What is benzenesulfinic acid sodium salt?

Benzenesulfinic acid sodium salt is a white crystalline powder or crystals as shown in Figure 1 and it is used as a polymer adhesive enhancers, plasticizers for plasticized and modified of polyamide, epoxy resin, phenolic resin. Benzenesulfinic acid sodium salt is used to reduce the adverse chemical interaction involved in the coupling of self/dual-cured composites to hydrated dentin and it is also designed for manufacturing of photography, pharmaceutical, electroplating industry, can be used as photo-reducing agent [1]. 

Figure 1 The appearance of Benzenesulfinic acid sodium salt

Benzenesulfinic acid sodium salt has been used in the synthesis of sulfones by the reaction of organic halides and sodium benzenesulfinate using higher alcohols or diols as solvents. It was also used in the synthesis of aryl sulfones via copper-catalyzed cross-coupling with boronic acids and vinyl sulfones via reaction with vicinal dibromides. When with alkynylselenonium salts, benzenesulfinic acid sodium salt yields (Z)-β-alkoxyvinylsulfones, and it undergoes rhodium-catalyzed desulfinative coupling with aldehydes to yield ketones.

LiXia Li and coworkers developed an efficient sulfonylation reaction of pyrazolones with benzenesulfinic acid sodium salt catalyzed by TBAI, and a wide variety of valuable sulfonated pyrazolones were obtained in good to excellent yields using water as solvent [2].

Scheme 1 The reaction of Benzenesulfinic acid sodium salt

There is a preparation route of diarylsulfones based on benzenesulfinic acid sodium salts and diaryliodonium salts (scheme 2).  The reaction takes place in the absence of any transition metal-catalyst or additional base. While a variety of solvents can be used for this reaction, best results were obtained with polar aprotic solvents such as

N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or N-methyl-2-pyrrolidone (NMP). This might be due to the improved solubility of the sulfinic acid sodium salts in polar solvents. In the apolar solvents, the reaction mixture continuously stays a suspension. While slightly higher yields were obtained in NMP and DMSO. Interestingly, this reaction is quite insensitive to air and moisture. 

Scheme 2 Preparation route of diarylsulfones based on benzenesulfinic acid sodium salts and diaryliodonium salts

Reference

[1] https://www.sigmaaldrich.com/catalog/product/aldrich/123579?lang=en&region=US
[2] Li-Xia Li et.al., Direct sulfonylation of pyrazolones with sodium sulfinates catalyzed by TBAI in water, Tetrahedron Letters, Volume 59, Issue 15, 11 April 2018, 1517-1520
[3] Frankfurt am Main, Preparation route of diarylsulfones based on benzenesulfinic acid sodium salts and diaryliodonium salts, Organic Letters, 2013, 1, pp. 188-191

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