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1.
Cai Y Liu X Li J Chen W Wang W Lin L Feng X 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(52):14916-14921
Highly diastereo‐ and enantioselective iodoamination of chalcones, 4‐aryl‐4‐oxobutenoates, and a trifluoro‐substituted enone has been accomplished in the presence of a chiral N,N′‐dioxide/[Sc(OTf)3] complex (0.5–2 mol %), delivering the desired vicinal anti‐α‐iodo‐β‐amino carbonyl compounds regioselectively in high yields (up to 97 %) and with excellent diastereoselectivities (>99:1 d.r.) and enantioselectivities (up to 99 % ee). Enantiopure syn‐α‐iodo‐β‐amino products could also be obtained from the isomerization of particular iodo compounds. TsNHX species (X=Cl, Br, I), generated from the reactions between the halo sources and TsNH2, were further confirmed as the active species in the haloamination reactions involved in the formation of the key halonium ion intermediates. A typical haloamination dependency was observed, with reactivity decreasing in the order NBS>NIS?NCS. 相似文献
2.
Development of a syn‐Selective Mannich Reaction of Aldehydes with Propargylic Imines by Dual Catalysis: Asymmetric Synthesis of Functionalized Propargylic Amines 下载免费PDF全文
Irati Lapuerta Dr. Silvia Vera Prof. Mikel Oiarbide Prof. Claudio Palomo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(21):7229-7237
Direct coupling of enolizable aldehydes with C‐alkynyl imines is realized affording the corresponding propargylic Mannich adducts of syn configuration, thus complementing previous methods that gave access to the anti‐isomers. The combination of proline and a urea Brønsted base cocatalyst is key for the reactions to proceed under very mild conditions (3–10 mol % catalyst loading, dichloromethane as solvent, ?20 °C, 1.2 molar equivalents of aldehyde) and with virtually total stereocontrol (syn/anti ratio up to 99:1; ee up to 99 %). Some possibilities of further chemical elaboration of adducts are also briefly illustrated. 相似文献
3.
Diastereoselectively Switchable Asymmetric Haloaminocyclization for the Synthesis of Cyclic Sulfamates 下载免费PDF全文
Dr. Yunfei Cai Pengfei Zhou Prof. Dr. Xiaohua Liu Jiannan Zhao Dr. Lili Lin Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6386-6389
An asymmetric synthesis of cyclic sulfamates by catalytic haloaminocyclization of primary sulfamate ester derivatives is described. The remarkable reversal of diastereoselectivity was found to be dependent on the halogen source and the chiral catalyst. By using privileged complexes of N,N′‐dioxides with Sc(OTf)3 or Lu(OTf)3 as the catalyst, a variety of enantioenriched syn‐ and anti‐cyclic sulfamates or related trans‐aziridines could be obtained in 92–99 % ee and up to 97 % yield. 相似文献
4.
