Search results for "Ketone"
showing 10 items of 337 documents
Novel prolinamide-supported polystyrene as highly stereoselective and recyclable organocatalyst for the aldol reaction
2008
A new prolinamide derivative anchored to a polystyrene support has been straightforwardly prepared and employed as heterogeneous catalyst in the direct asymmetric aldol reaction with good results in terms of yield and stereoselectivity. The optimal reaction conditions were found when a 1:2 (v/v) water/chloroform mixture was used. This mixture was the best compromise between the good swelling properties of chloroform and the formation of a concentrated organic phase due to the presence of water. Noticeably, the enantioselectivities obtained employing acetone as ketone were, to the best of our knowledge, the highest achieved with a supported proline derivative. This catalyst can be easily rec…
A unified synthetic approach to trachylobane-, beyerane-, atisane- and kaurane-type diterpenes
2006
A general synthetic approach to the polycyclic carbon skeleton of biogenetically related trachylobane, beyerane, atisane, and kaurane diterpenes from carvone is described. The skeleton of these diterpenes is prepared from a common intermediate, that is, 25, readily prepared from carvone using an IMDA reaction and an intramolecular diazo ketone cyclopropanation of an unsaturated ketone as key steps. The tetracyclic diterpene ring systems are obtained from this key trachylobane-type intermediate through the regioselective reductive cleavage of the cyclopropane ring, after adequate modification of the functionalization around the tricyclo[3.2.1.02,7]octane moiety.
Carbonylmolybdenum complexes with di(imino)pyridine and related ligands: Reduction of a di(imino)pyridine to an aminoiminopyridine system under mild …
2006
Abstract The reactions of [Mo(CO) 6 ] towards a 2,6-di(imino)pyridine L 1 and related ligands were studied. The reaction with L 1 afforded two new complexes, [Mo(CO) 4 L 1 ] ( 1 ) and [Mo(CO) 4 L 2 ] ( 2 ), where L 2 is the 2-amino-6-iminopyridine ligand arising from the hydrogenation of one imine function of L 1 ; similar reaction with a 2-acetyl-6-iminopyridine ligand L 3 afforded [Mo(CO) 4 L 3 ] ( 3 ). Compounds 1 , 2 and 3 have been fully characterised by IR, 1 H NMR and X-ray crystallography; they present a metal ion in a pseudo-octahedral environment, the three organic ligands acting with bidentate N 2 coordination modes. One of the imine functions in 1 , the amine function in 2 , and…
Part II. Chiral dirhodium (II) catalysts with ortho-metalated arylphosphane ligands in the enantioselective intramolecular cyclopropanation of a race…
2006
Abstract In this report, chiral dirhodium (II) with ortho -metalated phosphane ligands, namely ( M )-Rh 2 (O 2 CR) 2 (PC) 2 [PC = ortho -metalated aryl phosphane, O 2 CR = carboxylate bridging ligands) ( 1a–g ), have been used for the intramolecular cyclopropanation of racemic1-diazo-6-methyl-3-(2-propenyl)-5-hepten-2-one ( 2 ), containing both a tri- and monosubstituted carbon–carbon double bond, in pentane. The highest level of regiocontrol has been obtained with chiral catalyst Rh 2 (O 2 CCH 3 ) 2 [( p -MeC 6 H 3 )P( p -MeC 6 H 4 ) 2 ] 2 ( M )- 1c , affording favorably trisubstituted cyclopropane 3 versus monosubstituted cyclopropane 4 in 74:26 ratio. An exceptional diastereoselectivity…
A Highly Regio-, Diastereo- and Enantioselective Intramolecular Cyclopropanation Reaction of a Racemic α-Diazo Ketone Catalyzed by Chiral ortho-Metal…
2003
Abstract A series of racemic dirhodium(II) compounds with two ortho-metalated aryl phosphine ligands in a head-to-tail arrangement Rh2(O2CR)2(pc)2 (pc=ortho-metalated aryl phosphine) (1a–k) were tested in the regio- and stereoselective cyclopropanation of racemic 1-diazo-6-methyl-3-(2-propenyl)-5-hepten-2-one 2, which possesses two different reactive CC double bonds for a five-membered-ring formation. The complexes Rh2(O2CCH3)2(pc)2 {pc=[(C6H4)P(C6H5)2], [(p-CH3C6H3)P(p-CH3C6H4)2], and [(C6H4)P(C6H5)(C6F5)]} (1a–d) successfully enhanced the cyclopropanation of trisubstituted versus monosubstituted CC bonds to give an 80:20 selectivity ratio. The reaction occurred with excellent diastereos…
