Alkylation, of 2,4-pentanedione, with

Alkylation, of 2,4 pentanedione, with methallyl chloride and potassium carbonate, 47, 87... 

MalONIC ACID, ETHYLHYDROXY, DIETHYL ESTER, BENZOATE, 45, 37 Mfsitaidehydf, 47, 1 Mesitylcne, condensation with dichloro methyl methyl ether, 47, 1 Methalljl chloride in alkylation of 2,4-pentanedione with potassium carbonate, 47, 87... 

Bi(OTf)3-Catalyzed Alkylation of 2,4-Pentanediones with Activated Alkenes 135... 

Mg2,8Al-IJX) catalyzes the direct C-alkylation of 2,4-pentanedione with alkyl halides (560). For example, C-monoethylation of 2,4-pentanedione with ethyl iodide occurs at 100% selectivity and 87% conversion. Similarly, Choud-hary et al. used MgGa-LDHs that were treated with gaseous HCl as catalysts for benzylation of benzene and toluene with benzyl chloride at high conversion (561a,561b). 

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... 

Silver fluoborate, reaction with ethyl bromide in ether, 46, 114 Silver nitrate, complexing with phenyl-acetylene, 46, 40 Silver oxide, 46, 83 Silver thiocyanate, 45, 71 Sodium amide, in alkylation of ethyl phenylacetate w ith (2-bromo-ethyl)benzene, 47, 72 in condensation of 2,4-pentanedione and 1 bromobutane to give 2,4-nonanedione, 47, 92 Sodium 2 ammobenzenesulfinate, from reduction of 2 mtrobenzenesul-finic acid, 47, 5... 

The straightforward construction of substituted pyrone 4 proceeded as follows (see Scheme 6c). Alkylation of the monoanion of 2,4-pentanedione (8) with methyl iodide furnishes 3-methyl-2,4-pentanedione. Conversion of this substance into the corresponding dianion with sodium amide followed by selective carboxylation of the more basic site provides intermediate 7. Pyrone 4 is obtained after cyclization with l,l -carbonyldiimidazole and methylation of the resulting enol with dimethyl sulfate. 

Sodium amide, in alkylation, of di-phenylmethane, 48, 80 of ethyl phenylacetate with (2-bromoethyl)benzene, 47, 72 in condensation of 2,4-pentanedione and 1-bromobutane to give 2,4-nonanedione, 47, 92... 

This first example of a Bi(OTf)3-catalyzed Friedel-Crafts alkylation originated in the following procedures, including benzylations of 2,4-pentanediones or hydroarylation and hydroalkylation reactions. A related procedure was simultaneously developed by Bonrath et al. [39]. The authors utilized Bi(OTf)3 in the synthesis of (all-rac)-a-tocopherol (Vitamin E) [39], Besides rare earth metal triflates, such as Ga(OTf)3, Hf(OTf)3, Sc(OTf)3 and Gd(OTf)3, Bi(OTf)3 was shown to be the most efficient catalyst for the Friedel-Crafts-type reaction between trimethylhydroquinone acetate 10b and isophytols 11a, b. With only 0.02 mol% Bi(OTf)3 (substrate to catalyst ratio 5,000 1) the desired a-tocopherols 12a and 12b were isolated in excellent yields (Scheme 10). 

Reactions of 2,4-pentanedione or ethyl acetoacetate with ethene in the presence of manganese(III) acetate and copper(II) acetate in an autoclave under 50 atm at 60 °C give a mixture of 443 and 444 (equation 150). This reaction involves an oxidative 1,3-cyclization of alkyl radicals . 

In addition, the linear approach was represented by sequential dithiane coupling [21] of the epoxides for the necessary fragments to either side of the ketone function at C21. Another approach uses microbial reduction (baker s yeast) to set the stereocenter at C25 before elaboration of that fragment into a methyl acetylenic ketone [89]. This acetylenic ketone was condensed with the aldehyde partner representing Cl5-19 to give the aldol adduct which was cyclized in acid to afford a precursor similar to those obtained from acetylide addition to lactone B 3. Yet another linear assembly pathway involves the alkylation of the portion containing C23-27 of 22,23-dihydroavermectin B to the dianion of 2,4-pentanedione followed by another condensation to 3-be-nzyloxypropanal [108]. Subsequent acidic cyclization and standard chemistry provided the thermodynamic spiroketal. 

