Sulfides, a-chloro

M-1 s-1 alkyl phenyl selenides, aryl bromides, vinyl bromides, a-chloro esters, a-thiophenyl esters 104-102M 1 s-1 alkyl chlorides, alkyl phenyl sulfides, a-chloro and a-thiophenyl ethers. 

When thionyl chloride is used, diaryl sulfoxides are usually the main products. Unsymmetrical diaryl sulfides can be obtained by treatment of an aromatic compound with an aryl sulfenyl chloride (ArSCl) in the presence of a trace amount of iron powder.Aromatic amines and phenols can be alkylthiolated (giving mostly ortho product) by treatment with an alkyl disulfide and a Lewis acid catalyst. With certain substrates (primary amines with a chloro group, or a group not replaceable by chloro, in the para position), treatment with S2CI2 and NaOH gives thiophenolate salts ... 

Lactam sulfonium salts bearing a dihydrothiopyran skeleton with a sulfonio bridgehead have been synthesized. Tricyclic benzothiazinium salts 87 were prepared by [4+2+]-polar cycloaddition of a thionium intermediate 99, generated from the corresponding a-chloro sulfide 98, in the presence of silver perchlorate in moderate to good yields (see Equation (28) and Table 17) <1997J(P1)309>. Cycloaddition with isoprene 41b gave adducts 87b and 87c as a... 

Many of the reactions of A-chloro- and A-bromo-imides are extremely violent or explosive. Those observed include A-chlorosuccinimide with aliphatic alcohols or benzylamine or hydrazine hydrate A-bromosuccimmidc with aniline, diallyl sulfide, or hydrazine hydrate or 3-nitro-A-bromophthalimide with tetrahydrofur-furyl alcohol l,3-dichloro-5,5-dimethyl-2,4-imidazolidindione with xylene (violent explosion). Individually indexed compounds are ... 

For a review of a-chloro sulfides, sec Dilworth McKervey Tetrahedron 1986, 42, 3731 3752. 

Macrocyclic lactones. Ireland and Brown1 have adapted the Eschenmoser contraction of sulfides to a synthesis of five- and six-membered lactones. An example is formulated in equation (1). A hydroxy thioamide is esterified to give a chloro ester, which is then treated in sequence with Nal and phosphine I. The inelhod can also be used for preparation of macrocyclic lactones under high-dilution... 

The use of free-radical reactions for this mode of ring formation has received rather more attention. The preparation of benzo[6 ]thiophenes by pyrolysis of styryl sulfoxides or styryl sulfides undoubtedly proceeds via formation of styrylthiyl radicals and their subsequent intramolecular substitution (Scheme 18a) (75CC704). An analogous example involving an amino radical is provided by the conversion of A-chloro-ZV-methylphenylethylamine to iV-methylindoline on treatment with iron(II) sulfate in concentrated sulfuric acid (Scheme 18b)(66TL2531>. 

Alkoxy ketones.8 In the presence of ISi(CH3)3 or (CH3)3SiOTf, silyl enol ethers react with a-chloro ethers to give (3-alkoxy ketones selectively. Evidently ISi(CH3)3 activates only the C—Cl bond. Similarly, the reaction of silyl enol ethers with a-chloro sulfides gives rise only to P-alkylthio ketones. 

Z.4.4.2 Summary of Uses of a-Chloro Sulfides in Organic Synthesis... 

The first method involves sulfur monochloride addition to alkenes forming an a-chloro- disulfide (1), which can be reduced with sodium sulfide or aluminum amalgam. Unfortunately this procedure suffers from three drawbacks (i) low yields are realized on reduction of the disulfide (ii) an excess of al-kene (2-3 equiv.) is required to produce good yields and (iii) the reactions occur poorly with acyclic molecules in general. ... 

A more promising method involves the use of arenethiosulfenyl chlorides. These reagents oxidize alkenes to a-chloro-p-disulfidearenes (i.e. 2) in high yields. The intermediates are then reduced by sodium sulfide and cyclized to thiiranes in good to moderate yield. Unfortunately these arenethiosulfenyl chlorides must be prepared fix>m arenethiols and sulfur dichloride nevertheless, the yields of acyclic adducts are reliably mo(lerate. In addition, the arene substituents may be changed to modify the nuckophil-icity and reducibility of the reagent. ... 

Silver salts are also utilized to perform nucleophilic additions to disulfide bonds to yield sulfenamides (146). If alkyl halides are treated with stoichiometric AgBF4 in dimethyl sulfoxide solvent (DMSO, solvent), the corresponding aldehydes/ ketones will form in good yields. This reaction is an alternative to the well-known Swern oxidation (147). In addition, silver can drive the formation of dialkylper-oxonium ions from alkyl halides, which then oxidizes sulfoxides or sulfides (148,149). In the presence of AgN03, sulfides can be oxidized into a-chloro sulfoxides by SO2CI2 (Fig. 36) (150). 

The decontamination efficacy of radioprotective agent aminoethylisothiourea and cystamine on rat skin against SM was comparable to standard decontaminants, such as alco-holate, clay, and Fuller s earth (Knezevic and Tadic, 1996). A mixture containing bovine hemoglobin, gelatin, and poi (a Hawaiian foodstuff) on the hydrolytic kinetics of the mustard simulants, 2-chloroethyl ethyl sulfide, 2-chloro-ethyl methyl sulfide and 2-bromoethyl phenyl sulfide, is reported. The kinetic mechanisms and rate constants were dependent upon the mixtures concentration and viscosity (Cemy and Cemy, 1997). 

Chlorodimethylsulfonium chloride (generated from chlorine and dimethyl sulfide) can be used in the same way for preparation of a-chloro ketones. 

Aldehydes and ketones can be generated from a-chloro sulfides with CuCl2-CuO in high yields [25], The copper promoters can be used both as reagents and as Lewis-acid activators in this reaction to generate the chloro sulfide in situ from a-thio ketones, and 29 is converted directly to 30 in 80 % yield (Sch. 8). The 2-phenylthio-tetrahydropyran 31 could be hydrolyzed to the 2-hydroxy derivative 32, and the bis-phenylthio derivative leads directly to the lactone [26],... 

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