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1.
《Tetrahedron: Asymmetry》2000,11(3):835-841
Chiral C2-symmetric diphenylselenophosphoramides 1 and 2 were prepared from the reaction of diphenylselenophosphinic chloride with (1R,2R)-(−)-1,2-diaminocyclohexane and (1R,2R)-(+)-1,2-diphenylethylenediamine, respectively, in high yields. Another novel chiral ligand 3 was prepared from the reaction of diphenylselenophosphinic chloride with (R)-(+)-1,1′-binaphthyl-2,2′-diamine using butyllithium as the base. The ligands were used as catalytic chiral ligands in the titanium(IV) alkoxide-promoted enantioselective addition reaction of diethylzinc to aldehydes.  相似文献   

2.
《Tetrahedron: Asymmetry》2000,11(3):773-779
Chiral C2-symmetric diphenylthiophosphoramides 1 and 2 were prepared in high yields from the reaction of diphenylthiophosphinic chloride with (1R,2R)-(−)-1,2-diaminocyclohexane and (1R,2R)-(+)-1,2-diphenylethylenediamine, respectively. Another novel chiral ligand 4 was prepared from reaction of diphenylthiophosphinic chloride with (R)-(+)-1,1′-binaphthyl-2,2′-diamine using butyllithium as a base. They were used as catalytic chiral ligands in the silver(I)-promoted enantioselective allylation reaction of aldehydes with allyltributyltin.  相似文献   

3.
《Tetrahedron: Asymmetry》2000,11(20):4043-4047
Racemic 2,2′-bis[di(p-tolyl)stibano]-1,1′-binaphthyl (BINASb) (±)-2 has been prepared from 2,2′-dibromo-1,1′-binaphthyl 1 via 2,2′-dilithio-1,1′-binaphthyl intermediate, and has been resolved via the separation of a mixture of the diastereomeric Pd complexes 4A and 4B, derived from the reaction of (±)-2 with di-μ-chlorobis{(S)-2-[1-(dimethylamino)ethyl]phenyl-C,N}dipalladium(II) 3. The optically active BINASbs (S)-(+)-2 and (R)-(−)-2 have been shown to be effective chiral ligands for the rhodium-catalyzed asymmetric hydrosilylation of ketones.  相似文献   

4.
《Tetrahedron: Asymmetry》1999,10(19):3833-3848
A new series of chiral C2-symmetric bisferrocenyldiimine 1 and bisferrocenyldiamines 2 and 3 proved to be efficient ligands for the copper(I)-catalyzed asymmetric cyclopropanation, cyclopropenation, and aziridination of alkenes and alkynes to give high diastereo- and enantioselectivity as well as high chemical yields. In some instances the enantiomeric excesses of cyclopropanated products are among the highest (>97% ee) ever reported. Comparative studies show that stereoselectivity depends highly on the steric variation both in the ligand and the substrate. Other transition metal complexes incorporating some of these ligands such as Ru(3c)Cl2, [(NBD)Rh(2)]ClO4, [Cu(2)(MeCN)2]PF6, and Pd(2)Cl2 also demonstrated high enantioselectivity in cyclopropanation reactions.  相似文献   

5.
《Tetrahedron: Asymmetry》2007,18(6):729-733
Novel chiral tetraaza ligands, N1,N2-bis(2-(piperidin-1-yl)benzylidene)cyclohexane-1,2-diamine 1 and N1,N2-bis(2-(piperidin-1-yl)benzyl)cyclohexane-1,2-diamine 2, have been synthesized and fully characterized by analytical and spectroscopic methods. The structure of (R,R)-1 has been established by X-ray crystallography. Asymmetric transfer hydrogenation of aromatic ketones with the catalysts prepared in situ from [IrHCl2(COD)]2 and the chiral tetraaza ligands in 2-propanol gave the corresponding optically active secondary alcohols in high conversions and good ees (up to 91%) under mild reaction conditions.  相似文献   

