Thiophene-2-thiol

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. 

It was speculated that the process leading to the formation of the pentathiepin ring involved initial formation of be n zo [//] thiophene-2-thiol 117, which then reacted further in its thiolate anion form with the sulfur present in excess, and the growing sulfur chain so obtained finally attacked the neighboring 3-position of the thiophene ring, thus producing the pentathiepin 116 (Scheme 23) <2002JOC6220>. 

Neither the IR nor the H NMR spectra of benzo[3]thiophene-2-thiol shows any sign of the thio-keto isomer, which indicates that this substance exists essentially completely in the ene-thiol form. The reversible UV spectral change that this substance undergoes, from Amax = 275nm in 0.1 M HCl to Amax = 305nm in 0.1 M NaOH, may therefore be attributed to ionization of the enol to its enolate ion (Scheme 22) <2002JA9189>. 

Thienylthioethanols were obtained in high yields by the reaction of thiophen-2-thiols with ethylene oxide.The reaction of 2,4-dinitro-3-bromothiophen with sodium dimethylthiocarbamate or sodium t-butyl-trithiocarbonate yielded (142). Decomposition of (142b) in glacial acetic acid led to a mixture of (143) and (144) in moderate yield. The reaction of thiophen-3,4-dithiol with phosgene chloride, followed by nitration, gave (145). The reaction of thiophen-2-thiol with p-(methylsulphonyl)bromo-benzene was used for the preparation of 2-thienyl p-(methylsulphonyl)phenyl sulphide. 

Benzo[i>]thiophene-2-thiol reacts with pyrrolidine or morpholine, to give 2-pyrrolidino- or 2-morpholinobenzo[6]thiophene ( 80%).558... 

A mixture of thiophene and isomeric thienothiophenes (total yield of 85%) was prepared by the gas-phase reaction of dimethyl sulfide, diethyl disulfide, diethyl trisulfide and diethyl tetrasulfide with acetylene (89ZOR2588). It was also found that gaseous allyl 2-thienyl sulfide is transformed into a mixture of thiophene-2-thiol, bis(2-thienyl) sulfide and 2-methylthieno[2,3-i]thiophene at 350-410 °C in the presence of acetylene, the reaction gives these products along with thieno[2,3-i]thiophene (91KGS1312). Thermolysis (at 540 °C) of a mixture of di(prop-l-enyl) sulfide and 2-chloro(or bromo)thiophene affords a mixture of thieno[2,3-Z ]thiophene and thieno[3,2- )]thiophene (91ZOR354). 

An intermediate for the antiglaucoma drug dorzolamide was synthesized in 67% ee through asymmetric conjugate addition of thiophene-2-thiol to E)-3-crotonoyloxazolidin-2-one catalyzed by Sc(OTf)3 and Ph-pybox [126]. In addition, this catalytic system was proved to be successful in the Michael addition of thiophenol to the previous substrate (66% ee). 

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