Sulfonyl chlorides reduction with zinc

Thiophene-2-sulfonic acid is a strong acid, similar to benzenesulfonic acid. It forms a sulfonyl chloride with phosphoryl chloride which on reduction with zinc yields thiophene-2-sulfinic acid. 

Two sterically hindered /V-sulfonylated aminobomeols 42 were prepared from camphorquinone 11 and used after esterification for the formation of enolates which are alkylated or oxidized diastereoselectively (Sections D.1.1.1.3.2., D. 1.5.2.1., D. 1.5.2.3. and D.4.I.). The synthesis of these auxiliaries involves the reaction of camphorquinone 11 with 3,5-dimethylaniline to give the mono-imine by reaction with the sterically less hindered carbonyl group, followed by reduction with boranate and reaction with benzenesulfonyl chloride to give the exo.exo-product. or initial reduction with zinc/potassium hydroxide, then sulfonylation, and finally reduction with boranate to give the endo,endo-isomer21. 

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. 

Thiols can be prepared by the reduction of sulfonyl halides with LiAlHLj. UsualK the reaction is carried out on aromatic sulfonyl chlorides. Zinc and acetic acid, and... 

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]. 

The thioxanthone ring system comprises the nucleus for two of the more efficacious orally active antischitosomal drugs. One synthesis for these compounds starts with the chlorsulfonation of pora-chlorotoluene (21-1) to give the sulfonyl chloride (21-2). Treatment of the product with zinc in aqueous sulfuric acid leads to a reduction of the sulfonyl chloride to form the thiophenol (21-3). The key to the formation of this and related thioxanthones and xanthenes consists of the UUman reaction, which... 

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. 

Synthetically useful routes to dibenzo[c,e J[l,2]dithiins are normally based on cyclizations of biphenyI-2,2 -disulfonyl chlorides. A method applied successfully to the parent compound reduces the precursor with zinc in acetic acid to generate the bis thiol, which is then gently oxidized to the dithiin using iron(II) chloride (66HC(21-2)952). An alternative one-step reductive cyclization, which has been applied to the preparation of the 2,9- and 3,8-dinitro derivatives, involves reduction of the appropriate bis sulfonyl chlorides with hydriodic acid in acetic acid (68MI22600). Yet another reductive cyclization uses sodium sulfite followed by acidification, and these conditions lead to dibenzo[c,e][1,2]dithiin 5,5-dioxide. The first step of the reaction is reduction to the disodium salt of biphenyl-2,2 -disulfinic acid which, on acidification, forms the anhydride, i.e. dibenzo[c,e][l,2]dithiin 5,5,6-trioxide. This is not isolated, but is reduced by the medium to the 5,5-dioxide (77JOC3265). Derivatives of dibenzo[c,e] [1,2]dithiin in oxidation states other than those mentioned here are obtainable by appropriate oxidation or reduction reactions (see Section 2.26.3.1.4). 

Arylsulfonyl chlorides are reduced by zinc dust and sulfuric acid at 0° to give high yields of thiophenols Tin and hydrochloric acid and a mixture of phosphorus, potassium iodide, and phosphoric acid have also been used. Preliminary experiments with lithium aluminum hydride on both alkyl- and aryl-sulfonyl chlorides gave 45 50% yields of mercaptans. Halogen atoms on the benzene ring are stable during the reduction. ... 

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 present procedure is that of Adams and Ferretti. Another method is the reduction of 1,2-benzenedisulfonyl chloride with zinc powder. In a third method a 2-aminomercaptobenzene is diazotized and converted to an intermediate xanthate and then to the corresponding mercaptosulfonic acid. The latter can be converted to the dimercaptan either by (1) oxidation to a di-sulfonic acid, conversion to the disulfonyl chloride, and reduction to the dimercaptan, or (2) mild oxidation to the corresponding disulfide, conversion to the sulfonyl chloride disulfide, and reduction to the dimercaptan. 

Sulfinic acids are generally prepared by reduction of the readily available sulfonyl chlorides with zinc in neutral or basic aqueous solution.2 The reduction may also sometimes be achieved by treatment with tin(II) chloride or sodium sulfite (Scheme 1). Another route involves reaction of a Grignard reagent with sulfur dioxide (Scheme 1). 

Oxo-3-pyrazolin-4-sulfonic acids (Table XXXVI) are prepared by direct sulfonation738,745 with sulfuric acid and acetic anhydride or by chlorosulfonation with chlorosulfonic acid, followed by hydrolysis to the acid.1248,1249 The reaction of 2,3-dimethyl-l-phenyl-5-oxo-3-pyrazolin-4-sulfonyl chloride with urea forms a bis(5-oxo-2-pyrazolin-4-sulfonic acid) derivative,1249 the only such bis derivative reported. Reduction of the sulfonic acid chlorides with zinc and acid forms the corresponding mercapto compound.1249... 

Silicon compounds containing reactive aryl groups may be chlorosulfonated without loss of the silicon atom by the use of chlorosulfonic acid. Thus, tetraphenoxysilane 451 reacted with excess chlorosulfonic acid at 75-85 C (2j hours) to give the sulfonyl chloride 452. Subsequent reduction of 452 with zinc afforded 4-hydroxyphenylthiol 453 (72% yield, 99.6% purity) this provides an excellent synthetic route to this compound (Equation 140). ... 

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