Homologation reaction

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A homologation reaction, also known as homologization, is any chemical reaction that converts the reactant into the next member of the homologous series. A homologous series is a group of compounds that differ by a constant unit, generally a (-CH2-) group. The reactants undergo a homologation when the number of a repeated structural unit in the molecules is increased. The most common homologation reactions increase the number of methylene (-CH2-) units in saturated chain within the molecule.[1] For example, the reaction of aldehydes or ketones with diazomethane or methoxymethylenetriphenylphosphine to give the next homologue in the series.

Examples of homologation reactions include:

Some reactions increase the chain length by more than one unit. For example, the following are considered two-carbon homologation reactions.

Chain reduction[edit]

Likewise the chain length can also be reduced:

Gallagher-Hollander Degradation
Hooker reaction
Mechanistically oxidation causes ring-cleavage at the alkene group, extrusion of carbon dioxide in decarboxylation with subsequent ring-closure.

See also[edit]

References[edit]

  1. ^ Encyclopedia of Inorganic Chemistry doi:10.1002/0470862106.id396
  2. ^ D. Gray, C. Concellon and T. Gallagher (2004). "Kowalski Ester Homologation. Application to the Synthesis of β-Amino Esters". J. Org. Chem. 69 (14): 4849–4851. PMID 15230615. doi:10.1021/jo049562h. 
  3. ^ Vincent P. Hollander and T. F. Gallagher PARTIAL SYNTHESIS OF COMPOUNDS RELATED TO ADRENAL CORTICAL HORMONES. VII. DEGRADATION OF THE SIDE CHAIN OF CHOLANIC ACID J. Biol. Chem., Mar 1946; 162: 549 - 554 Link
  4. ^ On the Oxidation of 2-Hydroxy-1,4-naphthoquinone Derivatives with Alkaline Potassium Permanganate Samuel C. Hooker J. Am. Chem. Soc. 1936; 58(7); 1174-1179. doi:10.1021/ja01298a030
  5. ^ On the Oxidation of 2-Hydroxy-1,4-naphthoquinone Derivatives with Alkaline Potassium Permanganate. Part II. Compounds with Unsaturated Side Chains Samuel C. Hooker and Al Steyermark J. Am. Chem. Soc. 1936; 58(7); pp 1179 - 1181; doi:10.1021/ja01298a031