1115-69-1Relevant articles and documents
Synthesis and reactivity of 1,2- and 1,3-diphosphanes that contain four chiral rhenium fragments: Architecturally novel tetrametallo-DMPE and -DMPP species that are unprivileged ligands for enantioselective catalysis
Kromm, Klemenz,Eichenseher, Sandra,Prommesberger, Markus,Hampel, Frank,Gladysz
, p. 2983 - 2998 (2005)
Reactions of enantiopure (S)-[(η5-C5H 5)Re(NO)(PPh3)-(=CH2)]+ PF 6- [(S)-2] and PH2CH2(CH 2)nCH2PH2 (0.5 equiv.) give (S ReSRe)-[(η5-C5H 5)Re(NO)(PPh3){CH2PH2CH 2(CH2)n-CH2PH2CH 2}(Ph3P)(ON)Re(η5-C5H 5)]2+ 2PF6- [n = 0/1, (S ReSRe)-3/4; 65-62/77-58%]. Reaction of racemic 2 (BF 4- salt) and PH2(CH2) 2PH2 (0.5 equiv.) gives the meso and rac diastereomers of 3 (BF4- salts) in 28% and 38% yields after crystallization. Treatments of (SReSRe)-3/4 with fBuOK and then (S)-2 give the tetrarhenium complexes (SReSReS ReSRe)[{(η5-C5H 5)Re(NO)(PPh3)(CH2)}2{PHCH 2(CH2)n-CH2PH}{(CH 2)(Ph3P)(ON)Re(η5-C5H 5)}2]2+ 2PF6- [n = 0/1, (SReSReSReSRe)-7/8; 89-88/98-87%]. The crystal structure of (SReSReSReS Re)-7 is determined and its conformation analyzed. Reactions of (SReSReSReSRe)-7/8 and tBuOK give air-sensitive diphosphanes (SReSReSReS Re)-{(η5-C5H5)Re(NO)-(PPh 3)(CH2)}2{PCH2(CH2) nCH2P}{(CH2)(Ph3P)(ON) Re(η5-C5H5)}2 [n = 0/1, (S ReSReSReSRe)-9/10; 92/62%]. Additions of (a) PhIO give the corresponding dioxides (72/62 %), and (b) [Rh(NBD)2]+ PF6- give the corresponding chelates [(P-P)-Rh(NBD)]+ PF6- (75/82%) (NBD = norbornadiene). These catalyze hydrogenations of protected dehydroamino acids and hydrosilylations of propiophenone with only modest enantioselectivities. Similar results are obtained when (SReS ReSReSRe)-9/10 are applied in rhodium-catalyzed conjugate additions of aryl boronic acids, or palladium-catalyzed allylic alkylations. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
The methoxymethyl cation cleaves peptide bonds in the gas phase
Freitas, Michael A.,O'Hair, Richard A. J.,Dua, Suresh,Bowie, John H.
, p. 1409 - 1410 (1997)
Methoxymethyl cations and simple N-acyl amino acids and dipeptides react in the gas phase to form [M + MeOCH2]+ ions which fragment via a number of pathways including amide bond cleavage.
Enhancement of water solubility of poorly water-soluble drugs by new biocompatible N-acetyl amino acid N-alkyl cholinium-based ionic liquids
Jesus, Ana R.,Soromenho, Mário R.C.,Raposo, Luís R.,Esperan?a, José M.S.S.,Baptista, Pedro V.,Fernandes, Alexandra R.,Reis, Patrícia M.
, p. 227 - 232 (2019)
The major challenge of the pharmaceutical industry is to find potential solvents for poorly water-soluble drug molecules. Ionic liquids (ILs) have attracted this industry as (co-) solvents due to their unique physicochemical and biological properties. Herein, a straightforward approach for the enhancement of the water solubility of paracetamol and sodium diclofenac is presented, using new biocompatible N-acetyl amino acid N-alkyl cholinium-based ionic liquids as co-solvents (0.2–1 mol%). These new ionic liquids were able to increase the water solubility of these drugs up to four times that in pure water or in an inorganic salt solution. In the presence of these ILs, the drugs lipophilicity (log P was not significantly changed for paracetamol, but for sodium diclofenac it was possible to decrease significantly its lipophilicity. Concerning cytotoxicity in human dermal fibroblasts it was observed that ILs did not show a significant toxicity, and were able to improve cell viability compared with the respective precursors.
