Photocatalyzed cycloaromatization of vinylsilanes with arylsulfonylazides

Abstract

Sila-molecules have recently attracted attention due to their promising applications in medical and industrial fields. Compared with all-carbon parent compounds, the different covalent radius and electronegativity of silicon from carbon generally endow the corresponding sila-analogs with unique biological activity and physicochemical properties. Vinylsilanes feature both silyl-hyperconjugation effect and versatile reactivities, developing vinylsilane-based Smiles rearrangement will therefore provide an efficient platform to assemble complex silacycles. Here we report a practical Ir(III)-catalyzed cycloaromatization of ortho-alkynylaryl vinylsilanes with arylsulfonyl azides for delivering naphthyl-fused benzosiloles under visible-light photoredox conditions. The combination of experiments and density functional theory (DFT) energy profiles reveals the reaction mechanism involving α-silyl radical Smiles rearrangement.

Photocatalyzed Coupling–Cyclization of ortho-Alkynylaryl Vinylethers with Arylsulfonyl Azides

“…However, the existing methods mainly focus on forming furanyl Csp 2 –SO 2 bond in the C2/C3-position of benzofurans, the fabrication of the Csp 3 –SO 2 bond into benzofuranyl skeletons is very limited. , Although Lam demonstrated that sulfonyl radicals preferentially attacked the alkynyl moiety instead of the allyl group of allyl-tethered alkynes to enable the coupling–cyclization of enynes (Scheme a), vinylsilanes generally possess richer electron density than allyl CC double bonds due to the weaker electronegativity of the Si element and silyl hyperconjugation effect, leading to radicals that possibly prefer to attack the vinyl group instead of the alkynyl moiety. Therefore, we recently developed an Ir­(III)-catalyzed cycloaromatization of ortho -alkynylaryl vinylsilanes with arylsulfonyl azides for assembling naphthyl-fused benzosiloles under photoredox conditions, in which arylsulfonyl azides were employed as aryl radical precursors to be trapped by vinylsilanes via α-silyl radical Smiles rearrangement (Scheme b) . Our mechanism studies confirmed that the Si/O switch significantly affected the reactivity of vinylethers possibly due to the p−π conjugated effect between the oxygen’s lone pair and the CC double bond, leading to the formation of Csp 3 –SO 2 bonds.…”

Recent Advances in the Smiles Rearrangement: New Opportunities for Arylation

“…The reaction scope was capable of varying substituents on each phenyl ring involved in the cascade and producing unusual, bridged structures upon changing the vinylsilane to an allylsilane group. 54 Scheme 16 Radical Smiles cascade producing silicon-based heterocyclic scaffolds (W. Zeng and co-workers)…”

“…The reaction scope was capable of varying substituents on each phenyl ring involved in the cascade and producing unusual, bridged structures upon changing the vinylsilane to an allylsilane group. 54…”

“…All rights reserved. Synthesis 2022,54,[1908][1909][1910][1911][1912][1913][1914][1915][1916][1917][1918]…”

Visible-Light-Catalyzed in Situ Denitrogenative Sulfonylation of Sulfonylhydrazones

“…In this regard, Li employed 4CzIPN/Cu­(OTf) 2 as a combinated catalysis system to achieve a visible-light-catalyzed decarboxylative radical sulfonylation of sulfinates with redox-active aliphatic carboxylic esters (Scheme b) . More recently, we still described a photocatalyzed coupling–cyclization of sulfonylazides with vinylethers and vinylsilanes to furnish complex oxa- and sila-cycles via denitrogenation, respectively . Based on the fact that diazo esters, sulfonylazides, and sulfonylhydrazones possess similar multinitrogen skeletons, we therefore envisioned that sulfonylhydrazones could also possibly undergo photocatalytical denitrogenation to directly afford arylsulfones under mild conditions (Scheme c).…”