Cyclohexane carboxylation

The active variety of the terpene d-sylvestrene has been prepared synthetically by preparing the methyl-cyclohexane-carboxylic acid described above, and recrystallising its brucine salt. The acid contains a small quantity of the A acid, although the A variety predominates. The A acid was resolved by the brucine crystallisations, and an acid of rotation -t- 90° obtained. The synthetic process was then proceeded with, and the resulting terpene was found to be d-sylvestrene, having a rotation of -1- 66°. 

After one day standing in a refrigerator, the product was filtered and washed with water, thus yielding 5 g of 2-phenyl-2-hydroxy-cyclohexane-carboxylic acid, melting point (Kofler) 143°C to 145°C. 

In the petrochemical field, hydrogen is used to hydrogenate benzene to cyclohexane and benzoic acid to cyclohexane carboxylic acid. These compounds are precursors for nylon production (Chapter 10). It is also used to selectively hydrogenate acetylene from C4 olefin mixture. 

KA oil is used to produce caprolactam, the monomer for nylon 6. Caprolactam is also produced from toluene through the intermediate formation of cyclohexane carboxylic acid. 

The first step in producing caprolactam from benzoic acid is its hydrogenation to cyclohexane carboxylic acid at approximately 170°C and 16 atmospheres over a palladium catalyst ... 

As further examples, compounds 10 and 11 are both keto acids and mus be named as acids, but the parent name in 10 is that of a ring system (cyclo hexanecarboxylic acid) and the parent name in 11 is that of an open chair (propanoic acid). The full names are frrt/ s-2-(3-oxopropyl)cyclohexane carboxylic acid (10) and 3-(2-oxocyclohexyl)propanoic acid (11). 

The reaction of alkyl sulfates with alkoxide ions is quite similar to 10-12 in mechanism and scope. Other inorganic esters can also be used. One of the most common usages of the reaction is the formation of methyl ethers of alcohols and phenols by treatment of alkoxides or aroxides with methyl sulfate. The alcohol or phenol can be methylated directly, by treatment with dimethyl sulfate and alumina in cyclohexane. Carboxylic esters sometimes give ethers when treated with alkoxides (Bal2 mechanism, p. 473) in a very similar process (see also 10-24). 

In this section primarily reductions of aldehydes, ketones, and esters with sodium, lithium, and potassium in the presence of TCS 14 are discussed closely related reductions with metals such as Zn, Mg, Mn, Sm, Ti, etc., in the presence of TCS 14 are described in Section 13.2. Treatment of ethyl isobutyrate with sodium in the presence of TCS 14 in toluene affords the O-silylated Riihlmann-acyloin-condensation product 1915, which can be readily desilylated to the free acyloin 1916 [119]. Further reactions of methyl or ethyl 1,2- or 1,4-dicarboxylates are discussed elsewhere [120-122]. The same reaction with trimethylsilyl isobutyrate affords the C,0-silylated alcohol 1917, in 72% yield, which is desilylated to 1918 [123] (Scheme 12.34). Likewise, reduction of the diesters 1919 affords the cyclized O-silylated acyloin products 1920 in high yields, which give on saponification the acyloins 1921 [119]. Whereas electroreduction on a Mg-electrode in the presence of MesSiCl 14 converts esters such as ethyl cyclohexane-carboxylate via 1922 and subsequent saponification into acyloins such as 1923 [124], electroreduction of esters such as ethyl cyclohexylcarboxylate using a Mg-electrode without Me3SiCl 14 yields 1,2-ketones such as 1924 [125] (Scheme 12.34). 

FIGURE 7.36 Alternative pathway for the biodegradation of a cyclohexane carboxylate. 

Taylor DG, PW Trudgill (1978) Metabolism of cyclohexane carboxylic acid by Alcaligenes strain Wl. / Bacteriol 134 401-411. 

Skinner, Molnar Suarez (1964) studied the cement-forming potential of 28 liquid aromatic carboxylic acids with zinc oxide. Twelve yielded cohesive products of some merit. Of particular interest were cements formed with hydrocinnamic, cyclohexane carboxylic, p-tertiary butyl-benzoic, thiobenzoic and cyclohexane butyric acids. One of these cements is on the market as a non-eugenol cement. It is very weak with a compressive strength of 4 0 MPa, a tensile strength of 11 MPa and a modulus of 177 MPa, and is only suitable as a temporary material (Powers, Farah Craig, 1976). 

In a subsequent reaction, n-BuSnClg was reacted with the silver salt of cyclohexane carboxylic acid in the presence of wet solvent. This reaction gave the ladder formulation, 3, identified above, Equation 2. 

An example of a compound having a preferred boat conformation is that of [2.2.2] bicyclooctane. This compound must necessarily exist as a boat because its cis-4 hydroxy cyclohexane-carboxylic acid easily forms lactose and the water elimination must proceed through the boat conformation. The trans isomer will not lactonize. 

We have also investigated the electrooxidation of phenylethanoate, a system where there is no proton-loss pathway from the intermediate carbocation. Tab. 6.14 shows relative product ratios for phenylacetate in similiar conditions to those used for cyclohexane carboxylate, but employing 100 mA cm current density [59,60]. 

Column III shows the effect of ultrasound upon the product ratio with methanol as solvent. As can be seen there is now 53 % bibenzyl, 32 % of methyl ether and 6% of methyl ester (with a total of 5 % of other products) suggesting a slight shift towards the two-electron products, but with an overall diminuition of solvent discharge (approx. 6% ester) and side-reactions (approx. 6%). This result confirms the fact the phenyl acetate electrooxidation favours the one-electron route (to bibenzyl) in a wide range of conditions [61], and is much less sensitive to mechanistic switches by manipulation of parameters (e. g. ultrasound) than is cyclohexane carboxylate electrooxidation [54]. 

Nitrosylsulfuric acid reacts with cyclohexane carboxylic acid to form caprolactam. The starting material in such large-scale production of caprolactam is benzoic acid. The reactions are ... 

Supported catalysts were used for the hydrogenation of the aromatic ring of 4-amino-benzoicacid and its ethyl ester, whereas Raney nickel was applied to catalyze the cis trans isomerization of 4-amino-cyclohexane carboxylic acid. 

Aromatization of alicyclic compounds. Cyclohexane carboxylic acids maybe metabolized by a mitochondrial enzyme system to an aromatic acid such as benzoic acid. This enzyme system requires CoA, ATP, and oxygen and is thought to involve three sequential dehydrogenation steps after the initial formation of the cyclohexanoyl CoA (Fig. 4.36). The aromatase enzyme also requires the cofactor FAD. 

Epoxyethyl-3,4-epoxycyclohexane see 4-Vinylcyclohexene diepoxide) 3,4-Epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methyl-cyclohexane carboxylate... 

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