2.4- Pentanedione preparation

Compare the spectrum of VO(acac)2 with that of 2,4-pentanedione, prepared neat with salt plates. 

The product described here, 4-(4-chlorophenyl)butan-2-one, was previously prepared in the following ways a) by reduction of the corresponding benzalacetone, b) by catalyzed decarbonylation of 4-chlorophenylacetaldehyde by HFeiCO) in the presence of 2,4-pentanedione, - c) by reaction of 4-chlorobenzyl chloride with 2,4-pentanedione under basic catalysis (K2CO3 in EtOH), d) by reaction of 4-chlorobenzyl chloride with ethyl 3-oxobutanoate under basic catalysis (LiOH), - and e) by reaction of 3-(4-chlorophenyl )-propanoic acid with methyl lithium. - ... 

Comprehensive work in this field has been done by Slovak authors (98MI1, 95M1359, 96CCC269, 96CCC371, 97CCC99). They prepared 2-substituted (H, Me, Ph) 4-, 5-, 6-, and 7-nitrobenzoxazoles, which were then reduced to amines (not isolated) and subjected to subsequent nucleophilic substitution with activated enol ethers such as alkoxymethylene derivatives of malonic acid esters and nitrile, 3-oxobutanoic acid esters, pentanedione, or cyanoacetic acid esters to yield aminoethylenes 8. 

Dimelhvlisoxazole is prepared by reaction of 2.4-pentanedione with hydroxylamine. Propose a mechanism. 

The present procedure, which is characterized by its extreme simplicity, has been employed to prepare various ketones of type RCH2COCH3 from 2,4-pentanedione,3 as indicated in Table I. 

The residue from distillation of the title compound (prepared from ethyl orthoformate, pentanedione and acetic anhydride) at 165-170°C/13 mbar, is pyrophoric when hot. 

A preferable, three-step, procedure for preparing anhydrous bis(2,4-pentanedionato)zinc, m.p. 127°, in good yields involves (1) the preparation of bis(2,4-pentanedionato)zinc hydrate from zinc sulfate heptahydrate and 2,4-pentanedione in aqueous solution in the absence of heat, (2) conversion of the bis(2,4-pentanedionato)zinc hydrate into a bis (2,4-pentanedionato) zinc-methanol adduct, and (3) decomposition of the methanol adduct. 

Sodium amide, in alkylation, of di-pbenylmetliane, 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 preparation of, 48, 80 Sodium 2-aminobenzenesulfinate, from reduction of 2-nitrobenzenesul-finic acid, 47, 5... 

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... 

A similar acetylation procedure (without p-toluenesulfonic acid) has been employed to prepare other /3-diketones.5 As examples, cyclohexanone was converted to 2-acetylcyclohex-anone (73%) cyclopentanone yielded 2-acetylcyclopentanone (80%) 3-pentanone yielded 3-methyl-2,4-hexanedione (81%) dibenzyl ketone yielded l,3-diphenyl-2,4-pentanedione (72%), and acetophenone gave benzoylacetone (70%). 

In this procedure cis- [dihalobis(2,4-pentanedionato)titanium(IV)] complexes (halo = F, Cl, Br) are prepared in high yields through the reaction of a titanium tetrahalide with 2,4-pentanedione in dichloromethane. 

Although the halogenated chelates of chromium, cobalt, and rhodium would be difficult to prepare from the sensitive 3-halo-2,4-pentanediones, the copper (II) bromochelate was synthesized both from the bromodiketone and by direct bromination of copper acetylacetonate. The relatively labile copper chelates form much more rapidly than the kinetically stable chelates of chromium, cobalt, and rhodium. 

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. 

Iron(II) bis(acetylacetonate) has been prepared by reaction of iron(II) sulfate in aqueous solution with 2,4-pentanedione in the presence of bases such as pyridine and ammonia1 and by reaction of iron (II) chloride tetrahydrate in aqueous solution with the stoichiometric amounts of 2,4-pentanedione and piperidine.2 Neither publication reports yields and the lack of complete experimental details makes duplication difficult. The following procedure is a modification of that reported by Buckingham et al.2 and employs either anhydrous iron(II) chloride or the corresponding adduct with THF. The reaction is carried out in diethyl ether as solvent instead of water. 

Pentanedionates, with Ru and Os half-sandwiches, 6, 483 Pentanuclear silver(I)-rhenium(I) alkynyl rigid-rod complex, preparation, 2, 229-230... 

Cyclization of trienes.1 In combination with 2,2-bipyridyl (bpy), an iron(O) species prepared by reduction of iron(III) 2,4-pentanedionate with A1(C2H5)3 (3 equiv.) promotes cyclization of trienes (1) in which a 1,3-diene unit is tethered to an ally lie or homoallylic ether group. vic-Disubstituted cyclopentanes or cyclohexanes are formed, and the cisltrans disposition of the substituents is controlled by the geometry of the allylic double bond. Thus (Z,E-)1 is cyclized to trans-2, whereas (E,E)-1 is cyclized to cis-2. 

Tetrakis(2,4-pentanedionato) cerium (IV) has been prepared by air oxidation of tris(2,4-pentanedionato)cerium(III) in hot benzene solution1 and by the reaction of hydrous cerium(IV) oxide with excess 2,4-pentanedione (acetylacetone) in water. The procedures presented here are based on the former approach. 

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