Acetylacetone, Michael reactions

The Michael reaction of benzylidene acetophenone and benzylidene acetone with ethyl acetoacetate, nitromethane, and acetylacetone was studied by Musaliar and co-workers in the presence of a cetyltrimethy-lammonium bromide-containing aqueous micellar medium.50 The Michael reaction of various nitro alkanes with electrophilic alkenes is performed in NaOH (0.025-0.1 M) in the presence of cetyltrimethylam-monium chloride (CTACI) without any organic solvent (Eq. 10.23).51... 

Figure 6.26 Multiple hydrogen-bonding tertiary amine-functionalized thioureas screened in the asymmetric Michael reaction between trans-P-nitrostyrene and acetylacetone at 10mol% loading.

Acetylacetone has also been the subject of several studies when used as 1,3-dicarbonyl compound suitable to engage in a Michael reaction with nitroalkenes under H-bonding catalysis. In this context, Takemoto s catalyst 68a and valine-derived thiourea 74 have been tested in the reaction with acetylacetone with nitrostyrene furnishing good results, although no extensive study was carried out in order to evaluate the substrate scope with regard to the substitution at the nitroalkene. On the other hand, several functionalized thioureas have been expressly surveyed in this reaction, providing a detailed study... 

The second chapter of the book covered the advances in enantioselective nickel(ii)-catalysed conjugate additions. An important breakthrough in the history of the Michael reaction was the achievement of the Michael addition of p-dicarbonyl compounds to a broad variety of electrophiles catalysed by nickel acetylacetonate, described by Nelson in 1979-1980. Since this pioneering contribution, nickel has become one of the preferred metals in catalytic Michael reactions. Later, in 1988, Soai developed the first asymmetric conjugate additions performed under chiral nickel(ii) catalysis. Ever since. 

Papai et al. selected as model reaction the addition of 2,4-pentanedione (acetylacetone) to trans-(R)-mtrostyvQnQ, catalyzed by the bifunctional thiourea catalyst shown in Scheme 6 [46]. The analogous Michael-addition involving dimethyl malonate and nitroethylene as substrates, and a simplified catalyst was calculated at the same level of theory by Liu et al. [47]. Himo et al. performed a density functional study on the related cinchona-thiouTQa catalyzed Henry-reaction between nitromethane and benzaldehyde [48]. 

Scheme 7 Two alternative reaction routes for the organocatalytic Michael-addition of acetylacetone to nitrostyrene...

Knoevenagel adduct 239 of oxohomophthalimide 240 with malononitrile 27a in reactions with CH-acids behaves ambiguously (82CPB1215). Reactions of 239 with acetylacetone, ethyl esters of acetoacetic and ben-zoylacetic acids, as well as methyl pyruvate led to the formation of the desired spiropyrans 241. However, benzoylacetone, dibenzoylmethane, cyanacetamide, and oxindole always gave the same 242. Authors explain this feature in terms of a retro-cleavage of adducts of Michael product 239... 

A systematic investigation of the effect of Cl impurity was reported for a metal-catalyzed Michael addition of acetylacetone to methyl vinyl ketone in [BMIM]BF4 (77(5). The time required for the completion of the reaction was used as a measure of the effect of Cl . With a Ni(acac)2.2H20 catalyst, the Michael addition was completed in 2, 5, and 9h when the ionic liquid contained 0, 0.62, and 1.62% CP, respectively. 

Acetylacetone la (10 mmol), metliyl vinyl ketone 2a (10 mmol) and bismuth trichloride (0.32 g, 10% mol) were mixed together without solvent in an Erlen-meyer flask and placed in a commercial microwave oven (operating at 2450 MHz frequency) and irradiated for 15 min. The reaction mixture was allowed to reach room temperature and extracted with chloroform. Removal of solvent and the residue on purification by passing through a short column of silica gel using chloroform as eluent, affords the Michael adduct 4a in 90% yield without tlie formation of any side products. Similarly cadmium iodide (10% mol) was used in place of bismuth trichloride and the corresponding Michael adduct was isolated in 85% yields. 

Simple tertiary enaminones derived from acetylacetone and benzoylacetone react with acryloyl chloride to yield carbocyclic derivatives. The reaction proceeds via an initial Michael addition of the enaminone / -carbon to the enone107 (equation 76). Analogous behavior of cyclic enaminones leads, according to ring size, to tetrahydroindole, quinoline and benzazepine derivatives108 (equation 77). 

The Michael addition of anions of C-acids, such as acetylacetone or hydrocyanic acid, to phenyl vinyl ketone follows a scheme similar to (7). In the cases studied it was possible to neglect the acid-base properties of the adduct and the reverse elimination reaction (Hrubcova, 1964). Equations analogous to (9) and (10) were used and the pH-dependence of the determined formal rate constant at a given analytical concentration of the C-acid follows a dissociation curve with an inflexion at the pKa value of the C-acid. 

Rann et al. reported the dramatic influence of a new tailor-made, task-specific, and stable ionic liquid, butyl methyl imidazolium hydroxide ([bmim][OH]), in Michael addition. They have discovered that a task-specific ionic liqnid [bmim][OH] efficiently promoted the Michael addition of 1,3-dicarbonyl compounds, cyano esters, and nitro alkanes to a variety of conjugated ketones, carboxylic esters, and nitriles withont reqniring any other catalyst and solvent (Fig. 12.21) [16]. Very interestingly, all open-chain 1,3-dicarbonyl componnds such as acetylacetone, ethyl ace-toacetate, diethyl malonate, and ethyl cyanoacetate reacted with methyl vinyl ketone and chalcone to give the usual monoaddition products, whereas the same reactions with methyl acrylate or acrylonitrile provided exclusively bis-addition products. 

Several structurally different diketones (acetylacetone, methyl 2-oxocyclohex-ane carboxylate) and active methylene compounds (diethyl malonate, ethyl aceto-acetate) and thiols (methyl thioglycolate) underwent clean, fast, and efficient Michael addition with methyl vinyl ketone, acrolein, and methyl acrylate over NaY and Na beta zeolites [88] in high yield (70-80%). The reactions were performed in the absence of solvent, at room temperature, with 1 g catalyst per mmol donor. When HY zeolite was used instead of NaY formation of the desired Michael adduct was low and polymerization of Michael acceptor was the main reaction. 

The reaction may be performed in one stage by preparing the trichloro-methylsulfenamido heterocycle in situ in the presence of an aromatic amine l,2,4-thiadiazolo[4,3-a]pyridine derivatives (152), for example, have been produced in this way.139 Suitable enolate ions, e.g., acetylacetone or diethyl malonate, give rise to compounds of type 155,140 probably by the successive displacement (from 151) of a chloride ion, loss of hydrogen chloride, and cyclization of the resulting a,/)-unsaturated intermediate 154 by a Michael-... 

This chemisoy has recently been employed in a regioselective tandem /3-acetonation-a-allylation of strongly activated Michael substrates (Scheme 18), in which the starting allyl acetylacetonate 25 first generates the chelated (Tp-allyl)Pd complex 34 whose decarboxylation produces the corresponding enolate 35 that is added to the Michael substrate 32 to generate anion 36 the reaction is completed by the reaction of the latter species with the (rf-allyl)Pd complex, thereby releasing Pd(0) for the next catalytic cycle. ... 

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