Arylsulfinic acids, addition

Arylalkylsulfones ate important intermediates obtained by alkylation of arylsulfinic acids. The latter ate obtained by reduction of the corresponding sulfonyl chloride. This reduction process is simple and of general appHcation involving the addition of the isolated sulfonyl chloride paste to excess aqueous sodium sulfite followed by salting-out the product and isolation. With mote rigorous reduction conditions, such as zinc/acid, sulfonyl chlorides ate reduced through to aryknercaptans, eg, 2-mercaptonaphthalene is manufactured from naphthalene-2-sulfonyl chloride. 

The thiazine dyes used in the preparation of this type of leuco are obtained through oxidative coupling of phenothiazine with an active methylene compound or an aniline. The reduction of the dye 23 with zinc powder in acetic acid is straightforward.9 Treatment of the leuco 24 with acetic anhydride at 40°C yields a more air stable leuco 25.9 Addition of arylsulfinic acid to thiazine dyes such as 26 produces directly leuco dyes such as 27.Sb... 

Azidation.1 Arylsulfonyl azides generally react with enolates to effect net diazo transfer, but this hindered and electron-rich azide can effect azide transfer at the expense of diazo transfer. The nature of the enolate counterion also plays a role, with K being more effective than Na. In addition, acetic acid (or KOAc) is required as the quench for decomposition of the triazine intermediate to the azide with elimination of the arylsulfinic acid, ArS(0)0H. By use of these conditions, chiral N-acyloxazolidones such as 2 undergo diastereoselective azidation to give the azides 3 in 75-90% yield and in high optical purity (>91 9). These... 

Trisubstituted 2//-thiopyrans 299 add to arylsulfinic acids XC6H4S02H to afford sulfones 591. The addition was catalyzed with protons, and the detailed mechanism was discussed in reference 304. 

The 50 mol % excess of p-toluenesulfinic acid is required to obtain the best results. Using only 10-20 mole % excess of the sulfinic acid typically lowers the yield by 20-30%. This has been attributed to the known propensity of arylsulfinic acids to disproportionate.3 The checkers noted the presence of insoluble material after the addition of p-toluenesulfinic acid. This did not effect the yield. 

An efficient method for palladium(II) catalytic desulfitative conjugate addition of arylsulfinic acids with a, -unsaturated carbonyl compound has been developed. Experimental evidences for the key reacting intermediates including aryl Pd(II) sulfinic intermediate, aryl Pd(II), and C=0-Pd complexes were provided. The mechanism of the dehydrosulfenylation of 2-arylsulfinyl esters for furnishing enoates has been determined to be a homolytic process. The interception of the radical intermediate using a nitroxyl radical and mass spectrometry techniques were useful for identification of the intermediates involved in the dehydrosulfenylation of 2-arylsulfinyl esters. These data indicated that a radical-mediated process is operative. Tetrabutylammonium iodide has been found to promote deselenylation reaction of ) -chloro- and -oxyselenides to afford alkenes efficiently with formation of selenenyl iodides. A catalytic version of the transformation has also been developed. 

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