共查询到20条相似文献,搜索用时 31 毫秒
1.
Zhang H Mifsud M Tanaka F Barbas CF 《Journal of the American Chemical Society》2006,128(30):9630-9631
We report the development of direct catalytic, enantioselective, anti-selective Mannich-type reactions between unmodified ketones and alpha-imino esters under mild conditions. The reactions were performed using 5-10 mol % of (R)-3-pyrrolidinecarboxylic or (R)-beta-proline as catalyst in an environmentally benign solvent, 2-PrOH, at room temperature. The anti-Mannich products were obtained in good yields with high diastereo- and enantioselectivities (up to anti/syn >99:1, 99% ee). While (3R,5R)-5-methyl-3-pyrrolidinecarboxylic acid is an excellent catalyst for the anti-Mannich-type reactions of aldehydes, it did not efficiently catalyze the corresponding Mannich-type reactions of ketones; (R)-3-pyrrolidinecarboxylic acid did efficiently catalyze the Mannich-type reactions of ketones. (S)-Proline or (S)-2-pyrrolidinecarboxylic acid has been reported to catalyze the Mannich-type reactions of ketones to afford the syn-products. Thus, the position of the carboxylic acid group on the pyrrolidine ring directs the stereoselection of the catalyzed reaction, providing either syn- or anti-Mannich products. 相似文献
2.
Mitsumori S Zhang H Ha-Yeon Cheong P Houk KN Tanaka F Barbas CF 《Journal of the American Chemical Society》2006,128(4):1040-1041
The development of catalysts for Mannich-type reactions that afford anti-products with excellent diastereo- and enantioselectivities under mild conditions and low catalyst loadings (1-5 mol %) is reported. Based on principles gained from the study of (S)-proline-catalyzed Mannich-type reactions that afford enantiomerically enriched syn-products, (3R,5R)-5-methyl-3-pyrrolidinecarboxylic acid (RR35) has been designed to catalyze the direct enantioselective anti-selective Mannich-type reactions. Computational studies of the above reaction using HF/6-31G* level of theory suggested that this design would be highly effective. The catalyst was subsequently synthesized and studied in organocatalytic Mannich-type reactions between unmodified aldehydes and N-PMP-protected alpha-imino esters. In accord with the design principles and in quantitative agreement with the theoretical predictions, reactions catalyzed by this catalyst afforded anti-products in good yields with excellent diastereo- and enantioselectivities (anti:syn 94:6 to 98:2, >97 to >99% ee). 相似文献
3.
A series of chiral pyrrolidine quaternary derivatives were designed and synthesized. It was found that these derivatives are highly efficient organocatalysts for the asymmetric Michael addition reactions of aldehydes and ketones to nitroolefins with high yields (up to 96%), high enantioselectivities (up to 99% ee), and high diastereoselectivities (up to 97:3 dr). Furthermore, catalyst 7a could be recycled without remarkable loss of catalytic activity and stereoselectivity. 相似文献
4.
Dana Ferraris Brandon Young Christopher Cox Travis Dudding William J Drury Lev Ryzhkov Andrew E Taggi Thomas Lectka 《Journal of the American Chemical Society》2002,124(1):67-77
Methodology for the practical synthesis of nonnatural amino acids has been developed through the catalytic, asymmetric alkylation of alpha-imino esters and N,O-acetals by enol silanes, ketene acetals, alkenes, and allylsilanes using chiral transition metal-phosphine complexes as catalysts (1-5 mol %). The alkylation products, which are prepared with high enantioselectivity (up to 99% ee) and diastereoselectivity (up to 25:1/anti:syn), are protected nonnatural amino acids that represent potential precursors to natural products and pharmaceuticals. A kinetic analysis of the catalyzed reaction of alkenes with alpha-imino esters is presented to shed light on the mechanism of this reaction. 相似文献
5.