Amphoteric, water-soluble polymer-bound hydrogenation catalysts
Bergbreiter, David E.,Liu, Yun-Shan
, p. 3703 - 3706 (1997)
The synthesis of a water soluble polymer-bound hydrogenation catalyst that is homogeneous and active in basic aqueous media but insoluble and inactive in weakly acidic media is described. This catalyst is also active in organic solvents. In water, the catalyst can be recovered by acidifying the solution to a pH 5. In acetonitrile, the catalyst can be recovered by solvent (ether) precipitation. Activities of the catalyst are comparable to but in every case slightly lower than those of a structurally similar low molecular weight catalyst. Recovery and reuse of the polymeric catalyst is simpler and more efficient.
Racemization of Optically Active Aromatic N-Acetylamino Acids and Asymmetric Transformation of N-Acetyl-2-(4-hydroxyphenyl)glycine via Salt Formation with Optically Active α-Methylbenzylamine
Shiraiwa, Tadashi,Sakata, Shinji,Natsuyama, Hisashi,Fujishima, Keiko,Miyazaki, Hideya,et al.
, p. 965 - 970 (1992)
The racemization rates of N-acetyl-(S)-tyrosine, N-acetyl-(S)-phenylalanine, N-acetyl-(R)-2-(4-hydroxyphenyl)glycine , N-acetyl-(R)-2-phenylglycine, and N-acetyl-(S)-alanine were measured by use of (RS)-α-methylbenzylamine as base-catalyst.The first-order rate constant for racemization tended to increase with an increase in the polar substituent constant of the N-acetylamino acid side chain.The racemization appeared to be subject to the inductive effect by the side chain.An asymmetric transformation of (RS)-AcHpg by using (R)-MBA, based on the result of racemization, gave an optically pure salt of (R)-AcHpg with (R)-MBA by successive use of the filtrate as the solvent.Optically pure (R)-2-(4-hydroxyphenyl)glycine was separated from the salt in 87-90percent yield based on the starting (RS)-AcHpg.In addition, the asymmetric transformation of (R)-AcHpg was achieved by using (S)-MBA to give optically pure (S)-Hpg in 80percent yield after purification of the salt of (S)-AcHpg with (S)-MBA followed by hydrolysis.
Synthesis and reactivity of cationic iridium(I) complexes of cycloocta-1,5-diene and chiral dithioether ligands. Application as catalyst precursors in asymmetric hydrogenation
Dieguez, Montserrat,Orejon, Aranzazu,Masdeu-Bulto, Anna M.,Echarri, Raouf,Castillon, Sergio,Claver, Carmen,Ruiz, Aurora
, p. 4611 - 4618 (1997)
New chiral dithioether compounds (-)-2,2-dimethyl-4,5-bis(isopropylsulfanylmethyl)-1,3-dioxolane (-)-diospr and (+)-2,2-dimethyl-4,5-bis(phenylsulfanylmethyl)-1,3-dioxolane (+)-diosph were prepared from diethyl (+)-L-tartrate. An alternative synthetic method for preparing the previously described bis(methylsulfanylmethyl) dithioether (-)-diosme was devised. By co-ordinating of the dithioethers to different (cycloocta-1,5-diene)iridium(I) compounds chiral cationic complexes [Ir(cod){(-)-diosme}]BF4 1, [Ir(cod){(-)-diospr}]BF4·CH2Cl2 2 and [Ir(cod){(+)-diosph}]BF4 3 were synthesized and then studied by 1H, 13C NMR and FAB mass spectrometry. The complexes reacted with CO to give the corresponding binuclear tetracarbonyls [Ir2(μ-L)2(CO)4][BF]2 4-6. The dithioether ligands were replaced by PPh3 in 1-3 providing [Ir(cod)(PPh3)2]BF4. The addition of H2 to complexes 1 and 2 at -70°C gave cis-dihydridoiridium(III) complexes [IrH2(cod){(-)-L}]BF4 7 and 8 which are in equilibrium in solution with the parent complexes, depending on the temperature. Two possible diastereomers were distinguished for 8 at low temperatures. Complexes 1-3 were active precursors in the asymmetric hydrogenation of different prochiral dehydroamino acid derivatives and itaconic acid, at room temperature under an atmospheric pressure of H2, and the highest enantiomeric excess obtained was 47%.
