Diastereoselective synthesis of tertiary alcohols by nucleophilic addition to α-substituted-ß-keto esters (original) (raw)
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Convenient synthesis and characterization of molecules containing multiple β-keto ester units
Tetrahedron Letters, 2012
Three compounds containing two b-keto ester units and one containing three were obtained in good yields from sebacyl, terepthaloyl, isophthaloyl, and trimesoyl chlorides. In this one pot procedure the acid chlorides were first treated with ethyl acetoacetate and barium oxide and then with ethyl alcohol. The aliphatic ester exists mainly as keto ester with a very small amount of the enol tautomer. In the case of aromatic esters, all possible tautomers were found in considerable concentrations in deuterochloroform solution. Theoretical chemical shifts were estimated from GIAO/WP04/aug-cc-pVDZ/SCRF calculations, for a probable signal assignation for the corresponding tautomeric species. Our theoretical results are in agreement with experimental findings and account for negligible stability differences between the tautomers of each aromatic compound.
Selective One-Pot Synthesis of Allenyl and Alkynyl Esters from β-Ketoesters
Journal of Organic Chemistry, 2009
A convenient method is described for the dehydration of β-ketoesters to generate conjugated and deconjugated alkynyl esters and conjugated allenyl esters. This sequential one-pot method involves the formation of a vinyl triflate monoanion intermediate that leads to the selective formation of alkynes or allenes depending on additives and conditions used. Product outcomes appear to be a function of unique mono-and dianion mechanisms which are described.
Methods for the preparation of donor-acceptor (push-pull) cyclopropanes for the purpose of incorporating a single carbon between two carbonyl groups have been developed by a number of research groups (Scheme 1). Bieräugel described the cyclopropanation of a β-keto esterderived enamine, which upon hydrolysis provided homologated material. 2 Attempts by Saigo to mimic these results with silyl enol ethers were inefficient and provided mixtures of products when using zinc carbenoids, although reactions based on copper-carbenoids derived from diazoesters were more efficient. 3 A radical-based method for homologation of βdicarbonyls was reported by Dowd, although the one-carbon insertion was limited to α-substituted β-dicarbonyl starting materials. 4 A complementary strategy for the formation of donor-acceptor cyclopropanes was reported by Reissig, in which methyl ketone-derived enol ethers were reacted with stabilized rhodium carbenoids. 5 The resulting cyclopropanes could be converted cleanly to γ-keto esters through hydrolysis and used as nucleophilic species in tandem reaction processes. OMe O O Et 2 Zn (3 equiv), CH 2 I 2 (3 equiv) CH 2 Cl 2 , 0 °C, 45 min OMe O O 89-94% Org. Synth. 2014, 91, 248-259
Mild and High-Yielding Synthesis of β-Keto Esters and β-Ketoamides
Synthesis-stuttgart, 2010
Abstract: In the presence of sodium acetate, the reaction between 2,2,6-trimethyl-4H-1,3-dioxin-4-one and secondary or tertiary alcohols (including chiral ones) or primary or secondary amines could be carried out in refluxing tetrahydrofuran, under much milder conditions than those described in the literature. In these new conditions, side products normally observed using the traditional protocol were avoided, and b-keto esters and b-ketoamides were normally obtained in quantitative yields.
Selective One-Pot Synthesis of Allenyl and Alkynyl Esters from �-Ketoesters
J Org Chem, 2009
A convenient method is described for the dehydration of-ketoesters to generate conjugated and deconjugated alkynyl esters and conjugated allenyl esters. This sequential one-pot method involves the formation of a vinyl triflate monoanion intermediate that leads to the selective formation of alkynes or allenes depending on additives and conditions used. Product outcomes appear to be a function of unique mono-and dianion mechanisms which are described.