The Meyer–Schuster rearrangement is the

chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...

described as an

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

- catalyzed rearrangement of secondary and tertiary

propargyl alcohol Propargyl alcohol, or 2-propyn-1-ol, is an organic compound with the formula C3H4O. It is the simplest stable alcohol containing an alkyne functional group. Propargyl alcohol is a colorless viscous liquid that is miscible with water and most pol ...

s to α,β-unsaturated

ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

s if the alkyne group is internal and α,β-unsaturated

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

s if the alkyne group is terminal.Swaminathan, S.; Narayan, K. V. "The Rupe and Meyer-Schuster Rearrangements" '' Chem. Rev.'' 1971, ''71'', 429–438.
Review

Mechanism

The reaction proceeds by three major steps: (1) the rapid protonation of oxygen, (2) the slow,

rate-determining step In chemical kinetics, the overall rate of a reaction is often approximately determined by the slowest step, known as the rate-determining step (RDS or RD-step or r/d step) or rate-limiting step. For a given reaction mechanism, the prediction of the ...

comprising the 1,3-shift of the protonated hydroxy group, and (3) the keto-enol tautomerism followed by rapid deprotonation. Formation of the unsaturated carbonyl compound is irreversible. Solvent is important and solvent caging is proposed to stabilize the

transition state In chemistry, the transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. It is often marked w ...

Rupe rearrangement

The reaction of tertiary alcohols containing an α-

acetylenic In organic chemistry, the term acetylenic designates *A doubly unsaturated position (''sp''-hybridized) on a molecular framework, for instance in an alkyne such as acetylene Acetylene (Chemical nomenclature, systematic name: ethyne) is a chemi ...

group does not produce the expected aldehydes, but rather α,β-unsaturated

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated as ...

ketones via an

enyne An enyne is an organic compound containing a double bond (alkene) and a triple bond (alkyne). It is called a conjugated enyne when the double and triple bonds are conjugated. The term is a contraction of the terms alkene and alkyne. The si ...

intermediate. This alternate reaction is called the Rupe reaction, and competes with the Meyer–Schuster rearrangement in the case of tertiary alcohols. Mechanismus_Rupe-Umlagerung_V1

Use of catalysts

The traditional Meyer–Schuster rearrangement is induced by strong acids, which introduces competition with the Rupe reaction if the alcohol is tertiary. Milder conditions are possible with

transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinid ...

-based and

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...

catalysts (for example, Ru- and Ag-based catalysts).

Microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...

-radiation with catalyst to give excellent yields with short reaction times and good

stereoselectivity In chemistry, stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non- stereospecific creation of a new stereocenter or during a non-stereospecific transformation ...

Use in organic synthesis

The Meyer–Schuster rearrangement has been used in a variety of applications, from the conversion of ω-alkynyl-ω-carbinol

lactam A lactam is a Cyclic compound, cyclic amide, formally derived from an amino alkanoic acid through cyclization reactions. The term is a portmanteau of the words ''lactone'' + ''amide''. Nomenclature Greek_alphabet#Letters, Greek prefixes in alpha ...

s into enamides using catalytic PTSA to the synthesis of α,β-unsaturated

thioester In organic chemistry, thioesters are organosulfur compounds with the molecular structure . They are analogous to carboxylate esters () with the sulfur in the thioester replacing oxygen in the carboxylate ester, as implied by the thio- prefix ...

s from γ-sulfur substituted propargyl alcohols to the rearrangement of 3-alkynyl-3-hydroxyl-1''H''-

isoindole In organic chemistry and heterocyclic chemistry, isoindole consists of a benzene ring fused with pyrrole. The compound is an isomer of indole. Its reduced form is isoindoline. The parent isoindole is a rarely encountered in the technical lit ...

s in mildly acidic conditions to give the α,β-unsaturated carbonyl compounds. One of the most interesting applications, however, is the synthesis of a part of

paclitaxel Paclitaxel, sold under the brand name Taxol among others, is a chemotherapy medication used to treat ovarian cancer, esophageal cancer, breast cancer, lung cancer, Kaposi's sarcoma, cervical cancer, and pancreatic cancer. It is administered b ...

in a

diastereomer In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have di ...

ically-selective way that leads only to the ''E''-alkene. 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.

History

The reaction is named after Kurt Meyer and Kurt Schuster.) Reviews have been published by Swaminathan and Narayan,

References

{{DEFAULTSORT:Meyer-Schuster rearrangement Rearrangement reactions Name reactions