Shapiro olefination

It is a modification of the Shapiro olefin synthesis3 which allows the vinyl anion intermediate to be trapped with primary halides and other electrophiles. Use of triisopropylbenzenesulfonylhydrazones as the vinyllithium precursor4 is an improvement over previously4 used toluenesulfonylhy-drazones,5 6 which can be employed in the sequence provided excess sec-butyllithium (typically 4.5 equiv) and alkyl halide (3.0 equiv) are used. Methyl ketones (e.g., acetone, acetophenone, 2-octanone) can also be used and can be converted into their dianions using 2.2 equiv of the weaker base, n-butyllithium. The conditions described above, with the slight modifications noted, have been used for a variety of ketones as shown in Table I. 

In the laboratory of K. Mori the task of determining the absolute configuration of the phytocassane group of phytoalexins was undertaken. To this end, the naturally occurring (-)-phytocassane D was synthesized from (R)-Wieland-Miescher ketone. During the synthesis, a tricyclic ketone intermediate was subjected to the Shapiro olefination reaction to give the desired cyclic alkene in good yield. 

Related reactions Bamford-Stevens-Shapiro olefination ... 

BAMFORD - STEVENS CAGLIOTI. SHAPIRO Olefination Conversion of ketones to olefins via tosyl hydrazones with NaOR, LAH, LDA or BuLi... 

Manipulation of the carbonyl function to epoxide 3 was accomplished by conversion to the tosylhydrazone, Shapiro olefination, and epoxidation.The latter step occurred with high ster-eocontrol, as did the epoxide ring opening with acidic methanol. Oxidation to ketone 4 was then performed, and from this product the desired derivative 5 was obtained by known procedures. 

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." ... 

Finally, although not shown in the table, the material that is shown there can be combined with other reactions. The Slrecker amino acid synthesis, which is discussed again in Chapter 12, is among the most valuable, while the Shapiro Olefination and the related Bamford-Sfevens reaction have proved useful in producing alkenes from aldehydes and ketones. 

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 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 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. 

Mew olefin synthesis (2,418 19). Shapiro and Duncan report a detailed procedure for the preparation of p-toluenesulfonylhydrazine and its use for the synthesis of 2-bomene. 

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