6.
Hydrogen-transfer reduction processes are attracting increasing interest from synthetic chemists in view of their operational simplicity. The new chiral C2-symmetric ligands N,N′-bis-[(1S)-1-sec-butyl-2-O-(diphenylphosphinite)ethyl]ethanediamide, 1 and N,N′-bis-[(1S)-1-phenyl-2-O-(diphenylphosphinite)ethyl]ethanediamide, 2 and the corresponding ruthenium complexes 3 and 4 have been prepared and their structures have been elucidated by a combination of multi-nuclear NMR spectroscopy, IR spectroscopy, and elemental analysis. 1H–31P NMR, DEPT, 1H–13C HETCOR, or 1H–1H COSY correlation experiments were used to confirm the spectral assignments. The catalytic activity of complexes 3 and 4 in transfer hydrogenation of acetophenone derivatives by iso-PrOH has also been studied. Under optimized conditions, these chiral ruthenium complexes serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in iso-PrOH and act as excellent catalysts, giving the corresponding chiral alcohols in 99% yield and up to 75% ee. This transfer hydrogenation is characterized by low reversibility under these conditions.  相似文献   

7.
《Tetrahedron: Asymmetry》2005,16(7):1385-1391
In the aza-Baylis–Hillman reaction of N-sulfonated imines with 2-cyclohexen-1-one or 2-cyclopenten-1-one, we found that by using (R)-2′-dimethylphosphanyl-[1,1′]binaphthalenyl-2-ol LB1 as a chiral phosphine Lewis base, the corresponding Baylis–Hillman adducts 2 or 3 can be obtained in good yields and moderate enantiomeric excess. The structure of this chiral phosphine Lewis base on chiral induction in this reaction has also been discussed.  相似文献   

8.
Eight (biaryl)phosphite/pyridine ligands 12ad have been prepared by the modular functionalization of positions C-2 and C-3 of two d-glucopyranoside backbones. The chiral ligands were examined in the iridium-catalyzed asymmetric hydrogenation of poorly functionalized alkenes, as a function of the relative position of the coordinating groups and the geometric properties of the biaryl phosphite moieties. Enantiomeric excesses of up to 90% were achieved in the hydrogenation of E-2-(4-methoxyphenyl)-2-butene by using 1a and 1c, which seemingly combine the beneficial effect of the phosphite at the 2-position with the matching (Rax)-configuration of their encumbered biaryl substituents. The results of the hydrogenation of more challenging substrates, such as Z-trisubstituted alkenes, alkenes with a neighboring polar group or demanding 1,1-di-substituted alkenes, generally confirmed this trend, and in some significant cases, the chiral hydrogenated products were isolated with ees of 65–79%.  相似文献   

9.
《Polyhedron》2005,24(16-17):2189-2193
We prepared and characterized dinuclear copper(II) and mononuclear palladium(II) complexes coordinated with a pyridine-based open-shell ligand, 5-(4′,4′,5′,5′-tetramethylimidazoline-3′-oxide-1′-oxyl)-2(1H)-pyridone (=HL). In the copper(II) dinuclear complex [Cu2(L)4(DMF)2] (1), four deprotonated ligands are coordinated as bridging ligands to form a paddle-wheel type unit. In the palladium(II) complex trans-[PdCl2(HL)2] (2), two HL ligands in the neutral hydroxypyridine form are coordinated to the trans positions of the metal ion via the nitrogen atoms. The hydroxyl groups of the ligands are hydrogen-bonded to the chlorine atoms of neighboring molecules, thereby creating a hydrogen-bonded double-chain molecular arrangement. Magnetic susceptibilities of these complexes were measured and analyzed. The small intramolecular antiferromagnetic interaction in the latter complex may originate from superexchange through the diamagnetic metal center.  相似文献   

10.
A new series of chiral NHC–rhodium complexes has been prepared from the reactions between [Rh(COD)Cl]2, NaOAc, KI and dibenzimidazolium salt 4a or monobenzimidazolium salts 4bd, which are derived from chiral 2,2′-diamino-6,6′-dimethyl-1,1′-biphenyl, 2,2′-diamino-1,1′-binaphthyl or 6,6′-dimethyl-2-amino-2′-hydroxy-1,1′-biphenyl. The steric and electronic effects of the ligand play an important role in the complex formation. For example, treatment of chiral monobenzimidazolium salt 4b (with a NMe2 group) with 0.5 equiv of [Rh(COD)Cl]2 in the presence of NaOAc and KI in CH3CN at reflux gives a chiral Rh(I) complex 5b, while chiral monobenzimidazolium salt 4d (with a MeO group) affords a racemic Rh(I) complex 5d. Under similar reaction conditions, treatment of dibenzimidazolium salt 4a with 0.5 equiv of [Rh(COD)Cl]2 in the presence of NaOAc and KI gives a racemic Rh(III) complex 5a, while the dibenzimidazolium salt [C20H12(C7H5N2Me)2]I2 derived from chiral 2,2′-diamino-1,1′-binaphthyl affords a chiral Rh(III) complex [C20H12(C7H4N2Me)2]RhI2(OAc). All compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of the rhodium complexes have been further confirmed by X-ray diffraction analyses.  相似文献   

