Chiroptical activity of BINAP-stabilized undecagold clusters

Undecagold cluster compounds [Au11(BINAP)4X2]+ (X = Cl and Br) were synthesized by chemical reduction of the corresponding precursor complexes, Au2X2(BINAP), where BINAP represents the bidentate phosphine ligand 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl. The circular dichroism spectra of Au11 stabilized by the enantiomers [Au11(R-BINAP)4X2]+ and [Au11(S-BINAP)4X2]+ exhibited intense and mirror-image Cotton effect, whereas those of Au11(3+) clusters stabilized by achiral monodentate phosphine ligands did not. The origin of the chiroptical activity of [Au11(BINAP)4X2]+ is discussed in the context of the structural deformation of the Au11(3+) core.     

Catalytic Asymmetric Synthesis of α-Quaternary Proline Derivatives by 1,3-Dipolar Cycloaddition of α-Silylimines

Going pro: The title reaction between α-silylimines and activated olefins proceeds in the presence of a Cu(I) /DTBM-Segphos catalyst system with excellent diastereoselectivity and enantioselectivity. This process provides straightforward access to highly enantioenriched 5-unsubstituted α-quaternary proline derivatives. TMS=trimethylsilyl, DTBM-Segphos=5,5'-bis[di(3,5-di-tert-butyl-4-methoxyphenyl)phosphino]-4,4'-bi-1,3-benzodioxole.     

Ru-catalyzed asymmetric hydrogenation of alpha-phthalimide ketones and 1,3-diaryl diketones using 4,4'-substituted BINAPs

[reaction: see text] A family of tunable precatalysts [NH2Et2][{Ru(4,4'-BINAP)Cl}2(mu-Cl)3] was synthesized and used for highly enantioselective hydrogenation of phthalimide-protected amino ketones and 1,3-diaryldiketones. The bulky groups on the 4,4'-positions of BINAP were believed to be responsible for the enhancement of enantioselectivity (and diasteroselectivity) in these reactions.     

Asymmetric platinum group metal-catalyzed carbonyl-ene reactions: carbon-carbon bond formation versus isomerization

A comparative study of the carbonyl-ene reaction between a range of 1,1'-disubstituted or trisubstituted alkenes and ethyl trifluoropyruvate catalyzed by Lewis acid-platinum group metal complexes of the type [M{(R)-BINAP}]2+ (M = Pt, Pd, Ni; BINAP is 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) revealed subtle but significant differences in their reactivity. For instance, the palladium-based Lewis acid [Pd{(R)-BINAP}]2+ catalyzes the ene reaction between methylene cycloalkane to afford the expected alpha-hydroxy ester in good yield and excellent diastereo- and enantioselectivity. In contrast, under the same conditions, the corresponding [M{(R)-BINAP}]2+ (M = Pt, Ni) catalyzes isomerization of methylene cycloalkane and the ene reaction of the resulting mixture of methylene cycloalkane and 1-methylcycloalkene at similar rates to afford a range of -hydroxy esters in high regioselectivity, good diastereoselectivity, and good to excellent enantioselectivity. In addition, [Pt{(R)-BINAP}]2+ also catalyzes postreaction isomerization of the ene product as well as consecutive ene reactions to afford a double carbonyl-ene product. The sense of asymmetric induction has been established by single-crystal X-ray crystallography, and a stereochemical model consistent with the formation of (S)-configured -hydroxy ester has been proposed; the same model also accounts for the observed exo-diastereoselectivity as well as the level of diastereoselectivity.     

Synthesis, resolution, and applications of 2, 2'-bis(diphenylphosphino)-3,3'- binaphtho[2,1-b]furan

[structure: see text] A short five-step synthesis of (+/-)-2,2'-bis(diphenylphosphino)-3, 3'-binaphtho[2,1-b]furan (BINAPFu, 1) starting from 2-naphthoxyacetic acid is reported. The resolution of BINAPFu 1 was possible using our newly developed resolution procedure for phosphines wherein (1S)-camphorsulfonyl azide was used to prepare the bisphosphinimine of BINAPFu via the Staundinger reaction. BINAPFu consistently outperformed BINAP in an asymmetric Heck reaction between 2,3-dihydrofuran and phenyl triflate.     

