Corey-Claisen

Ester enolate Claisen, Ireland-Claisen, Reformatsky-Claisen, Corey-Claisen and Kazmaier-Claisen varients ... 

The recognition of consonant bifunctional relationships in the target molecule allows their disconnection by a retro-Claisen, a retro-aldol or a retro-Mannich condensation or by retro-Michael addition [equivalent, according to Corey s formalisation, to the application of the corresponding transforms (= operators) to the appropriate retrons]. 

Brooks, D. A. Claisen Isoxazole Synthesis In Name Reactions in Heterocyclic Chemistry, Li, J. J. Corey, E. J., Eds. Wiley Sons Hoboken, NJ, 2005, 220-224. (Review). 

Cammidge 126 Carpentier 387 Chan 188 Chung 18 Claisen 10 Corey 41, 181 Cosp 318, 386 Craig 150... 

The Claisen rearrangement has attracted much attention as an attractive tool for the construction of new carbon-carbon bonds. Taguchi et al. reported the enantioselective and regioselective aromatic Claisen rearrangement of catechol mono allylic ether derivatives by means of Corey s chiral boron reagent (Eq. 70) [53a,54]. The mechanism of enantioselectivity is that a rigid five-membered cyclic intermediate is formed by reaction of catechol mono allylic ethers with the chiral boron reagent and this is fol-... 

C—4 chirality to C—2 with concomitant introduction of a two-carbon chain was carried out by Claisen rearrangement, using triethyl orthoacetate. Deprotection and ring closure gave bicyclic lactone [41], which has been converted (26,27) to the Corey lactone and a synthetic equivalent. 

Claisen reanangement, 228, 236, 251 Clauson-Kaas reaction, 621 Clindamycin, 107,108 Compactin, 570 Cryptoqtorin, 570 Corey lactone, 549 Cyclic, 55... 

Corey, E. J., Lee, D. H. Highly enantioselective and diastereoselective Ireland-Claisen rearrangement of achiral allylic esters. J. Am. Chem. Soc. 1991, 113, 40264028. 

Rearrangements. By applying Corey s diazaborolidine catalyst to aromatic Claisen rearrangement, a chiral side chain is introduced into the ortho position of catechols. Highly enantioselective rearrangement of 0-allylimidates 111 containing a methoxybinaphthyl substituent has been witnessed. ... 

Accordingly, ( )-alcohol A was oxidized to give B. Asymmetric reduction of B with Corey s CBS reagent gave (5)-A (79% ee). The 5-configuration of A was confirmed by its conversion to the known lactone (5)-C. Then, the ester (5)-D prepared from (5)-A was subjected to the Claisen rearrangement to... 

Most [3,3]-sigmatropic rearrangements take place thermally, and the Cope, oxy-Cope and Claisen rearrangements are among the most important rearrangements in this class. Important variants of the Claisen rearrangement include the Johnson modification via orthoesters, the Eschenmoser modification via ketene N,O-acetals, the Ireland modification via ketene silylacetals and the Corey modification via boron ester enolates [696], The aza-Claisen rearrangement has also seen... 

Corey and Lee [696] have recently proposed a variant of the Ireland-Claisen rearrangement that uses boron enolates of allylic esters derived from 2.62. The E-crotyi (Re = Me) or E-cinnamyl (Rz = Ph) derivatives could be selectively transformed into the Z- or E-boron enolates 10.46 at low temperature (Figure 10.16). The rearrangements take place at about 0°C, and the Z-enolates lead vay selectively to anti acids 10.47 with an excellent enantiomeric excess while the E-enolates lead to syn acids 10.48, with an interesting selectivity if R = Me or Et (Figure 10.16). In most cases, the enantiomeric excesses are excellent however, when the reaction is conducted with ally] esters (R = H), the ee s are a little bit lower (74 - 84%). These results are interpreted via a chair transition state that minimizes steric interactions [696],... 

The synthesis of three fragments 278, 282, and 285 for the C21-C42 bottom segment is summarized in Scheme 41. The Eschenmoser-Claisen rearrangement of amido acetal of 276, which was prepared via 2-bromocyclohexenone by Corey s asymmetric reduction, afforded amide 277. Functional group manipulation including chain elongation provided Evans-type amide 278. The Evans aldol reaction of boron enolate of 279 with aldehyde 280 stereoselectively afforded 281, which was converted into aldehyde 282 through a sequence of seven steps... 

---