Potassium enolates catalyst

This procedure for the acetylation of methyl alkyl ketones to form /3-diketones is a modification5 of an earlier procedure, which used boron trifluoride gas as the catalyst.6 3-n-Butyl-2,4-pentanedione has also been prepared by the acetylation of 2-heptanone catalyzed with boron trifluoride gas,7 by the thermal rearrangement of the enol acetate of 2-heptanone,7 and by the alkylation of the potassium enolate of 2,4-pentanedione with n-butyl bromide.8... 

Polymer-supported reagent. HMPT supported on a polystyrene-type resin is a catalyst for SN2 reactions5-7 and for reduction of ketones by NaBIi4.7 It also has a marked effect on the alkylation of ethyl acetoacetate with diethyl sulfate. In the presence of solid HMPT the enolales undergo 60 70% O-alkylation. In the absence of HMPT, the lithium enolate does not react and the sodium and potassium enolates undergo C-alkylation (90-100%). There is some difference in the effect of solid and liquid I1MPT The solid HMPT increases the reactivity of the K. enolate more than the liquid form, whereas the reverse is true with the Li enolate.8... 

Potassium tert-butoxide reacts with copper iodide to generate a copper / -butoxide species 98 (Scheme 29). Activation of the alkyne 94 by this copper catalyst (intermediate 96) allows the enolate attack to afford the cyclic... 

Benzyl-6-methylcyclohexanone has been prepared by the hydrogenation of 2-benzylidene-6-methylcyclohexanone over a platinum or nickel catalyst, and by the alkylation of the sodium enolate of 2-formyl-6-methylcyclohexanone with benzyl iodide followed by cleavage of the formyl group with aqueous base. The 2,6-isomer was also obtained as a minor product (about 10% of the monoalkylated product) along with the major product, 2-benzyl-2-methylcyclohexanone by successive treatment of 2-methylcyclohexanone with sodium amide and then with benzyl chloride or benzyl bromide. Reaction of the sodium enolate of 2-formyl-6-methylcyclohexanone with potassium amide in liquid ammonia formed the corresponding dianion which was first treated with 1 equiv. of benzyl chloride and then deformylated with aqueous base to form 2-benzyl-2-methylcyclohexanone.i ... 

Potassium ferricyanide, 255 of silyl enol ethers and lithium enolates Iodosylbenzene, 151 Miscellaneous methods Palladium catalysts, 230 Tetrakis(trifluoroacetate)ruthenium,... 

The addition of Grignard reagents or organolithiums (alkenyl, alkyl, alkynyl, allyl or aryl) to nitroenamines (281)213 was reported by Severin to afford P-substituted-a-nitroalkenes.214 b Similarly, ketone enolates (sodium or potassium), ester enolates (lithium) and lactone enolates (lithium) react to afford acr-nitroethylidene salts (294) which, on hydrolysis with either silica gel or dilute acid, afford 7-keto-a,(3-unsaturated esters or ketones (295)2l4c-d or acylidene lactones (296).214 Alternatively, the salts (294, X s CH2) can be converted to -y-ketoketones (297) with ascorbic acid and copper catalyst. 

Akiyama s group employed naturally occurring L-quebrachitol 6 to prepare the C2-symmetrical 18-membered chiral crown ether 7 [14]. Compound 7 was found to be an active catalyst for the enantioselective Michael additions of glycine enolates. Thus, deprotonation of ester 8 using potassium tert-butoxide in dichloromethane (DCM) in the presence of crown ether 7 (20 mol %), followed by addition of a Michael acceptor, gave amino-acid derivatives 9 with up to 96% ee, as shown in Scheme 8.4. 

The optimal reaction conditions for reactions involving catalyst 33 and substrates 16a-c or 34 were investigated, and it was found that best results were obtained at room temperature [36] with toluene as the solvent [37] and with sodium hydroxide or sodium hydride as the base. In particular, the use of potassium hydroxide always gave lower enantioselectivities than sodium hydroxide, and lithium hydroxide was not effective in these reactions. Attempts to use aqueous sodium hydroxide as the base under liquid-liquid phase-transfer conditions resulted in the formation of a negligible amount of product [33,34]. An important finding of these optimization studies was the presence of a significant background reaction [38], Hence, one role of catalyst 33 must be to enhance the reactivity of an enolate when it is coordinated to the catalyst relative to the uncoordinated enolate. 

The simplest amino acid, glycine, would be an ideal starting material for the synthesis of more complicated amino acids but it does not easily form enols or enoiates. The methyl ester of the ben-zaldehyde imine has two electro n-withdra wing groups to help stabilization of the enolate and conjugate addition of acrylonitrile is now possible. The base used was solid potassium carbonate with a quaternary ammonium chloride as phase transfer catalyst. Simple hydrolysis of the alkylated product leads to the extended amino acid. 

Oxidations of aikynes (1, 947). A reinvestigation of this reaction indicates that oxidation to diketones is best effected in dry methylene chloride with excess powdered potassium permanganate and a phase-transfer catalyst (Adogen 464). Typical yields are 40-80%. If some water is also present, further oxidative cleavage of the enol of the diketone results in two carboxylic acids. An example is shown in equation (I). Oxidation of terminal aikynes to a carboxylic acid with one less carbon atom may also proceed through a dicarbonyl intermediate. 

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