Ethyl dimedone

Similar pyrimidine-to-pyridine conversions were also reported for purine and 8-azapurine with C-H active acetonitriles, ethyl acetoacetate, acetylacetone with dimedone 8-azapurine is converted into triazolotetra-hydroquinoline (Scheme 15) (73JCS(P1)1620, S(Pl)1625, S(P1)1794). 

In a 500-ml round-bottom flask is placed a mixture of 25 g (0.178 mole) of dimedone, 21.8 g (0,22 mole, 25 % excess) of pulverized maleic anhydride, 0.1 g of /7-toluenesulfuric acid, and 150 ml of isopropenyl acetate. The mixture is refluxed for 72 hours, then cooled, and the acetone is removed at room temperature on a rotary evaporator. The resulting solution is cooled to —20° in a Dry Ice bath, whereupon the product crystallizes. It is collected by filtration to yield the crude product in about 80% yield. Recrystallization from hexane-ethyl acetate and decolorization by Norit gives colorless crystals, mp 164-166°. 

Normal yS-dicarbonyl compounds such as ethyl acetoacetate 723 a or acetylace-tone 723 b are converted, as the free yS-dicarbonyl compounds or as their sodium salts, by TCS 14, 14/pyridine, or HMDS 2/TCS 14 into their enol silyl ethers 724a [216, 217, 219] and 724b [218]. Yet treatment of / -triketones such as 2-acetyl-dimedone 725 with HMDS 2 results, via the corresponding 2-enol trimethylsilyl... 

The cyano derivative of indandione 228 acting as an unsaturated nitrile reacts differently with 1,3-dicarbonyl compounds, depending on their nature (89CB1323). Acetylacetone and ethyl benzoylacetate provide spiro(indan-2,2 -pyrans) 229 acetoacetic esters give propellans 230 (proven by X-ray analysis). But only dimedone 103b among the ketones studied yields spirochromene 231 (Scheme 88). 

A new series of polyhydroquinolines 64 has been prepared by Shingare and co-workers [111] using nanosized Ni as a heterogeneous catalyst in a one-pot synthesis via Hantzsch condensation by reacting an aldehyde, dimedone, ethyl aceto-acetate and ammonium acetate in a domestic microwave oven. Ni (80 0.5 nm), having a higher surface to volume ratio, has given the best results in terms of short reaction times and excellent product yields. This method has demonstrated that Ni, in the form of nanoparticles, is a potential alternative catalyst for the Hantzsch... 

Dimedone (15 g, 0.107 mol) is dissolved in 100 mL dichloromethane. DMAP (2.61 g, 0.021 mol) and 30 mL triethylamine (0.22 mol) are added and the mixture stirred for 10 min. Acetic anhydride (12.2 mL, 0.129 mol) is added and the mixture stirred for 2 d under an inert atmosphere. The solvent is removed in vacuo by co-evaporation with toluene and the crude product is taken up in 300 mL ethyl acetate and washed with 5% HCl solution (3 x 300 mL). The organic solution is then dried over MgS04, filtered, and the solvent removed in vacuo to produce an oil that is filtered through a column of silica using hexane/ethyl acetate 3 2 solution as an eluent to afford the title compound as pale yellow crystals (-60% yield). 

The Knoevenagel reaction between benzaldehydes 22 and malononitrile or ethyl cyanoacetate 74 followed by condensation of the resulting ot,p-unsatu-rated nitriles 75 with dimedone (76) was performed in the presence of SiO2-(CH2)3-NEt2 (Scheme 3.22). ... 

The one-portion addition of the reagents in the model reaction between benzaldehyde, ethyl cyanoacetate and dimedone resulted in exclusive formation of the unwanted dimeric product 78 (Figure 3.3), as a consequence of the preferential condensation of benzaldehyde and dimedone due to the higher acidity of dimedone (p/y, 12.0) than that of ethyl cyanoacetate (pKa 13.1). 

Dihydropyridines 46 (R = H, Me, Ph R1, R3 = Me and CH2C(Me)2CH2- R2 = Et) having unsymmetrical substitution patterns at C-2, C-6 and C-3, C-5 positions have been formed by reactions of equivalent amounts of ethyl-/ -aminocro-tonate and methyl acetoacetate or dimedone, with respective oxazinanes 31 in acetic acid/acetonitrile (1 10 v/v). Since methyl acetoacetate and dimedone fail to react with oxazinanes under these reaction conditions, it may be visualized that the preference of the reactivity of oxazinanes with enamines over the enols facilitates the generation of intermediate 45, the precursor of 46 (93JCR(S)120). 

The allylation reaction was extended to various carbonucleophiles [7, 10-12], It was observed that the selectivity in the formation of mono- and diallylated compounds was very sensitive to the nature of carbonucleophile and its p Ka. The acyclic carbonucleophiles such as ethyl acetoacetate, acetylacetone, dimethyl malo-nate, dicyanomethane, and bis(phenylsulfone)methane, gave predominantly the monoallylated product (Eq. 2), although the cyclic carbonucleophiles such as te-tronic acid, dimedone, and barbituric acid gave predominantly the diallylated product (Eq. 3). 

In 1887, Claisen and Lowman reported that the condensation of 2 mol of an ester, such as ethyl acetate, in the presence of base gave the p-keto ester, ethyl acetoacetate (ethyl 3-oxobutanoate equation 1). The intramolecular equivalent was recognized by Dieckmann in 1894. He found that heating an adipic acid ester with sodium and a trace of alcohol led to cyclization, with the formation of a cyclopentanone (equation 2). The reaction was, at an early stage, extended to the acylation of ketones. Claisen himself reported the base-catalyzed reaction of acetophenone and ethyl benzoate to give dibenzoylmethane in 1887. This reaction, too, has an intramolecular parallel. The acylation of ketones with esters and other acid derivatives is sometimes called a Claisen condensation, although this usage is criticized by some writers and avoided by others. A widely used example of ketone acylation is the synthesis of a-formyl (hydroxymethylene) ketones (equation 3). Intramolecular variants of this reaction include the classical synthesis of dimedone (Scheme 1). 

A series of 9-(aryl)acridines have been synthesized by reaction of ethyl(arylmethylene)(cyano) acetate with dimedone in AcOH and in the presence of ammonium acetate (05MI76). 

With ethyl acetoacetate in the presence of trifluoroacetic acid dimedone gave the benzopyran 440 (69JOC2796). In another report, under the same conditions, the structure was found to be the benzopyran 441 together with the xanthene 442 (72JOC1337) (Scheme 90). 

Reaction of N-methyl-2-pyrrolidine diethylacetal with 2-aminomethy-lene-dimedone 457 (R = Rr = H or Me) afforded the dienediamine 459, which on heating in dilute hydrochloric acid gave 7,7-dimethyl-3-(/ -methylamino)ethyl-5,6,7,8-tetrahydrobenzo[t>]pyran-2,5-diones 460 (87KGS1477). 

Formylation of dimedone using ethyl orthoformate in the presence of acetic anhydride gave the 2-formyldimedone whose condensation with two moles of dimedone gave the xanthene 472 (57JCS4798), which can also be obtained directly from reaction of dimedone with triethyl... 

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