Chloroform, reaction with bromine

Arcus and Strauss sought to convert 1-phenylallyl alcohol (3) into the dibromide (5) by reaction with bromine in chloroform, carbon tetrachloride, or carbon disulfide buf absorption of bromine virtually stopped when 0.6-0.7 equivalent of bromine had been added, and the only product isolated was 1,2,3-tribromo-l-phenylpropane,... 

Bi(alkyl xanthates) [dithiodi(thioformates)], (RO—CS—S—)2, and thiuram disulfides [dithiodi(formamides)], (NH2—CS—S—)2, are formed by oxidation of xanthates and salts of dithiocarbamic acid, respectively. Thioureas can be dehydrogenated analogously to di(amidino) disulfide salts, [+NH2=C(NH2)—S—)2 2X , by a wide variety of oxidizing agents. Reaction with bromine in chloroform is particularly satisfactory for these reactions.799... 

When unsubstituted, C-5 reacts with electrophilic reagents. Thus phosphorus pentachloride chlorinates the ring (36, 235). A hydroxy group in the 2-position activates the ring towards this reaction. 4-Methylthiazole does not react with bromine in chloroform (201, 236), whereas under the same conditions the 2-hydroxy analog reacts (55. 237-239. 557). Activation of C-5 works also for sulfonation (201. 236), nitration (201. 236. 237), Friede 1-Crafts reactions (201, 236, 237, 240-242), and acylation (243). However, iodination fails (201. 236). and the Gatterman or Reimer-Tieman reactions yield only small amounts of 4-methyl-5-carboxy-A-4-thiazoline-2-one. Recent kinetic investigations show that 2-thiazolones are nitrated via a free base mechanism. A 2-oxo substituent increases the rate of nitration at the 5-position by a factor of 9 log... 

At 225—275°C, bromination of the vapor yields bromochloromethanes CCl Br, CCl2Br2, and CClBr. Chloroform reacts with aluminum bromide to form bromoform, CHBr. Chloroform cannot be direcdy fluorinated with elementary flourine fluoroform, CHF, is produced from chloroform by reaction with hydrogen fluoride in the presence of a metallic fluoride catalyst (8). It is also a coproduct of monochlorodifluoromethane from the HF—CHCl reaction over antimony chlorofluoride. Iodine gives a characteristic purple solution in chloroform but does not react even at the boiling point. Iodoform, CHI, may be produced from chloroform by reaction with ethyl iodide in the presence of aluminum chloride however, this is not the route normally used for its preparation. 

A good technical grade of carbon tetrachloride contains not more than the following amounts of impurities 1 ppm acidity as HCl, 1 ppm carbon disulfide if manufactured by carbon disulfide chlorination, 20 ppm bromine, 200 ppm water, and 150 ppm chloroform. The residue should not exceed 10 ppm on total evaporation. The product should give no acid reaction with bromophenol blue, and the starch iodine test should indicate the absence of free chlorine. 

Treatment with NCS in carbon tetrachloride converted the parent into the 2,3-dichloro derivative. The 2,3-dibromo compound was made similarly with NBS (74BSF2239), or with bromine in chloroform in the presence of sodium acetate (72CHE13). Monobromination is possible, but generally mixtures form with 2- and 3-bromo products in ratios of the order of 1 3 (72CHE13). It was possible to prepare 3-bromobenzo[h]sele-nophene by reaction of the 2,3-dibromo derivative with butyl lithium followed by hydrolysis. Four moles of bromine gave the 2,3,6-tribromo derivative from benzo[h]selenophene (74BSF2239). 

We reacted 2 first with bromine in chloroform at 10 C. iH NMR studies have revealed that the reaction mixture was very complex and consisted of six products. This mixture was submitted to silica gel column chromatography. Careful repeated chromatography followed by fractional crystallization allowed us to isolate ten products (Scheme 3). IR analysis indicated that a hydroxyl group was incorporated in compounds lfi-19. Therefore, we assume that these products have been formed by partial hydrolysis of compounds lfl-14. Structural determination of compounds lfl-19 revealed that the barrelene skeleton was rearranged completely. 

Reaction of compound 37 with bromine in chloroform results in mono-bromination a to the sulfur. Treatment of this brominated derivative with NaBH3CN in AcOH gives a mixture of products resulting from reduction of the C=N double bond and of elimination of HBr. Reaction of 44 with sodium ethoxide results in the ethoxy-substituted derivative 45, whereas reaction with pyridine gives the dehydrobrominated derivative 46. Reaction of either 44 or 46 with sodium cyanide in dimethyl sulfoxide (DMSO) gives the cyano-derivative 47 <1983HCA971> (Scheme 13). 

