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.
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.
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%.
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Sugi,Cullen
, p. 39 (1979)
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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.
Synthetic method of vardenafil hydrochloride impurities
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Paragraph 0034; 0046; 0054; 0062; 0070; 0078, (2018/04/01)
The invention discloses a synthetic method of vardenafil hydrochloride impurities, which relates to the technical field of pharmaceutical and chemical industry. The synthetic method comprises the following steps: taking alanine (A) as a raw material to react with acetic anhydride, generating 2-acetaminopropionic acid (B), enabling the 2-acetaminopropionic acid (B) to react with ethyl oxalyl monochloride, and generating a reaction product (C); enabling 2-ethoxybenzamidine hydrochloride (D) to react with hydrazine hydrate, generating a reaction product (E), enabling the reaction product (E) to react with the reaction product (C), and generating an impurity intermediate I (F); and enabling the impurity intermediate I (F) to generate an impurity intermediate II (G) under the effect of phosphorus oxychloride; performing sulfonation reaction on the impurity intermediate II (G) to generate a reaction product (H); and dropwise adding N-ethylpiperazine into the reaction product (H) to obtain a target product (I) 4-ethoxy-3-(3,4-dihydro-5-methyl-4-oxo-7-propylimidazole[5,1-f][1,2,4]-trizone-ketone) benzenesulfonic acid. The method is low in production cost, low in requirement on reaction conditions, favorable for the industrialized production and higher in purity of target products.
