Dithienyl Sulfide

The presence of an equivalent of potassium or sodium hydroxide is necessary to promote the substitution reaction of the 2-bromothiophene with cuprous oxide. 

The freshly precipitated cuprous oxide was dried at 110° before use. Commercial grades of cuprous oxide were found to give lower yields (ca. 35-40%) of the desired sulfide. Thecheckers dried cuprous oxide in a vacuum oven at 100° for 6 hours. 

2-Bromothiophene was supplied by Columbia Organic Chemicals, Inc. 2-Chloro- or 2-iodothiophenes may be used however, the former gives poorer yields of the sulfide. 

Nitrogen is passed through the system to provide an inert atmosphere, thereby preventing possible oxidation of the 2-thiophenethiol to the corresponding disulfide. 

Vigorous stirring helps to break up the thick sludge formed on addition of the reaction mixture to the acid and also serves to remove soluble inorganic salts. 

---

DITHIENYL SULFIDE, 50 75 1,3-Dithiolanes, 54, 37 Diynes, preparation, 50, 101 n-Dodecane, 53, 108 Double bond, exocyclic, selective hydrogenation, 53, 65 DURENE, I0D0—, 51, 94... 

DITHIENYL SULFIDE, 50, 75 Diynes, preparation, 50, 101 DURENE, IODO-, 51, 94... 

The submitters have also prepared 2,2 -dithienyl sulfide in 34% yield by condensation of 2-thiophenethiol with 2-bromothiophene in the presence of cuprous oxide in a quinoline-pyridine mixture. Challenger and Harrison6 have obtained 2,2 -dithienyl sulfide in 50-55% yield by treatment of 2-thienyl-magnesium bromide with excess sulfur. This sulfide may also be obtained in 20% yield by condensation of thiophene with sulfur monochloride, followed by pyrolysis of the resultant disulfide.7... 

Pyrolysis of 2,2 -dithienyl sulfide (312) at 500-600 °C under nitrogen and in the presence of hydrogen sulfide gives 244 [13] (Scheme 77). 

Dithienyl sulfides have been used for the synthesis of other isomeric dithienothiophenes, the former being obtained by the method of Fyodorov and Stoyanovich from thienyllithium and dithienyl disulfides. Dithienyl dsulfides were prepared from thiophene or 3-bromo-thiophene in high yields (Scheme 11). 

The authors also prepared four previously unknown isomers of dithienothiophene. Oxidation of 4-bromothiophene-3-thiol in aqueous KjFe(CN)s gave 4,4 -dibromo-3,3 -dithienyl disulfide (182) (90%), and 182 with 4-bromo-3-thienyllithium formed 4,4 -dibromo-3,3 -dithienyl sulfide (183) (83%). Ring closure of sulfide 183 furnish dithienothiophene (7) (20%) [Eq. (52)]. 

A 94% yield of 3,4 -dibromo-2,3 -dithienyl sulfide (184) was similarly achieved from 3-bromo-2-thienyllithium (180) and disulfide 182. Oxidative ring closure of the dilithium derivative of 184 gave dithienothiophene 8 in 29% yield [Eq. (53)]. 

Selective bromination of monobromo-substituted dithienyl sulfides with iV-bromosuccinimide afforded two more dithienothiophene isomers. From the reaction of 3-thienylIithium with disulfide 182 at —70°, 4-bromo-3,3 -dithienyl sulfide (185) was isolated. Bromination with 7 T-bromosuccinimide provided 2,4 -dibromo-3,3 -dithienyl sulfide (186) dilithiation of the latter followed by oxidative ring closure gave dithienothiophene 9 in 13% overall yield [Eq. (54)]. 

This synthetic process offers a route to the preparation of the isomeric dithienyl sulfides8 (2,3- and 3,3-) which cannot be prepared readily by any of the standard literature methods. Thus condensation of 2-thiophenethiol with 3-bromothiophene or 3-thiophenethiol with 2-bromothiophene gives 2,3 -dithienyl sulfide in 63.0 and 73.5% yields, respectively. Similarly, 3,3 -dithienyl sulfide is obtained in 48% yield. The method lias... 

In 1971, the first s5 thesis of 242 used transmetallation of 3-bromothiophene (5) then reaction with the electrophilic sulfur source (PhS02)2S. The resulting 3, 3 -dithienyl sulfide (248) was a,a -dilithiated and the carbon-carlxMi bmid made by oxidation with CuCl2 [95] (Scheme 60). 

The flash vacuum pyrolysis of the dithienodiazene (145), obtained by sulfide reduction of 4,4 -dinitro-3,3 -dithienyl, gave cyclobuta[c c ]dithiophene (146) <85CC880>. An oxiranocyclo-pentapyrrole undergoes a palladium(0)-catalyzed insertion of carbon dioxide to form a 1,3-dioxole <88JA6123>. 

---