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Dimethyl Malonate (dimethyl + malonate)
Selected AbstractsRh(II)-Catalyzed Enantioselective Cyclopropanation of Olefins with Dimethyl Malonate via in situ Generated Phenyliodonium Ylide.CHEMINFORM, Issue 11 2005Paul Mueller Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Dimethyl Malonate as a One-Carbon Source: A Novel Method of Introducing Carbon Substituents onto Aromatic Nitro Compounds.CHEMINFORM, Issue 4 2002N. Selvakumar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Better Performance of Monodentate P -Stereogenic Phosphanes Compared to Bidentate Analogues in Pd-Catalyzed Asymmetric Allylic AlkylationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2010Arnald Grabulosa Abstract The cationic allylpalladium complexes 3a,3f, 4a, 4e, 5e of type [Pd(,3 -2-Me-C3H4)P2]PF6 were synthesized using a group of monodentate P -stereogenic phosphanes, P=PPhRR, (a,f) and diphosphanes (PhRPCH2)2 (1a, 1e) or PhRPCH2Si(Me)2CH2PPhR (2e). The analogous cationic complexes with the disubstituted allyl group (,3 -1,3-Ph2 -C3H3) and monodentate phosphanes were not isolated as stable solids; only [PdCl(,3 -1,3-Ph2 -C3H3)P] (6a, 6d) were obtained. Palladium allyl complexes were screened as precatalysts in the allylic substitution of rac -3-acetoxy-1,3-diphenyl-1-propene (I) and (E)-3-acetoxy-1-phenyl-1-propene (III) with dimethyl malonate as the nucleophile. The various catalytic precursors showed a wide range of activity and selectivity. The bismonodentate phosphane complexes 3 are more active than the bidentate analogues. With regard to the regioselectivity, precursors containing monodentate phosphanes favour the formation of the linear product in the allylic substitution of cinnamyl acetate (III) compared with those containing bidentate phosphanes. With substrate I, compounds with the diphosphanes 1a and 1e, containing a five-membered chelate ring, gave low enantioselectivities (less than 10,% ee), but those with the diphosphane 2e, forming a six-membered chelate ring or with two monodentate phosphanes, afforded products with moderate enantioselectivity under standard conditions (ee up to 74,%). The results show that the performance of precursors containing monodentate phosphanes was superior to those containing bidentate ligands in both activity and selectivity. [source] Rhodium(II)-Catalyzed Inter- and Intramolecular Cyclopropanations with Diazo Compounds and Phenyliodonium Ylides: Synthesis and Chiral AnalysisHELVETICA CHIMICA ACTA, Issue 2 2005Ashraf Ghanem Different classes of cyclopropanes derived from Meldrum's acid (=2,2-dimethyl-1,3-dioxane-4,6-dione; 4), dimethyl malonate (5), 2-diazo-3-(silyloxy)but-3-enoate 16, 2-diazo-3,3,3-trifluoropropanoate 18, diazo(triethylsilyl)acetate 24a, and diazo(dimethylphenylsilyl)acetate 24b were prepared via dirhodium(II)-catalyzed intermolecular cyclopropanation of a set of olefins 3 (Schemes,1 and 4,6). The reactions proceeded with either diazo-free phenyliodonium ylides or diazo compounds affording the desired cyclopropane derivatives in either racemic or enantiomer-enriched forms. The intramolecular cyclopropanation of allyl diazo(triethylsilyl)acetates 28, 30, and 33 were carried out in the presence of the chiral dirhodium(II) catalyst [Rh2{(S)-nttl)4}] (9) in toluene to afford the corresponding cyclopropane derivatives 29, 31 and 34 with up to 37% ee (Scheme,7). An efficient enantioselective chiral separation method based on enantioselective GC and HPLC was developed. The method provides information about the chemical yields of the cyclopropane derivatives, enantioselectivity, substrate specifity, and catalytic activity of the chiral catalysts used in the inter- and intramolecular cyclopropanation reactions and avoids time-consuming workup procedures. [source] 5-Chloro-3-methylthio-1,2,4-thiadiazol-2-ium chlorides as useful synthetic precursors to a variety of 6a,4 -thiapentalene systemsHETEROATOM CHEMISTRY, Issue 1 2003Georges Morel Title salts 3 were easily obtained by treatment of formimidoyl isothiocyanates 1 with a twofold excess of methanesulfenyl chloride. They showed interesting chemical behavior toward several nitrogen and carbon nucleophiles. Substitution reactions with isothioureas and acetamide in the presence of triethylamine gave the 1H, 6H -6a,4 -thia-1,3,4,6-tetraazapentalenes 7 and 6H -6a,4 -thia-1-oxa-3,4,6-triazapentalene 9, respectively. Addition of p -toluidine furnished the 5-imino-thiadiazole derivatives 10, which reacted further with diverse heterocumulenes to yield the corresponding thiatriaza- and tetraazapentalene species 11. The N,N,-bis(1,2,4-thiadiazol-5-ylidene)diaminobenzenes 13 were also prepared and reacted with phenyl isothiocyanate. Two stable rotational isomers were separated for the 1,2-phenylene product 14b. Other ,-hypervalent sulfur compounds 16 were synthesized under similar conditions from salts 3 and methyl cyanoacetate or dimethyl malonate. The structural assignments were discussed on the basis of IR and NMR spectroscopic data and received additional support from X-ray analysis of substrate 16a. