Thio thiophenes

Few examples of cycloaddition reactions of the type [2 + 2+1] where fluorosubstituted compounds are participating are known. Perfluoro-2-butyne and elemental sulfur react to give tetrakis(trifluoromethyl)thio-phene [84JFC(25)47]. Analogously, a mixture of tetrakis(trifluoromethyl-thio)thiophene, 2,3,4-tris(trifluoromethylthio)-5-trifluoromethylthiophene, and tetrakis(trifluoromethylthio)-l,2-dithiin was obtained from bis(triflu-oromethylthio)acetylene and sulfur at 170°C (85JHC1631) (Scheme 91). 

A recently study has shown that polymerization of (2,5-dibromo-3-butyl-thio)thiophene using Mg, followed by Ni(dppp)Cl2 in refluxing anisole leads to an apparently regioregular poly[3-(butylthio)thiophene] that has a molecular weight of 5K. This polymer in contrast to the above Rieke polymer [190] is soluble in CHCI3, CCI4, toluene, benzene, THF, and CS2 [191]... 

Some more exotic electrophilic reagents have been applied successfully to thiophens. Thus, pentafluorobenzenesulphenyl chloride reacts with thiophen in ether in the presence of catalytic amounts of SnCl to give 2-pentafluorophenyl-thio-thiophen. Thiophen and 2-methylthiophen give trifiuoromethylthio-derivatives with trifluoromethanesulphenyl chloride in chloroform in the presence of pyridine. Electron-deficient aromatics such as 2,5-bis(trifluoromethylthio)-thiophen react with trifluoromethanesulphenyl chloride, in the presence of trifluoromethanesulphonic acid as catalyst, to give mainly the 3-chloro-derivative. Fluorinated immonium salts (103), obtained by the action of boron trifluoride on a-fluorinated amines, can be used for fluorinated acylation of... 

THIOPHENE AND THIOPHENE DERIVATIVES] (Vol 24) Poly(thio-l,4-phenylene) [25212-74-2]... 

Halogens react with benzo[6]furan by an addition-elimination mechanism to give 2- and 3-substituted products (76JCS(P2)266). Treatment of benzo[6]thiophene with chlorine or bromine in acetic acid gives predominantly 3-substituted products (71JCS(B)79). 2,2,3,3,4,5,6,7-Octachloro-2,3-dihydrobenzothiophene is obtained when benzo[6]thio-phene is treated with chlorine in the presence of 1 mole of iodine (80JOC2l5l). 

Rates of debromination of bromonitro-thiophenes and -selenophenes with sodium thio-phenoxide and sodium selenophenoxide have been studied. Selenophene compounds were about four times more reactive than the corresponding thiophene derivatives. The rate ratio was not significantly different whether attack was occurring at the a- or /3-position. As in benzenoid chemistry, numerous nucleophilic displacement reactions are found to be copper catalyzed. Illustrative of these reactions is the displacement of bromide from 3-bromothiophene-2-carboxylic acid and 3-bromothiophene-4-carboxylic acid by active methylene compounds (e.g. AcCH2C02Et) in the presence of copper and sodium ethoxide (Scheme 77) (75JCS(P1)1390). 

The introduction of the cheap and commercially available N,N-dimethylformamide, instead of A-methylformanilide in the POCI3 catalyzed Vilsmeier formylation of thiophene, has made 2-thio-... 

Campaigne et al. have used 3-thenyl bromide obtained by benzoyl peroxide-catalyzed, side-chain bromination of 3-methylthiophene with A -bromosuccinimide, as a starting material for 3-substituted thiophenes. - 22 3-Methylthiophene is now prepared commercially from itaconic acid. The reactive halogen in 3-thenyl bromide could be directly reacted with a variety of nucleophiles, such as cyanide, or malonate, to give more complex 3-substituted compounds. 3-Thenyl bromide was converted by the Sommelet reaction to 3-thio-phenealdehyde which, with silver oxide, was oxidized to 3-thio-... 

