2,5-cyclohexadiene-l-carboxylic acids

Therefore, using either direct Birch reduction alkylation or Birch reduction-protonation-enolate formation alkylation, both followed by auxiliary removal, it is possible to prepare either enantiomer of a desired 2,5-cyclohexadiene-l -carboxylic acid derivative in excellent enantiomeric purity from the same starting materials. 

With increasing steric hindrance, the rate of esterification is decreased and the formation of N-acylureas may become a serious side reaction. This is indicated by the decrease 1n yield 1n the esterification of 2,5-cyclohexadiene-l-carboxylic acid with different alcohols MeOH (95%), EtOH (84%), i-PrOH (75%), e-CgHjjOH (65%), t-BuOH (65%).Diminished acidity because of the influence of electron-donating substituents 1n aromatic carboxylic acids can also lead to low yields. 

Li added during 3 min. at 40° to a stirred suspension of 2-isopropylbenzoic acid in liq. NH3 and water, NH3 evaporated, and acidified with aq. 20%-HCl 2-iso-propyl-2,5-cyclohexadiene-l-carboxylic acid. Y 81%. - Isomeric 1,5-cyclohexa-diene-l-carboxylic acids may be obtained in the presence of ethanol instead of water, which is a more powerful proton donor. F. e. s. H. van Bekkum et al., R. 90,137 (1971). 

The decarboxylative arylation of 2,5-cyclohexadiene-l-carboxylic acids occurs under palladium catalysis (Scheme 4.82) [86]. 

Recently, the Chou group reported on the palladium-catalyzed decarboxylative coupling of substituted 2,5-cyclohexadiene-l-carboxylic acids. The products obtained are 5-arylcyclohexa-1,3-dienes. ... 

Emulsion polymerization with the chain transfer agent l-benzyl-2,5-cyclohexadiene-1-carboxylic acid was also used to prepare poly(ethyl acrylate-co-methacrylic acid). Poly(N-vinylpyrrolidone) was prepared using the chain transfer agent l-i-propyl-2,5-cyclohexadiene-1 -carboxylic acid. 

Strains of Pseudomonas putida are very versatile in metabolizing aromatic compounds, particularly to the corresponding 1,2-dihydro-l,2-diols. The hydroxylating enzyme of the P. putida mutant is not strongly substrate specific and alkyl, aryl and halogen functionalities are usually readily tolerated380. Thus, 4-bromobenzoic acid (1, R = Br) is converted to a. v-4-bro-mo-5,6-dihydroxy-l, 3-cyclohexadiene-l-carboxylic acid (2, R = Br) in 80% yield with 98% cc (determined by chiral NMR shift experiments on the 4-nitrobenzyl ester) 375. The absolute stereochemistry, (5R,6R), was determined by a single crystal X-ray analysis. 

The reduction of aromatic carboxylic acids by Na(Hg) may take place in the nucleus or in the carboxyl group. Phthalic acid is reduced to m w-3,5-cyclohexadiene-l,2-dicar-boxylic acid [102] or 2,5-cyclohexadiene-l,2-dicarboxylic acid [103], whereas certain phenolic carboxylic acids may be reduced to aldehydes. 

Chloro-4-diazo-3-oxidobenzoic Acid [called 2-Chioro-4 -diazo-3 oxo-l, 5-cyclohexadiene-I -carboxylic in CA 5 th Decennial Index, Formulas 41-50, p 2l8F(194 7-5 6)] C HgClN Ogi mw 198.5 6, N 14.11% ... 

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... 

Reiner AM, Hegeman GD (1971) Metabolism of benzoic acid by bacteria. Accumulation of (-)-3,5-cyclohexadiene-l,2-diol-l-carboxylic acid by a mutant strain of AlcaUgenes eutrophus. Biochemistry 10 2530-2536... 

Reiner, A. M. 1972. Metabolism of aromatic compounds in bacteria. Purification and properties of the catechol-forming enzyme, 3,5-cyclohexadiene-l,2-diol-l-carboxylic acid (NAD" ) oxidoreductase (de-carboxylating). J. Biol. Chem. 247 4960-4965. 

CN [6 -[6a,73( )]]-7-[ amino-l,4-cyclohexadien l-ylacetyl)amino]-3-methyI-8-oxo-5-th a-l-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid... 

Dimethyl- and 5,5-diethyl-1,3-cyclohexadienes (49a and 49b) [50] derived from the corresponding aUylic alcohols reacted with bis(phenylsulfonyl)ethylene 4b to give bis(phe-nylsulfonyl)bicyclo[2.2.2]octenes 51a and 51b, which underwent the modified Barton-Zard reaction (CNCH2 C02Et, DBU) to afford isomerically pure dihydroisoin-dole-l-carboxylates 52a and 52b in good yields (Table 15.3) [51]. Carboxylates 52a and 52b were reduced to the corresponding alcohols by treatment with LiAlfti in THF and these alcohols were immediately subject to cyclic tetrame-rization reaction under acidic conditions [51]. Porphyrins 53a-H2 and 53b-H2 were obtained as mixtures of... 

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