Asymmetric Henry reactions of aldehydes with various nitroalkanes catalyzed by copper(II) complexes of novel chiral N‐monoalkyl cyclohexane‐1,2‐diamines 下载免费PDF全文
A number of novel chiral diamines 3 , (1R,2R)‐N‐monoalkylcyclohexane‐1,2‐diamines, were designed and synthesized from trans‐cyclohexane‐1,2‐diamine and applied to the catalytic asymmetric Henry reaction of benzaldehyde and nitromethane to provide β‐nitroalcohol in high yield (up to 99%) and good enantiomeric excess (up to 89%). By using ligand (1R,2R)‐N1‐(4‐methylpentan‐2‐yl)cyclohexane‐1,2‐diamine ( 3g ), the reaction was optimized in terms of the metal ion, temperature, solvent and base. Further experiments indicated that the complex, 3g –Cu(OAc)2, was an efficient catalyst in the asymmetric Henry reaction between different aldehydes and nitromethane, and the desired products have been obtained with high chemical yields (up to 99%) and high enantiomeric excess (up to 93%). The optimized catalyst promoted the diastereoselective Henry reaction of various aldehyde substrates and nitroalkane, which gave the corresponding anti‐selective adduct with up to 99% yield and 83:17 anti/syn selectivity. Upon scaling up to gram quantities, the β‐nitroalcohol was obtained in good yield (96%) with excellent selectivities (93% ee). The chiral induction mechanism was tentatively explained on the basis of a previously proposed transition‐state model. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
A Powerful Chiral Phosphoric Acid Catalyst for Enantioselective Mukaiyama–Mannich Reactions 下载免费PDF全文
Dr. Fengtao Zhou Prof. Dr. Hisashi Yamamoto 《Angewandte Chemie (International ed. in English)》2016,55(31):8970-8974
A new BINOL‐derived chiral phosphoric acid bearing 2,4,6‐trimethyl‐3,5‐dinitrophenyl substituents at the 3,3′‐positions was developed. The utility of this chiral phosphoric acid is demonstrated by a highly enantioselective (ee up to >99 %) and diastereoselective (syn/anti up to >99:1) asymmetric Mukaiyama–Mannich reaction of imines with a wide range of ketene silyl acetals. Moreover, this method was successfully applied to the construction of vicinal tertiary and quaternary stereogenic centers with excellent diastereo‐ and enantioselectivity. Significantly, BINOL‐derived N‐triflyl phosphoramide constitutes a complementary catalyst system that allows the title reaction to be applied to more challenging imines without an N‐(2‐hydroxyphenyl) moiety. 相似文献
6.
Isiaka A. Owolabi U.V. Subba Reddy Madhu Chennapuram Chigusa Seki Yuko Okuyama Eunsang Kwon Koji Uwai Michio Tokiwa Mitsuhiro Takeshita Hiroto Nakano 《Tetrahedron》2018,74(36):4705-4711
A new type of amino amide organocatalysts was designed and synthesized from commercially available amino acids in easy steps. Their catalytic activities were examined in enantioselective crossed aldol reaction of various acyclic and cyclic ketones with aromatic aldehydes to afford the corresponding chiral anti-aldol adducts with good to excellent chemical yields, diastereoselectivities and enantioselectivities (up to 99%, up to syn:anti?=?1:99, up to 97% ee). 相似文献
7.
Efficient Synthesis of Differentiated syn‐1,2‐Diol Derivatives by Asymmetric Transfer Hydrogenation–Dynamic Kinetic Resolution of α‐Alkoxy‐Substituted β‐Ketoesters 下载免费PDF全文
Dr. Laure Monnereau Dr. Damien Cartigny Dr. Michelangelo Scalone Dr. Tahar Ayad Dr. Virginie Ratovelomanana‐Vidal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11799-11806
Asymmetric transfer hydrogenation was applied to a wide range of racemic aryl α‐alkoxy‐β‐ketoesters in the presence of well‐defined, commercially available, chiral catalyst RuII–(N‐p‐toluenesulfonyl‐1,2‐diphenylethylenediamine) and a 5:2 mixture of formic acid and triethylamine as the hydrogen source. Under these conditions, dynamic kinetic resolution was efficiently promoted to provide the corresponding syn α‐alkoxy‐β‐hydroxyesters derived from substituted aromatic and heteroaromatic aldehydes with a high level of diastereoselectivity (diastereomeric ratio (d.r.)>99:1) and an almost perfect enantioselectivity (enantiomeric excess (ee)>99 %). Additionally, after extensive screening of the reaction conditions, the use of RuII‐ and RhIII‐tethered precatalysts extended this process to more‐challenging substrates that bore alkenyl‐, alkynyl‐, and alkyl substituents to provide the corresponding syn α‐alkoxy‐β‐hydroxyesters with excellent enantiocontrol (up to 99 % ee) and good to perfect diastereocontrol (d.r.>99:1). Lastly, the synthetic utility of the present protocol was demonstrated by application to the asymmetric synthesis of chiral ester ethyl (2S)‐2‐ethoxy‐3‐(4‐hydroxyphenyl)‐propanoate, which is an important pharmacophore in a number of peroxisome proliferator‐activated receptor α/γ dual agonist advanced drug candidates used for the treatment of type‐II diabetes. 相似文献
8.
