Acetone, dibenzylidene

When an ethanolic solution containing both acetone and two equivalents of benzaldehyde is made alkaline with sodium hydroxide, rapid condensation occurs with the formation of dibenzal-acetone, or dibenzylidene-acetone. This... 

Temperature in degrees Centigrade 1,4-Diazobicyclo[2.2.2]octane Dibenzylidene acetone 1,2-Dibromoethane... 

Pd(OAc)2] or the complexes formed from it with tertiary phosphines can serve as catalysts (precursors), but [PdCb], [PdCl2(PPh3)2], [Pd(PPh3)4], [Pd(DBA)2] (DBA = dibenzylidene acetone) or [ PdCl(r -C3H5) 2] can also be used. It is well known that in the presence of water phosphines efficiently reduce Pd(II) to Pd(0). 

The first example involving a rhodium catalyst in an ene reaction was reported by Schmitz in 1976. An intramolecular cyclization of a diene occurred to give a pyrrole when exposed to rhodium trichloride in isobutanol (Eq. 2) [15]. Subsequently to this work, Grigg utilized Wilkinson s catalyst to effect a similar cycloisomerization reaction (Eq. 3) [16]. Opplozer and Eurstner showed that a n -allyl-rhodium species could be formed from an allyl carbonate or acetate and intercepted intramolecularly by an alkene to afford 1,4-dienes (Eq. 4). Hydridotetrakis(triphenylphosphine)rhodium(l) proved to be the most efficient catalyst for this particular transformation. A direct comparison was made between this catalyst and palladium bis(dibenzylidene) acetone, in which it was determined that rhodium might offer an additional stereochemical perspective. In the latter case, this type of reaction is typically referred to as a metallo-ene reaction [17]. 

A mixture consisting of phenoxazine (54 mmol), sodium t-butoxide (77 mmol), tris(dibenzylidene acetone)dipalladium(0) (1.1 mmol), and tri(/-butyl)-phosphine (1.1 mmol) were dissolved in 250 ml of xylene and then heated to 80°C for 12 hours. Thereafter, the reaction mixture was cooled to ambient temperature, quenched with 200 ml of distilled water, and extracted with xylene/water, 1 1. 

Keywords chalcone, dibenzylidene acetone, inclusion crystal, [2+2]photo-cycloaddition, cyclobutane... 

Reactions carried out with M2(DBA)3 (M — Pd, Pt DBA = dibenzylidene-acetone) and 3,5-di-t-butyl-l,2-benzquinone gave as major products the M(DBSQ)2 complexes [229]. In the case of palladium, an additional product Pd2[Pd(DBSQ)2]2 was detected, whose molecular structure consists of two planar cw-Pd(DBSQ)2 units bridged by two Pd atoms. The Pd atoms are sandwiched between semiquinone rings of adjacent Pd(DBSQ)2 units with three Pd — C lengths and an allyl structure 961 for the semiquinone rings ... 

Pd2(PhHC=CHCOCH=CHPh)3 (CHC13)] 0.067 Pd linked via three dibenzylidene-acetone groups. Co-ordination around Pd is trigonal through olefinic portion of ligand 10... 

A dry two-neck flask was charged with amine (1.00 mmol), triflate or bromide (1.20 mmol), base (1.40 mmol), ligand (10 mol%), palladium acetate (Pd(OAc)2) or tris-(dibenzylidene-acetone)dipalladium (0) (Pd2dba3) (5 mol%), and toluene (2.00 mL/mmol of amine). The reaction was flushed with N2 and heated at 80 °C. The mixture was diluted with ether, filtered through a pad of Celite, and the volatile components were removed reduced pressure to give a crude product, which was purified by flash column chromatography on silica gel. 