Cationic iridium complexes with chiral dithioether ligands: Synthesis, characterisation and reactivity under hydrogenation conditions
Flores-Santos, Leticia,Martin, Erika,Aghmiz, Ali,Dieguez, Montserrat,Claver, Carmen,Masdeu-Bulto, Anna M.,Munoz-Hernandez, Miguel Angel
, p. 2315 - 2323 (2005)
A series of cationic IrI complexes containing chiral dithioether ligands have been prepared in order to study the influence of the sulfur substituents and the metallacycle size on the acetamidoacrylate hydrogenation reaction. In the case of complexes 6, 7 and 10, a mixture of diastereomers is observed in solution due to the sulfur inversion processes. In contrast, this fluxional behaviour is efficiently controlled by using bicyclic ligands which inhibit the S-inversion in complexes 8 and 9. The solid-state structure of complex 10b shows only one diastereomer with the sulfur substituents in a relative anti disposition and in an overall configuration of SCS CSSSS at the coordinated dithioether ligand. Iridium com plexes containing seven- and six-membered metallacycles (6b-d, 7b,c, 10a,b) react with the substrate through S-ligand substitution, and the rate of this substitution is related to the position of the fluorine atom on the aromatic ring. On the contrary, complexes containing a bismetallacycle (8 and 9) are not displaced by the substrate. The catalytic hydrogenation activity of complexes 8 and 9 is analysed in terms of the high stability of the corresponding dihydride complexes (13 and 14). In both cases, only two of the four possible diastereomeric dihydride species are formed in solution. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).
Minisci-Type Alkylation of N-Heteroarenes by N-(Acyloxy)phthalimide Esters Mediated by a Hantzsch Ester and Blue LED Light
Kyne, Sara Helen,Li, Jiacheng,Siang Tan, Suan,Wai Hong Chan, Philip
supporting information, (2022/01/11)
A synthetic method that enables the Hantzsch ester-mediated Minisci-type C2-alkylation of quinolines, isoquinolines and pyridines by N-(acyloxy)phthalimide esters (NHPI) under blue LED (light emitting diode) light (456 nm) is described. Achieved under mild reaction conditions at room temperature, the metal-free synthetic protocol was shown to be applicable to primary, secondary and tertiary NHPIs to give the alkylated N-heterocyclic products in yields of 21–99%. On introducing a chiral phosphoric acid, an asymmetric version of the reaction was also realised and provided product enantiomeric excess (ee) values of 53–99%. The reaction mechanism was delineated to involve excitation of an electron-donor acceptor (EDA) complex, formed from weak electrostatic interactions between the Hantzsch ester and NHPI, which generates the posited radical species of the redox active ester that undergoes addition to the N-heterocycle.
1,3,2-Diazaphospholenes Catalyze the Conjugate Reduction of Substituted Acrylic Acids
Reed, John H.,Cramer, Nicolai
, p. 4262 - 4266 (2020/07/13)
The potent nucleophilicity and remarkably low basicity of 1,3,2-diazaphospholenes (DAPs) is exploited in a catalytic, metal-free 1,4-reduction of free α,β-unsaturated carboxylic acids. Notably, the reduction occurs without a prior deprotonation of the carboxylic acid moiety and hence does not consume an additional hydride equivalent. This highlights the excellent nucleophilic character and low basicity of DAP-hydrides. Functional groups such as Cbz group or alkyl halides which can be problematic with classical transition-metal catalysts are well tolerated in the DAP-catalyzed process. Moreover, the transformation is characterized by a low catalyst loading, mild reaction conditions at ambient temperature as well as fast reaction times and high yields. The proof-of-principle for a catalytic enantioselective version is described.
Reactivity of α-Amino Acids in the Reaction with Esters in Aqueous–1,4-Dioxane Media
Kochetova,Kustova,Kuritsyn
, p. 80 - 85 (2018/03/09)
The kinetics of the reaction of a series of α-amino acids with 4-nitrophenyl acetate, 4-nitrophenyl benzoate, and 2,4,6-trinitrophenyl benzoate in aqueous 1,4-dioxane medium has been studied. Kinetics of the reactions involving 4-nitrophenyl acetate and 2,4,6-trinitrophenyl benzoate has complied with the Br?nsted dependence and revealed linear correlation between rate constant logarithm and the energy difference of the frontier orbitals of α-amino acids anions.