Wang J Li H Lou B Zu L Guo H Wang W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(16):4321-4332
Chiral (S)-pyrrolidine trifluoromethanesulfonamide has been shown to serve as an effective catalyst for direct Michael addition reactions of aldehydes and ketones with nitroolefins. A wide range of aldehydes and ketones as Michael donors and nitroolefins as acceptors participate in the process, which proceeds with high levels of enantioselectivity (up to 99 % ee) and diastereoselectivity (up to 50:1 d.r.). The methodology has been employed successfully in an efficient synthesis of the potent H(3) agonist Sch 50917. In addition, a practical three-step procedure for the preparation of (S)-pyrrolidine trifluoromethanesulfonamide has been developed. The high levels of stereochemical control attending Michael addition reactions catalyzed by this pyrrolidine sulfonamide, have been investigated by using ab initio and density functional methods. Transition state structures for the rate-limiting C--C bond-forming step, corresponding to re- and si-face addition to the reactive conformation of the key enamine intermediates have been calculated. Analysis of these structures indicates that hydrogen bonding plays an important role in catalysis and that the energy barrier for si-face attack in reactions of aldehydes to form 2R,3S products is lower than that for the re-face attack leading to 2S,3R products. In contrast, the energy barrier for re-face addition is lower than that for si-face addition in reactions of ketones. The computational results, which are in good agreement with the experimental observations, are discussed in the context of the stereochemical course of these Michael addition reactions. 相似文献
6.
Mithun Kumar Debnath Wako Oyama Yuya Ono Takuya Sugimoto Rina Watanabe Naoki Haraguchi 《Journal of polymer science. Part A, Polymer chemistry》2021,59(11):1072-1083
Polymer microsphere-supported chiral pyrrolidine catalysts were successfully synthesized by a precipitation polymerization incorporating a methacrylate monomer bearing chiral N-Boc-pyrrolidine moiety, followed by removal of the N-Boc groups. The resulting polymeric catalysts were applied to the asymmetric Michael addition reactions of aldehydes with alkyl vinyl ketones. The effects of the comonomer, the molar ratios within the catalyst, the catalyst loading, the temperature, and the solvent on the catalytic performance were investigated in detail. The reactions were found to proceed smoothly in the absence of a solvent. A hydrophobic polystyrene-based chiral pyrrolidine catalyst exhibited high reactivity (up to 97% yield) and enantioselectivity (up to 95% ee) during these reactions. The catalyst could also be recovered and reused up to five times without significant loss of activity. 相似文献
7.
Guodong Chen Xiangkai Fu Chuanlong Wu Chao Li 《Research on Chemical Intermediates》2013,39(3):1069-1087
A new primary–tertiary diamine catalyst is easily prepared in a few steps from inexpensive, commercially available, enantiopure materials. This organocatalyst can be effective catalyzed the direct asymmetric aldol and Mannich reactions. The anti-aldol products can be obtained with up to a 99:1 anti/syn ratio and >98 % ee, while the syn-Mannich products could be obtained with up to a 99:1 syn/anti ratio and >99 % ee. Catalyst 1c can be used efficiently on a large scale with the enantioselectivities of the anti-aldol and syn-Mannich reactions being maintained at the same level, which offers a great possibility for application in industry. 相似文献
8.
Wang J Li H Mei Y Lou B Xu D Xie D Guo H Wang W 《The Journal of organic chemistry》2005,70(14):5678-5687
[reaction: see text] A new catalytic method for direct alpha-selenenylation reactions of aldehydes and ketones has been developed. The results of exploratory studies have demonstrated that L-prolinamide is an effective catalyst for alpha-selenenylation reactions of aldehydes, whereas pyrrolidine trifluoromethanesulfonamide efficiently promotes reactions of ketones. Under optimized reaction conditions, using N-(phenylseleno)phthalimide as the selenenylation reagent in CH2Cl2 in the presence of L-prolinamide (2 mol %) or pyrrolidine trifluoromethanesulfonamide (10 mol %), a variety of aldehydes and ketones undergo this process to generate alpha-selenenylation products in high yields. Mechanistic insight into the L-proline and L-prolinamide catalyzed alpha-selenenylation reactions of aldehydes with N-(phenylseleno)phthalimide has come from theoretical studies employing ab initio methods and density functional theory. The results reveal that (1) the rate-limiting step of the process involves attack of the enamine intermediate at selenium in N-(phenylseleno)phthalimide and (2) the energy of the transition state for the reaction catalyzed by prolinamide is lower than that promoted by proline. This result is consistent with experimental observations. The role of hydrogen bond interactions in stabilizing the transition states for this process is also discussed. 相似文献
9.
