Claisen rearrangement definition

R. E. Ireland and J. P. Vevert, A chiral total synthesis of (—) and (+) nonactic acids from carbohydrate precursors and the definition of the transition for the enolate Claisen rearrangement in heterocyclic systems, J. Org. Chem. 45 4259 (1980). 

Figure 14.51 shows four Ireland-Claisen rearrangements that exhibit simple diastereose-lectivity (see Section 11.1.3 for a definition of the term). The substrates are two cis, trans-iso-meric propionic acid esters. The propionic acid esters in Figure 14.51 are derived from achiral allyl alcohols. This is different from the situation in Figure 14.50. However, these esters contain a stereogenic C=C double bond. Both the esters in Figure 14.51 can be converted into their 7 "-enolates with LDA inpureTHF (cf. Figure 13.16). Silylation affords the two T -con-figured O-allyl-O-silyl ketene acetals A and D, respectively. Alternatively, the two esters of Figure 14.51 can be converted into their Z -enolates with LDA in a mixture of THF and DMPU (cf. Figure 13.17). Treatment with rert-BuMe,SiCl then leads to the Z-isomers B and C of the O-allyl-O-silyl ketene acetals A and D, respectively.

Figure 4 Definitions of geometrical parameters for the transition state of (a) Cope rearrangement (b) Claisen rearrangement...

A zinca ene reaction is by definition (M. B. Smith and J. March, Advanced Organic Chemistry—Reactions, Mechanisms, and Structure, 5th edition, Wiley, New York, 2001, p. 1377) not a rearrangement, because it involves two different molecules. Nevertheless, reactions of the type described in equation 30 are included in this review regardless whether the authors rationalized them by a metallo-ene or metallo-Claisen pathway. This is justified since the original mechanistic assumptions were modified later (see Section II.A.3). 

Definitive evidence for the sole intermediacy of 2-allylarenethiols was obtained from work on the rearrangements of allyl quinolyl sulphides - . For example, 3-methallylquinolyl sulphide (100), which rearranges in dimethylaniline to 101 and 102, gave in butyric anhydride quantitative yield of the butyryl derivative (103) of the Claisen product 104. Compounds 100 and 104 yielded 101 and 102 in the same proportions when heated under identical conditions. 

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