Reduction of sulfonyl chloride

Sulfinic acids can be prepared by reduction of sulfonyl chlorides. Though mostly done on aromatic sulfonyl chlorides, the reaction has also been applied to alkyl compounds. Besides zinc, sodium sulfite, hydrazine, sodium sulfide, and other reducing agents have been used. For reduction of sulfonyl chlorides to thiols, see 19-57. 

Complete reduction of sulfonyl chlorides to thiols can be achieved by lithium aluminum hydride [680,693], with zinc [696] and with hydriodic acid generated in situ from iodine and red phosphorus [230]. m-Nitrobenzenesulfonyl chloride, however, was reduced not to the thiol but to bis(m-nitrophenyl)disulfide by hydriodic acid in 86-91% yield [697]. 

Reduction of sulfonyl chlorides with Zn and acid yields first sulfinic acids and then thiophenols. C,H,SOXl > C H,SO H """ > C,H,SH... 

Attack by Hydrogen. Reduction of Sulfonyl Chlorides S-Hydro-de-chlorination or S-Dechlorination... 

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. 

Reduction of sulfonyl halides to disulfides. Two laboratories 9 10 have reported the reduction of sulfonyl chlorides to disulfides by ISi(CH,), or ClSi(CH, ),-Nal in... 

Reduction of sulfonyl chlorides with Zn and acid yields first sulfinic acids and then thiophenols. 

Zinc salts of sulfinic acids are formed by reduction of sulfonyl chlorides by zinc and hot water. The zinc salts may be converted to sodium salts by the action of sodium carbonate. Over-all yields of the sodium salts of -toluenesulfinic acid and 2-dibenzofuransulfinic acid are 64-67%. Equally good results have been obtained by reduction of sulfonyl halides with aqueous sodium sulfite. Complete reduction to sulfhydryl compounds occurs with certain reducing agents (method 509),... 

The reduction of sulfonyl chlorides may lead to sulfinates [265-267], thiosulfonates [267], disulfides, and mercaptans depending on the conditions in the presence of alkylating agents [266], sulfones or sulfides are among the products. 

Several thiols occur naturally for example, skunk secretion contains 3-methyll-butanethiol and cut onions evolve 1-propanethiol, and the thiol group of the natural amino acid cysteine plays a vital role in the biochemistry of proteins and enzymes (see Introduction, p. 2). Primary and secondary thiols may be prepared from alkyl halides (RX) by reaction with excess sodium thiolate (SN2 nucleophilic substitution by HST) or via the Grignard reagent and reaction with sulfur. Tertiary thiols can be obtained in good yields by addition of hydrogen sulfide to a suitable alkene. Thiols can also be prepared by reduction of sulfonyl chlorides (Scheme l).la,2a... 

Alkali sulfites have proved valuable for reduction of sulfonyl chlorides in the anthraquinone series.530... 

General directions for reduction of sulfonyl chlorides to sulfinic acids 543 A mixture of the sulfonyl chloride (20 g), sodium sulfite nonahydrate (50 g), and crushed ice (100 g) is shaken until the chloride has dissolved (about 3 h) the mixture is tested for alkalinity from time to time and dilute sodium hydroxide solution is added as necessary to prevent evolution of sulfur dioxide, whilst cooling by ice is maintained. Finally the mixture is filtered and the sulfinic acid is precipitated from the filtrate by gradual addition of concentrated hydrochloric acid. Yields average 80-90 %. 

Reduction of sulfonyl chlorides and sulfoxides. Arenesulfonyl chlorides (and sodium arenesulfonates) are reduced to diaryl disulfides, whereas sulfoxides undergo... 

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