Thiophenes, 2,3-, 2,4-, 3,4-dichloro

Benzo[b]thiophene-2-carboxylic acid, 3,4-dichloro-5-methoxy-synthesis, 4, 870... 

Thiophene, 3,5-di-t-butyl-2-methyl-sulfonation, 4, 764 Thiophene, 2,4-dicarboxy-synthesis, 4, 870 Thiophene, 2,3-dichloro-synthesis, 4, 933 Thiophene, 2,5-dichloro-synthesis, 4, 933 Thiophene, 3,4-dichloro-... 

Dichlorothiophene can also be used for the synthesis of 3-substituted thiophenes, since it can be smoothly acylated and chloro-methylated in the 3-position, and the halogens can then be readily removed at the appropriate stage. 3-Thenylsuccinic acid (28) has thus been obtained by treating 2,6-dichloro-3-thenylsuccinic acid with sodium amalgam. 2-Bromo-3-thenylbromide can be utilized in a similar way. ... 

Dichloro thiophene 1,1-dioxide (168) is stable and of particular interest in the Diels-Alder reactions . Thus, when 168 is treated with cyclopentadiene in acetone, adducts... 

Reaction of a dihalide with sodium sulfide is perhaps the most direct way of creating a sulfur bridge it has, for example, been used to synthesize the thiophene (8) from a dichloro-substituted precursor (9).9... 

Most reactive metabolites produced by CYP metabolic activation are electrophilic in nature, which means that they can react easily with the nucleophiles present in the protein side chains. Several functional groups are recurrent structural features in M Bis. These groups have been reviewed by Fontana et al. [26] and can be summarized as follows terminal (co or co — 1) acetylenes, olefins, furans and thiophenes, epoxides, dichloro- and trichloroethylenes, secondary amines, benzodioxoles (methylenediox-yphenyl, MDP), conjugated structures, hydrazines, isothiocyanates, thioamides, dithiocarbamates and, in general, Michael acceptors (Scheme 11.1). 

The tropone ring of cyclohepta[c]thiophen-6-one reacts preferentially at the C=C bond, instead of at the carbonyl group, with both dichloro- and dibromocarbene to give mono- and bis-adducts in relatively low yields (5-40%) [60]. Benzoquinones produce anfi-bis-insertion adducts in their reaction with chloroform (95%), or bromoform (57%), under basic conditions [29]. 

Ultraviolet absorption spectra of thiophene derivatives were recorded using isooctane as a solvent (8). An apparent hypsochromic effect caused by the second nitro group in 2,5-dichloro-3,4-dinitro-thiophene was noticed. 

