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| The '''Staudinger Synthesis''' is the [[chemical reaction]] described as an [[acid]]-[[catalysis|catalyzed]] [[rearrangement reaction|rearrangement]] of secondary and tertiary [[propargyl alcohol]]s to α,β-unsaturated [[ketone]]s if the alkyne group is internal and α,β-unsaturated [[aldehyde]]s if the alkyne group is terminal.<ref>Meyer, K. H.; Schuster, K. ''[[Chemische Berichte|Ber.]]'' '''1922''', ''55'', 819.({{DOI|10.1002/cber.19220550403}})</ref> Reviews have been published by Swaminathan and Narayan,<ref name="swaminathan">Swaminathan, S.; Narayan, K. V. "The Rupe and Meyer-Schuster Rearrangements" ''[[Chem. Rev.]]'' '''1971''', ''71'', 429–438. ([http://dx.doi.org/10.1021/cr60273a001 Review])</ref> Vartanyan and Banbanyan,<ref>Vartanyan, S. A.; Banbanyan, S. O. ''Russ. Chem. Rev.'' '''1967''', ''36'', 670. ([http://dx.doi.org/10.1070/RC1967v036n09ABEH001681 Review])</ref> and Engel and Dudley,<ref>Engel, D.A.; Dudley, G.B. ''[[Organic and Biomolecular Chemistry]]'' '''2009''', ''7'', 4149–4158. ([http://dx.doi.org/10.1039/b912099h Review])</ref> the last of which describes ways to promote the Meyer–Schuster rearrangement over other reactions available to propargyl alcohols.
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| [[Image:Meyer-Schuster Rearrangement Scheme.png|center|300px|The Meyer-Schuster rearrangement]]
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| When catalyzed by base, the reaction is called the [[Favorskii reaction]].
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| ==Mechanism==
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| [[File:Meyer-schuster-rearrangement.svg|center|600px|Meyer-Schuster Rearrangement]]
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| The [[reaction mechanism]]<ref>Li, J.J. In ''Meyer-Schuster rearrangement''; Name Reactions: A Collection of Detailed Reaction Mechanisms; Springer: Berlin, 2006; pp 380–381.({{DOI|10.1007/978-3-642-01053-8_159}})</ref> begins with the protonation of the alcohol which leaves in an [[elimination reaction|E1 reaction]] to form the [[allene]] from the [[alkyne]]. Attack of a water molecule on the [[carbocation]] and deprotonation is followed by [[tautomerization]] to give the [[carbonyl#α,β-Unsaturated carbonyl compounds|α,β-unsaturated carbonyl compound]].
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| Edens ''et al.'' have investigated the reaction mechanism.<ref>Edens, M.; Boerner, D.; Chase, C. R.; Nass, D.; Schiavelli, M. D. ''[[J. Org. Chem.]]'' '''1977''', ''42'', 3403–3408. ({{DOI|10.1021/jo00441a017}})</ref> They found it was characterized by three major steps: (1) the rapid protonation of oxygen, (2) the slow, [[rate-determining step]] comprising the [[sigmatropic reaction|1,3-shift]] of the protonated hydroxy group, and (3) the [[keto-enol tautomerism]] followed by rapid deprotonation.
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| In a study of the rate-limiting step of the Meyer–Schuster reaction, Andres ''et al.'' showed that the driving force of the reaction is the irreversible formation of unsaturated carbonyl compounds through [[carbonium ion]]s.<ref>Andres, J.; Cardenas, R.; Silla, E.; Tapia, O. ''[[J. Am. Chem. Soc.]]'' '''1988''', ''110'', 666–674. ({{DOI|10.1021/ja00211a002}})</ref> They also found the reaction to be assisted by the solvent. This was further investigated by Tapia ''et al.'' who showed [[cage effect (chemistry)|solvent caging]] stabilizes the transition state.<ref>Tapia, O.; Lluch, J.M.; Cardena, R.; Andres, J. ''[[J. Am. Chem. Soc.]]'' '''1989''', ''111'', 829–835. ({{DOI|10.1021/ja00185a007}})</ref>
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| ==Rupe rearrangement==
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| The reaction of tertiary alcohols containing an α-[[acetylenic]] group does not produce the expected aldehydes, but rather α,β-unsaturated [[methyl]] ketones via an [[enyne]] [[reaction intermediate|intermediate]].<ref>Rupe, H.; Kambli, E. ''[[Helv. Chim. Acta]]'' '''1926''', ''9'', 672. ({{DOI|10.1002/hlca.19260090185}})</ref><ref>Li, J.J. In ''Rupe rearrangement''; Name Reactions: A Collection of Detailed Reaction Mechanisms; Springer: Berlin, 2006; pp 513–514.({{DOI|10.1007/978-3-642-01053-8_224}})</ref> This reaction competes with the Meyer–Schuster rearrangement in the case of tertiary alcohols.