11.
Six new divalent lanthanide complexes using triglyme (trigly) and tetraglyme (tetgly) as achiral ligands have been prepared, using a facile synthetic method, in search for enantioselective solid-state reagents. The crystal structures of cis-[SmI2(trigly)thf] (1), trans-[YbI2(trigly)thf] (2), trans-[SmI2(trigly)dme] (3), trans-[YbI2(tetgly)] (4), trans-[EuI2(tetgly)thf] (5), and [Sm(tetgly)2][SmI3(tetgly)]I (6) have been determined. All complexes, except 5, are chiral. The 10-coordinate cation in 6 displays a helical chirality since the two tetraglyme ligands are wrapped around the samarium ion. Since trans-[YbI2(tetgly)] (4), which has a chiral arrangement of terminal methyl groups, crystallizes as a conglomerate, preferential crystallization and consequent enantioselective reduction of acetophenone was attempted, but resulted in racemic products, possibly on account of racemic twinning in 4.  相似文献   

12.
New highly constrained chiral C1-1,1′-bisisoquinoline ligands have been synthesized. X-ray crystallographic analysis of these ligands showed peculiar structural differences between the parent 1′,2′,3′,4′-tetrahydro-1,1′-bisisoquinoline and its alkyl, acyl and sulfonyl derivatives. The consequences of their geometrical conformations on enantioinduction were examined by employing the enantioselective addition of diethylzinc to aldehydes. Such conformations greatly affected the catalytic efficiency of these ligands.  相似文献   

13.
《Tetrahedron: Asymmetry》2005,16(21):3484-3487
The dirhodium-catalyzed aziridination of olefins with chiral sulfonimidamides as iminoiodane precursors has been investigated under stoichiometric conditions. Diastereoisomeric excesses of up to 82% have been achieved using [Rh2{(S)-nttl}4] as catalyst. Matching and mismatching effects were observed upon use of chiral rhodium(II) carboxylate catalysts.  相似文献   

14.
《中国化学快报》2023,34(3):107368
Synthetic conditions and ligands are the key structural defining factors of metal–organic frameworks (MOFs). Therefore, reasonable optimization of these aspects is considered to be an effective means for designing materials with novel structures and target functions. Herein, two novel Co(II)-based MOFs, namely [Co(HL)(dibp)]n (HL-8) and {[Co2(L)(OH)(dibp)]·DMA}n (HL-9) (H3L = 2′,6′-dimethyl-[1,1′-biphenyl]-3,4′,5-tricarboxylic acid; dibp = 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl]), have been hydrothermally synthesized and structurally characterized. HL-8 crystallizes in the orthorhombic system (Pna21) with a grid layer structure, while HL-9 crystallizes in the monoclinic P21/n space group assembled through Co4(OH)2 clusters with organic ligands. Remarkably, benefiting from the finite cage-like structure, HL-9 exhibited enhanced performance in carbon dioxide (CO2) adsorption/catalytic transformation and excellent size selectivity during dye molecular adsorption process.  相似文献   

15.
《Tetrahedron: Asymmetry》1999,10(2):207-211
The reaction of 2-lithiophenyldiphenylphosphine with phosphorus trichloride afforded the new unsymmetric phosphine, dichloro(2-diphenylphosphinophenyl)phosphine (4). Condensation of 4 with (a) (2R,3R)-dimethyl tartrate or (b) (S)-binaphthol in the presence of triethylamine gave new chiral phosphine-phosphonite ligands, (2R,3R)-[2-(2′-(diphenylphosphino)phenyl)-4,5-bis(carbomethoxy)-1,3,2-dioxaphospholane] ((2R,3R)-5) and (S)-[2-(diphenylphosphino)benzene][1,1′-binaphthalen-2,2′-diyl]phosphonite] ((S)-6). The analogous reaction of 4 with (1R,2S)-ephedrine using N-methylmorpholine as the base, gave [2-(2′-(diphenylphosphino)phenyl)-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholidine] (7) as a 95:5 mixture of diastereoisomers.  相似文献   