Similarly, 3-methylthio-2-alkanones are prepared by the reaction of a 3-alkyl-2,4-pentanedione with 1 mol equiv (important) of MeSS02Me in the presence of EtONa in EtOH at rt or potassium carbonate in acetone at reflux followed by addition of MeOH and reflux. An advantage of using weaker base K2CO3 in this reaction is that no bissulfenylation takes place even when excess sulfenylat-ing agent is used. The method was applied to an efficient synthesis of pseudoionone (eq 3). ... 

With the combination of dimethyl sulfoxide as solvent and NaH as base, di-alkylated derivatives in yields superior to those previously found can be obtained from malononitrile and 2,4-pentanedione with methyl iodide, butyl bromide, or benzyl chloride. Reaction conditions are mild and reaction times short.— E A soln. of malononitrile in dimethyl sulfoxide added during 15 min. to a stirred slurry of NaH in the same solvent, stirring continued 15 min. with occasional cooling, then benzyl chloride added during 20 min. with occasional cooling, and stirred 8.5 hrs. at room temp. dibenzylmalonitrile. Y 64.5-75.9%. F. e. s. J. J. Bloomfield, J. Org. Ghem. 26, 4112 (1961). 

Alkylation of the cyclization product 115 and the following hydrolysis gave 9-alkyl substituted 6-oxo-6,9-dihydroimidazo[4,5-/i]quinoline-7-carboxylic acid derivatives 119, compounds useful as antibacterials (no data) [80JAP(K)1], 4(7)-Aminobenzimidazole can react with 1,3-diketones as a bidentate nucleophile, but with 2,4-pentanedione in glacial acetic acid it gives a Combes product, l//-6,8-dimethylimidazo[4,5-/i]quinoline 120, accompanied by 4(7)-acetamido-benzimidazole (91T7459). 

Diiron enneacarbonyl, 50, 2J Diketones, from diazoketones and organoboranes, 53/ 82 3-DIKETONES FROM METHYL ALKYL KETONES 3-n-BUTYL-2,4-PENTANEDIONE, 51, 90 2,6-Dimethoxybenzaldehyde, by reduction of 2,6-dime thoxy-benzonitrile with Raney nickel alloy in formic acid,... 

In addition to 1-phenylethanol and benzyl alcohol, cinnamyl alcohol has also been utilized as alkylating reagent. In contrast to the Bi(OTf)3-catalyzed Friedel-Crafts alkylation of benzyl alcohols, in which the corresponding acetate was shown to be more reactive than the free benzyl alcohol (Scheme 8), in this case the alkylation with cinnamyl alcohol or the corresponding acetate provided almost similar results. With 5 mol% BifOTfh. the desired allylated 2,4-pentanediones were isolated in good yields (Scheme 15). 

Certain diazoketones, for example diazopyruvate, alkyl 2-diazo-3-oxobutyrate or 3-diazo-2,4-pentanedione, react with vinyl ethers under metal catalysis to give dihydrofurans rather than cyclopropanes l Most work on this type of transformation has been that of Wenkert and Alonsoand their respective groups. A representative example is shown in equation 107. Finally, carbenoid dimerization is also a competitive reaction in metal catalysed intermolecular cyclopropanation. However, control of the chemoselectiv-ity to favour the cyclopropanation is possible. In general, the dimeric product can be avoided by using excess of alkene or by very slow addition of the diazo compound to a mixture of alkene and catalyst... 

In the gas phase, the reaction of ethyl cations, C2H , with the ambident 2,4-pentanedione (which is 92% enolized at 25 °C in the gas phase) leads predominantly (>95%) to alkylation at the hard oxygen site and not at the soft carbon atom, as predicted by the HSAB concept [662]. Accordingly, the gas-phase alkylation of the enolate ion of cyclohexanone gives only the O- and no C-alkylation product [848], and the gas-phase acylation of acetophenone enolate with trifluoroacetylchloride leads predominantly to the 0-acylation product (0/C ratio = 6.0) [849]. 

Phosphoroisocyanatidites (e.g. 83) react with 3-alkylidene-2,4-pentanediones (e.g. 84a) or 2-alkylideneacetoacetic esters (e.g. 84b) to form phosphoranes (85,a,b) which decompose on heating to the cyclic phosphonates (86a, b)27. in an analogous study, dialkylalkynylphosphonates (87) have been shown to react with alkyl pyruvates (88) below 0°C to form mixtures of alkynyl phosphonates (90) and monocyclic tetraoxaphosphoranes (91) via (89)28. At 80°C, however, (89) reacts with excess (88) via (92) to form the bicyclic phosphorane (93). 

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