Synthesis of alkanes

Synthesis of Alkanes and Cycloalkanes 4.18A Hydrogenation of Alkenes and Alkynes... 

A highly versatile method for the synthesis of alkanes and other hydrocarbons from organic halides has been developed by E. J. Corey (Harvard University, Nobel Prize for Chemistry in 1990), G. H. Posner (The Johns Hopkins University), and by G. M. Whitesides (Harvard University) and H. O. House (Georgia Institute of Technology). 

The preparation of unfunctionalized alkanes on insoluble supports has only recently received attention. With the aim of preparing ever more elaborate molecules on solid phase, chemists are currently searching for robust methods to assemble complex carbon frameworks on insoluble supports. The synthesis of alkanes has also been investigated in this context. 

The synthesis of alkanes is exemplified by the following typical procedures. 

The synthesis of alkanes which involves the electrolysis of salts of carboxylic acids was first reported by Kolbe in 1849. The technique and the apparatus has been described in Section 2.17.6, p. 115, and the illustrative example relevant to this section is that of the preparation of hexacosane (the experimental details were originally supplied by Dr R. P. Linstead, C.B.E., F.R.S.). (See also Section 5.11.5, p.677). 

Fig. 1.47. Myers synthesis of atkanes from aldehydes via the sulfonylated hydrazones B and their silyl derivatives C. This procedure provides a skeletongenerating three-step synthesis of alkanes from aldehydes. In terms of Figure 1.2, the chain reaction F —> I involved is a "substitution reaction by fragmentation." (The sulfonylated hydrazide anion, which here results from the addition of R3-Li to the sulfonyl hydrazone C, does—at this reaction s temperature of-78 °C—not release toluene sulfinate. Compare the different behavior of the sulfonylated hydrazide anion C in the reaction of Figure 17.69, where a mesitylene sulfinate residue is eliminated at a temperature that is higher by 160 °C).

Synthesis of amino acids ch49 e Synthesis of alkanes cb31 Stereochemistry chl6 e Asymmetric synthesis ch45... 

Kolbe electrolytic reaction " for the synthesis of alkanes also involves the radicals as intermediates. For example, when a solution of diphenylacetic acid (2.41) is electrolyzed in DMF (dimethylformamide), the product 2.42 is obtained in 24% yield. 

The catalytic reduction of alkenes and alkynes are important methods for the synthesis of alkanes. The hydroboration and hydrosilylation of alkenes are alternatives to catalytic methods. Again, both the alkene and alkyne may have played an important role in the construction of the hydrocarbon chain. 

Protonolysis of Alkylboranes with Carboxylic Acids Synthesis of Alkanes... 

We have already encountered hydrogenation as the most useful method for preparing alkanes (Sec. 3.15). It is not limited to the synthesis of alkanes, but is a general method for the conversion of a carbon-carbon double bond into a carbon-carbon single bond using the same apparatus, the same catalyst, and very nearly... 

One of the classical reactions in organic chemistry for the synthesis of alkanes through symmetrical coupling of alkane carboxylic acids is the Kolbe reaction . There are... 

The effects of environmental factors such as light and temperature on the synthesis of alkanes and very long acids support the elongation-decarboxylation mechanism. For example, the synthesis of /1-C29 alkane and its oxygenated derivatives was increased by intense light, while the formation... 

Synthesis of Alkanals. Monoalkylation of 3-(phenylsulfo-nyl)propanal ethylene acetal (1) takes place at the position a to the phenylsulfonyl group on successive treatment with butyllithium and then with an alkyl halide. Deprotection of the acetal group and subsequent elimination of benzenesulfinic acid with a base produces the corresponding 2-alkenal (eq 1). ... 

He also developed a useful electrolytic process for the synthesis of alkanes. 

Synthesis of alkanes from a-silyl carbanions and carbonyl compounds. In cases where separation of p-sllyl alcohol diastereomers (e.g. 6) can be achieved, pure Z or E olefins can be isolated (see 1st edition). 

Fig. 1 Charge consumed in the electrochemical synthesis of alkanes of various chain length (main axis, dotted line) - charge in Faradays per mole of hydrocarbon, (secondary axis, solid line) - specific charge in kAh per kg of hydrocarbon the vertical dotted line shows the separation between gas-phase hydrocarbons (chain length < C4) and the liquid-phase hydrocarbons (chain length > C4)...

Fernandez, I., Khiar, N., Llm, J. M and Alcudia, F. (1992) Asymmetric synthesis of alkane- and arenesulfinates of diacetone-D-glucose an improved and genei route to both enantiomerically pure sulfoxides, /. Org, Chem.. 57,6789-6796. 

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