1.3- Diphenylpropane-l,3-dione

Attempts to influence the hydrogen bond by changes at the P-carbons, for example, as in l,3-diphenylpropane-l,3-dione, resulted in crystals whose structure showed them to be entirely of the keto tautomer with a cw-diketo conformation and a carbonyl-carbonyl dihedral angle of ca. 90° (Emsley et al., 1987). 

The compounds [(n -Cp)TiClL2] (HL = acac, l-phenylbutane-l,3-dione, or l,3-diphenylpropane-l,3-dione) have been prepared by the reaction of... 

Under optimized conditions, the 83-catalyzed (1 mol% loading) Michael addition of acetylacetone to various aryl nitroalkenes as well as alkyl nitroalkenes proceeded in good to excellent yields (80-97%) and enantioselechvities (82-99%) of the desired adducts 1-5 (Scheme 6.93). The authors also reported the successful enantioselective Michael addihon of l,3-diphenylpropane-l,3-dione (adduct in... 

Interesting results are obtained from the interaction of 2,3-dihydrodiazepines 104 with 2-diazo-l,3-diphenylpropane-l,3-dione 127. The reaction involves both the secondary amino group and the azomethine bond, thus leading to the formation of compounds 128 and 129 [115] (Scheme 4.41). 

As an illustration, a complete step-by-step analysis of the reaction of l,3-diphenylpropane-l,3-dione with acetophenone giving 2,4,6-triphenylpyrylium is presented below. Note that although many separate steps are involved, each of them is very simple when considered individually. Note also, that the dicarbonyl tautomer of the diketone is shown, which is in equilibrium with an appreciable percentage of mono-enol tautomer. 

The product of the reduction of [Co(bpy)3] by Cr, upon aerial oxidation, is a red dimeric species, postulated to have the structure [(H20)4Cr(/x-OH)2Cr(OH2)2]. This product and the stoichiometry of the reaction suggests a two-electron process, with the bpy ligand serving as a temporary bridging radical. An investigation of the Cr(II) reduction of [Co(pd)3] (pd = pentane-2,4-dione) in water/acetone mixtures reveals outer-sphere, and mono- and di-bridged ([H ] dependent) pathways.The effect of the cosolvent on the activation parameters is observed at an acetone mole fraction of 0.06, at which point its solvation of the activated complex becomes important. The reduction of [Co(en)2(dppd)] (dppd = l,3-diphenylpropane-l,3-dione) by Cr occurs by a multistep mechanism in which the first step is the formation of the [Co(en)2(dppd )] radical, which catalyzes the inner-sphere Co(III)/Cr(II) electron transfer process. " A molecular orbital study indicates that the [Co(en)2(dppd)] reduction likely involves attack of Cr " at the methine carbon of dppd, in contrast to the attack on an oxygen in the [Co(en)(pd)2] reduction. 

Representative procedure for the gold-catalyzed hydroalkylation of alkenes. 2-Cyclooct-2-enyl-I,3-diphenylpropane-l,3-dion ... 

A solution of AuCla (7.6 mg, 0.025 mmol) and AgOTf (19.3 mg, 0.075 mmol) was stirred in CH2CI2 (2 mL) at RT for 2 h. Dibenzoylmethane (112 mg, 0.5 mmol) was then added, which was followed by the addition of cycloocta-1,3-diene (128 pL, 1 mmol) via a syringe pump over 5 h, and the resulting solution was stirred overnight. The solvent was removed under reduced pressure, and 2-cyclooct-2-enyl-l,3-diphenylpropane-l,3-dione (65% yield) was isolated via column chromatography on silica gel (gradient eluent hexane EtOAc = 60 1 to 2 1). 

An aq. soln. of tetraethylammonium fluoride as powerful H-bond electron donor added to a soln. of l,3-diphenylpropane-l,3-dione in tetrahydrofuran, the solvents removed at ca. 90° under reduced pressure, the residue dissolved in chloroform, and stirred 1 hr. at 30° with excess methyl iodide 2-methyl-1,3-diphenyl-... 

The reaction between unsubstituted pyrrole and benzoylphenylacetylene is complicated by alkaline hydrolysis to give l,3-diphenylpropan-l,3-dione in enol form, phenylacetylene, and benzoic acid (Scheme 2.42). 

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