In 1995, Hartwig and Buchwald published concurrently their two groups results on tin-free amination of aryl halides [79,80], Instead of isolating or generating a tin amide in situ, the amination reactions were conducted by reacting an aryl halide with the combination of an amine and either an alkoxide or silylamide base (Eq. (5)). These reactions were typically conducted between 80 and 100 °C in toluene solvent. The catalysts used initially were 1, 3, or a combination of [Pd2(dba)3] (Sa) (dba = trans, trans-dibenzylidene acetone) and P(o-C6H4Me)3. Catalysts used subsequently will be described below. As shown in Table 7.1, secondary amines were viable substrates, but primary amines gave substantial yields with... 

CBZ COD Cp Cy DABCO dba DBE DBN DBU DCC DCE DDQ DEA DEAD Dibal-H Diphos-4 DMAP DME 0 II Carbobenzoxy = —COCH2Ph 1,5-Cyclooctadienyl Cyclopentadienyl Cyclohexyl 1.4- Diazabicyclo[2.2.2]octane Dibenzylidene acetone 1.2- Dibromoethane = BrCH2CH2Br 1,8-Diazabicyclo[5.4.0]undec-7-ene 1.5- Diazabicyclo[4.3.0]non-5-ene 1.3- Dicyclohexylcarbodiimide = C6H,3—N=C=N—C6H13 1.2- Dichloroethane = CICH2CH2CI 2.3- Dichloro-5,6-dicyano-1,4-benzoquinone Diethylamine = HN(CH2CH3)2 Diethylazodicarboxylate Diisobutylaluminum hydride 1.4- b s-(Diphenylphosphino)butane 4-Dimethylaminopyridine Dimethoxyethane 0... 

The double aldol product from acetone and benzaldehyde, known as dibenzylidene acetone (dba), is a constituent of some sun-protection materials and is used in organometallic chemistry as a metal ligand. It is easily made geometrically pure by a simple aldol reaction—again, reversible Michael addition equilibrates any Zproduct to E... 

There are many available complexes of palladium(O) and pal ladiumfl I). T etrak is tri ph e ny I ph osph i ne)pal I ad iu m (0). Pd PPh3)4, and tris dibenzylidene-acetone)dipalladium 0), Pd2 dba)3, or the chloroform complex, Pd2(dba)3-CHCI3 which is air-stable, are the most common sources of... 

The binuclear complexes (275) and (276), which interconvert on heating in solution, have been synthesized either by reaction of [RuCl2(CO)2(PPh2py)2] with [Pd2(dba)3] (dba = dibenzylidene-acetone) or from [Ru(CO)3(PPh2py)2] and [PdCl2(cod)].1459... 

Another approach can be the displacement of the surface Hgands by a reactive gas such as CO, leading to unstable intermediates that will eventually condense into particles. This procedure can be apphed to M(dba)2 (dba = dibenzylidene acetone M = Pd Pt) [26-28,33,34]. In this case, however, CO remains at the surface of the growing clusters and may modify their chemistry. The reaction conditions (temperature, gas pressure, concentration of precursors and stabilizers) have a strong influence on the nature of the particles formed, primarily on their size. 

The two component catalyst consists of a 1 3 molar ratio of tris(dibenzylidene-acetone)dipalladium and bis(2-diphenylphosphino)phenyl)ether, respectively. 

N-Arylation of amides was also performed by the author using (CuOTf)2 benzene and CS2CO3 with co-catalysts, 1,10-phenanthroline and dibenzylidene acetone, as illustrated in Eq. 1 below ... 

Addition of a catalytic amount of Pt(dba)2 (dba = dibenzylidene acetone) to reactions with a variety of C-arylaldimines and B2cat 2 in benzene or THF at 25°C yielded HBcat and a mixture of diboration, 4a-j, boration, 5a-j, and hydroboration products, 6a-j (Equation 5). Addition of one equivalent of a phosphine such as PPh3 or PCy3 to the Pt catalyst severely reduced activity, while Wilkinson s catalyst, RhCl(PPh3)3, gave much less of the diboration product. Both cationic and neutral rhodium complexes with chelating phosphines were also inactive. 

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