Selective One-Pot Synthesis of Allenyl and Alkynyl Esters from �-Ketoesters (original) (raw)
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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.
Chemistry - A European Journal, 2009
Cascade or tandem reactions, which shorten synthetic routes, are highly valuable reactions for many reasons such as obtaining complexity in one step, reduction of waste, time and labor, and above all, efficiency. [1] Thus, in continuation of our interest in developing cascade reactions starting from cycloalkanones tethered to alkynyl esters, [2] we investigated the reactivity of acetylenic w-ketoesters toward Lewis acids/ Lewis bases, especially toward tert-butyldimethylsilyltriflate (TBSOTf)/NEt 3 .
Contribution to the synthesis of chiral allenic esters
Tetrahedron Letters, 2003
A phosphorus ylide bearing a 10-phenylsulfonylisoborneol unit reacted with ketenes, generated in situ from acid chlorides and triethylamine, to give allenic compounds. The reaction with methylketene led to asymmetric induction with the selective synthesis of an allene with axial chirality corresponding to an S configuration. The structure of the chiral allene 10-phenylsulfonylisobornyl penta-2,3-dienoate was determined by X-ray crystallography. Chirooptical studies of the chiral allene derivatives were done.
Arkivoc, 2006
A protocol of nucleophilic addition to β-keto esters is reported, aimed to the synthesis of tertiary alcohols with high diastereomeric purity. The combined use of organocerium compounds and TiCl 4 makes the procedure very efficient and stereoselective with phenyl ketone derivatives. The effect of the nature of the ester function as well as the group bound to the ketone moiety was investigated and rationalized.
Amide/Ester Cross-Coupling via C−N/C−H Bond Cleavage: Synthesis of β-Ketoesters
Chen, J.; Joseph, D.; Xia, Y.; Lee, S. J. Org. Chem. 2021, 86(8), 5943-5953., 2021
Activated primary, secondary, and tertiary amides were coupled with enolizable esters in the presence of LiHMDS to obtain good yields of β-ketoesters at room temperature. Notably, this protocol provides an efficient, mild, and high chemoselectivity method to synthesis of β-alkylketoesters using the cross-coupling between aliphatic amides and esters. Meanwhile, gram-scale secondary and primary amides reacted via in situ generated activated tertiary amides and exhibited good reactivity when coupled with esters.
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.
Synthesis of allenes via thermal cycloreversion of .alpha.-alkylidene-.beta.-lactones
The Journal of Organic Chemistry, 1993
This paper describes the application of the solution-phase [2 + 21 cycloreversion of a-alkylidene-@-lactones as a practical method for the generation of substituted allenes. Upon heating in dimethylformamide solution at 110-125 OC, these unsaturated &lactone derivatives undergo decarboxylation to provide allenes in good to excellent yield. a-Alkylidene-&lactones are conveniently prepared via the phenylselenylation of @-lactone enolates followed by oxidative elimination of the resulting a-phenylseleno derivatives. The @-lactone starting materials are synthesized by the addition of thiol ester enolates to ketones and aldehydes according to our recently reported procedure. t On leave from Famitalia Carlo Erba S.r.1. (1) For recent reviews on the synthesis and chemistry of allenes, see: (a) Schuater, H. F.; Coppola, G. M. Allenes in Organic Synthesis;
Synthesis of Pentafluorophenyl- and Pyridinyl-3 Allenes
Journal of the Chinese Chemical Society, 2007
The allenes 1,2,3,4,5-pentafluoro-6-(3-phenylpropa-1,2-dienyl)benzene 4, 3-(3-phenylpropa-1,2dienyl)pyridine 11 and 3-(3-(pyridine-3-yl)propa-1,2-dienyl)pyridine 17 and the acetylenes 5, 12 and 16 were obtained by reduction of the corresponding propargylic acetates 3, 10 and 15 by Samarium(II) iodide in the presence of Pd(0). Base-promoted isomerisation of acetylene 12 provided allene 11 in a yield of 80%. 1-(Pentafluorophenyl)-3-phenylprop-2-yn-1-ol 2 was prepared from phenylacetylene and pentafluorobenzaldehyde. The condensation of nicotinaldehyde with trimethylsilylacetylene gave the 3-(trimethylsilyl)-1-(pyridine-3-yl)prop-2-yn-1-ol 7. The removal of the silyl group of 7 to acetylene 8 was done in basic conditions. The Pd catalysed condensation of the acetylene 8 with iodobenzene gave 3-phenyl-1-(pyridine-3-yl)prop-2-yn-1-ol 9. The Pd catalysed condensation of 8 with 3-bromopyridine gave the 1,3-dipyridin-3-yl-prop-2-yn-1-ol 14. The propargylic alcohols 2, 9 and 14 were converted to the acetates 3, 10 and 15 with acetic anhydride-pyridine.