Other workers have also made tributyltin-113 labelled compounds for environmental and metabolic studies. For instance, Brown and coworkers37 prepared bis(tributyltin-l 13) oxide by first refluxing tin-113, which was produced by neutron irradiation of metallic tin, in a bromine-chloroform solution for four hours. The resulting tin-113 tetrabromide was subsequently converted into tributyltin-113 bromide by reaction with three equivalents of unlabelled tetrabutyltin for four hours at 220 °C. The bis(tributyltin-113) oxide was finally obtained by hydrolysing the tributyltin-113 bromide with a KOH-95% ethanol solution... 

The reaction with permanganate constitutes a valuable and much-used test for unsaturation in an organic compound. The substance is dissolved in cold alcohol, a few drops of sodium carbonate solution are added, and then a drop.of dilute permanganate solution. Rapid disappearance of the red colour indicates the presence of a double bond. The Baeyer test can also be carried out in pure glacial acetic acid, which is stable towards permanganate. Another method of detecting double bonds is by the decolorisation of bromine. As a rule, chloroform is used as solvent. 

The reaction of arylisothiocyanates with guanidines (233) affords amidinothioureas (234), which can be converted into 3,5-diarylimino-l,2,4-thiadiazolines (235) directly on treatment with bromine in ethanol. Alternatively, (234) can be alkylated with benzyl chloride to give the S-benzyl derivative (236) which on treatment with bromine in chloroform gives (235) (Scheme 51) <87JIC675>. 

The reaction of arylthioamides (248) with phenylisocyanate affords the arenethiocarboxamide (249), which can be benzylated to give (250) and then converted into 5-aryl-3-oxo-2-phenyl-1,2,4-thiadiazoline (251) on treatment with bromine in chloroform. Alternatively, (249) can be transformed into (251) by direct oxidation with bromine (Scheme 56) <85IJC(B)977>. 

The 5-unsubstituted-l,2,3-triazol-4-ones (176, R = H) participate in electrophilic substitution reactions. Bromination in chloroform of anhydro-4-hydroxy-l,3-dimethyl-1,2,3-triazolium hydroxide (180) gave its 5-bromo derivative (182). The meso-ionic 3-aryl-1,2,3-triazol-4-ones (176, R = Me, R = Ar, R = H) gave 5-bromo derivatives (176, R = Me, R = Ar, R = Br) with bromine in acetic acid. Their reaction with sulphur monochloride gave the sulfide (189, X = S), and with thionyl chloride they gave the sulfoxide (189, X = SO). ... 

Halogenation of dibenzofuran produces the 2-halo compounds. Bromina-tion can be achieved in good yield with bromine in acetic acid " or with N-bromosuccinimide in boiling carbon tetrachloride. The 2,8-dibromo compound has been made, using dioxane dibromide. Chlorination of dibenzofuran in acetic acid in the presence of iron powder can be controlled to yield the 2-chloro or the 2,8-dichloro compounds. 2-Chlorodi-benzofuran is best prepared by reaction of dibenzofuran with phosphorus pentachloride. 2-Iododibenzofuran (45%) results from treatment of dibenzofuran with iodine in boiling chloroform in the presence of nitric acid. 2,8-Diododibenzofuran is best prepared by reaction of dibenzofuran with iodine and iodic acid in aqueous acetic acid. ... 

The reaction of 1,5-naphthyridine (1) with bromine in chloroform does not yield any brominated products (54JCS1879). However, treatment of (1) with bromine in oleum was found to give a mixture of the 3-bromo- (13) and the 3,7-dibromo-l,5-naphthyridines (14) in 10% and 35% yield respectively (65JOC1607, 67LA(707)242). With bromine in pyridine the yields were 27% of (13) and 10% of (14) (68JOC1384), and application of this procedure to 1,6-naphthyridine (2) gave a mixture of 3-bromo- (15), 8-bromo- (16) and 3,8-dibromo-... 

When diphenylacetylene dissolved in cold chloroform reacts with iodine monofluoride suspended in trichlorofluoromethane, the iodine atoms in the primary addition product are easily replaced by fluorine to give l,1,2,2-tetrafluoro-1,2-diphenylethane (60%) along with benzil (10%). Since the C —Br bond is stronger than the C —I bond, the reaction of bromine monofluoride with diphenylacetylene gives 1,1-dibromo-2,2-difluoro-1,2-diphenylethane (65%) and benzil (15%). 

Shkurko and Mamaev50,408 have studied the l//-benzothieno[3,2-6]-pyrrole system 391 extensively. Electrophilic substitution (e.g., Mannich reaction, acetylation, diazonium coupling) takes place at C-2, as predicted by MO calculations.4080 If position 2 is occupied, substitution occurs at C-3.44 The Vilsmeier reaction on the 2-aryl derivative gave the expected product, but bromination of the parent system 391 failed. A 3-bromo derivative was successfully obtained from the N-methyl compound 392 with bromine in chloroform.44... 

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