Thiophen tetrabromo

Vaitiekunas, A., and F. F. Nord Tetrabromo-Thiophene from 2-Bromothio-... 

Zwanenburg and Wynberg also proposed another route to the thienothiophene (112). 2,5-Dibromo-3,4-bisbromomethylthiophene (116) was cyclized with sodium sulfide to give 4,6-dibromo-l f,3/f-thieno[3,4-c]thiophene (117) in 60% yield 117 was then reduced to thienothiophene (112). l,3,7,9-Tetrabromo-4i/,67f,10.H, 12ff-dithieno-[3,4 C 3, 4 -/i][l,6]dithiecin (118) (18%) was also formed during the ring closure. Oxidation of thienothiophene (117) followed by reduction by zinc in acetic acid gave l/f,3H-thieno[3,4-c]thiophene 2,2-dioxide (119). ... 

Biedermann and Jacobson, who first prepared thieno[2,3-6]-thiophene (1) in 1886, characterized it as a 2,3,4,5-tetrabromo derivative with m.p. 172°. Later Capelle reported the isolation of a dibromo derivative of thienothiophene 1 with m.p. 122.5°, which was shown by Challenger and Harrison to be 2,3,5-tribromothieno[2,3-6]thiophene (m.p. 123°-124°). Capelle also obtained a tetrabromide, m.p. 223°, by bromination of the product of reaction of acetylene with sulfur. The tetrabromide seems to be identical with that prepared from the product of reaction of methane, acetylene, and hydrogen sulfide, m.p. 229°-230°, and is evidently 2,3,5,6-tetrabromothieno[3,2-6j-thiophene. ... 

Treatment of 2-methoxy-5-methylthiophene with NBS gave a 4 1 mixture of 3- and 4-bromo products, with some 3,4-dibromination also evident. The dibromination became more significant when 2 mol of NBS were used. Similarly 2-methoxythiophene gave the 3,5-dibromo derivative (84BAU1447). Bromination of 2-(2 -thienyl)-thiophenes (21) and 2-(3 -thienyl)-thiophenes gave the 5- and 2-bromo products in high yield [79CS157 91H(32)1805]. With four molar equivalents of bromine in acetic acid the tetrabromo derivative (22) was obtained in 97% yield. Reduction removed the 5,5 -bromines preferentially [91H(32)1805] (Scheme 9). This... 

Further bromination of 3,4,6-tribromo-5-hydroxybenzo[6]thio-phene affords the 2,3,4,6-tetrabromo derivative in the absence of acetate ion, and 3,4,4,6-tetrabromo-4,5-dihydrobenzo[6]thiophen-5-one in the presence of acetate ion. 421 On treatment of 3,4-dibromo-, 4,6-dibromo-, 3,4,6-tribromo-, or 2,3,4,6-tetrabromo-5-hydroxybenzo-[6]thiophene with nitric acid in acetic acid, the corresponding unstable orange crystalline 4-bromo-4-nitro-4,5-dihydrobenzo[6]thio-phen-5-one is obtained.152,421 Hence, once both positions ortho to the hydroxyl group in 5-hydroxybenzo[6]thiophene are occupied by bromine, the properties of these compounds are analogous to the properties of l-bromo-2-naphthol which, on bromination in acetic acid in the presence of acetate ion, affords l,l-dibromo-l,2-dihydro-naphthalen-2-one whereas, in its absence, it affords l,6-dibromo-2-naphthol.616 The behavior of l-bromo-2-naphthol and its derivatives on nitration is similar to that of 4,0-dibromo-5-hydroxybenzo[6]thio-phene and its derivatives.162,616... 

