- Enantioselective total synthesis of pinnaic acid and halichlorine
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The enantioselective total synthesis of the bioactive marine natural products pinnaic acid and halichlorine is reported in detail. Our total synthesis features the construction of the five-membered ring and C9 and C13 stereogenic centers through a palladium-catalyzed trimethylenemethane [3+2] cyclization; the installation of the nitrogen atom through a regioselective Beckmann rearrangement of a poorly reactive ketone; the stereoselective cyclization of the spiro ring through a four-step, one-pot hydrogenation- cyclization; and efficient connection of the sterically hindered lower chain through a reduced-pressure cross olefin metathesis reaction. Copyright
- Xu, Shu,Unabara, Daisuke,Uemura, Daisuke,Arimoto, Hirokazu
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supporting information
p. 367 - 375
(2014/01/06)
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- Enantioselective baeyer-villiger oxidation: Desymmetrization of meso cyclic ketones and kinetic resolution of racemic 2-arylcyclohexanones
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Catalytic enantioselective Baeyer-Villiger (BV) oxidations of racemic and meso cyclic ketones were achieved in the presence of chiral N,N'-dioxide-Sc III complex catalysts. The BV oxidations of prochiral cyclohexanones and cyclobutanones afforded series of optically active μ- and γ-lactones, respectively, in up to 99% yield and 95% ee. Meanwhile, the kinetic resolution of racemic 2-arylcyclohexanones was also realized via an abnormal BV oxidation. Enantioenriched 3-aryloxepan-2-ones, whose formation is counter to the migratory aptitude, were obtained preferentially. Both the lactones and the unreacted ketones were obtained with high ee values.
- Zhou, Lin,Liu, Xiaohua,Ji, Jie,Zhang, Yuheng,Hu, Xiaolei,Lin, Lili,Feng, Xiaoming
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p. 17023 - 17026
(2013/01/15)
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- Enantioselective baeyer-villiger oxidation: Desymmetrization of meso cyclic ketones and kinetic resolution of racemic 2-arylcyclohexanones
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Catalytic enantioselective Baeyer-Villiger (BV) oxidations of racemic and meso cyclic ketones were achieved in the presence of chiral N,N'-dioxide-Sc III complex catalysts. The BV oxidations of prochiral cyclohexanones and cyclobutanones afforded series of optically active μ- and γ-lactones, respectively, in up to 99% yield and 95% ee. Meanwhile, the kinetic resolution of racemic 2-arylcyclohexanones was also realized via an abnormal BV oxidation. Enantioenriched 3-aryloxepan-2-ones, whose formation is counter to the migratory aptitude, were obtained preferentially. Both the lactones and the unreacted ketones were obtained with high ee values.
- Zhou, Lin,Liu, Xiaohua,Ji, Jie,Zhang, Yuheng,Hu, Xiaolei,Lin, Lili,Feng, Xiaoming
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supporting information
p. 17023 - 17026,4
(2012/12/12)
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- Synthesis and AChE inhibitory activity of new chiral tetrahydroacridine analogues from terpenic cyclanones
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This work describes the enantioselective synthesis of a new series of terpenic chiral 9-aminotetrahydroacridine analogues. Several chiral ketones were synthesized from natural monoterpenes in an optically active form and subjected to the cyclodehydration reactions with anthranilonitrile in the presence of BF3·Et2O as catalyst. The 9-aminotetrahydroacridine analogues were tested as acetylcholinesterase (AChE) inhibitors. Based on qualitative structure-activity relationship some trends are suggested.
- Santos Pisoni, Diego dos,Sobieski da Costa, Jessé,Gamba, Douglas,Petzhold, Cesar Liberato,César de Amorim Borges, Antonio,Ceschi, Marco Antonio,Lunardi, Paula,Saraiva Gon?alves, Carlos Alberto
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scheme or table
p. 526 - 535
(2010/04/06)
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- An improved protocol for the oxidative cleavage of alkynes, alkenes, and diols with recyclable Ru/C
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Efficient synthesis of carboxylic acids from alkynes; aldehydes from alkenes and diols employing Ru/C-based recyclable catalytic system is reported with good to excellent yields. Georg Thieme Verlag Stuttgart.
- Vijay Kumar,Prakash Reddy,Sridhar,Srinivas,Rama Rao
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experimental part
p. 739 - 742
(2009/07/18)
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- Supported ruthenium nanoparticle catalyst for cis -dihydroxylation and oxidative cleavage of alkenes
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The present invention relates to the use of nanosized metal particles (e.g., ruthenium) grafted on inert solid support for oxidation of alkenes. The supported metal catalyst can effect cis-dihydroxylation and oxidative cleavage of alkenes to give the respective cis-diols and carbonyl products.
