Search results for "nucleophilic addition"
showing 10 items of 63 documents
The [3,3′-Co(1,2-C2B9H11)2]– anion as a platform for new materials: synthesis of its functionalized monosubstituted derivatives incorporating synthon…
2003
[3,3′-Co(8-C5H10O-1,2-C2B9H10)(1′,2′-C2B9H11)] (2) was synthesized by reaction of the caesium salt of [Co(C2B9H11)2]− with dimethyl sulfate in the presence of sulfuric acid as catalyst and tetrahydropyrane as solvent; the zwitterionic compound (2) yielded [3,3′-Co(8-C4H4N-(CH2)5-O-1,2-C2B9H10)(1′,2′-C2B9H11)]− (6), [3,3′-Co(8-C8H6N-(CH2)5-O-1,2-C2B9H10)(1′,2′-C2B9H11)]− (7), and [3,3′-Co(8-C12H8N-(CH2)5-O-1,2-C2B9H10)(1′,2′-C2B9H11)]− (8) through the nucleophilic addition of potassium pyrrolyl, indolyl and carbazolyl, respectively. The nucleophilic addition of the same salts on [3,3′-Co(8-C4H8O2-1,2-C2B9H10)(1′,2′-C2B9H11)] (1) yielded, respectively, [3,3′-Co(8-C4H4N-(CH2)2-O-(CH2)2-O-1,2-C…
The nucleophilic addition of nitrones to carbonyl compounds: insights on the nature of the mechanism of the l-proline induced asymmetric reaction fro…
2004
Abstract The mechanism of the l -proline induced asymmetric nitrone–aldol reaction of N -methyl- C -ethylnitrone with dimethyl ketomalonate has been studied by using density functional theory at B3LYP/6-31G** level. The reaction was initialized by the addition of l -proline to the nitrone to form an aminal, which by elimination of the hydroxylamine gave a chiral enamine. The nucleophilic addition of this chiral enamine to dimethyl ketomalonate corresponds to stereoselective C–C bond-formation step. Further nucleophilic addition of hydroxylamine to the zwitterionic intermediate formed in the enamine addition gave a second aminal, which by l -proline elimination afforded the corresponding β-h…
Reactivity of the di-μ-hydroxo-complexes [{Pd(NN)}2(μ-OH)2][ClO4]2 (NN=bis(pyrazol-1-yl)alkanes) towards protic electrophiles. Hydration of coordin…
2000
Abstract The hydroxo-complexes [{Pd(μ-OH)(NN)}2][ClO4]2 (NN=bpzm:bis(pyrazol-1-yl) methane: a-compounds, bpzm*:bis(3,5-dimethylpyrazol-1-yl)methane; b-compounds) react with a wide variety of weak protic electrophiles H(LL) in a 1:2 molar ratio to give the mononuclear cationic palladium(II) derivatives of general formula [Pd(LL)(NN)][ClO4] [LL=2-pyridine-methoxo (OCH2-py) (1a,b); picolinate (pic) (2a,b); 8-hydroxiquinolinate (oxin) (3a,b)] or the dinuclear complexes [{Pd(NN)}2(μ-ox)][ClO4]2 [ox=oxalate: (4a,b)] and [{Pd(μ-LL)(NN)}2][ClO4]2 [LL=pyrazolate (pz) (5a,b); p-thiocresolate (SC6H4Me-p) (6a,b); triazolate (tz) (7b); thiophenolate (SPh) (8b)] when reacting with oxalic acid, azole…
2020
The facile synthesis and detailed investigation of a class of highly potent protease inhibitors based on 1,4-naphthoquinones with a dipeptidic recognition motif (HN-l-Phe-l-Leu-OR) in the 2-position and an electron-withdrawing group (EWG) in the 3-position is presented. One of the compound representatives, namely the acid with EWG = CN and with R = H proved to be a highly potent rhodesain inhibitor with nanomolar affinity. The respective benzyl ester (R = Bn) was found to be hydrolyzed by the target enzyme itself yielding the free acid. Detailed kinetic and mass spectrometry studies revealed a reversible covalent binding mode. Theoretical calculations with different density functionals (DFT…
1978
Synthesis and characterization of polymeric derivatives of the folic acid antagonist, Methotrexate, N-[4-(N-methyl-2,4-diamino-6-pteridinylmethylamino)benzoyl] glutamic acid (1a), a widely used antitumor agent, are described. Derivatives of poly(L-lysine), poly(iminoethylene), poly(vinyl alcohol), and carboxymethylcellulose with various contents (3–15 mole-%) of substituted repeating units were prepared by polymer-analogous amidation and transesterification of the dimethyl ester of 1a and with N-[2-(N-methylmorpholinio)ethyl]carbodiimide p-toluenesulfonate as coupling reagent. By nucleophilic addition reactions of the pteridinyl amino groups under mild conditions, 1a was bound without cross…