Kun Xu Guoyin Lai Zhenggen Zha Susu Pan Prof. Dr. Huanwen Chen Prof. Dr. Zhiyong Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(39):12357-12362
A highly anti‐selective asymmetric Henry reaction has been developed, affording synthetically versatile β‐nitroalcohols in a predominately anti‐selective manner (mostly above 15:1) and excellent ee values (mostly above 95 %). Moreover, the anti‐selective Henry reaction was carried out in the presence of water for the first time with up to 99 % ee. The catalytic mechanism was proposed based on the detection of the intermediates by extractive electrospray ionization mass spectrometry (EESI‐MS). Furthermore, the anti adducts have been successfully transformed into the biochemically important (+)‐spisulosine and a pyrroloisoquinoline derivative. 相似文献
9.
Trisphosphine‐Chelate‐Substituted Molybdenum and Tungsten Nitrosyl Hydrides as Highly Active Catalysts for Olefin Hydrogenations 下载免费PDF全文
Dr. Subrata Chakraborty Dr. Olivier Blacque Dr. Thomas Fox Prof. Heinz Berke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12641-12654
Reaction of [M(NO)Cl3(NCMe)2] (M=Mo, W) with (iPr2PCH2CH2)2PPh (etpip) at room temperature afforded the syn/anti‐[M(NO)Cl3(mer‐etpip)] complexes (M=Mo, a ; W, b ; 3 a,b (syn,anti); syn and anti refer to the relative position of Ph(etpip) and NO). Reduction of 3 a,b (syn,anti) produced [M(NO)Cl2(mer‐etpip)] ( 4 a,b (syn)), [M(NO)Cl(NCMe)(mer‐etpip)] ( 5 a,b (syn,anti)), and [M(NO)Cl(η2‐ethylene)(mer‐etpip)] ( 6 a,b (syn,anti)) complexes. The hydrides [M(NO)H(η2‐ethylene)(mer‐etpip)] ( 7 a,b (syn,anti)) were obtained from 6 a,b (syn,anti) using NaHBEt3 (75 °C, THF) or LiBH4 (80 °C, Et3N), respectively. 7 a,b (syn,anti) were probed in olefin hydrogenations in the absence or presence of a hydrosilane/B(C6F5)3 mixture. The 7 a,b (syn,anti)/Et3SiH/B(C6F5)3 co‐catalytic systems were highly active in various olefin hydrogenations (60 bar H2, 140 °C), with maximum TOFs of 5250 h?1 ( 7 a (syn,anti)) and 8200 h?1 ( 7 b (syn,anti)) for 1‐hexene hydrogenation. The Et3SiH/(B(C6F5)3 co‐catalyst is anticipated to generate a [Et3Si]+ cation attaching to the ONO atom. This facilitates NO bending and accelerates catalysis by providing a vacant site. Inverse DKIE effects were observed for the 7 a (syn,anti)/Et3SiH/(B(C6F5)3 (kH/kD=0.55) and the 7 b (syn,anti)/Et3SiH/(B(C6F5)3 (kH/kD=0.65) co‐catalytic mixtures (20 bar H2/D2, 140 °C). 相似文献
10.
