Succinic 2,3-dibromo

Halogenation. Succinic acid and succinic anhydride react with halogens through the active methylene groups. Succinic acid heated in a closed vessel at 100°C with bromine yields 2,3-dibromosuccinic acid almost quantitatively. The yield is reduced in the presence of excess water as a result of the formation of brominated hydrocarbons. The anhydride gives the mono- or dibromo derivative, depending on the equivalents of bromine used. 

Two hundred and seventy-six grams (94.3 cc., 1.72 moles) of bromine (Note 7) is now added as rapidly as possible through the dropping funnel, the rate of addition being so controlled that the Friedrichs condenser is continuously about half full of the refluxing liquid (Note 8). This operation takes about one hour (Note 9). After about 100 g. of bromine has been added, the dibromo-succinic acid forms rapidly and separates in tiny white needles. At the completion of the reaction there should be a slight excess of bromine, as indicated by the red color of the solution. Occasionally 5-10 g. of bromine has to be added at this point to insure an excess. 

Dimethyl bromosuccinate was prepared from bromosuccinic acid by the diazomethane method (26) using the procedure of Eisenbraun, Morris, and Adolphen (27). It was distilled under vacuum (0.08-0.1 Torr) at 45°-49°C to yield a clear colorless oil. Thin layer chromatography with benzene as the solvent on SiC>2 yielded a symmetrical single spot, indicating either a pure compound or no separation with this particular solvent. Its mass spectrum had a very small peak corresponding to the parent compound, but none to a dibromo compound. The mass spectrum for dimethyl bromosuccinate was not found in the literature, but that for dimethyl succinate also has a small peak corresponding to the parent compound (25). 

It was found that v/c-dihaloalkanes were highly stereospecifically reduced at a mercury cathode to the corresponding olefins in high yields, Eq. (32) [215]. The resulting electrochemistry suggests that the elimination of halogen atoms from the tro/z -periplanar conformation is strongly preferred. The detailed stereochemical course of the reaction was discussed by Brown and coworkers [216]. the stereospecific reduction of a, a -dibromo-succinates to fumarates and maleates was also reported earlier [217]. 

Dibromo derivatives of succinic,548,581 glutaric,582 adipic,583 and pimelic acid584 are examples of compounds prepared by these methods. To obtain the diesters the crude a -dibromo dicarbonyl dihalides are treated with the required alcohol the preparation of diethyl 2,5-dibromoadipate by way of the crude dichloride is described as a typical example in Organic Syntheses.585... 

Debromination and decyanation. A selective synthesis of 6a-bromopenicillinates is accomplished by partial reduction of the 6,6-dibromo compounds (7 examples, 88-100%). a-Bromoacetic esters undergo reductive coupling to give succinic esters."... 

R RgCX—R3R4CX, the products of the initial two-electron electrode reaction are the halide ions and a more unsaturated species, RjR2C=CRgR4. The dualistic nature of the reaction can be illustrated in terms of the reduction of the meso, a, a -dibromo-succinic acid which forms only fumaric acid over the normal pH range and of the racemic a, a -dibromosuccinic acid which also forms maleic acid in varying amount in the intermediate pH range associated with the presence of the mono anion. ... 

Synthesis.—The classical Fischer synthesis of porphyrins from dipyrromethenes has been markedly improved" by using bromine in refluxing formic acid instead of the much harsher conditions previously employed i.e. heating in molten succinic acid) substantially higher yields of centrosymmetric porphyrins (2) were obtained in this way by self-condensation of 5-bromo-5 -methyl-pyrromethenes (1), and of other less symmetrical porphyrins (5) by condensation of 5,5 -dimethyl-pyrromethenes (3) with 5,5 -dibromo-pyrromethenes (4). The synthesis... 

Halogen-Substituted Compounds. Elving and co-workers [22, 83] investigated the reduction of meso- and racemic dibromo-succinic acids at a mercury cathode. At all pH values the meso acid gave only fumaric acid, i,e., trans-elimination of bromine occurred. Racemic dibromosuccinic acid gives various products depending on the pH fumaric acid alone is also formed in strongly acidic and alkaline solutions, i.e., cis-elimination of bromine occurs, but at pH values between 0.4 and 6.9 a mixture of fumaric acid and maleic acid is formed, and the latter is the main product at pH 4 (70% yield). 

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