1.3- Butadiene-2,3-dicarboxylic acid synthesis

Pure crystalline 2,3-dicyanobutadiene has been prepared in high yield by gas-phase thermolysis of cyclobutene (2).2,8 Analogous thermolysis of derivatives of cyclobutene-1,2-dicarboxylic acid appears to represent general procedures for the synthesis of derivatives of butadiene-2,3-dicarboxylic acid of high purity.2,12 These... 

The selective hydrogenation of 1,5-cyclooctadiene (1,5-COD) and 1,5,9-cyclodode-catriene (1,5,9-CDT), cyclic oligomers of 1,3-butadiene, to the corresponding monoenes has been the subject of considerable interest, since the hydrogenation may constitute one of the steps leading to the synthesis of C8 and C12 lactams, dicarboxylic acids, and their derivatives. 

An important variation in butadiene polymerization technology is the reductive dimerization of butadiene, using stoichiometric, instead of catalytic, quantities of sodium. This process has been developed by National Distillers into a commercial synthesis of a mixture of 10-carbon dicarboxylic acids, and a 10,000,000-pound-per-year plant is under construction to exploit this reaction (7). Esso has recently developed a similar process for the synthesis of dimeric dicarboxylic acids from the reaction between sodium and cyclopentadiene, but there has been no indication yet that it intends to commercialize this reaction (8). 

This product contains two molecules of butadiene and two molecules of carbon dioxide, and it is assumed that it is formed by intermole-cular dimerization of two allyl carboxylato groups. However, till now the synthesis of the C-ig-dicarboxylic acid occurs only stoichio-m trically. The synthesis requires an overall reaction time of 4 days and about 5 g of the starting iron complex are necessary to form one gram of the acid. 

The syntheses of mono- and dicarboxylic acids via ionic reaction steps starting from butadiene and carbon dioxide are well studied reactions. For instance, Cg-, C13- and C-]7-monocarboxylic acids as well as Ciq-dicarboxylic acids can be prepared in the presence of sodium [72,73]. Also metal phenolates catalyze the synthesis of acyclic dicarboxylic acids. When sodium phenolate is dissolved in dimethylformamide and CO2 and butadiene are added and reacted 3 hrs at 50 C, muconic acid is formed in 81 % yield. Hydrogenation of muconic acid leads to adipic acid [741. In a similar reaction, Thiele s acid, that is tricyclo-[5.2.1.02 6]deca-3.8-diene-4.9-dicarboxylic acid, is formed by two moles of cyclopentadiene and two moles of carbon dioxide [79 (Equation 13). 

The diol 4 had never been described in the literature before we used it in the synthesis of 1. Initially, we tried to synthesize it using an enantioselective Diels-Alder reaction between a chiral fumarate equivalent 5 (Scheme 10.1) and butadiene 6, followed by double-bond dihydroxylation [41]. However, a more effective protocol for large-scale synthesis could finally be based on the procedure shown in Scheme 10.2, leading to enantiomericaUy pure (lS,2S)-cyclohex-4-ene-1,2-dicarboxylic acid 7 [42]. Here, a Bolm desymmetrization of tetrahydrophthahc anhydride 8 using quinine leads to monoester 9 in 89% ee. The monoester 9, in turn, can be epimerized to the trans isomer 10 which is hydrolyzed to obtain 7, after crystallization. This intermediate is the starting material for the synthesis of 4 and of other conformationally constrained DCCHD to be used as monosaccharide mimics [43, 44]. Our current best protocol for the large-scale synthesis of 7 is reported at the end of this chapter. 

Hydroxycarbonylation and alkoxycarbonylation of alkenes catalyzed by metal catalyst have been studied for the synthesis of acids, esters, and related derivatives. Palladium systems in particular have been popular and their use in hydroxycarbonylation and alkoxycarbonylation reactions has been reviewed.625,626 The catalysts were mainly designed for the carbonylation of alkenes in the presence of alcohols in order to prepare carboxylic esters, but they also work well for synthesizing carboxylic acids or anhydrides.137 627 They have also been used as catalysts in many other carbonyl-based processes that are of interest to industry. The hydroxycarbonylation of butadiene, the dicarboxylation of alkenes, the carbonylation of alkenes, the carbonylation of benzyl- and aryl-halide compounds, and oxidative carbonylations have been reviewed.6 8 The Pd-catalyzed hydroxycarbonylation of alkenes has attracted considerable interest in recent years as a way of obtaining carboxylic acids. In general, in acidic media, palladium salts in the presence of mono- or bidentate phosphines afford a mixture of linear and branched acids (see Scheme 9). 

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