96854-34-1Relevant academic research and scientific papers
Copper(I)-Catalyzed Asymmetric Vinylogous Aldol-Type Reaction of Allylazaarenes
Wang, Si-Qing,Liu, Zong-Ci,Yue, Wen-Jun,Yin, Liang
supporting information, p. 4604 - 4608 (2021/01/21)
A vinylogous aldol-type reaction of allylazaarenes and aldehydes is disclosed that affords a series of chiral γ-hydroxyl-α,β-unsaturated azaarenes in moderate to excellent yields with high to excellent regio- and enantioselectivities. With (R,RP)-TANIAPHOS and (R,R)-QUINOXP* as the ligand, the carbon-carbon double bond in the products is generated in (E)-form. With (R)-DTBM-SEGPHOS as the ligand, (Z)-form carbon-carbon double bond is formed in the major product. In this vinylogous reaction, aromatic, α,β-unsaturated, and aliphatic aldehydes are competent substrates. Moreover, a variety of azaarenes, such as pyrimidine, pyridine, pyrazine, quinoline, quinoxaline, quinazoline, and benzo[d]imidazole are well-tolerated. At last, the chiral vinylogous product is demonstrated as a suitable Michael acceptor towards CuI-catalyzed nucleophilic addition with organomagnesium reagents.
Chiral Ion-Pair Organocatalyst-Promoted Efficient Enantio-selective Reduction of α-Hydroxy Ketones
Zhang, Yiliang,He, Li,Shi, Lei
, p. 1926 - 1931 (2018/03/27)
The enantioselective reduction of α-hydroxy ketones with catecholborane has been developed employing 5 mol% of an 1,1′-bi-2-naphthol (BINOL)-derived ion-pair organocatalyst. This methodology provides a straightforward access to the corresponding aromatic 1,2-diols in high yields (up to 90%) with excellent enantioselectivities (up to 97%). Furthermore, the α-amino ketones also could be reduced with moderate ee values under mild reaction condition. (Figure presented.).
Highly diastereo- and enantioselective allylboration of aldehydes using α-substituted allyl/crotyl pinacol boronic esters via in situ generated borinic esters
Chen, Jack L.-Y.,Scott, Helen K.,Hesse, Matthew J.,Willis, Christine L.,Aggarwal, Varinder K.
supporting information, p. 5316 - 5319 (2013/05/21)
Readily available, α-substituted allyl/crotyl pinacol boronic esters often give low E/Z selectivity (with Z favored) in reactions with aldehydes. We found that addition of nBuLi to the pinacol boronic ester followed by trapping of the alkoxide with TFAA leads to an intermediate allyl borinic ester which undergoes allylboration with very high E selectivity. The substrate scope includes primary to tertiary alkyl α-substituents, crotyl substrates, and the previously unreported β-methallyl pinacol boronic esters. The latter give very high Z selectivity under standard conditions which is completely reversed to high E selectivity under the new conditions. Monitoring the reaction by 11B NMR confirmed that the reaction proceeds through a borinic ester intermediate.
Organocatalytic direct asymmetric crossed-aldol reactions of acetaldehyde in aqueous media
Qiao, Yupu,Chen, Qiankun,Lin, Sirong,Ni, Bukuo,Headley, Allan D.
supporting information, p. 2693 - 2696 (2013/04/24)
A new type of diarylprolinol-based catalyst, which contains a dioctylamino group in the presence of a newly developed ionic liquid supported (ILS) benzoic acid as cocatalyst, is shown to be an effective catalytic system for the asymmetric direct crossed-aldol reaction of acetaldehyde in aqueous media using brine. For the reactions studied, the catalyst loading could be reduced to 5 mol %; high yields (up to 97%) and high enantioselectivities (up to 92% ee) were also achieved for a wide variety of aromatic aldehyde.
Palladium-catalyzed synthesis of enantiomerically pure α-substituted allylboronic esters and their addition to aldehydes
Fernandez, Enrique,Pietruszka, Joerg,Frey, Wolfgang
supporting information; experimental part, p. 5580 - 5589 (2010/11/17)
Tartrate-derived boronic esters 2 can be subjected to palladium-catalyzed carbonyl allylations with SnCl2 to obtain enantiomerically pure α-substituted allylboronic esters 8 and 9. The reaction proceeds regioselectively and with high, simple diastereoselectivity to form anti-products. Their addition to aldehydes yields enantiomerically enriched homoallylic alcohols 17 and 18, respectively. Synthesis, characterization, and a mechanistic rational is presented here.
