Claisen rearrangement of allyl ester

Cartxjxylalion and subsequent allylation of alkyl heterocycles (via Claisen rearrangement of allyl esters)... 

CLAISEN IRELAND Rearrangment Rearrangement ol allyl phenyl ethers to o (or p-)allylphenols or of allyl vinyl ethers to 7,5-unsaturated aldehydes or ketones (Claisen) Rearrangement of allyl esters as enolate anions to Y. unsaturated acids (Ireland)... 

Claisen rearrangement. The enolate Claisen rearrangement of allyl esters of dipeptides is under chelation control by the addition of MnClj. 

Claisen rearrangement of allyl esters. Ireland and Mueller6 report that lithium enolates of allyl esters rearrange rapidly at room temperature or slightly above to the corresponding y,<5-unsaturated acids. Thus the allyl ester (1) is converted into the lithium enolate (2) by treatment with lithium isopropylcyclohexylamide in THF at —78°. The solution of (2) is then allowed to warm to 25° for 10 min. The y,S-unsaturated acid (3)... 

A synthesis of a-substituted S-unsaturated acids exploits the facile Claisen rearrangement of allyl ester enolates, which can be generated by conjugate addition of organocopper reagents to ally 2-alkenoates. ... 

Stereochemical control of enolization of esters. In continuation of studies on the Claisen rearrangement of allyl esters (4, 307-308), Ireland and Willard have observed that the stereochemistry of enolization of these esters (1) and (2) can be controlled to a marked extent by the solvent used. Thus Claisen rearrangement of (1) through the enolate obtained in THF alone gives the acids (3) and... 

A Claisen rearrangement of allylic esters is also effected by TMSOTf in the presence of triethylamine when chiral esters are employed the transfer of chirality is, however, quite low. Higher degrees of 1,4-asjtmmetric transmission are reached if bulkier silyl Inflates and bulkier amines are employed (eq 43). ... 

Lithium N-isopropylcyclohexylamidel trimethylchlorosilane Claisen rearrangement of allyl esters 7, -Ethylenecarboxylic acids... 

Scheme 6.6 Mechanism of asymmetric Claisen rearrangement of allyl esters catalyzed by chiral...

A synthetically valuable reaction sequence is the chlorodifluoroacetylation of various substituted allylic alcohols and the subsequent Reformatskii-Claisen rearrangement of the ester thus formed to interesting 2,2-difluoropentenoic acid derivatives [25] (equation H) Comparable sequences have been reported for ally monofluoroacetates [26] and allyl 3,3,3-trifiuoropropanoates [27] (equations 15 and 16). 

Sattelkau and Eilbracht90 have exploited the Claisen rearrangement of allyl vinyl ethers in their synthesis of several spiro compounds. As shown below in equation 62, 7,9-dimethyl-l,4-dioxa-spiro[4,5]decan-8-one, 118, was converted to a ,/J-unsaturated ester 119 which was reduced to allyl alcohol 120906. Allyl vinyl ether 121 underwent a rhodium-catalyzed Claisen rearrangement to afford 7r,13r-dimethyl-l,4-dioxa-(8rC9)-dispiro[4.2.4.2]tetradecan-10-one (122) in 36% yield. 

The Claisen rearrangement of allyl vinyl ethers is a classic method for the stereoselective synthesis of y,J-unsaturated esters. The allylic C-H activation is an alternative way of generating the same products [135]. Reactions with silyl-substituted cyclohexenes 197 demonstrate how the diastereoselectivity in the formation of 198 improves (40% to 88% de) for the C-H insertion reactions as the size of the silyl group increases (TMS to TBDPS) (Tab. 14.14). Indeed, in cases where there is good size differentiation between the two substituents at a methylene site, high diastereo- and enantioselectivity is possible in the C-H activation. 

The chelated ester enolate Claisen rearrangement of allylic glycinates 9 is carried out with zinc(II) chloride, which is added to the enolate at — 78 C (Table 19). The rearrangement occurs as the reaction mixture is allowed to warm to room temperature over 1 hour. The 2-amino-3,3-difluoro-4-[(2-methoxyethoxy)methoxy] alk-4-enoic acids 10 arc converted directly into the corresponding methyl esters, which can be hydrolyzed to the methyl 2-amino-3,3-difluoro-4-oxoal-kanoates. 

Table 19. Synthesis of 2-Amino-3,3-difluoro-4-[(2-methoxyethoxy)meth-oxy]alk-4-cnoic Acids 10 by the Chelated Ester Enolate Claisen Rearrangement of Allylic Glycinates 943...

Claisen rearrangement of aUylic alcohols to ethyl dienoates. Claisen rearrangement of allylic alcohols with an orthoacetate is known to provide 2-carbon homologated y,8-unsaturated esters (6, 607-608). Reaction with the phenylsulfinylorthoacetate 1 is accompanied by an in situ sulfoxide elimination to provide 2-carbon homologated dienoate esters (equation I). This novel reagent was used to convert the... 

Since its discovery in 1912, the Claisen rearrangement of allyl vinyl ethers (1 - 2 equation 1) has become one of the most powerful tools for stereoselective carbon-carbon bond formation. Much of its current popularity is due to the subsequent development of a series of new variants of this 3,3-sigma-tropic rearrangement. In 1940, Carroll reported the base-catalyzed rearrangement of -keto esters and allylic alcohols to alkenic ketones (3 4 5 equation 2). Twenty years later. Saucy and Marbet dem-... 

In the acid-catalyzed ortho ester Claisen rearrangement of allylic alcohol (303) with trimethyl orthobutyrate, diastereomers (304), (305) and (306) were isolated in a ratio of 63 30 7 (Scheme 53). The 3,3-sigmatropic rearrangement occuned with a high degree of stereofacial selectivity from the p-face of the allylic alcohol (a >13 1 for Ht). In contrast, Qaisen rearrangement of the enol ether (307) at 135-140 C (PhH, sealed tube) provid the desired -dicarbonyl compound (308) as a single diastereomer at... 

Allyl Claisen rearrangements of carbonate esters have already been discussed under ester rearrangement reactions (see Table 7). 

Recently, Claisen rearrangement of allyl-vinyl ether prepared from glycal ester with Tebbe reagent was reported [91]. In contrast to the Ireland-Claisen rearrangement, in principle, a non-enolizable ester can be employed (O Scheme 63). This method was applied for the synthesis of C-disaccharide. 

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