Jiang Wang Pan‐Lin Shao Xin Lin Baode Ma Jialin Wen Xumu Zhang 《Angewandte Chemie (International ed. in English)》2020,59(41):18166-18171
An unprecedented Ir/f‐amphox‐catalyzed asymmetric hydrogenation of racemic 2,3‐syn‐dihydroxy‐1,4‐diones is presented involving dynamic kinetic resolution, which produces (1R,2R,3R,4R)‐tetraols. This protocol constitutes an efficient and straightforward approach to accessing sugar alcohols bearing four contiguous stereocenters. The strategy exhibits various advantages over existing methods, including excellent yields (up to 98 %), exceptional stereoselectivities (up to 99:1 dr, 99.9 % ee), operational simplicity and substrate generality. Moreover, the nature of the reaction was revealed as a stepwise transformation by in situ Fourier‐transform infrared spectroscopy and isolation of intermediates. 相似文献
11.
Binuclear trans‐Bis(β‐iminoaryloxy)palladium(II) Complexes Doubly Linked with Pentamethylene Spacers: Structure‐Dependent Flapping Motion and Heterochiral Association Behavior of the Clothespin‐Shaped Molecules 下载免费PDF全文
Masaya Naito Hiroyuki Souda Hiroshi Koori Dr. Naruyoshi Komiya Prof. Takeshi Naota 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):6991-7000
The synthesis, structure, and solution‐state behavior of clothespin‐shaped binuclear trans‐bis(β‐iminoaryloxy)palladium(II) complexes doubly linked with pentamethylene spacers are described. Achiral syn and racemic anti isomers of complexes 1 – 3 were prepared by treating Pd(OAc)2 with the corresponding N,N′‐bis(β‐hydroxyarylmethylene)‐1,5‐pentanediamine and then subjecting the mixture to chromatographic separation. Optically pure (100 % ee) complexes, (+)‐anti‐ 1 , (+)‐anti‐ 2 , and (+)‐anti‐ 3 , were obtained from the racemic mixture by employing a preparative HPLC system with a chiral column. The trans coordination and clothespin‐shaped structures with syn and anti conformations of these complexes have been unequivocally established by X‐ray diffraction studies. 1H NMR analysis showed that (±)‐anti‐ 1 , (±)‐anti‐ 2 , syn‐ 2 , and (±)‐anti‐ 3 display a flapping motion by consecutive stacking association/dissociation between cofacial coordination planes in [D8]toluene, whereas syn‐ 1 and syn‐ 3 are static under the same conditions. The activation parameters for the flapping motion (ΔH≠ and ΔS≠) were determined from variable‐temperature NMR analyses as 50.4 kJ mol?1 and 60.1 J mol?1 K?1 for (±)‐anti‐ 1 , 31.0 kJ mol?1 and ?22.7 J mol?1 K?1 for (±)‐anti‐ 2 , 29.6 kJ mol?1 and ?57.7 J mol?1 K?1 for syn‐ 2 , and 35.0 kJ mol?1 and 0.5 J mol?1 K?1 for (±)‐anti‐ 3 , respectively. The molecular structure and kinetic parameters demonstrate that all of the anti complexes flap with a twisting motion in [D8]toluene, although (±)‐anti‐ 1 bearing dilated Z‐shaped blades moves more dynamically than I‐shaped (±)‐anti‐ 2 or the smaller (±)‐anti‐ 3 . Highly symmetrical syn‐ 2 displays a much more static flapping motion, that is, in a see‐saw‐like manner. In CDCl3, (±)‐anti‐ 1 exhibits an extraordinary upfield shift of the 1H NMR signals with increasing concentration, whereas solutions of (+)‐anti‐ 1 and the other syn/anti analogues 2 and 3 exhibit negligible or slight changes in the chemical shifts under the same conditions, which indicates that anti‐ 1 undergoes a specific heterochiral association in the solution state. Equilibrium constants for the dimerizations of (±)‐ and (+)‐anti‐ 1 in CDCl3 at 293 K were estimated by curve‐fitting analysis of the 1H NMR chemical shift dependences on concentration as 26 M ?1 [KD(racemic)] and 3.2 M ?1 [KD(homo)], respectively. The heterochiral association constant [KD(hetero)] was estimated as 98 M ?1, based on the relationship KD(racemic)=1/2 KD(homo)+1/4 KD(hetero). An inward stacking motif of interpenetrative dimer association is postulated as the mechanistic rationale for this rare case of heterochiral association. 相似文献
12.
