- Catalytic asymmetric [4+2]-cycloaddition of dienes with aldehydes
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Despite its significant potential, a general catalytic asymmetric [4+2]-cycloaddition of simple and electronically unbiased dienes with any type of aldehyde has long been unknown. Previously developed methodologies invariably require activated, electronically engineered substrates. We now provide a general solution to this problem. We show that highly acidic and confined imidodiphosphorimidates (IDPis) are extremely effective Br?nsted acid catalysts of the hetero-Diels-Alder reaction of a wide variety of aldehydes and dienes to give enantiomerically enriched dihydropyrans. Excellent stereoselectivity is generally observed and a variety of scents and natural products can be easily accessed.
- Liu, Luping,Kim, Hyejin,Xie, Youwei,Fares, Christophe,Kaib, Philip S.J.,Goddard, Richard,List, Benjamin
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supporting information
p. 13656 - 13659
(2017/11/06)
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- Antimony(v) cations for the selective catalytic transformation of aldehydes into symmetric ethers, α,β-unsaturated aldehydes, and 1,3,5-trioxanes
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1-Diphenylphosphinonaphthyl-8-triphenylstibonium triflate ([2][OTf]) was prepared in excellent yield by treating 1-lithio-8-diphenylphosphinonaphthalene with dibromotriphenylstiborane followed by halide abstraction with AgOTf. This antimony(v) cation was found to be stable toward oxygen and water, and exhibited exceptional Lewis acidity. The Lewis acidity of [2][OTf] was exploited in the catalytic reductive coupling of a variety of aldehydes into symmetric ethers of type L in good to excellent yields under mild conditions using Et3SiH as the reductant. Additionally, [2][OTf] was found to selectively catalyze the Aldol condensation reaction to afford α-β unsaturated aldehydes (M) when aldehydes with 2 α-hydrogen atoms were used. Finally, [2][OTf] catalyzed the cyclotrimerization of aliphatic and aromatic aldehydes to afford the industrially-useful 1,3,5 trioxanes (N) in good yields, and with great selectivity. This phosphine-stibonium motif represents one of the first catalytic systems of its kind that is able to catalyze these reactions with aldehydes in a controlled, efficient manner. The mechanism of these processes has been explored both experimentally and theoretically. In all cases the Lewis acidic nature of the antimony(v) cation was found to promote these reactions.
- Arias Ugarte, Renzo,Devarajan, Deepa,Mushinski, Ryan M.,Hudnall, Todd W.
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supporting information
p. 11150 - 11161
(2016/07/20)
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- A convenient approach for the synthesis of 1,3,5-trioxanes under solvent-free conditions at room temperature
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A series of environmentally benign bis-SO3H-functionalized Bronsted acidic ionic liquids were synthesized by using aliphatic polyamines and 1,3-propanesultone as the source chemicals. These ionic liquids acted as efficient inexpensive and recyclable catalysts for cyclotrimerization of aliphatic aldehydes at room temperature under solvent-free conditions. The reactions proceeded smoothly with good to excellent isolated yields (66.9-97.6 %=) and were generally complete in 1.5 h when the amount of ionic liquids was 0.1 mol%. The ionic liquids could be recovered readily and reused five times without any significant loss in their catalytic activity. Graphical abstract: [Figure not available: see fulltext.]
- Li, Xinzhong,Lin, Qi,Cao, Rong
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p. 1017 - 1022
(2014/06/09)
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- A convenient solvent-free preparation of 1,3,5-trioxanes
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In the presence of a small amount of trimethylsilyl chloride, aldehydes gave at room temperature in solvent-free conditions the corresponding 1,3,5-trioxanes with good to excellent yields.
- Augé, Jacques,Gil, Richard
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p. 7919 - 7920
(2007/10/03)
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- Cyclotrimerization of Aliphatic Aldehydes Catalysed by Keggin-type Heteropoly Acids and Concomitant Phase Separation
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The acid-catalysed cyclotrimerization of aliphatic aldehydes has been examined through comparison of heteropoly acids with other acid catalysts.A Keggin-type heteropoly acid such as phosphomolybdic acid catalyses the cyclotrimerization of aldehydes, such as ethanal, propanal, butanal, 2-methylpropanal, 2,2-dimethylpropanal, hexanal, octanal, and decanal, to produce the respective 2,4,6-trialkyl-1,3,5-trioxanes in high yields.Catalysts turnover number of the heteropoly acid is more than 10000 for propanal cyclotrimerization.In addition to the high catalytic activities, the reaction mixture spontaneously separates into two phases, a produ ct phase and a catalyst phase, at high conversions of aldehyde.For propanal cycltrimerization, the reaction mixture separates into two liquid phases, and the recovered catalyst phase may be repeatedly applied to the reaction without additional care in isolation of the catalyst.The phase separation phenomenon has been concluded to be caused by the insolubility of the heteropoly acid coordinated with propanal in the product 2,4,6-triethyl-1,3,5-trioxane.
- Sato, Satoshi,Furuta, Hiromi,Sodesawa, Toshiaki,Nozaki, Fumio
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p. 385 - 390
(2007/10/02)
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- OXIDATION OF PRIMARY ALCOHOLS TO ALDEHYDES CATALYZED BY RUTHENIUM COMPOUNDS
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The RuCl3 and RuO2*nH2O catalyzed oxidation of alkanes, aromatic fatty acids, alcohols, citronellol and hydroxycitronellol by NaOCl was studied in the diphase system CCl4-aqueous NaOCl at pH 13-13.5.At 60 - 65 deg C, using 1-2 mole percent of catalyst and a 1.5-fold molar excess of NaOCl, primary alkanols (hexanol-1, 2-ethylhexanol-1, decanol-1, hexadecanol-1) benzyl and 3-phenylpropyl alcohols, and hydroxycitronellol are converted to the corresponding aldehydes with a selectivity of 70-90percent and a yield of over 75percent.
- Ogibin, Yu. N.,Ilovaiskii, A. I.,Nikishin, G. I.
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