Iodination benzo thiophene

Diiodobenzo[f ]thiophene is prepared by treating the bis(mercuric chloride) derivative with iodine. Benzo[ >]thiophenes having an iodine atom at the 4-, 5-, 6- and 7-positions are obtained in high yield from the appropriate diazonium salt by the usual replacement reactions. 

Iodination of 4 with molecular iodine in the presence of mercuric oxide formed the 3-iodo derivative (52JA4951 66CJC2283). Iodine in tetrahydro-furan oxidatively cyclized /3-(3-benzo[b]thienyl)-a-mercaptoacrylic acids rather than iodinating the thiophene ring [70JCS(C)2431]. 

Halogens react with benzo[ ]furan by an addition-elimination mechanism to give 2- and 3-substituted products (76JCS(P2)266). Treatment of benzo[ ]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[ ]thiophene is treated with chlorine in the presence of 1 equivalent of iodine (80JOC2151). 

Benzo(6]thiophene halogenation, 57, 294 iodination, 59, 254 resonance energy, 56, 352 Ru, Ir complexes, 58, 150 Benzo[6]thiophene, 3-benzoyl-, reaction with hydrazine, 56, 128 Benzo[l)]thiophene, 3-bromo-, chlorination, 57, 293 Benzo[6]thiophene, 4-fluoro-, 60, 17 Benzo[/>)thiophene, 4,5,6,7-tetrafluoro-2,3-dihydro-2-methyl-, 60, 28 Benzo(e]thiophenes, resonance energy,... 

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. 

In the context of preparing benzothienyloxy phenylpropanamines as inhibitors of serotonin and norepinephrine uptake, a group from Eli Lilly and Company has developed a two-step synthesis of benzo[fo]thiophenes (Scheme 6.193) [354]. Thus, a 2-mercapto-3-phenylpropenoic acid derivative was cyclized with iodine in 1,2-dimethoxyethane at 120 °C to give 5-fluoro-4-methoxybenzothiophene-2-carboxylic acid in 67% yield. Decarboxylation under strongly basic conditions involving 1,8-di-azabicyclo[5.4.0]undec-7-ene (DBU) as base in N,N-dimethylacetamide (DMA) as... 

Iodobenzothiophene 15 was prepared by iodination of 2-trifluoroacetylamino-benzo[6]thiophene (14), although the same reaction with the regioisomeric 3-trifluoroacetylammobenzo[b]thiophene gave only unidentified polymeric material [13]. In another case, thienylpyridine 16 could be either brominated [14], or iodinated to give 17 [15,16]. 

Controlled chlorination of benzo[6]thiophene gives 3-chlorobenzo[6]thiophene similarly, the 3-bromo derivative can also be obtained (70AHC(ll)l77). Excess halogen leads to the 2,3-dihalo derivative. Iodination in the presence of HgO gives 3-iodobenzo[6]thiophene. 

Friedel-Crafts acylation of benzo[6]thiophene using a variety of catalysts gives a mixture of isomers, in which the 3-isomer predominates in a ratio of about 4 1. The milder catalysts, such as boron trifluoride etherate or iodine, give the best yields, since there is less destruction of the ring. While aluminum chloride gives the 3-isomer in about 9 1 ratio over the 2-isomer, the total yield is only 38%, as contrasted to yields over 70% with milder catalysts (70AHC(11)177). 

Treatment of the disulfide (90) with iodine in dioxane under various conditions gives low yields of 5,6-dimethoxy-2,3-dihydrobenzo[6]-thiophene.346 At high temperatures in ethylene glycol a mixture of this compound and the dehydrogenated product, 5,6-dim ethoxy-benzo[6]thiophene, is obtained. These observations demonstrate the importance of the double bond in the side chain of the mercapto-acrylic acids (88) in promoting their cyclization. 

Photoirradiation of 158e in the presence of iodine affords the benzo[6]naphtho[2,l-d]thiophene (159) 158a-d similarly give the appropriate methyl-substituted compounds.465 With ethyl diazo-... 

