7554-23-6Relevant academic research and scientific papers
A cheap metal for a challenging task: nickel-catalyzed highly diastereo- and enantioselective hydrogenation of tetrasubstituted fluorinated enamides
Guan, Yu-Qing,Han, Zhengyu,Li, Xiuxiu,You, Cai,Tan, Xuefeng,Lv, Hui,Zhang, Xumu
, p. 252 - 256 (2019)
Nickel-catalyzed asymmetric hydrogenation of challenging tetrasubstituted fluorinated enamides has been achieved, affording chiral α-fluoro-β-amino esters in high yields with excellent diastereo- and enantioselectivities (up to 98% yield, >99?:?1 dr, up t
β-Amino esters from the reductive ring opening of aziridine-2-carboxylates
Zhao, Wenjun,Lu, Zhenjie,Wulff, William D.
, p. 10068 - 10080 (2015/02/19)
A general study is undertaken to examine the scope of the reductive ring opening of aziridine-2-carboxylates with samarium diiodide. The competition between C-C and C-N bond cleavage is examined as a function of the nature of the N-substituent of the aziridine, the nature of the substituent in the 3-position of the aziridine, and whether the substituent in the 3-position is in a cis or trans relationship with the carboxylate in the 2-position. The desired C-N bond cleavage leads to β-amino esters that are the predominant products for most aziridines with an N-activating group. However, C-C cleavage products are observed with an aryl group in the 3-position; this can be particularly pronounced with cis-aziridines where a nearly equal mixture of the two is observed. Exclusive formation of the C-N cleavage product is observed for all aziridines with the strongly N-activating p-toluene sulfonate group. Similarly high selectivity is observed for the 2-trimethylsilylethyl sulfonate group (SES), which is easier to remove. The utility of these methods is illustrated in the synthesis of protected forms of (R)-β3-DOPA and l-DOPA from the same aziridine, the former by SmI2-mediated reductive opening at C-2 and the latter by palladium-mediated reductive opening at C-3.
Carica papaya lipase catalysed resolution of β-amino esters for the highly enantioselective synthesis of (S)-dapoxetine
You, Pengyong,Qiu, Jian,Su, Erzheng,Wei, Dongzhi
, p. 557 - 565 (2013/03/13)
An efficient synthesis of the (S)-3-amino-3-phenylpropanoic acid enantiomer has been achieved by Carica papaya lipase (CPL) catalysed enantioselective alcoholysis of the corresponding racemic N-protected 2,2,2-trifluoroethyl esters in an organic solvent. A high enantioselectivity (E > 200) was achieved by two strategies that involved engineering of the substrates and optimization of the reaction conditions. Based on the resolution of a series of amino acids, it was found that the structure of the substrate has a profound effect on the CPL-catalysed resolution. The enantioselectivity and reaction rate were significantly enhanced by switching the conventional methyl ester to an activated trifluoroethyl ester. When considering steric effects, the substituted phenyl and amino groups should not both be large for the CPL-catalysed resolution. The mechanism of the CPL-catalysed enantioselective alcoholoysis of the amino acids is discussed to delineate the substrate requirements for CPL-catalysed resolution. Finally, the reaction was scaled up, and the products were separated and obtained in good yields (≥ 80 %). The (S)-3-amino-3- phenylpropanoic acid obtained was used as a key chiral intermediate in the synthesis of (S)-dapoxetine with very high enantiomeric excess (> 99 %). A carica papaya lipase catalysed resolution of N-protected β-phenylalanine esters has been developed. High enantioselectivity was achieved by two strategies that involved engineering of the substrates and optimization of the reaction conditions. After 50 % conversion, the products were separated and used as key chiral intermediates for the synthesis of (S)-dapoxetine with > 99 % ee. Copyright
Oxidative nucleophilic substitution: Transformation of alkylboronic derivatives
Cazorla, Clément,Métay, Estelle,Lemaire, Marc
experimental part, p. 8615 - 8621 (2011/11/30)
An efficient amidation reaction is described in this paper. Potassium alkyltrifluoroborate salts can be transforming to amides from nitriles in the presence of copper acetate and boron trifluoride. An extension of this reaction allowed the formation of amines, ethers, and C-C bond.
Iridium-catalyzed hydrogenation of β-dehydroamino acid derivatives using monodentate phosphoramidites
Enthaler, Stephan,Erre, Giulia,Junge, Kathrin,Schroeder, Kristin,Addis, Daniele,Michalik, Dirk,Hapke, Marko,Redkin, Dmitry,Beller, Matthias
scheme or table, p. 3352 - 3362 (2009/04/07)
The iridium-catalyzed asymmetric hydrogenation of 13 different β-dehydroamino acid derivatives to give optically active β-amino acid esters has been examined. Readily accessible monodentate octahydrobinaphthol- based phosphoramidites were used as chiral ligands. Good to excellent enantioselectivities and yields were obtained for the E isomers, whereas poorer catalyst performance was found for the Z isomers. Importantly, to obtain high enantioselectivity, substitution at the 3,3′-positions of the ligands was necessary. Enantioselectivities of up to 94% ee were achieved under optimized conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Improving conversion and enantioselectivity in hydrogenation by combining different monodentate phosphoramidites; a new combinatorial approach in asymmetric catalysis
Pena, Diego,Minnaard, Adrian J.,Boogers, Jeroen A.F.,De Vries, Andre H. M.,De Vries, Johannes,Feringa, Ben L.
, p. 1087 - 1089 (2007/10/03)
Although mixing chiral ligands to improve the enantioselectivity has been previously reported in asymmetric catalysis, this was only done with combinations of chiral bidentate ligands. This new concept is explored for the enantioselective catalytic hydrog
Sulfur-containing heterocycles: Facile synthesis of 4H-1,3-thiazines by the reaction of 3-N-acylamino ketones with Lawesson's reagent
Ori, Mayuko,Nishio, Takehiko
, p. 111 - 116 (2007/10/03)
The treatment of 3-N-acylamino ketones with Lawesson's reagent [LR: 2,4- bis(p-methoxyphenyl)-1,3,2,4-dithiaphosphetane 2,4-disulfide] afforded the sulfur-containing heterocycles, 4H-1,3-thiazines in moderate to good yields, along with the corresponding 3-N-thioacylamino ketones.
Reduction of 2-acylaziridines by samarium(II) iodide. An efficient and regioselective route to β-amino carbonyl compounds
Molander, Gary A.,Stengel, Peter J.
, p. 8887 - 8912 (2007/10/03)
A convenient method for the reduction of 2-acylaziridines, aziridine-2- carboxylates and aziridine-2-carboxamides is described. The reduction of all of the substrates examined was extremely rapid and highly regioselective, giving rise to β-amino carbonyl compounds. This method appears to be general for all of the classes of aziridines mentioned above, and also tolerates a variety of nitrogen protecting groups.
