Metal-free desilylative C–C bond formation by visible-light photoredox catalysis

Abstract

A novel metal-free desilylative C–C bond formation from simple organosilanes by visible-light acridinium photoredox catalysis is presented.

Recent advances in visible light-activated radical coupling reactions triggered by (i) ruthenium, (ii) iridium and (iii) organic photoredox agents

“…Molander et al, using ammonium silane catecholates 743 and the photoactivated 4CzIPN as oxidant, 236 showed that the liberated radicals add to imines 742 to afford benzylic amine products 744 (Scheme 202). On the other hand, Mancheño et al used benzyltrialkylsilanes as sources of benzyl radicals, but a strong oxidant, a mesitylacridinium salt was needed to liberate the radical in this case and the chemistry was limited to benzyl radicals, 237 while Bode et al liberated alkoxyakyl radicals from trimethylsilyloxy groups using triphenylpyrylium salts as photoredox reagents for cyclisation reactions in flow-based chemistry (not shown here). 238 Liberated alkyl radicals were also used 239 as precursors to acyl radicals 745 for addition to Michael acceptors yielding products 746.…”

Silicon‐Derived Singlet Nucleophilic Carbene Reagents in Organic Synthesis

“…Silicon functional groups can be employed in cross-coupling reactions More recently, Mancheno and co-workers reported the use of silyl groups to access radical intermediates that underwent the Giese reaction with electrondeficient alkenes. [7] The key radical intermediate is generated following oxidation of the carbon-silicon bond via a singlet electron transfer process facilitated by an acridinium photocatalyst (Scheme 2).…”

Martin Silicates as Versatile Radical Precursors in Photoredox/ Nickel Dual Catalysis

“…The alkynylation reaction involving an alkynyl bromide gave 20 in fair yield, as did vinylation with the corresponding vinyl bromide to give 21 , which also demonstrated tolerance of the reaction toward a Boc protecting group. The cross-coupling permitted the installation of primary nonactivated alkyl groups including a butyl group ( 25 ), a (trimethylsilyl)methyl group without overoxidation ( 26 ), 20 or a 3-oxopropyl unit ( 27 ). Moderate to good yields were obtained with secondary alkyl chains, including tetrahydropyranyl ( 4 – 18 ), cyclohexyl ( 22 ), and sec -butyl ( 24 ) (Scheme 4 ).…”