Seyferth-Gilbert homologation 3564560 221674976 2008-06-25T15:53:30Z Chem-awb 4806773 [[Category:Name reactions]] using [[Project:AutoWikiBrowser|AWB]] The '''Seyferth-Gilbert homologation''' is a the [[chemical reaction]] of an [[aryl]] [[ketone]] '''1''' (or [[aldehyde]]) with dimethyl (diazomethyl)phosphonate '''2''' and [[potassium tert-butoxide]] to give substituted [[alkyne]]s '''3'''.<ref name="seyferth1971">{{cite journal | author = D. Seyferth, R. S. Marmor and P. Hilbert | title = Reactions of dimethylphosphono-substituted diazoalkanes. (MeO)2P(O)CR transfer to olefins and 1,3-dipolar additions of (MeO)2P(O)C(N2)R | year = 1971 | journal = [[J. Org. Chem.]] | volume = 36 | issue = 10 | pages = 1379–1386 | doi = 10.1021/jo00809a014}}</ref><ref name="gilbert1982">{{cite journal | author = J. C. Gilbert and U. Weerasooriya | title = Diazoethenes: their attempted synthesis from aldehydes and aromatic ketones by way of the Horner-Emmons modification of the Wittig reaction. A facile synthesis of alkynes | year = 1982 | journal = [[J. Org. Chem.]] | volume = 47 | issue = 10 | pages = 1837–1845 | doi = 10.1021/jo00349a007}}</ref> Dimethyl (diazomethyl)phosphonate '''2''' is often called the '''Seyferth-Gilbert reagent'''.<ref name="brown1996">{{cite journal | author = D. G. Brown, E. J. Velthuisen, J. R. Commerford, R. G. Brisbois and T. H. Hoye | title = A Convenient Synthesis of Dimethyl (Diazomethyl)phosphonate (Seyferth/Gilbert Reagent) | year = 1996 | journal = [[J. Org. Chem.]] | volume = 61 | issue = 7 | pages = 2540–2541 | doi = 10.1021/jo951944n}}</ref> [[Image:Seyferth-Gilbert Homologation Scheme.png|center|320px|The Seyferth-Gilbert homologation]] This reaction is called a ''[[Homologation reactions|homologation]]'' because the product has exactly one additional [[carbon]] more than the starting material. ==Reaction mechanism== Deprotonation of the Seyferth-Gilbert reagent '''A''' give an anion '''B''' which reacts with the ketone to form the oxaphosphatane '''D'''. Elimination of dimethylphosphate '''E''' gives the [[vinyl]] [[diazo]]-intermediate '''Fa''' and '''Fb'''. The generation of [[nitrogen]] gas gives a [[vinyl]] [[carbene]] '''G''' which via a [[1,2-rearrangement|1,2-migration]] forms the desired alkyne '''H'''. [[Image:Seyferth-Gilbert Homologation Mechanism.png|center|600px|The mechanism of the Seyferth-Gilbert homologation]] ==Bestmann modification== Dimethyl (diazomethyl)phosphonate can be generated [[in situ]] from dimethyl-1-diazo-2-oxopropylphosphonate (also called '''Bestmann's reagent''') by reaction with [[methanol]] and [[potassium carbonate]]. Reaction of Bestmann's reagent with aldehydes gives terminal alkynes often in very high yield.<ref name="muller1996">{{cite journal | author = S. Müller, B. Liepold, G. Roth and H. J. Bestmann* | title = An Improved One-pot Procedure for the Synthesis of Alkynes from Aldehydes | year = 1996 | journal = [[Synlett]] | volume = | issue = 06 | pages = 521–522 | doi = 10.1055/s-1996-5474}}</ref><ref name="roth2004">{{cite journal | author = G. Roth, B. Liepold, S. Müller and H. J. Bestmann | title = Further Improvements of the Synthesis of Alkynes from Aldehydes | year = 2004 | journal = [[Synthesis]] | volume = | issue = 1 | pages = 59–62 | doi = 10.1055/s-2003-44346}}</ref> [[Image:Bestmann's Reagent Scheme.png|center|300px|Bestmann's reagent]] The use of the milder potassium carbonate makes this procedure much more compatible with a wide variety of [[functional group]]s. ==References== <references /> ==See also== *[[Corey-Fuchs reaction]] *[[Horner-Wadsworth-Emmons reaction]] *[[Wittig reaction]] [[Category:Carbon-carbon bond forming reactions]] [[Category:Rearrangement reactions]] [[ja:セイファース・ギルバート増炭反応]] [[Category:Name reactions]]