Dr. Christopher R. Emerson Dr. Lev N. Zakharov Prof. Dr. Paul R. Blakemore 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(48):16342-16356
Four putative functionalized α‐chloroakyllithiums RCH2CHLiCl, where R=CHCH2 ( 18 a ), CCH ( 18 b ), CH2OBn ( 18 c ), and CH[O(CH2)2O] ( 18 d ), were generated in situ by sulfoxide–lithium exchange from α‐chlorosulfoxides, and investigated for the stereospecific reagent‐controlled homologation (StReCH) of phenethyl and 2‐chloropyrid‐5‐yl ( 17 ) pinacol boronic esters. Deuterium labeling experiments revealed that α‐chloroalkyllithiums are quenched by proton transfer from their α‐chlorosulfoxide precursors and it was established that this effect compromises the yield of StReCH reactions. Use of α‐deuterated α‐chlorosulfoxides was discovered to ameliorate the problem by retarding the rate of acid‐base chemistry between the carbenoid and its precursor. Carbenoids 18 a and 18 b showed poor StReCH efficacy, particularly the propargyl group bearing carbenoid 18 b , the instability of which was attributed to a facile 1,2‐hydride shift. By contrast, 18 d , a carbenoid that benefits from a stabilizing interaction between O and Li atoms gave good StReCH yields. Boronate 17 was chain extended by carbenoids 18 a , 18 b , and 18 d in 16, 0, and 68 % yield, respectively; α‐deuterated isotopomers D ‐ 18 a and D ‐ 18 d gave yields of 33 and 79 % for the same reaction. Double StReCH of 17 was pursued to target contiguous stereodiads appropriate for the total synthesis of (?)‐epibatidine ( 15 ). One‐pot double StReCH of boronate 17 by two exposures to (S)‐D ‐ 18 a (≤66 % ee), followed by work‐up with KOOH, gave the expected stereodiad product in 16 % yield (d.r.~67:33). The comparable reaction using two exposures to (S)‐D ‐ 18 d (≤90 % ee) delivered the expected bisacetal containing stereodiad (R,R)‐DD ‐ 48 in 40 % yield (≥98 % ee, d.r.=85:15). Double StReCH of 17 using (S)‐D ‐ 18 d (≤90 % ee) followed by (R)‐D ‐ 18 d (≤90 % ee) likewise gave (R,S)‐DD ‐ 48 in 49 % yield (≥97 % ee, d.r.=79:21). (R,S)‐DD ‐ 48 was converted to a dideuterated isotopomer of a synthetic intermediate in Corey’s synthesis of 15 . 相似文献
13.
A Concise and Highly Enantioselective Total Synthesis of (+)‐anti‐ and (−)‐syn‐Mefloquine Hydrochloride: Definitive Absolute Stereochemical Assignment of the Mefloquines 下载免费PDF全文
Ettore J. Rastelli Prof. Don M. Coltart 《Angewandte Chemie (International ed. in English)》2015,54(47):14070-14074
A concise asymmetric (>99:1 e.r.) total synthesis of (+)‐anti‐ and (?)‐syn‐mefloquine hydrochloride from a common intermediate is described. The key asymmetric transformation is a Sharpless dihydroxylation of an olefin that is accessed in three steps from commercially available materials. The Sharpless‐derived diol is converted into either a trans or cis epoxide, and these are subsequently converted into (+)‐anti‐ and (?)‐syn‐mefloquine, respectively. The synthetic (+)‐anti‐ and (?)‐syn‐mefloquine samples were derivatized with (S)‐(+)‐mandelic acid tert‐butyldimethylsilyl ether, and a crystal structure of each derivative was obtained. These are the first X‐ray structures for mefloquine derivatives that were obtained by coupling to a known chiral, nonracemic compound, and provide definitive confirmation of the absolute stereochemistry of (+)‐anti‐ as well as (?)‐syn‐mefloquine. 相似文献
14.
