Sulfinic Acids and Related Compounds 23. Preparation of Sulfinic Acids by the Reaction of Sulfonyl Halides with Thiols

The reaction of arene- and alkanesulfonyl halides with p-thiocresol in the presence of triethylamine at - 76°C gives triethylammonium sulfinates, which after acidification afford sulfinic acids of 95-100% purity in yields of 51-92% for 18 typical representatives. The synthesis succeeds in certain instances where conventional reduction with aqueous sodium sulfite fails and in other instances often is superior. The method is rapid, mild, selective, convenient, and general, although a few limitations are reported. Characterizations of the sulfinic acids are effected by titration with aqueous sodium nitrite, by IR and ¹H-NMR spectra, by preparation of either a S-benzylthiuronium salt or a p-nitrobenzyl ester, and either by elemental analyses or comparison with reported melting points of the acids and derivatives as appropriate.