α-Silyl Ethers as Hydroxymethyl Anion Equivalents in Photoinduced Radical Electron Transfer Additions

Nucleophilic α-hydroxymethyl radicals can be generated from α-silyl ethers by irradiation in the presence of 9,10-anthracenedicarbonitrile (ADC) and biphenyl (BP). Under these conditions the hydroxymethyl radicals are not oxidized further but add directly to electron-poor alkenes [Eq. (a); EWG=electron-withdrawing group]. The radical adduct undergoes back electron transfer to form the carbanion, which is protonated. R=PhCH2, tBuMe2Si, Me; TMS=Me3Si.