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Page/Page column 4; 7
(2008/06/13)
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- Ruthenium nanoparticles supported on hydroxyapatite as an efficient and recyclable catalyst for cis-dihydroxylation and oxidative cleavage of alkenes
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Impregnation of hydroxyapatite with colloidal ruthenium results in the formation of a catalyst that effects cis-dihydroxylation and oxidative cleavage of alkenes to their respective cis-1,2-diols and carbonyl products in good to excellent yields (see scheme). The supported ruthenium catalyst can be easily recycled and reused for consecutive reaction runs without significant deterioration of the catalytic activities. R1, R2 = H, alkyl, aryl.
- Ho, Chi-Ming,Yu, Wing-Yiu,Che, Chi-Ming
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p. 3303 - 3307
(2007/10/03)
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- Osmium tetroxide-promoted catalytic oxidative cleavage of olefins: An organometallic ozonolysis
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A mild, organometallic alternative to ozonolysis utilizing oxone and OsO4 is presented. This is a direct oxidation of olefins via the carbon-carbon cleavage of an osmate ester by the action of oxone. Twenty-four different olefins were converted to their corresponding ketones or carboxylic acids in high yields (> 80%). Free alcohols, acetate- and benzyl-protected alcohols, and 1,2-diols were stable under these conditions. This method should be applicable for traditional organic synthesis. Copyright
- Travis, Benjamin R.,Narayan, Radha S.,Borhan, Babak
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p. 3824 - 3825
(2007/10/03)
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- Ruthenium-catalyzed oxidative cleavage of olefins to aldehydes
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Three oxidation protocols have been developed to cleave olefins to carbonyl compounds with ruthenium trichloride as catalyst (3.5 mol %). These methods convert olefins that are not fully substituted to aldehydes rather than carboxylic acids. While aryl olefins were cleaved to aromatic aldehydes in excellent yields by using the system of RuCl3-Oxone-NaHCO3 in CH3CN-H2O (1.5:1), aliphatic olefins were converted into alkyl aldehydes with RuCl3-NaIO4 in 1,2-dichloroethane-H2O (1:1) in good to excellent yields. It is noteworthy that terminal aliphatic olefins were cleaved to the corresponding aldehydes in excellent yields by using RuCl3-NaIO4 in CH3CN-H2O (6:1).
- Yang,Zhang
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p. 4814 - 4818
(2007/10/03)
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- Synthesis of versatile chiral intermediates by enantioselective conjugate addition of alkenyl Grignard reagents to enamides deriving from (R)-(-)- or (S)-(+)-2-aminobutan-1-ol
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Conjugate addition of but-3-enylmagnesium bromide to the chiral crotonamide (R)-(+)- and (S)-(-)-3, followed by hydrolysis and oxidation, afforded enantiopure (R)-(+)- and (S)-(-)-3-methyladipic acids 8, respectively. Conjugate addition of vinylmagnesium chloride to the chiral crotonamide and cinnamamides (R)-(+)-3-5, followed by hydrolysis, gave the alkenoic acids (S)-12-14, respectively. Iodolactonization of the latter led to the 5-iodomethyllactones (+)-15-17, which were reduced by means of n- Bu3SnH into the trans-disubstituted 5-methyllactones (+)-19-21, respectively. Treatment of the iodomethyllactone (+)-16 with LiMe2Cu or n- Bu2CuLi furnished the trans-5-alkyl-4-phenyllactones (-)-22 or (+)-23.
- Brown, Eric,Deroye, Christelle,Touet, Joel
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p. 1605 - 1614
(2007/10/03)
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- DETERMINATION OF THE ABSOLUTE STRUCTURES OF CIS-TRIKENTRIN A AND TRANS-TRIKENTRIN A BY SYNTHESIS OF THEIR ENANTIOMERS
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(-)-cis-Trikentrin A (20) and (-)-trans-trikentrin A (21) were synthesized from (R)-3-methyladipic acid by way of pyrrole derivatives 14, 15, and 17, establishing the absolute structure of the natural cis- and trans-trikentrins A to be 1 and 2.
- Muratake, Hideaki,Natsume, Mitsutaka
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p. 5771 - 5772
(2007/10/02)
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- Synthesis and Chiroptical Properties of Some Piperidin-2-ones
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The synthesis of optically pure (R)-(+)-4-isopropylpiperidin-2-one, (R)-(+)-4-isopropyl-4-methylpiperidin-2-one, and (R)-(+)-5-methylpiperidin-2-one in high yields from monocyclic terpene precursors are described.The CD spectra of these compounds are reported, and the chiroptical properties of δ-lactams are examined in terms of current theories for the amide chromophore.It is concluded that slight, conformationally induced nonplanarity of the amide chromophore is responsible for signs of the longest wavelenght bands in the CD spectra of these and related compounds.
- Jackman, L. M.,Webb, R. Lee,Yick, H. C.
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p. 1824 - 1831
(2007/10/02)
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