EINECS 203-468-6, see Ethylenediamine EINECS 203-470-7, see Allyl alcohol EINECS 203-472-8, see Chloroacetaldehyde EINECS 203-481-7, see Methyl formate EINECS 203-523-4, see 2-Methylpentane EINECS 203-528-1, see 2-Pentanone EINECS 203-544-9, see 1-Nitropropane EINECS 203-545-4, see Vinyl acetate EINECS 203-548-0, see 2,4-Dimethylpentane EINECS 203-550-1, see 4-Methyl-2-pentanone EINECS 203-558-5, see Diisopropylamine EINECS 203-560-6, see Isopropyl ether EINECS 203-561-1, see Isopropyl acetate EINECS 203-564-8, see Acetic anhydride EINECS 203-571-6, see Maleic anhydride EINECS 203-576-3, see m-Xylene EINECS 203-598-3, see Bis(2-chloroisopropyl) ether EINECS 203-604-4, see 1,3,5-Trimethylbenzene EINECS 203-608-6, see 1,3,5-Trichlorobenzene EINECS 203-620-1, see Diisobutyl ketone EINECS 203-621-7, see sec-Hexyl acetate EINECS 203-623-8, see Bromobenzene EINECS 203-624-3, see Methylcyclohexane EINECS 203-625-9, see Toluene EINECS 203-628-5, see Chlorobenzene EINECS 203-630-6, see Cyclohexanol EINECS 203-632-7, see Phenol EINECS 203-686-1, see Propyl acetate EINECS 203-692-4, see Pentane EINECS 203-694-5, see 1-Pentene EINECS 203-695-0, see cis-2-Pentene EINECS 203-699-2, see Butylamine EINECS 203-713-7, see Methyl cellosolve EINECS 203-714-2, see Methylal EINECS 203-716-3, see Diethylamine EINECS 203-721-0, see Ethyl formate EINECS 203-726-8, see Tetrahydrofuran EINECS 203-729-4, see Thiophene EINECS 203-767-1, see 2-Heptanone EINECS 203-772-9, see Methyl cellosolve acetate EINECS 203-777-6, see Hexane EINECS 203-799-6, see 2-Chloroethyl vinyl ether EINECS 203-804-1, see 2-Ethoxyethanol EINECS 203-806-2, see Cyclohexane EINECS 203-807-8, see Cyclohexene EINECS 203-809-9, see Pyridine EINECS 203-815-1, see Morpholine EINECS 203-839-2, see 2-Ethoxyethyl acetate EINECS 203-870-1, see Bis(2-chloroethyl) ether EINECS 203-892-1, see Octane EINECS 203-893-7, see 1-Octene EINECS 203-905-0, see 2-Butoxyethanol EINECS 203-913-4, see Nonane EINECS 203-920-2, see Bis(2-chloroethoxy)methane EINECS 203-967-9, see Dodecane EINECS 204-066-3, see 2-Methylpropene EINECS 204-112-2, see Triphenyl phosphate EINECS 204-211-0, see Bis(2-ethylhexyl) phthalate EINECS 204-258-7, see l,3-Dichloro-5,5-dimethylhydantoin... 

A member of the class has been prepared from TeCl4 and 3,4-dihthio-2,5-dichloro-thiophene. " ... 

Reaction of Dichloro Ethers ivith Allylbenzo bi thiophenes... 

The synthesis of cycloproparenes resulting from formal fusion of a cyclopropene to furan and thiophene has been attempted with limited success. Reaction of the dichloro-oxabicyclohexane 180 (X = O) " afforded a cyclopropene 181 which ring-opened to a vinylcatbene 182, but the cycloproparene 183 was not produced. Similarly, the thia-analogue 180 (X = S) could not be converted to 184. The intermediate cyclopropenes and/or vinylcarbenes have been trapped. A cyclopropathiophene derivative 186 was generated, however, from 185. Although it was not isolable, it afforded a bis-adduct 187 when it was produced in the presence of isobenzofuran (45)." ... 

In 1972 Wright prepared 3-chlorothieno[3,2-6]thiophene-2-carbonyl chloride (94) in 11-13% yield by heating 3-(2-thienyl)acrylic acid, thionyl chloride, and pyridine, a method of synthesis of benzo[6]-thiophene-2-carbonyl chloride derivatives. " Methyl 3,5-dichloro-thieno[3,2-6]thiophene-2-carboxylate (95) and methyl 2-chloro-3-(5-chloro-2-thienyl)acrylate were also isolated. When fte reaction was carried out in refluxing toluene or chlorobenzene, the acid chloride (94)... 

Similarly, 3-(3-selenienyl)acrylic acid yields 30-40% 3,5-dichloro-selenopheno[2,3-6]thiophene-2-carbonyl chloride (103) and 15% 2-chloro-3-(2,4,5-trichloro-3-selenienyl)acryloyl chloride, together with other products [Eq. (33)]. (Experimental details for the 3-(3-furyl)and 3-(3-selenienyl)acrylic acid reactions were not given in ref. 83). 

