- Binuclear Pd(I)-Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes
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Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>107 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh- or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)-Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.
- Zhang, Yang,Torker, Sebastian,Sigrist, Michel,Bregovi?, Nikola,Dydio, Pawe?
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supporting information
p. 18251 - 18265
(2020/11/02)
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- OZONE-FACILITATED SELECTIVE OXIDATION OF ALKANES IN LIQUID CARBON DIOXIDE
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A process for the ozonolysis of an alkane may comprise combining an alkane and ozone in a liquid phase medium comprising CO2 under conditions sufficient to oxidize the alkane to produce one or more non-combustion products. The liquid phase medium may be free of a super acid.
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Paragraph 0037
(2018/03/06)
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- Efficient and selective Al-catalyzed alcohol oxidation via oppenauer chemistry
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A highly active and selective Al-based catalytic Oppenauer (O) oxidation is reported. Quantitative and selective oxidations of a variety of benzylic, propargylic, allylic, and aliphatic primary and secondary alcohols were achieved using nitrobenzaldehyde derivatives as the oxidant and simple aluminum compounds as precatalysts. Copyright
- Graves, Christopher R.,Zeng, Bi-Shun,Nguyen, SonBinh T.
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p. 12596 - 12597
(2008/02/03)
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- Reductive alkylation of electronegatively-substituted alkenes by alkylmercury halides
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Photolysis of alkylmercury halides in the presence of electronegatively-substituted 1-alkenes yields adduct radicals [RCH2CH(EWG).] that in some cases react with RHgX to form RCH2CH(HgX)(EWG), e.g., EWG = (EtO)2PO or PhSO2. When the EWG is carbonyl or cyano, the resonance stabilized adduct radicals fail to react with the alkyl mercury halide. In these cases photolysis with RHgCl/KI in Me2SO leads to the adduct mercurial via reaction of the adduct radicals with RHgI2-. The reactions of tertiary-enolyl adduct radicals are inefficient with RHgX/KI, and disproportionation of the adduct radicals is the major reaction pathway. For secondary- or tertiary-adduct radicals the reductive alkylation products are formed in excellent yield by reaction with RHgCl and silyl hydrides in Me2SO solution in a process postulated to involve RHgH as an intermediate. The relative reactivities of a number of α,β-unsaturated systems toward t-Bu. have been measured by competitive techniques. The results demonstrate a high reactivity of s-cis enones relative to the s-trans conformers.
- Russell, Glen A.,Shi, Bing Zhi,Jiang, Wan,Hu, Shuiesheng,Kim, Byeong H.,Baik, Woonphil
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p. 3952 - 3962
(2007/10/02)
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- EFFECTS OF SALTS ON THE KINETIC OF OXIDATION OF ALKENES BY THALLIC SALTS IN AQUUEOUS SOLUTIONS
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The kinetics of oxidation of alkenes by thallic sulphate in aqueous solutions, involving the two reaction steps - the hydroxythallation and the dethallation - was studied, and the effect of salts on the kinetics was examined; this made it possible to specify more precisely the reaction mechanism and to suggest a qualitative model of the reaction coordinate.It was found that in homogeneous as well as in heterogeneous reaction conditions, the reaction can be accelerated appreciably by adding tetraalkylammonium salts.These salts not only operate as catalysts of the phase transfer, but also exert a significant kinetic effect, which can be explained with a simplification in terms of a stabilization of the transition state of the reaction.
- Strasak, Milan,Majer, Jaroslav
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p. 693 - 700
(2007/10/02)
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- Synthesis of aldehydes and products of such synthesis
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The disclosure describes the production of complex aliphatic, unsaturated and cycloalkane aldehydes utilizing heterocyclic ring compounds, such as oxazines, particularly dihydro-1,3-oxazines. The oxazines are treated with an alkali metal-alkane compound, such as butyl lithium in the presence of an organic solvent at subzero temperature to form an anion of the oxazine. This anion is then alkylated in the anhydrous reaction mixture by introduction of a suitable halide, epoxide or ketone while still at a subzero temperature and mixture is permitted to warm up to room temperature, following which the reaction mixture is acidified, as with hydrochloric acid to pH 2 to 3, extracted and then made basic, as with caustic alkali with cooling. The reaction mixture is then extracted, as with ether, to produce after evaporation the alkylated dihydro-1,3-oxazine. The alkylated dihydro-1,3-oxazine is then reacted with an alkali metal or sodium borohydride or borodeuteride or borotritide, with cooling to subzero temperatures at about a neutral pH and then transferred into a basic aqueous environment following extraction of the aqueous layer with an organic solvent, such as ether, to give a tetrahydro-1,3-oxazine. This compound may then be converted to the aldehyde desired by steam distillation or by hydrolysis in the presence of a dilute or weak acid, such as hydrochloric or oxalic acid. The aldehydes may then be extracted. These aldehydes are useful as components or intermediates in flavoring or perfumes, in insect attractants and repellants, and in pharmaceuticals.
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