Self-assembly of coordination polymers: evidence for dynamic exchange between oligomers in solution and the isolation of a homochiral decagold(I) oligomer

Reactions of the precursor molecules [Au2(mu-BINAP)(O2CCF3)2], 1a, racemic BINAP, 1b, S-BINAP (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) with the easily exchanged linear bis(pyridine) ligand 1,2-trans-bis(4-pyridyl)ethylene (bipyen) gave the polymeric complex [{Au2(mu-R-BINAP)0.5(mu-S-BINAP)0.5(mu-bipyen)}n](CF3CO2)2n, 2a, but either the polymer [{Au2(mu-S-BINAP)(mu-bipyen)}n](CF3CO2)2n, 2b, or the remarkable oligomeric [Au10(mu-S-BINAP)5(mu-bipyen)4(kappa1-bipyen)2](CF3CO2)10, 3, respectively. The type of oligomer 3 is a missing link in the ring-opening polymerization of macrocyclic coordination compounds.     

Metal-dependent reactions of bulky metal(II) amides M[N(SiMe3)2]2 with 3,3'-disubstituted binaphthols (HO)2C20H10(SiR3)2-3,3': selective conversion of one equivalent -OH group to a silyl ether -OSiMe3

The outcome of the reaction of the bulky metal(II) amides M[N(SiMe3)2]2. nTHF (M = Be, Zn, Ge, Sn, n = 0; M = Mg, Ca, n = 2) with (R)-3,3'-bis(trimethylsilyl)-1,1'-bi-2,2'-naphthol ((R)-1) or (S)-3,3'-bis(dimethylphenylsilyl)-1,1'-bi-2,2'-naphthol ((S)-9) depends on the identity of the metal and the nature of the 3,3'-substituents. When M = Be, Zn, or Ge, these amides serve as useful silylation agents that convert only one of the equivalent hydroxyl groups of the binaphthol (R)-1 to a trimethylsilyl ether, whereas the reactions of (R)-1 with the Mg, Ca, or Sn amides generate a polynuclear complex. The reaction pathway for these interconversions was qualitatively monitored using NMR ((1)H and (9)Be) spectroscopy. Treatment of Ge[N(SiMe3)2] 2 with (S)-9 yields both a silyl ether and the chelated germanium(II) binaphthoxide (S)-[Ge{O2C20H10(SiMe2Ph)2-3,3'}{NH3}], which was structurally characterized.     

Thermomorphic system with non-fluorous phase-tagged Ru(BINAP) catalyst: facile liquid/solid catalyst separation and application in asymmetric hydrogenation

The thermomorphic BINAP derivative 1 tagged with long alkyl chains was prepared from (S)-5,5'-diamino BINAP and applied to Ru-catalyzed asymmetric hydrogenation of beta-ketoesters under homogeneous conditions in 3:1 (v/v) ethanol/1,4-dioxane at 60 degrees C with high enantioselectivity (up to 98% ee). Results indicated that the Ru(1) catalyst was easily recovered by simple cooling and precipitation and could be used for at least four cycles without any loss of enantioselectivity.     

Additive effects of amines on asymmetric hydrogenation of quinoxalines catalyzed by chiral iridium complexes

