Enol ether, synthesis

B 0 0 R D Enol ether synthesis Synthesis of chloioethers and enol ethers Irom aliphatic aldehydes. 

Figure 12.25 shows how acetals can be brominated electrophihcally because of the (weakly) acidic reaction conditions. Proper acidity and electrophihcity is ensured by the use of pyri-dinium tribromide (B). This reagent is produced from pyridinium hydrobromide and one equivalent of bromine. Pyridinium tribromide is acidic enough to cleave the acetal A into the enol ether G. This cleavage succeeds by way of an El elimination like the one encountered in Figure 9.32 as an enol ether synthesis. The enol ether G reacts with the tribromide ion via the bromine-containing oxocarbenium ion H and the protonated acetal D to form the finally isolated neutral bromoacetal C. (The reaction can be conducted despite the unfavorable equilibrium between the acetal A and the enol ether G, since G continuously reacts and is thus eliminated from the equilibrium.)... 

BOGER Heterocycle synthesis 40 BOORO Enol ether synthesis 4i BORCH Reduction 42 Bormann 404 Borodin 183 Borsche 123... 

Ganz, I, Kunz, H, Carbohydrates as chiral auxiliaries. [2+2] Cycloadditions to enol ethers, Synthesis, 1353-1357, 1994. 

Jauch, J. Stereochemistry of the Rubottom oxidation with bicyclic silyl enol ethers synthesis and dimerization reactions of bicyclic a-hydroxy ketones. Tetrahedron 1994, 50,12903-12912. 

Sosnovskikh, V. Y., Irgashev, R. A., Khalymbadzha, I. A. and Slepukhin, P. A. (2007) Stereoselective hetero-Diels-Alder reaction of 3-(trifluoroacetyl)chromones with cyclic enol ethers synthesis of 3-aroyl-2-(trifluoromethyl)pyridines with to-hydroxyalkyl groups. Tetrahedron Lett., 48, 6297-6300. 

Solvolysis of Halocarbene Adducts of Enol Ethers. Synthesis of a, -Unsaturated Carbonyl... 

Unique successful hydroxylations with ozone and mCPBA First Successful Method Epoxidation of Silyl Enol Ethers (Rubottom Oxidation) Method, mechanism, and isolation of intermediates Chemo- regio- and stereoselectivity synthesis of fused y-laclones Hydroxylation of Amino-ketones via Silyl Enol Ethers Synthesis of vinca alkaloids and model compounds... 

The carbonyl group of an ester function can be converted to the corresponding methylene compound using Tebbe s reagent. The reaction can thus be considered as a general method of enol ether synthesis. An example of this reaction is given in Scheme 5. The same conversion can be achieved by reagents prepared from the reduction of 1,1-dibromoalkanes with zinc and TiCU in the presence of TMEDA. °... 

The isomerization of ally ethers with a transition metal catalyst, though normally used as a method of deprotection of the allyl group,can be considered as a convenient method of enol ether synthesis. The conversion of (22) to the propenyl ether (23) serves as an example. ... 

BOORD Enol ether synthesis Synthesis ol chloroethers and enoi ethers from aliphatic aldehydes. 

Jullien, J. Pechine, J.M. Perez, F Piade, J.J. Flash vacuum thermolysis of 3-keto-trimethylsilyl-enol-ethers. Synthesis of allenic and furanic derivatives. Tertrahedron 1982, 38, 1413-1416. 

The aldol condensation is a very attractive route to a,p-unsaturated carbonyl compounds. The application of this reaction is nevertheless rather limited, since numerous side reactions usually occur amongst these are self-condensation of the ketone, Michael-type addition to the newly formed product, or Cannizzaro reactions. As a consequence, poor yields are obtained in most cases [90]. In the enol ether condensation, described earlier, these side reactions are less troublesome. A disadvantage of the enol ether condensation compared to the aldol condensation is that strongly acidic conditions have to be used to cleave the intermediate in the enol ether synthesis. 

Another silyl enol ether synthesis developed by Reich utilized systems where the Brook rearrangement led to y elimination from the... 

The concept of silyl enol ether synthesis via / -elimination from a Brook rearrangement-derived carbanion also appeared in Wicha s studies on additions of 1-phenyl-l//-tetrazol-5-yl (PT) sulfonyl anions to acyl silanes. When PT sulfone 34 was deprotonated in the presence of acyl(triphenyl)silane, ketone 36 was isolated in good yield after hydrolysis of the silyl enol ether intermediate 35. The mechanism involved addition of the... 

Wang W Li YL, Wang XS (2012) Highly efficient synthesis of 7-aryl-pyrano[3,4-c] pyrazolo[4,3-f]quinoline derivatives catalyzed by iodine. ARKIVOC vi 214-221 Lin XF, Cui SL, Wang YG (2006) Molecular iodine catalyzed one-pot synthesis of substituted quinolines from imines and aldehydes. Tetrahedron Lett 47 3127-3130 Jin G, Zhao J, Han J, Zhu S, Zhang J (2010) Iodine-promoted imino-Diels-Alder reaction of fluorinated imine with enol ether synthesis of 2-perfluorophenyl tetrahydroquinoline derivatives. Tetrahedron 66 913-917... 

Enol Ether Synthesis. A 2-(trimethylsilyl)ethyl-based dithioorthoformate was prepared via copper(II) bromide-promoted oxidative coupling of bis(phenylthio)-methyltributylstannane. The dithioorthoformate thus prepared is treated with a titanocene(II) reagent followed by the addition of ketones or esters to promote alkoxymethylidenation as exemplified in eq 32. ... 

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