access a broad range of ε-keto-γ-butenolides[3] 4 and γ-benzyl butenolides[2] 6 in a single step and moderate to good yields. The synthetic value of these scaffolds is demonstrated through their conversion into unprecedented fused heterobicyclic lactones 5 and bioactive[4] phenyl-γ-valerolactone metabolites 7, highlighting 2-silyloxyfurans as key reactive hubs for expanding the scope of vinylogous radical chemistry