1 - cycloalkene cycloalkanone

Hydroboration of cyclic trimethylsilyl eno ethers synthesis of cycloalkenes. Cycloalkanones can be converted into the corresponding cycloalkenes by conversion to the trimethylsilyl enol ether, hydroboration, and treatment with acid, usually aqueous HCl. The sequence is illustrated for cyclohexanone (equation I). 

In fact, treatment of cycloalkanone enamines with thallium triacetate, followed by rapid treatment with sodium hydroxide afforded /r[Pg.947]

Cycloalkanones. The synthesis of cycloalkenes by intramolecular coupling of a diketone with a Ti(0) reagent (8, 483) has been extended to a cycloalkanone synthesis. Thus reaction of a keto ester with TiCli/LiAlHj in the presence of triethylamine results in cycloalkanones in moderate to high yield. ... 

The reductive coupling of carbonyl compounds with formation of C-C double bonds was developed in the early seventies and is now known as McMurry reaction [38, 39]. The active metal in these reactions is titanium in a low-valent oxidation state. The reactive Ti species is usually generated from Ti(IV) or Ti(III) substrates by reduction with Zn, a Zn-Cu couple, or lithium aluminum hydride. A broad variety of dicarbonyl compounds can be cyclized by means of this reaction, unfunctionalized cycloalkenes can be synthesized from diketones, enolethers from ketone-ester substrates, enamines from ketone-amide substrates [40-42], Cycloalkanones can be synthesized from external keto esters (X = OR ) by subsequent hydrolysis of the primary formed enol ethers (Scheme 9). 

Hydroxymercuration and thallium(III) oxidation of cycloalkenes, 1-methylcycloalkenes and methylenecycloalkanes have been reported to yield ring-contracted aldehydes, ring-contracted ketones and ring-expanded cycloalkanones, respectively. 

The experience available for the PE spectra of cycloalkanones, cycloalkenones and cycloalkenes can be summarized by two statements ... 

Cycloalkanones are converted into the corresponding a-epoxy-sulphoxide using chloromethyl phenyl sulphoxide. Pyrolysis of the epoxide yields the cycloalkene carbaldehyde (Scheme 52). One-carbon homologation of heptanal to -oct-2-en-l-al was accomplished using the same strategy. ... 

An oxidative cleavage of cycloalkanones to unsaturated aldehyde-esters has been developed. Thus, for example, cyclononanone was converted into 2,2-dithio-trimethylenecyclononanone, which was cleaved using lead(iv) acetate (66 %), and the product so obtained treated with methanol and sodium periodate to give (208 in = 5). Cyclododecanone was similarly converted into (208 n = 8). 1,2-Bis(trimethyl-silyloxy)cycloalkenes, prepared by acyloin condensations, have been converted into 2-alkyl-2-hydroxycycloalkanones by treatment with methyl-lithium and an alkyl halide, and the oximes of these a-hydroxyketones cleaved to give open-chain co-cyanoketones using mesyl chloride-pyridine. ... 

The oxidation of cycloalkenes to cycloalkanones in fair yields by the Jones reagent is catalysed by mercuric ions and is less expensive than the palladium-based Wacker method. It can also be applied to unprotected olefin carboxylic acids. 

The cycloalkene trifluoromethanesulphonates (inflates) have been used to generate the bent vinyl cations whose preferred geometry is calculated to be linear. In agreement, the solvolysis rates of cyclic Inflates decrease with decreasing ring size. The products are exclusively cycloalkanones when water is present, e.g. (380) -> (381). ... 

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