Kazmaier-Claisen

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

Further variations of the Claisen rearrangement protocol were also utilized for the synthesis of allenic amino acid derivatives. Whereas the Ireland-Claisen rearrangement led to unsatisfactory results [133b], a number of variously substituted a-allenic a-amino acids were prepared by Kazmaier [135] by chelate-controlled Claisen rearrangement of ester enolates (Scheme 18.47). For example, deprotonation of the propargylic ester 147 with 2 equiv. of lithium diisopropylamide and transmetallation with zinc chloride furnished the chelate complex 148, which underwent a highly syn-stereoselective rearrangement to the amino acid derivative 149. 

Kazmaier, U. Synthesis of y,5-unsaturated amino acids via ester enolate Claisen rearrangement of chelated allylic esters. Amino Acids... 

Kazmaier, U. Application of the chelate-enolate Claisen rearrangement to the synthesis of y,5-unsaturated amino acids. Liebigs Ann. Chem. 

Kazmaier, U., Mues, H., Krebs, A. Asymmetric chelated Claisen rearrangements in the presence of chiral ligands-scope and limitations. Chem.-Eur. J. 2002, 8, 1850-1855. 

Kazmaier, U., Synthesis of quaternary amino acids containing P.v- as well as 7,S-unsaturated side chains via chelate-enolate Claisen rearrangement. Tetrahedron Lett., 31, 5351, 1996. 

Other variants of Claisen rearrangement [31] (Kazmaier [32], Ireland [33], and Johnson [34]) gave no rearranged product. 

Some advancement has been described for the development of a catalytic enantioselective ester enolate Claisen rearrangement. The strong Lewis basic carboxylate functionality present in the Claisen product effectively coordinates with Lewis or Bronsted acids prohibiting the catalytic turnover. Corey has reported the use of stoichiometric bromoborane 175 to generate chiral boron enolate which undergoes [3,3]-sigmatropic rearrangement to yield 176. ° Kazmaier relied on excess quinidine 178 to provide for asymmetric induction in the conversion of 177 to amino acid 179. ... 

For our specific synthesis, the allyl ester substrate for the Ireland-Claisen 1 was obtained in a 78% yield through a l-ethyl-3-(3-dimethylaniinopropyl) carbodiimide (EDC) coupling reaction between a trifluoroacetyl-protected glycine and allyl alcohol (Scheme 2). Reaction conditions discovered by Kazmaier were then used to perform the Ireland-Claisen reaction and... 

III-47 can be synthesized by heland-Claisen ester rearrangement but only on small scale Kazmaier et al. [126], Chandan and Moloney [127]. 

As a single example of asymmetric enolate Claisen rearrangement assisted by a chiral ligand, Kazmaier and Krebs reported that the treatment of allyl aminoac-etatesa with LiHMDS in the presence of Al(Oi-Pr)3 and quinine gives the Claisen product with excellent diastereo- and enantioselectivity (Scheme 6.165) [195]. 

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