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| [[Image:Rupe-rearrangement.svg|center|600px|The Rupe rearrangement]]
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| ==Use of catalysts==
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| While the traditional Meyer–Schuster rearrangement uses harsh conditions with a strong acid as the catalyst, this introduces competition with the Rupe reaction if the alcohol is tertiary.<ref name="swaminathan"/> Milder conditions have been used successfully with [[transition metal]]-based and [[Lewis acid]] catalysts (for example, Ru-<ref>Cadierno, V.; Crochet, P.; Gimeno, J. ''[[Synlett]]'' '''2008''', 1105–1124. ({{DOI|10.1055/s-2008-1072593}})</ref> and Ag-based<ref>Sugawara, Y.; Yamada, W.; Yoshida, S.; Ikeno, T.; Yamada, T. ''[[J. Am. Chem. Soc.]]'' '''2007''', ''129'', 12902-12903. ({{DOI|10.1021/ja074350y}})</ref> catalysts). Cadierno ''et al.'' report the use of [[microwave chemistry|microwave]]-radiation with InCl<math>_3</math> as a catalyst to give excellent yields with short reaction times and remarkable [[stereoselectivity]].<ref>Cadierno, V.; Francos, J.; Gimeno, J. ''[[Tetrahedron Lett.]]'' '''2009''', ''50'', 4773–4776.({{DOI|10.1016/j.tetlet.2009.06.040}})</ref> An example from their paper is given below:
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| [[Image:Cadierno-microwave-catalysis.svg|center|Cadierno et al.'s microwave-assisted catalysis]]
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| ==Applications==
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| The Meyer–Schuster rearrangement has been used in a variety of applications, from the conversion of ω-alkynyl-ω-carbinol [[lactam]]s into enamides using catalytic PTSA<ref>Chihab-Eddine, A.; Daich, A.; Jilale, A.; Decroix, B. ''[[J. Heterocycl. Chem.]]'' '''2000''', ''37'', 1543–1548.({{DOI|10.1002/jhet.5570370622}})</ref> to the synthesis of α,β-unsaturated [[thioester]]s from γ-sulfur substituted propargyl alcohols<ref>Yoshimatsu, M.; Naito, M.; Kawahigashi, M.; Shimizu, H.; Kataoka, T. ''[[J. Org. Chem.]]'' '''1995''', ''60'', 4798–4802.({{DOI|10.1021/jo00120a024}})</ref> to the rearrangement of 3-alkynyl-3-hydroxyl-1''H''-[[isoindole]]s in mildly acidic conditions to give the α,β-unsaturated carbonyl compounds.<ref>Omar, E.A.; Tu, C.; Wigal, C.T.; Braun, L.L. ''[[J. Heterocycl. Chem.]]'' '''1992''', ''29'', 947–951.({{DOI|10.1002/jhet.5570290445}})</ref> One of the most interesting applications, however, is the synthesis of a part of [[paclitaxel]] in a [[diastereomer]]ically-selective way that leads only to the ''E''-alkene.<ref>Crich, D.; Natarajan, S.; Crich, J.Z. ''[[Tetrahedron]]'' '''1997''', ''53'', 7139–7158.({{DOI|10.1016/S0040-4020(97)00411-0}})</ref>
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| [[Image:Meyer-schuster-taxol.svg|center|Part of the synthesis of taxol using the Meyer-Schuster rearrangement]]
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| The step shown above had a 70% yield (91% when the byproduct was converted to the Meyer-Schuster product in another step). The authors used the Meyer–Schuster rearrangement because they wanted to convert a hindered ketone to an alkene without destroying the rest of their molecule.
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| ==References==
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| {{reflist}}
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| {{DEFAULTSORT:Meyer-Schuster rearrangement}}
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| [[Category:Rearrangement reactions]]
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| [[Category:Name reactions]]
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