- Palladium-catalyzed oxidative rearrangement of diaryl alkenyl carbinols to β,β-diaryl α,β-unsaturated ketones
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An unusual oxidative palladium-catalyzed rearrangement of diaryl alkenyl carbinols to β,β-diaryl α,β-unsaturated ketones is described. The geometry of the alkene product is not determined by the electronic nature of the aryl substitutents but rather is determined by substitution pattern on the aryl rings. The reaction proceeds in good yields, utilizes oxygen at atmospheric pressure as the terminal oxidant, and tolerates a variety of functional groups on the aryl rings.
- Rosa, David,Orellana, Arturo
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supporting information; experimental part
p. 3648 - 3651
(2011/09/16)
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- The utilization of supercritical carbon dioxide in the palladium- catalyzed hydroarylation of β-substituted-α,β-enones
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The utilization of supercritical carbon dioxide (scCO2) has a beneficial effect on the palladium-catalyzed reaction of acyclic β- substituted-α,β-enones with aryl iodides and hydroarylation (formal conjugate addition) products were isolated in good to high yields. The hydroarylation to vinylic substitution ratio is usually high.
- Cacchi, Sandro,Fabrizi, Giancarlo,Gasparrini, Francesco,Pace, Paola,Villani, Claudio
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p. 650 - 652
(2007/10/03)
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- Reactivity in acid-catalyzed carbon-carbon heterolysis
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Equilibrium and rate constants have been determined for the acid-catalyzed heterolysis of two alcohols, 9-xanthydrol and p-anisyldiphenylmethanol, and two sulfides, (9-xanthyl) methyl sulfide and (7-tropyl) methyl sulfide. These data together with literature information are compared with rate constants for acid-catalyzed C-C heterolysis of several (9-xanthyl) compounds, (7-tropyl) compounds, a set of 3-arylcyclobutanones, and two 2-arylnitrocyclopropanes, all of which fragment to carbocations plus a carbon-centered nucleofuge. The fragmentation mechanisms are shown to be A1 or A1(ion pair) except for the 2-arylnitrocyclopropanes which cleave in trifluoroacetic acid by a concerted mechanism. Rate comparisons among several unstrained substrate sets indicate that O-centered nucleofuges undergo acid-catalyzed heterolysis ca. 103-104 faster than S-centered nucleofuges and ca. 109-1014 faster than the C-centered nucleofuges used here. Factors assisting C-C heterolysis (and their effectiveness) include the acidity of the medium (strong); the basicity and nucleofugality of the nucleofuge (moderate); the stability of the electrofugic carbocation (strong); and relief of ring strain (enormous). Compared with acyclic cleavages, rate accelerations worth ca. 15 kcal/mol (for cyclobutanones) and ca. 27 kcal/mol (for nitrocyclopropanes) are found. These effects are discussed in terms of transition-state structure, aided by computational evidence.
- Cao, Weiguo,Erden, Ihsan,Grow, Richard H.,Keeffe, James R.,Song, Jiangao,Trudell, Mary B.,Wadsworth, Teri L.,Xu, Fu-Pei,Zheng, Ji-Bin
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p. 1009 - 1034
(2007/10/03)
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- CONJUGATE ADDITION VS. VINYLIC SUBSTITUTION IN PALLADIUM-CATALYSED REACTION OF ARYL HALIDES WITH β-SUBSTITUTED-α,β-ENONES AND -ENALS
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The reaction of β-substituted-α,β-enones and -enals with aryl halides in the presence of a palladium catalyst has been investigated.The outcome of the reaction was found to be greatly dependent on the nature of the added base.Tertiary amines tend to favour the formation of conjugate addition-type products while sodium bicarbonate or sodium acetate that of vinylic substitution products.Usually, the use of sodium acetate produced results comparable or better than those obtained with sodium bicarbonate.Furthermore, in the reaction of aryl halides containing strongly electron-withdrawing groups, sodium acetate afforded a dramatic increase in the yield of vinylic substitution products.
- Amorese, A.,Arcadi, A.,Bernocchi, E.,Cacchi, S.,Cerrini, S.,et al.
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p. 813 - 828
(2007/10/02)
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- THE-PALLADIUM-CATALYSED REDUCTIVE ADDITION OF ARYL IODIDES TO PROPARGYL ALCOHOLS: A ROUTE TO γ,γ-DIARYL ALLYLIC ALCOHOLS
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The reaction of aryl iodides with ethynyl and arylethynyl, dialkyl carbinols in the presence of the tri- or dialkylammonium formate-palladium reagent provides a convenient route to γ,γ-diarylallylic alcohols.In the presence of arylethynyl, alkylcarbinols a lack of regioselectivity was observed and mixtures of β,γ-, γ,γ-diarylallylic alcohols, and α,β-unsaturated ketones were obtained.
- Arcadi, A.,Cacchi, S.,Marinelli, F.
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p. 5121 - 5132
(2007/10/02)
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- Palladium-Catalyzed Conjugate Addition Type Reaction of Aryl Iodides with α,β-Unsaturated Ketones
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Aryl iodides have been found to react with α,β-unsaturated ketones in the presence of catalytic amounts of palladium, an excess of formic acid, and triethylamine, giving rise to conjugate addition type products.The electron-withdrawing power of the group attached to the olefinic double bond, the substituent β to the carbonyl group, and the basic reaction medium appear to effect greatly the conjugate addition/vinylic substitution ratio.
- Cacchi, S.,Arcadi, A.
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p. 4236 - 4240
(2007/10/02)
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