Rhodium‐Catalyzed Desymmetrization by Hydroformylation of Cyclopentenes: Synthesis of Chiral Carbocyclic Nucleosides 下载免费PDF全文
Cai You Biao Wei Xiuxiu Li Yusheng Yang Yue Liu Prof. Dr. Hui Lv Prof. Dr. Xumu Zhang 《Angewandte Chemie (International ed. in English)》2016,55(22):6511-6514
Excellent enantioselectivities (up to 97 % ee) and diastereoselectivities (up to >99:1 d.r.) have been achieved in the desymmetrization of cyclopentenes by catalytic hydroformylation. This novel methodology provides an efficient and concise synthetic route to chiral cyclopentane carboxaldehydes. The key intermediate, (1S,3S)‐(3‐hydroxymethyl)cyclopentanol, for the synthesis of carbocyclic‐ddA was obtained in three steps. 相似文献
15.
Asymmetric Synthesis of Tetrahydroindolizines by Bimetallic Relay Catalyzed Cycloaddition of Pyridinium Ylides 下载免费PDF全文
Dong Zhang Prof. Dr. Lili Lin Jian Yang Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Angewandte Chemie (International ed. in English)》2018,57(38):12323-12327
A highly enantioselective synthesis of tetrahydroindolizines by catalytic multicomponent cycloaddition reactions of diazoacetate, pyridine, and alkenyloxindole was developed. Under the relay catalysis, involving an achiral iron(III) catalyst and chiral N,N′‐dioxide‐scandium(III) complex, a series of tetrahydroindolizines bearing different substituents were obtained in moderate to high yields (up to 99 %) with excellent diastereo‐ and enantioselectivities (up to >19:1 d.r., 99 % ee). 相似文献
16.
The title compounds were prepared by aldol reaction of anisaldehyde and the respective N,N‐dibenzyl glycinates. Deprotection of the nitrogen atom with Pearlman’s catalyst delivered the unprotected β‐hydroxytyrosine esters, which were further N‐protected as N,N‐phthaloyl (Phth) and N‐fluorenylmethylcarbonyloxy (Fmoc) derivatives. The Friedel–Crafts reaction with various arenes was studied employing these alcohols as electrophiles. It turned out that the facial diastereoselectivitiy depends on the nitrogen protecting group and on the ester group. The unprotected substrates (NH2) gave preferentially syn‐products but the anti‐selectivity increased when going from NHFmoc over NPhth to NBn2. If the ester substituent was varied the syn‐preference increased in the order Me <Et <iPr. The reactions were shown to be fully stereoconvergent and proceeded under kinetic product control. A model is suggested to explain the facial diastereoselectivity based on a conformationally locked benzylic cation intermediate. The reactions are preparatively useful for the N‐unprotected isopropyl ester, which gave Friedel–Crafts alkylation products with good syn‐selectivity (anti/syn=21:79 to 7:93), and for the N,N‐dibenzyl‐protected methyl ester, which led preferentially to anti‐products (anti/syn=80:20 to >95:5). Upon acetylation of the latter compound to the respective acetate, Bi(OTf)3‐catalyzed alkylation reactions became possible, in which silyl enol ethers served as nucleophiles. The respective alkylation products were obtained in high yield and with excellent anti‐selectivitiy (anti/syn≥95:5). 相似文献
17.