The additive effects of amines were realized in the asymmetric hydrogenation of 2-phenylquinoxaline, and its derivatives, catalyzed by chiral cationic dinuclear triply halide-bridged iridium complexes [{Ir(H)[diphosphine]}(2) (μ-X)(3) ]X (diphosphine=(S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [(S)-BINAP], (S)-5,5'-bis(diphenylphosphino)-4,4'-bi-1,3-benzodioxole [(S)-SEGPHOS], (S)-5,5'-bis(diphenylphosphino)-2,2,2',2'-tetrafluoro-4,4'-bi-1,3-benzodioxole [(S)-DIFLUORPHOS]; X=Cl, Br, I) to produce the corresponding 2-aryl-1,2,3,4-tetrahydroquinoxalines. The additive effects of amines were investigated by solution dynamics studies of iridium complexes in the presence of N-methyl-p-anisidine (MPA), which was determined to be the best amine additive for achievement of a high enantioselectivity of (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline, and by labeling experiments, which revealed a plausible mechanism comprised of two cycles. One catalytic cycle was less active and less enantioselective; it involved the substrate-coordinated mononuclear complex [IrHCl(2) (2-phenylquinoxaline){(S)-BINAP}], which afforded half-reduced product 3-phenyl-1,2-dihydroquinoxaline. A poorly enantioselective disproportionation of this half-reduced product afforded (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline. The other cycle involved a more active hydride-amide catalyst, derived from amine-coordinated mononuclear complex [IrCl(2) H(MPA){(S)-BINAP}], which functioned to reduce 2-phenylquinoxaline to (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline with high enantioselectivity. Based on the proposed mechanism, an Ir(I) -JOSIPHOS (JOSIPHOS=(R)-1-[(S(p) )-2-(dicyclohexylphosphino)ferrocenylethyl]diphenylphosphine) catalyst in the presence of amine additive resulted in the highest enantioselectivity for the asymmetric hydrogenation of 2-phenylquinoxaline. Interestingly, the reaction rate and enantioselectivity were gradually increased during the reaction by a positive-feedback effect from the product amines.     

3,3'-Bis(diphenylphosphino)-1,1'-disubstituted-2,2'-biindoles: easily accessible, electron-rich, chiral diphosphine ligands for homogeneous enantioselective hydrogenation of oxoesters

Racemic (+/-)-3,3'-bis(diphenylphosphinyl)-1,1'-dimethyl-2, 2'-biindole (1c) (N-Me-2-BINPO) and (+/-)-3, 3'-bis(diphenylphosphinyl)-1,1'-bis(methoxymethyl)-2,2'-biindole (1d) (N-MOM-2-BINPO) were synthesized in satisfactory yields following a three-step reaction sequence, starting from indole. Resolution of racemic 1c and 1d was achieved through fractional crystallization of their diastereomeric adducts with optically active dibenzoyl tartaric acids, followed by alkaline decomplexation of the diastereomerically pure salts. Their trichlorosilane reduction gave enantiopure phosphines (+)- and (-)-(1a) (N-Me-2-BINP) and (+)- and (-)-(1b) (N-MOM-2-BINP). The electrochemical oxidative potential of 1a and 1b was found to be 0. 52 and 0.60 V, respectively. Both the enantiomers of (1a) were tested as ligands of Ru(II) in asymmetric hydrogenation reactions of alpha- and beta-oxoesters. Reactions were found to be outstandingly fast and enantioselection quite good. Comparative kinetic experiments on the hydrogenation reaction of methyl acetoacetate carried out with 1a, 1c, BINAP, and other biheteroaromatic diphosphines as ligands of Ru(II) demonstrated that all the reactions follow a first-order kinetic. A linear relationship was found between the kinetic constant log and the electrochemical oxidative potential of the diphosphine ligand.     

A new class of chiral organogermanes derived from C2-symmetric dithiols: synthesis,characterization and stereoselective free radical reactions

A new class of dithiostannanes and dithiogermanes have been prepared from 1,1'-binaphthyl-2,2'-dithiol and 3,3'-bis(trimethylsilyl)-1,1'-binaphtho-2,2'-dithiol. While reduction of 4-butyl-4-chloro-3,5-dithia-4-stanna-cyclohepta[2,1-a;3,4-a']dinaphthalene to the corresponding tin hydride was unsuccessful, 4-tert-butyl-3,5-dithia-4-germa-cyclohepta[2,1-a;3,4-a']dinaphthalene and 4-tert-butyl-2,6-bis(trimethylsilyl)-3,5-dithia-4-germa-cyclohepta[2,1-a;3,4-a']dinaphthalene were obtained by reduction of the parent germanium chlorides with NaBH(4) and LiBH(4), respectively. Kinetic constants for hydrogen transfer to a primary alkyl radical were measured for both germanium hydrides. Reduction of alpha-halo carbonyl compounds by these germanium hydrides occurs with moderate ee values (up to 42%), while hydrogermylation of methyl methacrylate occurs with low selectivity (<3/1) for the former hydride but high selectivity (>10/1) for the latter.     

