Diene-carboxylic acids

An electron-withdrawing substituent leads to a product where it is bound to a saturated carbon center. Benzoic acid 9 is reduced to the cyclohexa-2,5-diene carboxylic acid 10 ... 

Figure 1 summarizes the chemical structures of the topochemically polymerizable 1,3-diene monomers providing stereoregular 1,4-trans polymer (Scheme 6) [ 16]. Most of the polymerizable monomers contain benzyl, naphthylmethyl, and long alkyl-chain substituents in their chemical structures. The (ZyZ)-, (E,Z)-, and ( , )-muconic and sorbic acids as well as the other diene carboxylic acids are used as the ester, amide, and ammonium derivatives. In contrast to this, the carboxylic acids themselves have crystal structures unfavorable for polymerization while they undergo [2-1-2] photodimerization, as has already been described in the preceding sections.

Peroxyacetic acid oxidation is similar to the peroxytrifluoroacetic acid (Deno) oxidation (28). These peroxide systems are reported to selectively oxidize the aromatic portions of molecules while leaving aliphatic portions intact (29). Peroxyacetic acid will oxidize aromatic units to phenolic units via hydroxylation. These phenolic moieties will oxidize rapidly to ortho and para quinones, the latter of which are unstable are undergo ring fission to form diene carboxylic acids (30). 

The asymmetric intramolecular ene reaction of 1,3-oxazolidin-2-one derivatives of a diene carboxylic acid is also promoted by a stoichiometric amount of the chiral titanium reagent (6) to give cyclopentane or cyclohexane derivatives with high optical purity (eq 14). ... 

Allene carboxylic acids have been cyclized to butenolides with copper(II) chloride. Allene esters were converted to butenolides by treatment with acetic acid and LiBr. Cyclic carbonates can be prepared from allene alcohols using carbon dioxide and a palladium catalyst, and the reaction was accompanied by ary-lation when iodobenzene was added. Diene carboxylic acids have been cyclized using acetic acid and a palladium catalyst to form lactones that have an allylic acetate elsewhere in the molecule. With ketenes, carboxylic acids give anhydrides and acetic anhydride is prepared industrially in this manner [CH2=C=0 + MeC02H (MeC=0)20]. 

For example, it would not work in the case of the reaction between butadiene carboxylic acid 6.208 and acrylic acid 6.209. The curly arrows 6.207 establish that C-4 of the diene carboxylic acid can be expected to be electrophilic, just like C-3 of the acrylic acid. The partial positive charges ought to repel each other and the adduct expected would be the meta adduct 6.211. In contrast, the reaction gives mainly the ortho adduct 6.210.777... 

Enantiopure l,2-cis-dihydroxycyclohexa-3,5-diene carboxylic acids have considerable synthetic potential as building blocks in chiral synthesis. Such cis-diols can be produced from benzoic acid derivatives by the action of toluate- 1,2-dioxygenase of Pseudomonas putida mt-2125 or homologous enzymes of a different origin (Fig. 16.6-... 

Chorlsmic Acid- C3R-irans)-3-f(i-Garhoxyeffun-yt)oxyJ-4-hydroxy-1,5-cyclohexadiene- l-ca rboxylic acid 3-euolpyruvic ether of rrnns-3,4-dihydroxycyclohexa-l,5-diene carboxylic acid o - 5-carboxy -1,2-dihydro-2 -hydroxy phenox y)ac ryli c acid. mol wt 226.19. C... 

I The saponins isolated in the plant possess aglycones of three skeletons cycloartane, ursane and oleanane, with some variation in each structure—type. It s very interesting to discover such cycloartane-type saponins, that its side-chain has been modified naturally to conjugated diene-carboxylic acid, which formed amide with 2 -amino-3, 4 -dimethyl-y-lactone moiety. 

Other examples of the use of intramolecular Diels-Alder reactions in preparative chemistry have appeared the o-quinodimethane (186), produced as a transient intermediate in the pyrolysis of the analogous benzocyclobutene, cyclizes to give (187 65%), the desulphurization of which (Raney nickel) affords a potential intermediate for the preparation of tetracyclic diterpenes. Elevated temperatures result in the isomerization of (188) into the internal [4 -I- 2] adduct (189) in which it is clear that a cyano-group has acted as a dienophile (189) is the result of a subsequent double-bond shift, and the structure was validated by crystallographic structure analysis. Bridged y-lactams have been successfully prepared by the intramolecular Diels-Alder reactions of NN-diallyl- and iV-(l,l-dimethylprop-2-yn-l-yl)amides of various penta-2,4-diene carboxylic acids. Thus, pyrolysis of (190) gave an 80%... 

The total synthesis starts with a four-step synthesis of 8-nitroocta-2,7-diene carboxylic acid ester 26 (Scheme 9.22). 

Ethylene- from 2,4-diene-carboxylic acid esters Organocopper compds. as reactants... 

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