Remote Construction of Chiral Vicinal Tertiary and Quaternary Centers by Catalytic Asymmetric 1,6‐Conjugate Addition of Prochiral Carbon Nucleophiles to Cyclic Dienones 下载免费PDF全文
Yuan Wei Zunwu Liu Xinxin Wu Jie Fei Xiaodong Gu Xiaoqian Yuan Prof. Dr. Jinxing Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(52):18921-18924
An unprecedented remote construction of chiral vicinal tertiary and quaternary centers by a catalytic asymmetric 1,6‐conjugate addition of prochiral carbon nucleophiles to cyclic dienones has been developed. Both 5H‐oxazol‐4‐ones and 2‐oxindoles were found to be very efficient carbon nucleophiles in this reaction at a remote position, giving products with excellent enantio‐ and diastereoselectivities (up to 99 % ee and >19:1 d.r. for 5H‐oxazol‐4‐ones and up to 97 % ee and >19:1 d.r. for 2‐oxindoles). 相似文献
18.
Stereoselective Synthesis and Retentive Trapping of α‐Chiral Secondary Alkyllithiums Leading to Stereodefined α,β‐Dimethyl Carboxylic Esters 下载免费PDF全文
Varvara Morozova Dr. Kohei Moriya Dr. Peter Mayer Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):9962-9965
The treatment of α‐chiral secondary alkyl iodides with tBuLi at ?100 °C leads to the corresponding secondary alkyllithiums with high retention of configuration. Subsequent quenching with various electrophiles such as Bu2S2, DMF, MeOB(OR)2, or Et2CO provides the desired products with retention of configuration. Furthermore, a transmetalation with CuBr?P(OEt)3 also allows retentive trapping with acid chlorides and ethylene oxide. The quenching of the resulting alkyllithiums with ClCO2Et furnishes stereoselectively syn‐ and anti‐ethyl‐2,3‐dimethyl ester carboxylates (d.r.>94 %). Related esters bearing three adjacent stereo‐controlled centers (stereotriads) have also been prepared. This method has been applied to the synthesis of the ant pheromone (±)‐lasiol in 26 % overall yield (four steps) with d.r.=97:3 starting from commercially available cis‐2,3‐epoxybutane. 相似文献
19.
Diastereodivergent Asymmetric Michael Addition of Cyclic Azomethine Ylides to Nitroalkenes: Direct Approach for the Synthesis of 1,7‐Diazaspiro[4.4]nonane Diastereoisomers 下载免费PDF全文
Chun‐Yan Li Wu‐Lin Yang Prof. Dr. Xiaoyan Luo Prof. Dr. Wei‐Ping Deng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(52):19048-19057
The first highly diastereoselective and enantioselective catalytic asymmetric Michael addition of cyclic azomethine ylides with nitroalkenes have been developed to diastereodivergently generate either the syn or anti adducts by employing N,O‐ligand/Cu(OAc)2 and N,P‐ligand/Cu(OAc)2 catalytic systems. Both catalytic systems exhibit broad substrate applicability to afford the corresponding Michael adducts in good to excellent yields, with excellent levels of diastereo‐ (up to 99:1 diastereomeric ratio) and enantioselectivities (up to >99 % enantiomeric excess). Importantly, the chiral 1,7‐diazaspiro[4.4]nonane diastereomer derivatives can be easily obtained in good yields through facile NaBH4 reduction of the Michael adducts. 相似文献
20.
Asymmetric Palladium‐Catalyzed Alkene Carboamination Reactions for the Synthesis of Cyclic Sulfamides 下载免费PDF全文
Zachary J. Garlets Kaia R. Parenti Prof. Dr. John P. Wolfe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5919-5922
The synthesis of cyclic sulfamides by enantioselective Pd‐catalyzed alkene carboamination reactions between N‐allylsulfamides and aryl or alkenyl bromides is described. High levels of asymmetric induction (up to 95:5 e.r.) are achieved using a catalyst composed of [Pd2(dba)3] and (S)‐Siphos‐PE. Deuterium‐labelling studies indicate the reactions proceed through syn‐aminopalladation of the alkene and suggest that the control of syn‐ versus anti‐aminopalladation pathways is important for asymmetric induction. 相似文献