Diaryls sulfinic acids

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

Andersen (75,76), as well as Mislow (221), discovered that the ORD curves of alkyl aryl sulfoxides show a strong Cotton effect in the region below 250 nm. An extensive study by Mislow and his coworkers (47) led to the following empirical rules, correlating the sign of the Cotton effect with the absolute configurations of chiral dialkyl, alkyl aryl, and diaryl sulfoxides, as well as menthyl esters of aromatic sulfinic acids ... 

Thiols can be prepared by the reduction of sulfonyl halides652 with LiAIH4. Usually, the reaction is carried out on aromatic sulfonyl chlorides. Zinc and acetic acid, and HI. also give the reduction. Sulfonic acids have been reduced to thiols with a mixture of triphenyl-phosphine and either Ii or a diaryl disulfide.633 Disulfides RSSR can also be produced.634 For the reduction of sulfonyl chlorides to sulfinic acids, see 0-118. 

Over palladium catalysts in acetone-water, arenesulfonyl chlorides are converted to the corresponding sulfinic acids, and further slowly to diaryl disulfide (eq. 13.100).183,184... 

Aryl sulfones have been prepared from sulfinic acid salts, aryl iodides and Formation of thiocyanates from unactivated aryl halides has been accomplished with charcoal supported copper(l) thiocyanate. " The copper catalyzed reaction of Na02SMe and aryl iodides give the aryl methyl sulfone. " A similar synthesis of diaryl sulfones has been reported using a palladium catalyst. " ... 

The tosyl group could alternatively be eliminated during the reaction when a base, such as l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), was present, as is the case for the photolysis of 1,2-diaryl-l-tosylstilbenes that led to phenanthrenes or their heterocyclic analogues in one step (Scheme 14.15, path h). These results were consistent with a mechanism involving a base-induced ehmination of p-toluene-sulfinic acid from 9-tosyl-4a,4b-dihydrophenanthrene as intermediate, formed by photochemical cyclization of the starting ethene [88]. 

Sulfinate anions have been used as nucleophiles in palladium-catalyzed allylic alkylation [143]. More recently, both Cu- and Pd-catalyzed couplings of sulfinate anions with aryl halides have also been reported as a means to generate unsymmetrical diaryl sulfones, which are common motifs in bioactive molecules [38, 93, 144—148]. Similarly, Cu-catalyzed coupling of arylboronic acids with sulfinate anions has been reported [95,149,150]. Notably, Kantam and co-workers found that the use of ionic liquids permits Cu(OAc)2-catalyzed sulfone synthesis at ambient temperature and with convenient product separation and catalyst recyclability (17) [150]. 

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