Iodination of benzo[6]thiophene in benzene in the presence of mercuric oxide gives exclusively 3-iodobenzo[6]thiophene.411-413... 

Halobenzo[6]thiophenes are readily obtained from the corresponding 2-benzo[6]thienyllithium by the reactions described in Section VII. 2-Iodo-3-methylbenzo[6]thiophene is obtained by treatment of the 2-acetoxymercury compound with iodine.496... 

Benzo[6]thienylethylenes are readily obtained by elimination of water from the appropriate alcohol. For example, 3-vinylbenzo[6]-thiophene is conveniently prepared by heating l-(3-benzo[6]thienyl)-ethanol with potassium hydrogen sulfate469,471 or by heating 2-(3-benzo[6]thienyl)ethanol with molten alkali.470 2-Vinylbenzo[fe]thio-phene is obtained by pyrolyzing the acetate of l-(2-benzo[6]thienyl)-ethanol.466,620 Other benzo[6]thiophene alcohols have been dehydrated by heating them with oxalic acid,483 iodine,358,465,467,528 or potassium hydrogen sulfate,465,467 or alone.349,485... 

The thermal reaction, catalysed by Cu(acac)2, of thiobenzophenones with ylides coming from bis arylsulphonyl methane is also likely to proceed by an initial transylidation the main products are here benzo[c]thiophenes [35,36], The car-banionic carbon of iodonium ylides is devoid of nucleophilic character, yet PhI=C(S02Ph)2 gave, with iodomethane, the methylated iododisulphone MeC(I)(S02Ph)2 (68%). This reaction, performed at room temperature without any catalyst, is probably the result of a nucleophilic attack from iodine of iodomethane to iodine of the ylide [37]. 

Dinitro-6-phenyliodonium phenolate (146) is a stable iodonium zwitterion484. It reacts under photolytic conditions with various alkenes, alkynes and aromatic compounds to afford 2,3-dihydrobenzo[ ]furans, benzo[6]furans and 6-aryl-2,4-dinitrophenols. The mechanism involves hypervalent iodine compounds (iodinanes, 147) and is illustrated for the reaction with an aromatic compound (equation 127). Compounds 148 are the major products when ArH = PhH, PhOCH3 or 1,4-dimethoxybenzene. With furan and thiophene, 149 is the principal product. The reaction does not proceed with chlorobenzene and nitrobenzene. 

Iodination of benzo[6]thiophene in benzene in the presence of mercury(II) oxide gives exclusively 3-iodobenzo[6]thiophene, and 2-iodobenzo[ ]thiophene is formed exclusively by reaction of iodine on the 2-lithio derivative (Section 3.14.3.9). 2,3-... 

A flexible and convergent access to 2,3-disubstituted benzo[b]thiophenes has been developed (Scheme 22). The most concise approach involves a sequential coupling of an o-bromoiodobenzene with benzylthiol and zinc acetylides leading to the adduct 78. Treatment with iodine followed by an iodine/magnesium exchange and acylation provides the polyfunctional benzofuran derivatives. a... 

Like the 1,1-dioxides, the parent benzo[b]thiopbenes will also undergo photoaddition of alkenes to give cyclobutane derivatives. In the sensitized addition of 1,2-dichloroethene, the four possible stereoisomers 16 are formed which one predominates depends on the stereochemistry of the starting alkene.163 Those isomers which can undergo trans elimination of HC1 will react with base to give the cyclobutene derivative (cf. 14). Bcnzo[fc]thiophene will add photochemically across the C=N bond of 2,5-diphenyl-1,3,4-oxadiazole in the presence of a sensitizer, to give the trans-fused adduct 17 [R = R2 = H (trans)].164 Sensitized addition to 2- or 3-methylbenzo-[b]thiophene gives the more usual cis-fused products 17 [R1 = H, R2 = Me (cis)] and 17 [R1 = Me, R2 = H (cis)] respectively. However, with 3-methyl-benzofb] thiophene in the presence of iodine, the orientation of addition is reversed and the cis adduct 18 is obtained. 3-Pyrrolidinobenzo[b]thiophene... 

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