Karmakar A Maji T Wittmann S Reiser O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(39):11024-11029
The CoCl(2)/L-proline (1:2) system was found to be an excellent catalyst for direct aldol reactions. Excellent yields (up to 93%) and a significant improvement in diastereoselectivity (anti/syn up to 45:1) as well as enantioselectivity (up to more than 99% ee) compared with using proline as the sole catalyst were observed. This catalyst system was successfully applied to both cyclic and acyclic ketones in combination with aromatic and aliphatic aldehydes. In situ chelation of CoCl(2) and proline (1:2) is proposed to promote the reaction through a six-membered Zimmermann-Traxler type transition state involving the positioning of proline-enamine and the aldehyde through chelation to Co(II). 相似文献
10.
Asymmetric hydrogenation of acetophenone in the presence of Ru(II) catalysts coordinated by TolBINAP and a series of chiral 1,2-diamines was studied. The sense and degree of enantioselectivity were highly dependent on the N-substituents of the diamine ligands. The N-substituent effect was discussed in detail. Among these catalysts, the (S)-TolBINAP/(R)-DMAPEN-Ru(II) complex showed the highest enantioselectivity. The mode of enantioface selection was interpreted by using transition state models based on the X-ray structure of the catalyst precursor. The chiral catalyst effected the hydrogenation of alkyl aryl ketones and arylglyoxal dialkyl acetals to afford the chiral alcohol in >99% ee in the best cases. Hydrogenation of racemic benzoin methyl ether with the chiral catalyst through dynamic kinetic resolution gave the anti-alcohol (syn:anti = 3:97) in 98% ee, while the reaction of alpha-amidopropiophenones resulted in the syn-alcohols (syn:anti = 96:4 to >99:1) in >98% ee. 相似文献
11.
Chao Wang 《Tetrahedron letters》2009,50(20):2363-2296
4-Trifluoromethanesulfonamidyl prolinol tert-butyldiphenylsilyl ether bifunctional organocatalyst 3a is a highly efficient catalyst for the asymmetric Michael addition reactions of ketones and aldehydes to nitrostyrenes, leading to syn-selective adducts with excellent yields (>99%), high diastereoselectivities (up to 99:1 dr) and excellent enantioselectivities (up to 99% ee). Control experiments suggested that the trans-configuration relationship between the bulky group (-CH2OTBDPS) and the sulfonamido group at the 4-position of the pyrrolidine ring was important to achieve high yield and stereoselectivity. 相似文献
12.
[STRUCTURE: SEE TEXT] Mannich reactions between aldehydes and N-p-methoxyphenyl-protected alpha-imino ethyl glyoxylate have been performed using (S)-pipecolic acid as catalyst. The reactions give both syn- and anti-products (dr=1.4-2:1) with high enantioselectivities (>98% ee). In contrast, (S)-proline-catalyzed reactions give mainly syn-products with high enantioselectivities. Computational studies reveal that the energetic preference between the transition structures involving the s-cis-enamine and the s-trans-enamine is smaller for the pipecolic acid as compared to proline, yielding the (2S,3R)-anti and the (2S,3S)-syn Mannich product in nearly equal amounts. 相似文献
13.
Highly enantioselective direct aldol reaction catalyzed by cinchona derived primary amines 总被引:2,自引:0,他引:2
Highly enantioselective aldol reactions of aldehydes with cyclic ketones catalyzed by a primary amine derived from cinchonine are reported. Aromatic aldehydes reacted with various cyclic ketones cleanly to afford the anti-aldol adducts in up to 99% yield, with good diastereoselectivities (up to 9 : 1) and excellent enantioselectivities (up to 99% ee). 相似文献
14.
