Ester enolate Claisen rearrangement 630 Subject

The ene ester 5, prepared from (L)-malic acid via 4, was subjected to the ester enolate Claisen rearrangement under Ireland conditions to give stereoselectively the C-16 to C-22 fragment 6 containing an U-trisubstituted double bond of the immunosuppressant FK-506 (7) isolated from Streptomyces tsukubaensis440. 

An electrochemical oxidative decarboxylation in combination with an ester enolate Claisen rearrangement was reported by Wuts et al. (Scheme 5.2.26) [51]. A variety of allylic esters such as 97 was subjected to an Ireland-Qaisen rearrangement, and the resulting acids (98) obtained were submitted to electrolytic decarboxylation in a divided cell to afford ketals 99. The use of the divided cell was necessary to suppress side reactions such as alkene reduction. 

Enolates of allyl esters of a-amino acids are also subject to chelation-controlled Claisen rearrangement.249... 

The ester 7-1 gives alternative stereoisomers when subjected to Claisen rearrangement as the lithium enolate or as the silyl ketene acetal. Analyze the respective transition structures and develop a rationale to explain these results. 

The success of the Claisen-Cope rearrangement need not be limited to the production of aldehydes via enol ethers. Allylic alcohol (58) is successively transposed into a mixture of allylic isomers (59 Scheme 4), and is subjected to an orthoester Claisen rearrangement at 150 "C to provide ester (61). The moderate temperature of the Claisen step permits the isolation of an intermediate (c/. Scheme 3) prior to the final Cope rearrangement (195 C) to. y-unsaturated esters (60). The esters (60) are a 55 45 mixture of ( )- and (Z)-double bond isomers owing to the near equal steric bulk of the methyl and acetic acid residues in the transition state for the Cope rearrangement. ... 

The ability of charged substituents to accelerate the 3,3-sigmatropic reiarrangement of allyl vinyl ethers (the Claisen rearrangement) has also been documented. The effect of oxyanion substituents on the rate and course of aliphatic Claisen rearrangements has been the subject of particular attention. " In 1972, Ireland and Mueller reported that the lithium enolate derivatives of allyl esters undergo rapid and effi-... 

---