On heating a solution of 3,4-dibromo-4-nitro-4,5-dihydrobenzo[6]-thiophen-5-one (Section VI, 1,4) in benzene, 3-bromobenzo[6]thio-phene-4,5-quinone is obtained.497 The unstable product readily condenses with ethyl cyanoacetate in the presence of base to give 3-bromo-7-(carbethoxy cyanomethyl)benzo[6]thiophene-4,5-quinone. The 4-bromo-4-nitro-4,5-dihydrobenzo[6]thiophen-5-ones prepared by nitration of 3,4-dibromo-,152,421 4,6-dibromo-,152 3,4,6-tri-bromo-,421 and 2,3,4,6-tetrabromo-5-hydroxybenzo[6]thiophene421 decompose similarly to the corresponding 4,5-quinones on being boiled in benzene. 

Figure 17. Expanded computer plot of the molecular ion region of Tetrabromo-thiophene from mass 388 to 407. Peaks at 391, 393, and 405 are caused by PFK. The peak at m/e 400 is slightly saturated.

In the same way that benzocyclobutene (89) may be prepared by desulfonylation of l,3-dihydrobenzo[c]thiophene 2,2-dioxide, the following compounds may also be prepared 3,4,5,6-tetrabromo-benzocyclobutene 95 naphtho[6]cyclobutene (92a) (>60% yield) 96... 

The dimethyl ester of 3,4-dimethyl-2,5-thiophenedicarboxylic acid (377) was converted into 4,6-dicyano-l//,3//-thieno[3,4-c]thiophene (379) via the known intermediate (378) <64JOCl9l9>. Compound (379) was tetrabrominated photochemically, leading to 4,6-dicyano-l,l,3,3-tetrabromo-1 //,3//-thieno[3,4-c]thiophene (380), which lost bromine upon heating in DMF, or with sodium iodide in acetone to give l,3-dibromo-4,6-dicyanothieno[3,4-c]thiophene (164) (94JOC2223) (Scheme 33). 

As mentioned above, thieno[3,4-c]thiophene is most difficult to synthesize compared to all other isomeric thienothiophenes. A few of its derivatives are known tetraphenyl- (67JA3639, 73JA2558, 73JA2561), tetrakis(alkylthio)- (85JA5801), tetra(2-thienyl)- [42], tetrabromo-, l,3-dibromo-4,6-dicyano-, l,3-dibromo-4,5-bis (methoxycarbonyl)- (94JOC2223), l,4-bis(rert-butylthio)-3,6-diphenyl- and 3,6-di (2-thienyl)thieno[3,4-c]thiophenes (98JOC163). 

The reaction of 33 with a tetrabromo derivative of thiophene with a bicyclo spiranic structure afforded 36 in 86% yield. The two orthogonal 7r-conjugated systems in 36 may function as a self-contained electronic device (see Section 14.2.2.2). 

Cycloheptatriene.—Synthesis. Details have been published on the preparation of specifically substituted cycloheptatrienes by the cycloadditon of cyclopropenes to thiophene-1,1-dioxides followed by expulsion of S02. Substituted tropones have been obtained from the furan adducts of bromo-oxyallyl cations e.g. treatment of l,l,3,3-tetrabromo-4-methylpentan-2-one with di-iron nonacarbonyl in the presence of furan gave adduct (141) which was converted into a-thujaplicin (142). Acid hydrolysis of the norbornyl ketal (143) followed by warming to 70 "C gave 7,7-dimethyl-cycloheptatriene. ... 

Direct bromination by bromine in acetic acid or in chloroform allows the synthesis of 2-bromo-, 2,5-dibromo-, 2,3,5-tribromo- and 2,3,4,5-tetrabromo-thiophenes [104, 105]. Microwave-assisted mono-, di-, tri- and tetrabrominations of thiophene have been described [83]. An example of 2,4,5-tribromination of 3-hexylthiophene using bromine in acetic acid is shown in Scheme 68 [106]. 

Thieno[3,2-b]thiophenes carrying either four phenyl (75) or four 2-thienyl groups (76) were constructed using Suzuki cross-couplings of tetrabromo-TT (74) with phenyl- or thiophene-2-boronic acids [39] Scheme 18). 

Acetyl thiophene - 657 Acetyl dl tryptophan - 251 Acetyl dl valine - 251 Acetylene tetrabromide (see Tetrabromo-ethane)... 

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