Methods of synthesis of 3-chloro- and 3,4-dichloro-thiophenes have usually involved tedious procedures in which tri- and tetra-chloro derivatives are dechlorinated by reductive or other methods. Gthanolic potassium hydroxide converted 2,3,4,5-tetrachlorothiophene into a 50 50 mixture of 2,4- and 3,4-dichlorothiophenes direct heating of the same tetrachloro substrate gave a mixture of 2,3- and 2,4-dichloro isomers (48JA1158). 3,4,5-Trichlorothiophene was readily prepared by the reaction of 1,1,2,3-tetrachloro-l,3-butadiene with sulfur (82JOU348). 

Cross-coupling reactions between organoboranes and heteroaryl halides are effectively catalyzed by Pd(0) in the presence of a base. Couplings in simple pyrimidines are illustrated by the reaction between 2-chloropyrimidine and 2- or 3-thiophene- and selenophene-boronic acids which give the corresponding 2-substituted pyrimidines (921) (Scheme 72). In 2,4-dichloro- or 2,4-dibromo-pyrimidine it is the 4-halo substituent which is the more reactive. 

Chlorine and bromine react with thiophene to give successively the halogenation products shown (70-73). The bromination can be interrupted at the intermediate stages monochloro and dichloro derivatives have been obtained preparatively by chlorination with MeCONHCl. Addition products are also formed during chlorination prolonged action (with Cl2-I2) gives the dihydrothiophene derivative (74 Z = S). Iodination (I2-HgO) results in mono- and di-iodothiophenes (70) and (71) (X = I) only. Substituted compounds are halogenated as expected, e.g. (75). 

A new synthetic route to alkyl-substituted quinones has relied on the photochemical reaction of 2,3-dichloro-l,4-naphthoquinone with a thiophene derivative (77CL851). Irradiation of a benzene solution of the quinone and thiophene by a high pressure mercury lamp gave photoadduct (295) in 56% yield. Desulfurization of this compound over Raney nickel (W-7) gave the 2-butyl-1,4-naphthoquinone derivative (296 Scheme 62). Alkyl-substituted quinones such as coenzyme Q and vitamin K, compounds of important biological activity, could possibly be prepared through such methodology. 

Sulfonylations under Friedel-Crafts conditions (A1C13) are known in the thiophene series. Thus 2,5-dichlorothiophene with benzenesulfonyl chloride gives phenyl 2,5-dichloro-3-thienyl sulfone (63AHC(1)1). 

Maleic thioanhydride and its dichloro derivative function as dienophiles. Cycloaddition with cyclopentadiene and butadiene has been reported (Scheme 155) (72AHC(14)33l). Succinic thioanhydride undergoes bis-Wittig condensations (Scheme 156) the product from ethoxycarbonylmethylenetriphenylphosphorane aromatizes to the thiophene-2,5-bis-acetic ester (454) (75LA1967). 

A concerted elimination-cyclization mechansim, involving a sulfenyl halide in a 1,3-butadiene-1-thio system, is the most probable mechanism for the formation of benzo[6 Jthiophenes from cinnamic acids or 4-aryl-2-butanones by treatment with thionyl chloride. The reactions shown in Scheme 5 have been carefully worked out, and the intermediates isolated (75JOC3037). The unique aspect of this synthesis is the reduction of the sulfinyl chloride (a) by thionyl chloride to form the sulfenyl chloride (b). The intermediate (b) was isolated and converted in pyridine to the 3-chlorobenzo[6]thiophene-2-carbonyl chloride in 36% yield (73TL125). The reaction is probably initiated by a sulfenyl ion attack on the aromatic ring, since it is promoted by electron-releasing groups para to the site of ring closure. For example, when X in (36) was N02, a 23% yield of (37), a mixture of 5-and 7-nitro derivatives, was obtained, but when X in (36) was OMe, a 54% yield of (37) was obtained, contaminated with some 3,4-dichloro-5-methoxybenzo[6]thiophene-2-carboxylic acid. 

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