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:95,105, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10106 [source] Reactivity of selected volatile organic compounds (VOCs) toward the sulfate radical (SO4,)INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2001Ch. George Rate constants for a series of alcohols, ethers, and esters toward the sulfate radical (SO4,) have been directly determined using a laser photolysis set-up in which the radical was produced by the photodissociation of peroxodisulfate anions. The sulfate radical concentration was monitored by following its optical absorption by means of time resolved spectroscopy techniques. At room temperature the following rate constants were derived: methanol ((1.6 ± 0.2) × 107 M,1 s,1); ethanol ((7.8 ± 1.2) × 107 M,1 s,1); tert -butanol ((8.9 ± 0.3) × 105 M,1 s,1); diethyl ether ((1.8 ± 0.1) × 108 M,1 s,1); MTBE ((3.13 ± 0.02) × 107 M,1 s,1); tetrahydrofuran (THF) ((2.3 ± 0.2) × 108 M,1 s,1); hydrated formaldehyde ((1.4 ± 0.2) × 107 M,1 s,1); hydrated glyoxal ((2.4 ± 0.2) × 107 M,1 s,1); dimethyl malonate (CH3OC(O)CH2C(O)OCH3) ((1.28 ± 0.02) × 106 M,1 s,1); and dimethyl succinate (CH3OC(O)CH2CH2C(O)OCH3) ((1.37 ± 0.08) × 106 M,1 s,1) where the errors represent 2,. For the two latter species, we also measured the temperature dependence of the corresponding rate constants. A correlation of these kinetics with the bond dissociation energy is also presented and discussed. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 539,547, 2001 [source] Novel Cinchona -Aminobenzimidazole Bifunctional OrganocatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Lei Zhang Abstract Efficient Cinchona -derived chiral 2-aminobenzimidazole catalysts were prepared by the coupling of 5,7-bis(trifluoromethyl)-2-chlorobenzimidazole with C(9S)-aminodihydroquinine or C(9R)-aminodihydroquinidine and successively applied to the Michael addition of dimethyl malonate to nitroolefins as very efficient chiral Lewis acid bifunctional organocatalysts (up to >99% ee). [source] Novel [Ruthenium(substituted-tetramethylcyclopentadiene) (2-quinolinecarboxylato)(allyl)] Hexafluorophosphate Complexes as Efficient Catalysts for Highly Regioselective Nucleophilic Substitution of Aliphatic Allylic SubstratesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2008Hui-Jun Zhang Abstract Stable [ruthenium(R-substituted-tetramethylcyclopentadiene)(2-quinolinecarboxylato)(1-R,-substituted-allyl) hexafluorophosphate (R=Me, R,=H, Me, n- Pr, Ph; R=t- Bu, R,=Me) and [ruthenium(pentamethylcyclopentadiene)(2-quinolinecarboxylato)(1- n -propylallyl)] tetrafluoroborate (4,a), as allylruthenium(IV) complexes, have been synthesized in one step, starting from [ruthenium(R-substituted-tetramethylcyclopentadiene)tris(acetonitrile) hexafluorophosphate or tetrafluoroborate complexes, quinaldic acid, and allylic alcohols. Single stereoisomers are obtained and the X-ray single crystal structure determinations of 3b (R=t- Bu, R,=Me) and 4,a allow one to specify the preferred arrangement. Complexes 3a (R=R,=Me) and 3b are involved as precatalysts favoring the formation of branched products in regioselective nucleophilic allylic substitution reactions, starting from ethyl 2- (E) -hexen-1-yl carbonate and chlorohexene as unsymmetrical aliphatic allylic substrates. Phenols, dimethyl malonate, and primary (aniline) and secondary (pyrrolidine, piperidine) amines have been used as nucleophiles under mild basic conditions. For the first time, the regioselectivity in favor of the branched product obtained from purely aliphatic allylic substrates is close to the high regioselectivity previously reached starting from cinnamyl-type substrates in the presence of ruthenium catalysts. [source] Memory Effects in Palladium-Catalyzed Allylic Alkylations of 2-Cyclohexen-1-yl AcetateADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17-18 2007Nina Svensen Abstract The objective of this work was to characterize the enantiospecificity of the allylic alkylation of enantioenriched 2-cyclohexen-1-yl acetate with the enolate ion of dimethyl malonate catalyzed by unsymmetrical palladium catalysts. The precatalysts employed were (,3 -allyl)PdLCl, where L is a monophosphine ligand [PPh3, PCy3, P(2-BiPh)Cy2, or P(t- Bu)3], all of which afforded enantiospecificity to some extent (5,47,%). Quantum mechanical calculations show that, theoretically, the enantiospecificity should be high due to a preference for the "trans to P" transition state in both formation of the ,3 -allyl intermediate and nucleophilic attack. However, the observed enantiospecificity is relatively low due to isomerization of the ,3 -allyl intermediate and/or dynamic equilibria between the catalytically active (,3 -allyl)PdLCl species and [(,3 -allyl)PdL2]+ or [(,3 -allyl)PdCl]2. It was also observed experimentally that increasing the bulk of the phosphine inhibits formation of the [(,3 -allyl)PdL2]+ complexes, significantly increasing the observed enantiospecificity for some of the ligands. [source] New Recoverable Poly(ethylene glycol)-Supported C1 - Diamino-oligothiophene Ligands for Palladium-Promoted Asymmetric Allylic Alkylation (AAA) ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 12-13 2006Marco Bandini Abstract A new class of chiral C1 -symmetrical diamino-oligothiophene ligands easy-grafted on a soluble polymeric support (MeOPEG5000) is described. The diamines were found to be effective promoting agents for the [Pd(0)]-catalysed asymmetric allylic alkylation (AAA) of dimethyl malonate in high yields and excellent enantioselectivity (ee up to 99,%). The supported chiral ligand was readily recovered by precipitation and filtration was recycled up to three times without an appreciable loss in activity. The recycle of the organometallic catalytic system was also investigated. [source] | ||||||||||