Homologation reaction

<h2 id="chain-reduction">Chain reduction</h2>
<p>Likewise the chain length can also be reduced: 
</p>
<ul><li>In the <a href="/facts/Gallagher%25E2%2580%2593Hollander_degradation/uymNlrBz">Gallagher–Hollander degradation</a> (1946) <a href="/facts/Pyruvic_acid/qJTgl4J9">pyruvic acid</a> is removed from a linear aliphatic <a href="/facts/Carboxylic_acid/U4xuMosy">carboxylic acid</a> yielding a new acid with 2 carbon atoms less.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> The original publication concerns the conversion of <a href="/facts/Bile_acid/ojTJzf0c">bile acid</a> in a series of reactions: <a href="/facts/Acid_chloride/R4ppUXre">acid chloride</a> (2) formation with <a href="/facts/Thionyl_chloride/nWwvNtvd">thionyl chloride</a>, diazoketone formation (3) with <a href="/facts/Diazomethane/KyBPQTGb">diazomethane</a>, chloromethyl ketone formation (4) with <a href="/facts/Hydrochloric_acid/HqItJlUT">hydrochloric acid</a>, <a href="/facts/Organic_reduction/6DdmXG4S">organic reduction</a> of chlorine to methylketone (5), <a href="/facts/Ketone_halogenation/fNlKCCUq">ketone halogenation</a> to 6, <a href="/facts/Elimination_reaction/7LSBwU3P">elimination reaction</a> with <a href="/facts/Pyridine/X817hCch">pyridine</a> to <a href="/facts/Enone/gAflh5z4">enone</a> 7 and finally oxidation with <a href="/facts/Chromium_trioxide/ENafKcAm">chromium trioxide</a> to <i>bisnorcholanic acid</i> 8.</li></ul>

<ul><li>In the <a href="/facts/Hooker_reaction/5Cn3xcav">Hooker reaction</a> (1936) an alkyl chain in a certain <a href="/facts/Naphthoquinone/y1zTWRB9">naphthoquinone</a> (phenomenon first observed in the compound <a href="/facts/Lapachol/6wuuEe5R">lapachol</a>) is reduced by one <a href="/facts/Methylene_(compound)/vIPU9NXl">methylene</a> unit as <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a> in each <a href="/facts/Potassium_permanganate/nyjjuDlo">potassium permanganate</a> <a href="/facts/Organic_oxidation/6DdmXG4S">oxidation</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a></li></ul>

Mechanistically oxidation causes ring-cleavage at the alkene group, extrusion of <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a> in <a href="/facts/Decarboxylation/Uugc18fz">decarboxylation</a> with subsequent ring-closure.
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Homologous_series/7PKCuvzm">Homologous series</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Encyclopedia of Inorganic Chemistry doi:10.1002/0470862106.id396 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>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. doi:10.1021/jo049562h. PMID 15230615. <a href="/wiki/J._Org._Chem." target="_blank">/wiki/J._Org._Chem.</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>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 Archived 2009-01-07 at the Wayback Machine <a href="/wiki/J._Biol._Chem." target="_blank">/wiki/J._Biol._Chem.</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>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 <a href="/wiki/J._Am._Chem._Soc." target="_blank">/wiki/J._Am._Chem._Soc.</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>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 <a href="/wiki/J._Am._Chem._Soc." target="_blank">/wiki/J._Am._Chem._Soc.</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
</ol>

Homologation reaction open-in-new

Homologation reaction