We report the α-arylation of ketones with a range of aryl chlorides with enantioselectivities from 90 to 99% ee catalyzed by the combination of Ni(COD)(2) and (R)-BINAP and the coupling of ketones with a range of heteroaryl chlorides with enantioselectivities up to 99% ee catalyzed by Ni(COD)(2) and (R)-DIFLUORPHOS. The analogous reactions of bromoarenes occur with much lower enantioselectivities. Mechanistic studies showed that the difference in the rates of decomposition of the arylnickel(II) halide intermediates to {[(R)-BINAP]NiX}(2) likely accounts for the difference in the enantioselectivities of the reactions of bromoarenes and chloroarenes. This catalyst decomposition can be overcome by conducting the reactions with [(R)-BINAP]Ni(η(2)-NC-Ph) (4), which undergoes oxidative addition to haloarenes at room temperature. 相似文献
15.
Asymmetric synthesis of trans-alkenyl alpha-amino esters was realized by chiral phosphoric acid catalyzed transfer hydrogenation of beta,gamma-alkynyl alpha-imino esters. Utilizing Hantzsch esters as the hydrogen donor, both the alkyne and imine moieties of beta,gamma-alkynyl alpha-imino esters were reduced to afford trans-alkenyl alpha-amino esters with up to 96% ee. 相似文献
16.
Hiroshi Furuno Tetsuji Hayano Takeshi Kambara Yuichi Sugimoto Takeshi Hanamoto Yumiko Tanaka Yong Zhi Jin Takumi Kagawa Junji Inanaga 《Tetrahedron》2003,59(52):10509-10523
Various trivalent rare earth-chiral phosphate complexes [(R)-1-RE, (R)-3-RE, and (R)-4-Ce] were prepared and evaluated as a Lewis acid catalyst for the asymmetric hetero-Diels–Alder reaction of aldehydes with the Danishefsky's diene. Some of them effectively promoted the reaction at room temperature in the presence or absence of achiral additives under homogeneous conditions to afford the corresponding cycloadducts with high ee's (up to 99% ee). During these reactions, remarkably high asymmetric amplifications (positive nonlinear effects) were observed as the first example in the metal ion–chiral ligand 1:3 catalytic system. A scandium catalyst bearing the H8-BNP ligand, (R)-3-Sc, could be recovered after the reaction and successfully reused for the next round of reactions. In addition, the hetero-Diels–Alder reaction of -keto esters was effectively catalyzed by the ytterbium complex, (R)-1-Yb, without any additives thus producing the asymmetric quaternary carbon in excellent enantioselectivities (up to >99% ee). 相似文献
17.
Chelation-controlled reduction of chiral beta-alkoxy ketones containing a competing beta'-oxygen functionality has been investigated. Various syn-1,3-diols were prepared conveniently by reduction of beta-alkoxy ketones with LiI/LiAlH(4) (syn:anti selectivity up to >99:1). The corresponding beta-alkoxy ketones were derived from nitro-aldol reactions of chiral alkoxy aldehydes with a series of nitro compounds. This methodology is utilized in a short and efficient synthesis of the delta-lactone moiety of the HMG-CoA reductase inhibitors compactin and mevinolin. 相似文献
18.
Kano T Yamaguchi Y Tokuda O Maruoka K 《Journal of the American Chemical Society》2005,127(47):16408-16409
A direct asymmetric Mannich reaction using a novel axially chiral amino trifluoromethanesulfonamide (S)-3 has been developed in highly anti-selective and enantioselective manners. Thus, in the presence of a catalytic amount of (S)-3, the reactions between aldehydes and the alpha-imino ester 4 proceed smoothly to give the functional beta-amino aldehydes with significantly higher anti/syn ratio and enantioselectivity than previously possible. 相似文献
19.
A highly efficient catalytic system composed of a simple and commercially available chiral primary diamine (1R,2R)-cyclohexane-1,2-diamine(6) and trifluoroacetic acid (TFA) was employed for asymmetric Aldol reaction in em-PrOH at room temperature. A loading of 10%(molar fraction) catalyst 6 with TFA as a cocatalyst could catalyze the Aldol reactions of various ketones or aldehydes with a series of aromatic aldehydes, furnishing Aldol pro- ducts in moderate to high yields(up to >99%) with enantioselectivities of up to >99% and diastereoselectivities of up to 99:1. 相似文献
20.
Proline anthranilamide-based pseudopeptides were shown to be effective organocatalysts for enantioselective direct aldol reactions of a selection of aldehydes with various ketones with excellent yield, enantioselectivity up to 99% and anti to syn diastereoselectivity up to 25:1. 相似文献