16.
The [Pd(N-N)Cl2] complexes have been obtained, as yellow solids, in almost quantitative yields; N-N indicate bidentate chiral ligands (Sa)-1, (Sa)-2, (S,S)-3, (R,R)-4, containing the rigid 2-pyridinyl or 8-quinolinyl building block skeleton and the C2-symmetric chiral framework trans-2,5-dimethylpyrrolidinyl or (S)-(+)-2,2′-(2-azapropane-1,3-diyl)-1,1′-binaphthalene. The ligands pairs have the same C2-symmetric chiral framework but different building block skeleton, beyond that for the basicity in the N-donor atoms, for rigidity and flexibility features. The N-N ligands act as chelating ligands leading a square planar geometry. The compounds [Pd(S,S-3)Cl2] and [Pd(R,R-4)Cl2] have been also characterised by X-ray diffraction. The rigidity and flexibility features of (S,S)-3 and (R,R)-4 ligands induce a different orientation of the trans-2,5-dimethylpyrrolidinyl moiety with respect to the pyridinyl and quinolinyl plane. This work shows that intrinsic rigidity and flexibility are not enough to define the ligand properties and to preview the effects that they induce on the reactivity of the metal complex.  相似文献   

17.
《Tetrahedron: Asymmetry》1999,10(17):3259-3261
New chiral (+)-2,2′-O,O-(1,1′-binaphthyl)-dioxo-N,N-diethylphospholidine 1 and its borane complex 3 were prepared from (S)-binaphthol and their use as catalysts in enantioselective borane reductions of prochiral acetophenone were investigated. Enantiomeric excesses of up to 98.5% have been obtained using 6 mol% of 1 at room temperature and using 6 mol% of 3 at 100°C.  相似文献   

18.
《Tetrahedron: Asymmetry》2006,17(2):205-209
(3R)-3-[N-(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoic acid 7a has been synthesized by an asymmetric hydrogenation of enamine ester 3 using chiral ferrocenyl ligands I and II in conjunction with [Rh(COD)Cl]2. The direct reduction of 3 provides amino ester 1b in 93% ee, which was isolated as an (S)-camphorsulfonic acid salt to upgrade the enantiomeric excess to >99%. A more concise approach was developed involving the in situ protection of 1b using di-tert-butyldicarbonate. This approach provided the desired N-Boc amino ester 7b directly from the hydrogenation with 97% ee, which was upgraded to >99% ee upon crystallization.  相似文献   

19.
Novel chiral norephedrine-based β-amino alcohol ligands containing a thiophene ring were prepared from norephedrine and substituted furan carbaldehydes (methyl- or ethyl-substituted) and used in combination with VO(acac)2 for the asymmetric oxidation of aryl methyl sulfides using H2O2 as an oxidant. Amino alcohol derived Schiff bases 4,5ab gave higher enantiomeric excesses than amino alcohol-derived reduced Schiff based ligands 6,7ab. Of these chiral ligands, (1S,2R)-5b and (1S,2R)-7b gave high yields (90%) with moderate to high enantioselectivities (78%, 96% ee, respectively). The oxidation of other aryl methyl sulfides with (1S,2R)-5b and (1S,2R)-7b as ligands afforded the corresponding sulfoxides in 60–89% yields and with 92–99% ee.  相似文献   

20.
A convenient synthesis of chiral 3,3′-disubstituted 1,1′-binaphthyl-2,2′-disulfonic acids (BINSA, 1) was developed. The key was directed ortho-lithiation of BINSA methyl ester 2 with n-BuLi and subsequent reaction with an electrophile. Electrophiles such as Br2, I2, Me3SiOTf, and i-PrOB(Pin) reacted smoothly with 3,3′-dilithiated BINSA methyl ester, and the corresponding 3,3′-dihalo-, 3,3′-bis(trimethylsilyl)-, and 3,3′-diboryl-BINSA derivatives were obtained in yields of 21–78%. This simple synthetic method is highly attractive since the ability to prepare 3,3′-disubstituted BINOLs in advance can be useful.  相似文献   

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