Photoinduced Sulfonylation Reactions through the Insertion of Sulfur Dioxide

Abstract

Recent advances in the photoinduced sulfonylation reactions through the insertion of sulfur dioxide are summarized. Among the approaches developed in the sulfonylation reactions, the insertion of sulfur dioxide via radical process can be accomplished with the assistance of photoredox catalysis in the presence of visible light or under ultraviolet irradiation, depending the substrates used in the reactions. Under ultraviolet irradiation, the conversion can be completed under metal‐ and additive‐free conditions. It is noteworthy that alkyl halides possessing eliminable β‐hydrogen atom are effective as alkyl radical precursors with the insertion of sulfur dioxide. Two parts, according to the photoinduced reaction pathways, are introduced: (a) photo‐initiated formation of radical with the subsequent capture of sulfur dioxide; (b) photo‐assisted single electron transfer (SET) after insertion of sulfur dioxide. During the transformation, an oxidative or reductive single electron transfer would occur under visible light photoredox catalysis.

Photoredox‐Catalyzed Functionalization of Alkenes with Thiourea Dioxide: Construction of Alkyl Sulfones or Sulfonamides

“…[8] In the meantime, the combination of aryl/alkyl radicals and sulfur dioxide was discovered to provide a green and efficient way to generate sulfonyl radicals, avoiding the use of sulfonyl precursors. [9] During the process, different radical precursors, including aryldiazonium tetrafluoroborates, [10] aryl/alkyl halides, [11] diaryliodonium salts [12] and others [13] could be reduced to generate aryl radicals, which would capture the sulfur dioxide released from DABCO·(SO 2 ) 2 or inorganic sulfites leading to aryl/alkyl sulfonyl radical intermediates. Therefore, diverse sulfonyl compounds could be prepared efficiently and environmentally friendly with the insertion of sulfur dioxide, particularly from the low-cost inorganic sulfites.…”

“…Various sulfonyl precursors such as sulfonyl chlorides, sulfonyl azides, sulfonyl selenides, sulfonyl cyanides, sulfinic acids, sodium sulfinates, sulfonyl hydrazides and equivalents could be converted to the corresponding sulfonyl group by a single electron transfer (SET) process in the presence of radical initiators, light, catalysts or electricity (Scheme , eq a) . In the meantime, the combination of aryl/alkyl radicals and sulfur dioxide was discovered to provide a green and efficient way to generate sulfonyl radicals, avoiding the use of sulfonyl precursors . During the process, different radical precursors, including aryldiazonium tetrafluoroborates, aryl/alkyl halides, diaryliodonium salts and others could be reduced to generate aryl radicals, which would capture the sulfur dioxide released from DABCO·(SO 2 ) 2 or inorganic sulfites leading to aryl/alkyl sulfonyl radical intermediates.…”

Advances in photochemical and electrochemical incorporation of sulfur dioxide for the synthesis of value-added compounds

“…Alternatively, SO 2 can be oxidized electrocatalytically to SO 3 on Co phthalocyanines with gas diffusion electrodes. 22 Currently, there is intense research interest in sulfur chemistry and the direct incorporation of SO 2 into organic molecules, 18,23,[24][25][26][27][28][29][30][31][32][33][34][35] which is originated in the broad bioactivity of sulfur-containing molecules making them extraordinarily interesting in drug discovery, agrochemicals, and medicinal chemistry. 24,36 Among, the different approaches, radical processes are especially well-suited for the direct fixation of SO 2 .…”

“…In the past years, various photochemical methodologies for the fixation of SO 2 have been reported. 27,29 Surprisingly, this trend has not reached organic electrosynthesis, yet. In this review we give an overview of different working techniques for using SO 2 and recent advances on its application in electro-and photochemical preparation of organic products.…”

Generation of Sulfonylated Tetrazoles through an Iron-Catalyzed Multicomponent Reaction Involving Sulfur Dioxide

“…Sulfones are subjects of great interest in the area of pharmaceuticals and agrochemicals ( Drews, 2000 ; Feng et al., 2016 ; Patai et al, 1988 ). In recent years, sulfonylation reaction via a radical process with sulfur dioxide surrogates, DABCO·(SO 2 ) 2 and inorganic sulfites, has proven to be a promising approach for the synthesis of diverse sulfone-containing molecules ( Bisseret and Blanchard, 2013 ; Chen et al., 2020 ; Deeming et al., 2014 ; Emmett and Willis, 2015 ; Gong et al., 2020 ; He et al., 2020 ; Li et al., 2020a , 2020b ; Liu et al., 2020 ; Meng et al., 2020 ; Nair et al., 2020 ; Qiu et al., 2018a , 2018b ; Wang et al., 2019 ; Ye et al., 2019 , 2020a , 2020b , 2020c ; Zheng and Wu, 2017 ; Zhou et al., 2020 ). Recently, our group described a copper-catalyzed four-component reaction of terminal alkynes, aryldiazonium tetrafluoroborates, DABCO·(SO 2 ) 2 , and potassium halide, giving rising to a range of β-halo alkenylsulfones ( Xiang et al., 2017 ).…”