- A new type of phosphaferrocene-Pyrrole-phosphaferrocene P-N-P pincer ligand
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A 2-ethoxycarbonylphosphaferrocene was reduced to the corresponding 2-hydroxymethyl derivative, which was condensed with pyrrole in a 2:1 ratio in the presence of BF3 to give a phosphaferrocene-pyrrole- phosphaferrocene pincer ligand. This tridentate ligand, in turn, reacted with [Rh(acac)(CO)2] to yield a rhodium carbonyl pincer complex. This complex was characterized by X-ray crystal structure analysis and tested in the hydroformylation of internal olefins.
- Tian, Rongqiang,Ng, Yongxiang,Ganguly, Rakesh,Mathey, Francois
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scheme or table
p. 2486 - 2488
(2012/06/04)
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- Rhodium catalyzed hydroformylation of β-pinene and camphene: effect of phosphorous ligands and reaction conditions on stereoselectivity
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The effect of phosphorous ligands on the rhodium catalyzed hydroformylation of β-pinene and camphene has been studied. In unmodified systems, β-pinene undergoes a fast isomerization to α-pinene. At longer reaction times and higher temperatures, the isomerization equilibrium is shifted resulting in the 80 percent chemoselectivity for β-pinene hydrofromylation products (97 percent trans). The addition of various diphosphines or phosphites improves the chemoselectivity and shifts the hydroformylation towards cis aldehyde 3a. Both the rate and diastereoselectivity of the hydroformylation of β-pinene are largely influenced by the basicity of auxiliary ligands, but surprisingly no correlation between their steric characteristics and the diastereoselectivity of the catalytic system has been revealed for the ligands with cone angles 128-165 deg. The systems with more basic ligands show lower activities, higher diastereoselectivities and usually higher chemoselectivities in the β-pinene hydroformylation. Camphene gives linear aldehyde 6, with virtually 100 percent regio- and chemoselectivity in both modified and unmodified systems. The addition of phosphorous ligands favors the formation of endo isomer 6b:6a/6b ca. 1/1.5 , whereas the ratio ca. 1/1 unmodified systems. Neither steric nor electronic parameters of the ligands have been found to influence significantly the diastereoselectivity of the camphene hydroformylation.
- Barros, Humberto J. V.,Ospina, Maria L.,Arguello, Eduardo,Rocha, William R.,Gusevskaya, Elena V.,Santos, Eduardo N. dos
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p. 150 - 157
(2007/10/03)
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- Tripinyltrioxanes
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Tripinyltrioxanes of the general formula (I): STR1 in which the radicals Pin are either dextrorotatory (+) or laevorotatory (-) pinyl radicals; a process for the production of (I) by treatment of an enantiomeric mixture of (+)-3-formylpinane and (-)-3-formylpinane (II) with an acid in an organic solvent and fractional precipitation of the trimeric compound (I); and redissociation of (I) into the pure enantiomers (II) with a catalytic amount of an acid.
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- Pinane derivatives
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Pinanes substituted by a group X in the 3-position which group is formyl, or its alkyl-acetals or alkyl-hemiacetals, carboxylic acid, carboxylic acid chloride, carboxylic acid amide, hydroxymethyl or aminomethyl substituted in a specific manner at the nitrogen, the optical isomers of these compounds and a process for their manufacture by hydroformylation of α-pinene in the presence of rhodium catalysts, and conversion of the 3-formylpinane first produced into the above derivatives by conventional methods.
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- Resolution of racemic pantolactone
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A process for resolving racemic α-hydroxy-β,β-dimethyl-γ-butyrolactone, referred to as D,L-pantolactone, into its optical antipodes, based on the separation of diastereomeric salts of D,L-pantoic acid (α,γ-dihydroxy-β,β-dimethylbutyric acid), produced from D,L-pantolactone, by means of (-)-3-aminomethylpinane, (+)-3-aminomethylpinane or one of their acid addition salts, as a new resolving agent.
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