The position of substitution in disubstituted thiophenes can, in most cases, easily be deduced from the directing effect of each substituent. Thus with a - -M-substituent in the 2-position and a —M-substituent in the 5-position, both substituents direct the entering group to the 3-position as is exemplified by the nitration of methyl 2-bromo-5-thiophenecarboxylate to methyl 2-bromo-3-nitro-5-thio-phenecarboxylate (109) or in the chlororaethylation of methyl 2-methyl-5-thiophenecarboxylate to methyl 2-methyl-3-chloromethyl-5-thiophenecarboxylate (110). °... 

Competitive metalation of thiophene and 2-methylthiothiophene with a deficiency of n-butyllithium gave only 2-methylthio-5-thio-phenecarboxylic acid, showing the activating effect of the methylthio group. ... 

The thiophene analog of chloramphenicol (255) has been synthesized,as also have been similar structures. The antibacterial activity of all was much lower than that of the natural antibiotic. The thioamide of 2-thenoic acid has been prepared in a study of potential antitubercular compounds. It did not surpass thioisonico-tinamide in antitubercular activity. The thiosemicarbazones of thio-phenealdehydes and ketones (cf. Section VII,D) show high activity against Mycobacterium tuberculosis, but are very toxic. The thiosemi-carbazone of 4-(2-thienyl)-3-buten-2-one has been reported to be capable of completely inhibiting the in vitro growth of M. tuberculosis even in relatively low concentrations. ... 

Fusion of an additional heterocyclic ring onto a benzodiazepine is well known to considerably increase potency. This increase in potency is apparently maintained when the benzene ring is replaced by thiophene. Thiophene aminoketone 161 is converted to the benzodiazepine analogue 164 via chloroacetamide 162 and then glycine derivative 163 by the same sequence as that used in the benzene series. Treatment of the product 164 with phosphorus pentasulfide gives the thio-amide 165 reaction of that intermediate with hydrazine leads to the amino amidine 166. Conden-... 

D) Preparation of 4-[1 -Methyl-Piperidyl-(4 )]-9,10-Dihydro-4H-Benzol4,5]Cyciohepta[1,2-b] Thiophen-(4)-ol 0.94 g of magnesium filings which have been activated with iodine are covered with a layer of absolute tetrahydrofuran and etched with a few drops of ethylene bromide. A solution of 5.0 g of 1-methyl-4-chloropiperidine in 5 ml of tetrahydrofuran is then added dropwise and boiling then effected for a further hour under reflux. After cooling to room temperature, the solution of 4.5 g of 9,lO-dihydro-4H-benzo[4,5] cyclohepta[1,2-b] thio-phen-(4)-one in 5 ml of tetrahydrofuran is added dropwise. 

Intramolecular palladium catalyzed thio-enolate S-arylation has been used in a route to a set of fused benzo[ ]thiophenes, as illustrated by the conversion of the substrate 10 into the product 11 <06T11513>. 

Substituted derivatives of l-(tetrahydrobenzo[b]thiophen-2-yl-3-carboxylate)-5-phenyl-6-thio-l,2,4-triazin-4-one have been synthesized by heterocyclization reactions of different hydrazones obtained from 2-amino-tetrahydrobenzo[b]thiophene-3-carboxylate with phenyl isothiocyanate <00PS275>. Reaction of 5-methyl isothiosemicarbazide with a-amino acid vicinal tricarbonyl reactive substrates 1 and 2 yields 1,2,4-triazine substituted a-amino acids, as an equimolar mixture of regioisomers 3a/3b and 4a /4b, respectively <00JCS(P1)299>. 

Thus, many polymers with different conductivity were synthesized. To cite a few, these are polythiophene [158], 3-methylthiophene [159], polymers of 3-thiophene-acetic acid and methyl 3-thiophene-acetate [160], poly(2,5-thienylenevinylene) [161], poly(benzo[h]-thiophene) [162], poly(naphto[2,3-c]thio-phene) [163], poly(dithieno[3,2-h 2, 3 -fii]-thiophene) [164], poly(3- -hexylthiophene)... 

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