Shapiro olefin synthesis

It is a modification of the Shapiro olefin synthesis which allows the vinyl anion intermediate to be trapped with pnmary halides and other electrophiles. Use of triisopropylbenzenesulfonylhydrazones as the vinyllithium precursor is an improvement over previously" used toluenesulfonylhy-drazones/ 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. 

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. 

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. 

New Olefin Synthesis. Shapiro and Heath report a new synthesis in which an aliphatic tosylhydrazone having an a-hydrogen is treated with an alkyllithium in ether or hexane to give an olefin in high yield. Examples ... 

Transposition of an enone function. Patel and Reusch have used the Shapiro-Heath olefin synthesis (2, 418-419) in a method for transposition of a cyclic enone function (c/. Wharton reaction, 1, 419). The method is illustrated... 

Shapiro-Heath olefin synthesis (2, 418-419 4, 511 5, 678-679 6, 598-599). Vedejs has mentioned that LDA can be used instead of alkyllithiums for conversion of the more typical tosylhydrazones into olefins at 0" in THF. This variation was used in the synthesis of a new (CH)i2-hydrocarbon (1). 

Shapiro-Heath olefin synthesis (2, 403 3, 284 4, 485-489 5, 678 680). Dauben and co-workers have reported that the stereochemistry of the hydrazone group alTects the course of the reaction. Thus the isomeric tosylhydrazoncs of pulegonc. (la) and (lb), behave difierently (la) is converted exclusively or prcdominanlly under these conditions to the diene (2), whereas (lb) always gives a mixture oft2) ami (3). with the latter diene predominating. It appears that at least two reaction pathways are involved. 

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. 

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. 

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. 

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