Photochemical Transformations of Some Neoclerodane and Labdane Diterpene Ketones
1999
Some neoclerodane (2–4) and labdane (5 and 6) diterpene ketones having a β- or γ-hydroxy function, an α-epoxy group, or an α-olefinic double bond have been irradiated at λ = 313 nm in dry solvents (benzene or methanol). Fruticolone (2) yielded the naturally occurring 5,6-seco-neoclerodan-6,1α-olide derivative fruticolide (1), while hispanolone (5) gave the δ-lactone 8, both transformations involving a Norrish type I photoreaction. The α,β-unsaturated ketone derivative 4 was transformed into 7 by a stereoselective intramolecular [2+2] cycloaddition reaction involving its furanic 13(16)-double bond. Finally, the α-epoxy ketone 6 was rearranged to the 10(98)abeo-labda-7,9-dione derivative 10. …
Multinuclear NMR study of 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one (fenchone) and its six monochlorinated derivatives
1990
1H, 13C and 17O NMR spectra of fenchone and six monochlorofenchones have been recorded. The second-order 1H NMR spectra were analysed by an iterative computer program. The 1H and 13C chlorine-induced substituent chemical shifts (SCS) were calculated. The vicinal coupling constants proved to be essential in the assignment of the chemical shifts of the geminal methyls. No clear correlation was observed between the chemical shifts of the carbonyl oxygen and the carbonyl carbon. All monochlorofenchones were previously unknown compounds and were synthesized for this work.
Highly Diastereoselective Arylation of (S)-Mandelic Acid Enolate: Enantioselective Synthesis of Substituted (R)-3-Hydroxy-3-phenyloxindoles and (R)-B…
2005
An easy access to substituted (R)-3-hydroxy-3-phenyloxindoles, (R)-benzylic acids, and benzophenones is described. The reaction of the lithium enolate of the (2S,5S)-cis-1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde with several o- and p-halonitrobenzenes proceeds readily to give the corresponding arylation products in good yields and diastereoselectivities. The reduction of the nitro group with Zn/HCl/EtOH in the o-nitro arylation products with concomitant intramolecular aminolysis of the dioxolanone moiety leads directly to enantiomerically pure (R)-3-hydroxy-3-phenyloxindoles. On the other hand the basic hydrolysis of the dioxolanone moiety in all t…
Nucleophilic substitutions in the isoindole series as a valuable tool to synthesize derivatives with antitumor activity
2011
Abstract A novel synthetic approach to the synthesis of 3-substituted isoindoles through nucleophilic substitution of 3-halo derivatives by charged carbon, and neutral nitrogen, oxygen, and sulfur nucleophiles, assisted by a 1-acyl group, is reported. Aryl-thio-isoindoles, obtained through a direct nucleophilic substitution with sulfur nucleophiles, showed cytotoxic activity, with GI50 values from micromolar to sub-micromolar concentrations, against the total number of cell lines investigated.
Inhibitoren der Korrosion 23 (1) - Gibt es eine Struktur- Wirkungs-Beziehung bei organischen Inhibitoren der Korrosion von Aluminium?
1978
Uber 400 organische Verbindungen wurden routinemasig darauf gepruft, ob sie die Auflosung des Aluminiums in In Salzsaure in Gegenwart von 2,5% NaCl und bei einer Konzentration von 10−2 Mol/l der zu prufenden Verbindung beeinflussen. Es wurde versucht, eine “Struktur-Wirkungs-Beziehung” zu erstellen. Eingehender diskutiert wurden folgende Verbindungsklassen: Arsenverbindungen, Phosphon- und Phosphinsauren, aromatische Aldehyde und Ketone, aromatische und aliphatische Carbonsauren, zweiwertige Phenole, Tetrazoliumsalze und formazane, Sulfoxide und aromatische Sulfonsauren, Sulfonamide und Sulfone. Bei einer Auswahl von Inhibitoren wurde die Abhangigkeit der Schutzwirkung von deren Konzentrati…