Cyclohexadiene carboxylates

In the same work, the authors performed reactions in open vessel systems, either in the absence of solvent or on silica gel support in dry media . The cycloaddition of ethyl 1,3-cyclohexadiene carboxylate 81 to ethyl propiolate 82 was improved compared with the harsh classical conditions (benzene at 320 °C for 24 h) (Scheme 11.22). No specific microwave effects were observed in this reaction this was in accordance with results from ah initio calculations which indicated a synchronous mechanism with similar polarity (dipole moment) in both ground and transition states. 

The biosynthetic origin of the cyclohexanecarboxylic acid moiety of the mycotrienins I (95) and II (96) was also considered to be shikimic acid (119) [184,204]. Cell-free extracts of Streptomyces collinus were tested with various cyclohexene- and cyclohexadiene-carboxylic acids in order to determine the latter stages of the conversion of 119 to cyclohexanecarboxylic acid. It was demonstrated that the final three steps of this process involve reduction of the a,P-double bond of 1,2(6)-cyclohexadienylcarbonyl CoA, an isomerization of the double bond of the resulting 2-cyclohexenylcarbonyl CoA to afford 1-cyclohexenylcarbonyl CoA, and a subsequent reduction of the newly formed a,P-double bond. Both of the reduction steps were shown to require NADPH as a cofactor [212]. 

The diacetoxylation of E,E)- and ( ,Z)-2.4-hexadiene (351 and 353) is stereospecific, and 2,5-dimethylfurans (352 and 354) of different stereochemistry have been prepared from the isomers. Two different carboxylates are introduced with high cis selectivity by the reaction of 1,3-cyclohexadiene and... 

Chemical Name 7-[ (Amino-1,4-cyclohexadien-1-yl-acetyl)amino] -3-methoxy-B-oxo-5-thia-1 -azabicyclo [4.2.0] -oct-2-ene-2-carboxylic acid... 

Chemical Name 6-[D-2-amino-2-(1,4-cyclohexadien-1-vl)acetamido] -3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0] heptane-2-carboxylic acid... 

The cationic pathway allows the conversion of carboxylic acids into ethers, acetals or amides. From a-aminoacids versatile chiral building blocks are accessible. The eliminative decarboxylation of vicinal diacids or P-silyl carboxylic acids, combined with cycloaddition reactions, allows the efficient construction of cyclobutenes or cyclohexadienes. The induction of cationic rearrangements or fragmentations is a potent way to specifically substituted cyclopentanoids and ring extensions by one-or four carbons. In view of these favorable qualities of Kolbe electrolysis, numerous useful applications of this old reaction can be expected in the future. 

Carboxylic esters can be converted to their homologs (RCOOEt RCH2-COOEt) by treatment with Br2CHLi followed by BuLi at —90°C. The ynolate RC=COLi is an intermediate.If the ynolate is treated with 1,3-cyclohexadiene, followed by NaBH4, the product is the alcohol RCH2CH2OH. ... 

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... 

Benzyne l,3-Cyclohexadien-5-yne (8, 9) (462-80-6) Benzenediazonium-2-carboxylate Benzenediazonium, o-carboxy-, hydroxide, inner salt (8) Benzenediazonium, 2-carboxy-, hydroxide, inner salt (9) (1608-42-0)... 

In the case of 1,3-cyclohexadiene with Me2Zn, the dicarboxylation afforded the /rdicarboxylic acid 96 (Scheme 33). In contrast, when Ph2Zn was used instead of Me2Zn as a transmetallation agent, the phenylative carboxylation occurred in high regio- and stereoselectivity to give the l,4-m-substituted-2-cyclohexene 97, as a result of reductive elimination from the phenyl-7r-allylnickel intermediate, prior to the second carboxylation reaction (Scheme 33).47... 

Cyclobutyl-cis-4-trans-5-dimethyl- 1,3-dioxolane, by reaction of erythro-3-methane-sulfonyloxy-2-butyl cyclo-butanecarboxylate with sodium borohydride, 51, 12 hydrolysis to cyclobutane-carboxaldehyde, 51, 13 3,5—CYCLOHEXADIENE—1, 2-DI CARBOXYLIC ACID, 50, 50 A1 a-Cyclohexaneacetaldehyde, 53, 104... 

Cycloalkenone-2-carboxylates tautomerize to conjugated dienols in the presence of either acids or bases. Iron(III) catalysts have also been found to promote enone-dienol equilibration, and, at room temperature, dimerization64. Thus, treating 87 with 1 mol% iron(III) chloride hexahydrate in methylene chloride at room temperature affords 88 in 81% yield (equation 46). The cyclohexadiene-cyclohexanone is in a rapid equilibrium with its triendiol tautomer, 89 (equation 47). 

