Winter olefin synthesis

Transformation of diols to the corresponding olefins by sequential treatment with l,r-thiocarbonyldiimidazole and trimethylphosphite. 

A mechanism involving a carbene intermediate is also viable as it is supported by pyrolysis studies  

1 Cornforth, J. W. In The Chemistry of Penicillin Princeton University Press New Jersey, 1949, 700. 

Vicinal diol is oxidized to the two corresponding carbonyl compounds using Pb(OAc)4. 

Transformation of diols to the corresponding olefins by sequential treatment with l,r-thiocarbonyldiimidazole and trimethylphosphite. Also known as Corey-Winter reductive elimination, or Corey-Winter reductive olefmation. 

An acyclic mechanism is possible as well. It is much slower than the cyclic mechanism, but is operative when the cyclic intermediate can not form  

1 Criegee, R. Ber. Dtsch. Chem. Ges. 1931, 64, 260. Rudolf Criegee (1902—1975) was bom in DUsseldorf, Germany. He earned his Ph.D. at age 23 under K. Dimroth at Wurzburg. Criegee became a professor at Technical Institute at Karlsruhe in 1937, a chair in 1947. He was known for his modesty, mater-of-factness, and his breadth of interests. 

Name Reactions A Collection of Detailed Mechanisms and Synthetic Applications, DOI 10.1007/978-3-319-03979-4 75, Springer International Publishing Switzerland 2014 

Winter, R. A. E. J. Am. Chem. Soc. 1963, 85, 2677-2678. Roland A. E. Winter works at Ciba Specialty Chemicals Corporation, USA. 

Mergott, D. J. Corey-Winter olefin synthesis. In Name Reactions for Functional Group Transformations, Li, J. J., Ed. Wiley Hoboken, NJ, 2007, pp 354-362. (Review). 

Name Reactions, 4th ed., DOI 10.1007/978-3-642-01053-8 68, Springer-Verlag Berlin Heidelberg 2009 

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The Corey-Winter olefin synthesis is based on the stereospecific loss of carbon dioxide or carbon disulfide from the carbenes formed by treatment with bivalent organophosphorus compounds of thionocarbonates or trithiocarbonates [218-220]. 

Corey-Winter olefin synthesis. The Corey-Winter olefin synthesis (1, 1233-1234) involves treatment of a thionocarbonale with trimethyl phosphite ... 

Corey-Winter olefin synthesis (I. I23.3-I234). Chong and Wiseman were able to demonstrate the transient existence of bicyclo[3.2.l]octenc-l (2, a bridgehead alkene which violates Bredt s rule) by application of the Corey-Winter olefin synthesis. Thus treatment of the thionocarbonatc (I) with triethyl phosphite at reflux (165°) fur 24 hr. in the presence of I,3-diphenyli obenzofurane (1, 342-343 2, 178-179) leads to the formation of two Diels-Alder adducts (3) and (4) derived from (2). 

Corey-Winter olefin synthesis. Synthesis of olefins from 1,2-diols and thiocarbonyldiimidazole. Treatment of the intermediate cychc thionocarbo-nate with trimethylphosphite yields the olefin by els elimination. 

The Corey-Winter olefin synthesis is a two-step transformation of a diol 1 to an olefin 3.1"3 A cyclic thionocarbonate 2 is prepared from the diol 1, and subsequent heating of 2 with phosphite affords olefin 3. 

However, evidence opposing the intermediacy of a carbene species in the Corey-Winter olefin synthesis also exists.3 Thermal decomposition of hydrazone salt 14, which is proposed to proceed via carbene 12, leads to a mixture of products 13, 15, and 16.7 Thus, an alternative mechanism has been proposed for the Corey-Winter reaction that invokes a phosphorus ylide. In this mechanistic scenario, initial reaction of thionocarbonate 10 with trimethylphosphite affords zwitterion 11. Cyclization generates... 

The Corey-Winter olefin synthesis has been performed on p-lactam derivatives.18 This olefination was employed in cases where traditional Wittig-type olefination of the corresponding aldehyde led to disappointing results. In one example, treatment of 40 with carbonyldiimidazole and exposure of the resulting thionocarbonate to P(OMe)3 afforded olefin 41 in 81% yield. 

Corey-Winter olefin synthesis (1, 1233-1234 2,439-441 3,315-316 4, 269-270, 541-542 5,34, 661). Vedejs and Wu converted thionocarbonates into olefins by alkylation with methyl iodide (90°, DME, sealed tube) followed by reduction (zinc dust—ethanol or magnesium amalgam—THF). This two-step procedure was used for preparation of the cyclobutene (2) in this case the reaction with triethyl phosphite was immeasurably slow. 

COREY-WINTER OLEFIN SYNTHESIS Methyl iodide. N,N -Thiocarbonyldiimidazole. 

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