2.4- pentanedione, reaction with

Ketones with labile hydrogen atoms undergo enol acetylation on reaction with ketene. Strong acid catalysis is required. If acetone is used, isoptopenyl acetate [108-22-5] (10) is formed (82—85). Isopropenyl acetate is the starting material for the production of 2,4-pentanedione (acetylacetone) [123-54-6] (11). 

By learning to recognize such three-atom groupings within larger structures, resonance forms can be systematically generated. Look, for instance, at the anion produced when H+ is removed from 2,4-pentanedione by reaction with a base. How many resonance structures does the resultant anion have ... 

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... 

OS 52[ [OS 53[ [OS 54[ [OS 55[ [R 4b[ [P 38[ In a two-micro-mixing tee chip reactor, substrates with diketone moieties of known different reactivity, such as 2,4-pentanedione, benzoylacetone and diethyl malonate, were processed, each with the same acceptor ethyl propiolate [8]. Also, a reaction with the less alkynic Michael acceptor methyl vinyl ketone was carried out. 

The compound XLII, obtained by the reaction of 2,4-pentanedione (acetylacetone) with D-glucose, also undergoes dehydration easily,8 giving a... 

When the second component is an a,/i-unsaturated aldehyde, somewhat different results are reported. Thus crotonaldehyde reacts with ethyl aceto-acetate to give 4/f-pyran 65,86 whereas 3-substituted crotonaldehydes with 1,3-cyclohexadiones afford 67 to 80% of the corresponding 2//-pyrans 66. ° The reaction with 1,3-pentanedione proceeded also in the second way,110 but the former cyclization with ethyl benzoylacetate gave no pyran.8 If asymmetrically substituted 1,3-cyclohexadienone components are used, the formation of mixtures of isomeric 2//-pyrans may be expected, as shown in Eq. (2)."°... 

The tris and bis complexes of acetylacetone (2,4-pentanedione) (167) with chromium(III) have been known for many years (168,169).739 The tris compound is generally prepared by the reaction of an aqueous suspension of anhydrous chromium(III) chloride with acetylacetone, in the presence of urea.740 Recently a novel, efficient synthesis of tris(acetylacetonato)chromium-(III) from Cr03 in acetylacetone has been reported.741 The crystal structure of the tris complex has been determined.744 A large anisotropic motion was observed for one of the chelate rings, attributed to thermal motion, rather than a slight disorder in the molecular packing. 

For such hex-3-enopyranosid-2-uloses as 127 or 129, reaction with lithium dimethylcuprate,261 or with anions of malonic ester-type, methylene components in the presence of bis(2,4-pentanedionate)-Ni(II) catalyst,263 affords, in each case, the 1,4-addition products (128 and 130, respectively), in which the branching group is in the axial orientation. The methyl-branched pyranosides 126 and 128, readily accessible in this way, have been of use as chiral precursors for the synthesis of multistria-tins.264-285... 

The formation of a mixture of pyrylium salts when 2-acetylpyridine and chalcone reacted in perchloric acid was overcome by treating the reactants with ethanolic sodium hydroxide. The pentanedione was isolated and subsequently oxidized by reaction with chalcone and boron trifluoride (82JCS(P1)125). 

Moreover, 3-benzoyl-2,4-pentanedione (215) is obtained when benzoylchloride is employed to the acetylacetone derivate i94143) whereas the reaction with benzaldehyde results a mixture of 3-benzylidene-2,4-pentanedione (213) and 3-[a-hydro-xy-benzyl]-2,4-pentanedione (214)143 ... 

Glyoxal can be formed by oxidation of glycolaldehyde (e.g., in Scheme 2.5), but it can also be formed by autoxidation of unsaturated fats and by enzymic degradation of serine.60 2-Oxopropanal can be obtained by retroaldolisation of 1- and 3-deoxyglucosone or by hydrolysis of diacetylformoin (see Scheme 2.5). Butanedione can also be derived from diacetylformoin, but by reduction, dehydration, and hydrolysis (see Scheme 2.5). 2,3-Pentanedione can be formed from butanedione by aldol reaction with formaldehyde, dehydration, and reduction or by aldol condensation of hydroxyacetone and acetaldehyde, followed by dehydration. 

Hydrazine and methylhydrazine were determined in aqueous solution at 0.1—50 ppm levels in the form of the corresponding pyrazoles [112] produced by a condensation reaction with 2,4-pentanedione (Scheme 5.11). The pH. of the aqueous solution was adjusted to 6—9 with the aid of 1 N NaOH or 1 N H2S04 and 50 jul of 2,4-pentanedione were added to a 100-ml portion. The mixture was mixed thoroughly and allowed to stand at room temperature for at least 1 h. Samples of 5 (A were analysed on 30% mixture of Amine 220 and Apiezon L (1 5) at 130°C. 

Similar reactions of diethylaminosulfur trifluoride take place with 2,4-pentanedione (acetylacetone), with butyl acetoacetate, and with ethyl 3-oxooctanoate, giving the corresponding difluoro compounds as E/Z mixtures in the ratio of 1 1 [9]. 

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... 

Bromopropanamides 199 reacted with potassium enolates of different P-dicarbonyl compounds. The reaction with the potassium salt of 2,4-pentanedione 200 afforded oxazolidin-4-one 201 in good yield <03TL4121>. 

Another interesting ketyl cyclization is that reported for a 1,5-pentanedione derivative on reaction with magnesium [Eq. (20) 52]. 

The use of ethyl [2-13C]acetoacetate instead of diethyl [2-t3CJmafonafe in the condensation reaction with 4H-pyran-4-one afforded ethyl 4-hydroxy[1 -13C]benzoate in 87% yield. In this case, 1.1 equiv of 4H-pyran-4-one and 1.1 equiv of potassium tert-butoxide were optimal. The addition of catalytic amounts of the base was not satisfactory. Ethyl [2-13C]acetoacetate was prepared from ethyl (2-13C]acetate as described for diethyl [2-13C]matonate.16 The maximum yield for this reaction on a 10-mmol scale was only 70% after distillation. 4H-Pyran-4-one reacted with nitromethane and potassium tert-butoxide (each 1.1 equiv) to afford 4-nitrophenol in 75% yield after purification by flash chromatography. This gives easy access to 4-nitro[4-13C]phenol. With 2,4-pentanedione, the condensation with 4H-pyran-4-one under the same reaction conditions gave 4-hydroxyacetophenone in 45-50% yield after purification. 

Treindl and Kaplan (1981) studied the kinetics of oxidation of 2,4-pentanedione with Ce(IV) ions. The modified B-Z reaction with 2,4-pentanedione as substrate exhibited oscillations with an increasing amplitude even in the absence of stirring. 

Cyclization with 1,3-dicarbonyl compounds can give high yields of fused pyrimidines [2249, 2722] the halogen of 3-bromo-2,4-pentanedione (which would be expected to be labile) survives the reaction with a 3-aminopyrazole to give a fused bromodimethylpyrimidine in good yield [3426]. 

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