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. 

Benzoylformate decarboxylase (BFD EC 4.1.1.7) belongs to the class of thiamine diphosphate (ThDP)-dependent enzymes. ThDP is the cofactor for a large number of enzymes, including pyruvate decarboxylase (PDC), benzaldehyde lyase (BAL), cyclohexane-1,2-dione hydrolase (CDH), acetohydroxyacid synthase (AHAS), and (lR,6] )-2-succinyl-6-hydroxy-2,4-cyclohexadiene-l-carboxylate synthase (SHCHC), which all catalyze the cleavage and formation of C-C bonds [1]. The underlying catalytic mechanism is summarized elsewhere [2] (see also Chapter 2.2.3). 

Ethyl 2,6,6,trimethyl-l,3-cyclohexadiene-l-carboxylate [35044-59-8, the commercial quality also contains the a.- [25044-57-6] and 7-isomers isomers [35044-58-7]... 

Aryl- or alkenylpalladium complexes can be generated in situ by the trans-metallation of the aryl- or alkenylmercury compounds 386 or 389 with Pd(II) (see Section 6). These species react with 1,3-cyclohexadiene via the formation of the 7r-allylpalladium intermediate 387, which is attacked intramolecularly by the amide or carboxylate group, and the 1,2-difunctionalization takes place to give 388 and 390[322], Similarly, the ort/w-thallation of benzoic acid followed by transmetallation with Pd(II) forms the arylpalladium complex, which reacts with butadiene to afford the isoeoumarin 391, achieving the 1,2-difunctionalization of butadiene[323]. 

Benzyl alcohol linkers, such as those described in Section 3.1.1.1, can also be cleaved by palladium-catalyzed hydrogenolysis. Carboxylic acids have, for example, been obtained by hydrogenolysis of insoluble benzyl esters with Pd(OAc)2/DMF/H2 [89,161]. Resin-bound benzylic carbamates [162,163] and amides [164] can also be released by treatment with Pd(OAc)2 in DMF in the presence of a hydrogen source, such as 1,4-cyclohexadiene or ammonium formate. These reactions are quite surprising, because they require the formation of metallic palladium within the gelated beads. 

Complexes of carbonic or carboxylic acid anions have been used as hydroformylation catalysts for various alkenes. The bicarbonate complex [Rh(H)2(02COH)(PPr 3)2] as catalyst enabled 1-hexene to be converted to aldehydes using paraformaldehyde as source of hydrogen and carbon monoxide in place of the more usual gas mixture.338 The acetate complex [Rh(OAc)CO(PPh3)2] (74) has been shown to effect the selective hydroformylation of cyclic dienes. The cyclohexadienes gave predominantly dialdehydes, whereas 1,3- and 1,5-cyclooctadiene gave the saturated monoaldehydes.339... 

Palladium catalysts that are free of halide ions effect the dimerization and carboxylation of butadiene to yield 3,8-nonadienoate esters. Palladium acetate, solubilized by a tertiary amine or an aromatic amine, gives the best yields and selectivities (equation 57).87 Palladium chloride catalyzes the hydrocarboxylation to yield primarily 3-pentenoates.88 The hydrocarboxylation of isoprene and chloroprene is regio-selective, placing the carboxy function at the least-hindered carbon (82% and 71% selectively) minor amounts of other products are obtained (equation 58). Cyclic dienes such as 1,3-cyclohexadiene and 1,3-cyclooctadiene are similarly hydrocarboxylated. 

Dienes (allenes) are also used for heteroannulation with 68 and 69. The eight-membered nitrogen heterocycle 78 is constructed by the reaction of 1,2-undecadiene (77) with o-(3-aminopropyl)iodobenzene (76) [34]. The lactones are prepared by trapping the 7i-allyl intermediates with carboxylic acids as an oxygen nucleophile. The unsaturted lactone 81 is prepared by the reaction of /1-bromo-v,/ -unsaturated carboxylic acid 79 with the allene 80 [35]. In the carboannulation of 82 with 1,4-cyclohexadiene (83), the 1,3-diene 85 is generated by / -elimination of 84, and the addition of H-PdX forms the 7i-allylpalladium 86, which attacks the malonate to give 87 [36],... 

Thus, according to Scheme 28, (-)-shikimic acid 169 was converted to cyclohexadiene derivative 170 via esterification of carboxyl group, protection of the m-disposed hydroxyls, and elimination of the remaining carbinol moiety. Catalytic dihydroxylation of 170 gave unsaturated esters 171 and 172 as a separable 1 1 mixture. The 5,5a-unsaturated isomer 171 was finally elaborated into the desired (-)-MK7607 (174) via simple protection-reduction-deprotection sequence. 

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