Shapiro-Heath reaction

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, 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. 

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. 

The formation of unrearranged alkenes, generally the less substituted isomers, by treatment of ketone derived / -toluenesulfonylhydrazones with alkyl lithium reagents is known as the Shapiro reaction R. H. Shapiro, M. J. Heath, J. Am. Chem. Soc. 89, 5734 (1967). Use of A -diethylaminosulfonylhydrazones J. Kang et al, Bull. Korean Chem. 13,192 (1992). 

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