Organic metal compound and process for preparing optically-active alcohols using the same
-
Page/Page column 7; 12, (2009/04/24)
The present invention provides an asymmetric reduction catalyst effective in preparing optically-active alcohol compounds having various functional groups, and a process for preparing optically-active alcohol compounds using said asymmetric reduction catalyst. The organic metal compound of the present invention is represented by the following general formula (1): wherein R1 and R2 may be mutually identical or different, and are an alkyl group, a phenyl group, a naphthyl group, a cycloalkyl group, or an alicyclic ring formed by binding R1 and R2, which may have a substituent; R3 is a hydrogen atom or an alkyl group; Cp is a cyclopentadienyl group, which may have a substituent, bound to M1 via a π bond; X1 is a halogen atom or a hydrido group; M1 is rhodium or iridium; and * denotes asymmetric carbon.
Diastereo- and enantiomerically pure allylboronates: Their synthesis and scope
Pietruszka, Joerg,Schoene, Niklas,Frey, Wolfgang,Grundl, Li
experimental part, p. 5178 - 5197 (2009/07/18)
Allylboronates are highly attractive reagents for allyl additions. Enantiomerically pure, stable reagents with a stereogenic centre in a-position to boron are especially versatile, albeit often difficult to synthesize. Starting from boron-containing allyl alcohols 6 and 7, which are discussed in detail herein, a set of reagents were obtained via [3,3]-sigmatropic rearrangements and consecutive transformations in the side chain. The configurations could be established first by chemical correlation, but also by X-ray crystallography (16, 18, 34, and 39). Allyl additions were performed resulting in the formation of predominantly (Z)-configured homoallylic alcohols (31, 43-45) with high enantiomeric excess. Detailed investigations on the matched-mismatched interaction between the reagents 15/16 (and ent-15/ent-16, respectively) and isopropylidene glyceraldehyde 42 d are presented.
Lewis base activation of Lewis acids: Catalytic, enantioselective vinylogous aldol addition reactions
Denmark, Scott E.,Heemstra Jr., John R.
, p. 5668 - 5688 (2008/02/10)
(Chemical Equation Presented) The generality of Lewis base catalyzed, Lewis acid mediated, enantioselective vinylogous aldol addition reactions has been investigated. The combination of silicon tetrachloride and chiral phosphoramides is a competent catalyst for highly selective additions of a variety of α,β-unsaturated ketone-, 1,3-diketone-, and α,β- unsaturated amide-derived dienolates to aldehydes. These reactions provided high levels of γ-site selectivity for a variety of substitution patterns on the dienyl unit. Both ketone- and morpholine amide-derived dienol ethers afforded high enantio- and diastereoselectivity in the addition to conjugated aldehydes. Although α,β-unsaturated ketone-derived dienolate did not react with aliphatic aldehydes, α,β-unsaturated amide-derived dienolates underwent addition at reasonable rates affording high yields of vinylogous aldol product. The enantioselectivities achieved with the morpholine derived-dienolate in the addition to aliphatic aldehydes was the highest afforded to date with the silicon tetrachloride-chiral phosphoramide system. Furthermore, the ability to cleanly convert the morpholine amide to a methyl ketone was demonstrated.
Phosphoramidate and phosphate prodrugs of (-)-β-D-(2R,4R)-dioxolane- thymine: Synthesis, anti-HIV activity and stability studies
Liang, Yuzeng,Narayanasamy, Janarthanan,Schinazi, Raymond F.,Chu, Chung K.
, p. 2178 - 2189 (2007/10/03)
A series of phosphoramidate and phosphate prodrugs of DOT were synthesized via dichlorophosphate or H-phosphonate chemistry and evaluated for their anti-HIV activity against LAI M184V mutants in PBM cells as well as for their cytotoxicity. The antiviral and cytotoxic profiles of the prodrugs were compared with that of the parent compound (DOT), and it was found that four aryl phosphoramidates 5, 18, 20, and 26 showed a significant enhancement (8- to 12-fold) in anti-HIV activity without cytotoxicity. Chemical stability of these prodrugs was evaluated in phosphate buffer at pH values of biological relevance (i.e., pH 2.0 and 7.4). Enzymatic hydrolysis was also studied in esterase or lipase in buffer solution. Chemical stability studies indicate that the phosphoramidates have good chemical stability at pH 2.0 and at pH 7.4 phosphate buffer. Phosphoramidate prodrugs were hydrolyzed in vitro by esterase or lipase and found to be better substrates for lipases than for esterases. 1,3-Diol cyclic phosphates showed potent anti-HIV activity without increasing the cytotoxicity compared with that of DOT and have good chemical and enzymatic stability. Long-chain lipid phosphates, although showed potent anti-HIV activity, exhibited increased cytotoxicity.
Candida Rugosa lipase-catalyzed kinetic resolution of β-hydroxy- β-arylpropionates and δ-hydroxy-δ-aryl-β-oxo-pentanoates
Xu, Chengfu,Yuan, Chengye
, p. 2169 - 2186 (2007/10/03)
A simple and convenient method was reported for the preparation of optically active β-hydroxy-β-arylpropionates, δ-hydroxy-δ- aryl-β-oxo-pentanoates and their butyryl derivatives via CRL-catalyzed hydrolysis. The optically active products are potential precursors of some chiral pharmaceuticals and natural products.