WEITERE SELEKTIVITÄTSSTUDIEN AM BEISPIEL EINES ARYLSULFONYLACETYLENS
1984
Abstract With 1-(phenylsulfonyl)propyne-(1) 1 as a model compound, we have investigated the competition reactions with RSH, RNH2 and ROH (R=n-Bu). With RSH and RNH2, the cis-trans-isomeric olefins 2 to 5 are formed. ROH does not react under these conditions. The compounds 6 and 7 are obtained only with ROH as the alcoholate. The reactivity of 1 with nucleophiles is increased in comparison to phenylvinyl sulfone; the selectivity of 1 is, however, decreased. The difference in reactivity of 1 and phenylvinyl sulfone corresponds to ca. 10:1. Mit 1-(Phenylsulfonyl)-propin-(1) 1 als Modellverbindung haben wir die konkurrierenden Umsetzungen mit RSH, RNH2 und ROH (R=n-Bu) studiert. Mit RSH und RNH…
Base-Dependent Stereodivergent Intramolecular Aza-Michael Reaction: Asymmetric Synthesis of 1,3-Disubstituted Isoindolines
2013
The nucleophilic addition (A(N)) / intramolecular aza-Michael reaction (IMAMR) process on Ellman's tert-butylsulfinyl imines, bearing a Michael acceptor in the ortho position, is studied. This reaction affords 1,3-disubstituted isoindolines with a wide range of substituents in good yields and diastereoselectivities. Interestingly, careful choice of the base for the aza-Michael step allows either the cis or the trans diastereoisomers to be exclusively obtained. This stereodivergent cyclization has enabled the synthesis of C2-symmetric bisacetate-substituted isoindolines. In addition, bisacetate isoindolines bearing two well-differentiated ester moieties are also noteworthy because they may a…
Aza-Henry Reaction of Isatin Ketimines with Methyl 4-Nitrobutyrate en Route to Spiro[piperidine-3,3′-oxindoles]
2015
A new enantioselective route to spiro[piperidine-3,3′-oxindoles] from isatin ketimines is described. The aza-Henry reaction of N-Boc-isatin ketimines with methyl 4-nitrobutyrate in the presence of a Ph2BOX-CuBr2 complex provided the corresponding nitro amino esters with good diastereoselectivity and excellent enantioselectivity (up to >99% ee). The aza-Henry adducts were transformed into spiro[piperidine-3,3′-oxindoles] after reduction of the nitro group to oxime, and cleavage of the N-Boc group and lactamisation.
Diastereoselective Synthesis of Enantioenriched Trifluoromethylated Ethylenediamines and Isoindolines Containing Two Stereogenic Carbon Centers by Nu…
2020
Fluoroform, HFC-23, is an industrial byproduct from the synthesis of polytetrafluoroethylene and is a vastly underused resource; however, its physicochemical properties have hindered progress toward synthetic uses. Herein, we describe the use of HFC-23 as a cheap trifluoromethylating agent in two reactions for the highly diastereoselective synthesis of medicinally attractive chiral amines with two stereogenic carbon centers: a base-dependent, stereodivergent nucleophilic addition to synthesize enantioenriched vicinal diamines and a tandem nucleophilic addition/aza-Michael sequence toward enantioenriched isoindolines.
ChemInform Abstract: Tandem Nucleophilic Addition-Intramolecular Aza-Michael Reaction: Facile Synthesis of Chiral Fluorinated Isoindolines.
2011
A highly stereoselective synthesis of fluorinated 1,3-disubstituted isoindolines is described. To this end, a tandem reaction consisting of a diastereoselective addition of fluorinated nucleophiles to Ellman’s N-(tert-butanesulfinyl)imines followed by an intramolecular aza-Michael reaction has been developed. This strategy allows for the construction of isoindolines bearing several degrees of fluorination (mono-, di-, or trifluoromethyl as well as heavier fluorinated groups). In the majority of all cases, the products are formed as single isomers.