Johnson-Corey-Chaykovsky reaction

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The Johnson-Corey-Chaykovsky reaction , also known as the Corey-Chaykovsky reaction or CCR , is a chemical reaction in organic chemistry for the synthesis of epoxides , aziridines, and cyclopropanes . It was discovered by A. William Johnson in 1961 and further developed by EJ Corey and Michael Chaykovsky . With the addition of a sulfur ylide , the reaction leads to a ketone , aldehyde , imine or enone to form the corresponding three-membered ring system. In the reaction, the trans substitution is favored diastereoselectively , regardless of the original configuration. The synthesis of epoxides using this method represents an alternative to the traditional epoxidation of olefins .

Johnson-Corey-Chaykovsky Reaction

The reaction is widely used for epoxidation via methylene transfer and has been used in several notable total syntheses .

history

The original publication by Johnson described the reaction of 9-dimethylsulfonium fluorenylide with substituted benzaldehyde derivatives. The Wittig reaction actually aimed at did not take place; instead, a benzalfluorenoxide was obtained. Johnson pointed out that the reaction between the sulfur ylide and benzaldehyde is not like the phosphorus. and arsenylidene led to the benzalfluorenes.

The first example of a Johnson – Corey – Chaykovsky reaction

The subsequent development of dimethyloxosulfonium methylide (CH 3 ) 2 SOCH 2 and dimethylsulfonium methylide (CH 3 ) 2 SCH 2 by Corey and Chaykovsky, also known as Corey-Chaykovsky reagents, established the reaction as an effective methylene transfer reaction in organic chemistry.

mechanism

The reaction mechanism of the Johnson-Corey-Chaykovsky reaction consists in the first step of a nucleophilic addition of the ylid to a carbonyl or imine group. The negative charge is transferred to the heteroatom . The sulfonium cation is a good leaving group and is released through formation of the three-membered ring. In the related Wittig reaction, the formation of the much stronger phosphorus-oxygen double bond prevents oxirane formation and instead olefination takes place via a four-membered cyclic intermediate.

Mechanism of the Johnson – Corey – Chaykovsky reaction

The observed trans -diastereoselectivity results from the reversibility of the first nucleophilic addition, which allows an equilibrium to be established in favor of the preferred anti- betaine versus the formation of the syn- betaine. Adding the ylid creates a betaine with neighboring charges; Calculations based on density functional theory have shown that the rate-determining step is the rotation of the central bond into the conformer that allows the necessary nucleophilic addition of the sulfonium.

Selectivity in the Johnson – Corey – Chaykovsky reaction

See also

Individual evidence

  1. ↑ a b Varinder K. Aggarwal, Jeffery Richardson: The complexity of catalysis: origins of enantio- and diastereocontrol in sulfur ylide mediated epoxidation reactions . In: Chemical Communications . No. 21, 2003, p. 2644. doi : 10.1039 / b304625g .
  2. ↑ Varinder K. Aggarwal, Caroline L. Winn: Catalytic, Asymmetric Sulfur Ylide-Mediated Epoxidation of Carbonyl Compounds: Scope, Selectivity, and Applications in Synthesis . In: Accounts of Chemical Research . 37, No. 8, 2004, pp. 611-620. doi : 10.1021 / ar030045f .
  3. ↑ Yu.G. Gololobov, AN Nesmeyanov, VP lysenko, IE Boldeskul: Twenty-five years of dimethylsulfoxonium ethylide (corey's reagent) . In: Tetrahedron . 43, No. 12, 1987, pp. 2609-2651. doi : 10.1016 / S0040-4020 (01) 86869-1 .
  4. ↑ a b An-Hu Li, Li-Xin Dai, Varinder K. Aggarwal: Asymmetric Ylide Reactions: Epoxidation, Cyclopropanation, Aziridination, Olefination, and Rearrangement . In: Chemical Reviews . 97, No. 6, October 1, 1997, pp. 2341-2372. doi : 10.1021 / cr960411r .
  5. ↑ Eoghan M. McGarrigle, Eddie L. Myers, Ona Illa, Michael A. Shaw, Samantha L. Riches, Varinder K. Aggarwal: Chalcogenides as Organocatalysts . In: Chemical Reviews . 107, No. 12, December 1, 2007, pp. 5841-5883. doi : 10.1021 / cr068402y .
  6. ^ A. William Johnson, Robert B. LaCount: The Chemistry of Ylids. VI. Dimethylsulfonium Fluorenylide — A Synthesis of Epoxides1 . In: Journal of the American Chemical Society . 83, No. 2, Jan. 1, 1961, pp. 417-423. doi : 10.1021 / ja01463a040 .

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