- Rhodium-catalyzed anti-Markovnikov hydroamination of vinylarenes
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The transition metal-catalyzed anti-Markovnikov hydroamination of unactivated vinylarenes with a rhodium complex of DPEphos is reported. The reaction of electron-neutral or electron-rich vinylarenes with a variety of secondary amines in the presence of catalyst forms the products from anti-Markovnikov hydroamination in high yields. Reactions of morpholine, N-phenylpiperazine, N-Boc-piperazine, piperidine, 2,5-dimethylmorpholine, and perhydroisoquinoline reacted with styrene to form the amine product in 51-71% yield. Reactions of a variety of vinylarenes with morpholine generated amine as the major product. Reactions of morpholine with electron-poor vinylarenes gave lower amine:enamine ratios than reactions of electron-rich vinylarenes at the same concentration of vinylarene, but conditions were developed with lower concentrations of electron-poor vinylarene to maintain formation of the amine as the major product. Reactions of dimethylamine with vinylarenes were fast and formed amine as the major product. Mechanistic studies on the hydroamination process showed that the amine:enamine ratio was lower for reactions conducted with higher concentrations of vinylarene and that one vinylarene influences the selectivity for reaction of another. A mechanism proceeding through a metallacyclic intermediate that opens in the presence of a second vinylarene accounts for these and other mechanistic observations. Copyright
- Utsunomiya, Masaru,Kuwano, Ryoichi,Kawatsura, Motoi,Hartwig, John F.
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p. 5608 - 5609
(2007/10/03)
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- The first rhodium-catalyzed anti-markovnikov hydroamination: Studies on hydroamination and oxidative amination of aromatic olefins
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The first transition-metal-catalyzed regiospecific anti-Markovnikov hydroamination of aromatic olefins is reported. Styrene and substituted styrenes react with secondary aliphatic amines, especially morpholine and Narylpiperazines, in the presence of cationic rhodium complexes to give 2- aminoethenylbenzene and 2-aminoethylbenzene derivatives. Cationic [Rh(cod)2]+BF4- and various phosphines (l:2-mixture) were employed as in situ catalysts. According to labeling experiments, there is no evidence that the hydroamination is a consecutive hydrogenation of a previously formed enamine. Hydroamination with simple secondary amines, for example piperidine, can also be achieved by the use of a higher olefin concentration and higher reaction temperatures than those given in previously published reaction procedures. Kinetic investigations of the major reaction pathway reveal that the reaction rate of the oxidative amination and the hydroamination is dependent on the styrene and on the catalyst concentration, and independent of the amine concentration. Experiments that employed deuterium-labeled amines (N-D) provided evidence that the mechanism involves an amine- activating pathway. The substituents on the styrene, the phosphine ligand, and the solvent influence the yield of the aminations and the enamine:alkylamine ratio.
- Beller,Trauthwein,Eichberger,Breindl,Herwig,Mueller,Thiel
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p. 1306 - 1319
(2007/10/03)
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- ALDEHYDE-ENAMINES FROM α-OXOCARBOXYLIC ACIDS. A FACILE AND GENERAL ROUTE TO ALDEHYDES VIA DECARBOXYLATION OF α-OXOCARBOXYLIC ACIDS CARRYING β-HYDROGENS
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When α-oxocarboxylic acids carrying β-hydrogens are treated with a secondary amine in boiling benzene with azeotropic removal of water, they decarboxylate quantitatively to form aldehyde-enamines which subsequently are hydrolyzed to the corresponding aldehydes in high yields.
- Stamos, Ioannis K.
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p. 459 - 462
(2007/10/02)
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