Olefins Shapiro reaction

The Bamford-Stevens reaction and the Shapiro reaction share a similar mechanistic pathway. The former uses a base such as Na, NaOMe, LiH, NaH, NaNHa, heat, etc., whereas the latter employs bases such as alkyllithiums and Grignard reagents. As a result, the Bamford-Stevens reaction furnishes more-substituted olefins as the thermodynamic products, while the Shapiro reaction generally affords less-substituted olefins as the kinetic products. 

The Shapiro reaction provides a convenient, easy and straightforward method to convert ketones into a plethora of olefinic substances in high yields. Many of these vinyllithium derivatives are useful for further synthetic manipulations. No attempt is made in this chapter to cover all the applications of the Shapiro reaction and only few representative examples will be described. A variety of polyolefins such as 119, used for cation olefin cyclization, can be stereospecifically formed in a concise and modular approach in a single step from the components shown in equation 42 via the Shapiro reaction . 

Shapiro Reaction Treatment of the tosylhydrazone of an aldehyde or a ketone with a strong base leads to the formation of an olefin, the reaction being formally an elimination accompanied by a hydrogen shift. This reaction is called Shapiro reaction. 

The Bamford-Stevens synthesis is related to the Shapiro reaction (Shapiro and Heath, 1967 reviews Shapiro, 1976 Adlington and Barrett, 1983), in which a 4-toluenesulfonyl hydrazone of an aldehyde or a ketone is treated with at least two equivalents of a very strong base, usually, methyllithium (see Organic Syntheses examples of Chamberlin et al., 1983, and Shapiro et al., 1988). The Shapiro reaction leads to an olefin by a hydrogen shift. The mechanism has been proposed by Casanova and Waegell (1975) as given in (2-34). This mechanism involves a diazenide anion 2.81 as intermediate. 

Shapiro reaction. (2, 418-419 6, 598-600). Several laboratories have used EDA instead of an alkyllithium for decomposition of tosylhydrazones of ketones to olefins. Trisubstituted alkenes can be prepared by this modification in moderate yields from tosylhydrazones that contain only tertiary a-hydrogens. This modification also favors formation of the (Z)-disubstituted olefin. ... 

This reaction was initially reported by Shapiro in 1967. It is a synthesis of olefins by means of a base-promoted decomposition of p-toluenesulfonylhydrazones of the corresponding ketones or aldehydes. Therefore, it is generally known as the Shapiro reaction, or Shapiro elimination." Occasionally, it is also referred to as the Shapiro olefination, Shapiro lithiation reaction, Shapiro fragmentation, or Shapiro degradation." ... 

The Shapiro reaction of tosylhydrazones with base has now been extended as a route to a wider variety of functionalized olefins. Thus, treatment of tosylhydrazones, which contain only a tertiary a-hydrogen, with lithium iso-propylamide, can now yield trisubstituted olefins. The yields are only moderate, but the procedure is convenient. Regiospecifically generated tosyl-hydrazone dianions may be trapped with aldehydes and ketones to give, on neutralization, /3-hydroxytosylhydrazones further treatment with alkyl-lithium reagents yields allylic and homoallylic alcohols. These procedures are exemplified in Scheme 21. 

Shapiro and Related Reactions Organic Reactions 1990, 39, 1 1976, 23, 405 - Reaction of a tosylhydrazone with a strong base to give an olefin. 

The reduction of a carbonyl group to an olefin has been accomplished by the Shapiro modification5 of the Bamford-Stevens reaction and by the hydride reduction of the corresponding enol ether,6 enol acetate,7 or en-amine.8 The nickel reduction of the thioketal has also been used successfully.9... 

J. J. Eisch, P. O. Otieno, K. Mackenzie, and B. W. Kotowicz, Electronic and Steric Design of Novel Group 13 Lewis Acids and Their Synthesis via Metal-Tin Exchange Reactions (1) Toward the Ideal Olefin Polymerization Catalyst, in Group 13 Chemistry From Fundamentals to Appheations , ACS Symposium Series 822, eds. P. J. Shapiro and D. A. Atwood, American Chemical Society, Washington, DC, 2002, p. 88. 

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