Regiospecific Displacement of the C-B Bond of Tris[4-(substituted)furan-3-yl]boroxines with C-Sn Bond and C-O Bond: Syntheses of 3,4-Disubstituted Furans and 4-Substituted-3(2H)-furanones,

Tris[4-(substituted)furan-3-yl]boroxines 2 , prepared from the corresponding 4-(substituted)-3-(trimethylsilyl) furan 1, were converted successfully to 4-(substituted)-3-(tributylstannyl)furans 3 through palladium-catalyzed cross-coupling reactions with tributylstannyl chloride. Palladium-catalyzed cross-coupling reactions of 3 with organohalides afforded 3,4-disubstituted furans 4 . Regiospecific iodination of 4-(trimethylsilyl)-3-((tributylstannyl) furan ( 3a ) gave 4-iodo-3-(trimethylsilyl)furan ( 5 ), which reacted with excess ethyl acrylate under a common Heck-condition to produce 2,3-bis(trans-ethoxycarbonylvinyl)-4-(trimethylsilyl)furan ( 6 ). A thermal 6-electrocyclic reaction followed by dehydration converted 6 into benzo[2,3-6]furan 8 . Oxidation of 2 generated the corresponding 4-substituted-3(2H)-furanones 9 .     

BINAP versus BINAP(O) in asymmetric intermolecular Mizoroki-Heck reactions: substantial effects on selectivities

2,2′‐Bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP) was employed as chiral ligand in the enantioselective intermolecular Mizoroki–Heck reaction, whereas the use of cognate BINAP(O) (monooxidized BINAP) is unprecedented. The regio‐ and enantioselectivity of the arylation of representative cyclic alkenes changes dramatically in the presence of hemilabile BINAP(O) instead of BINAP. The arylation of 2,3‐dihydrofuran is perfectly regiodivergent (98:2 versus 0:100) and the arylation of cyclopentene is only enantioselective with BINAP(O) [60 versus 10 % enantiomeric excess (ee)]. Use of [Pd₂(dba)₃] ? dba (dba=dibenzylideneacetone) instead of Pd(OAc)₂ produces as high as 86 % ee in the arylation of cyclopentene.     

RuCl2[(S)-P-Phos]-[(S)-DAIPEN]催化芳香酮的不对称加氢反应

研究了钌-双膦-二胺配合物催化剂RuCl2[(S)-P-Phos]-[(S)-DAIPEN] [P-Phos: 2,2',6,6'-四甲氧基-4,4'-双(二苯基膦基)-3,3'-二吡啶, DAIPEN: 1,1-二(4-甲氧苯基)-2-异丙基-1,2-乙二胺]催化芳香酮不对称加氢反应的性能, 考察了不同的碱、叔丁醇钾浓度、反应溶剂、底物/催化剂摩尔比等因素对反应活性和对映选择性的影响. 在苯乙酮、叔丁醇钾、催化剂的摩尔比为1000:20:1, 氢气压力为2 MPa, 反应温度为30 ℃时, 苯乙酮的转化率和α-苯乙醇的对映选择性(ee)分别达到了100%和88.5%, 2'-溴苯乙醇的ee 值可达97.1%.     

Cyclotrimerization reactions of arynes and strained cycloalkynes

The use of arynes and related species as substrates in metal-catalyzed cycloaddition reactions leads to structurally interesting products. Palladium-catalyzed cyclotrimerization of arynes provides a new method for the synthesis of polycyclic aromatic hydrocarbons. For instance, the chemoselective formal [2 + 2 + 2] cocycloaddition of 2,3-triphenylynes with alkynes affords extended triphenylenes, which are good candidates to behave as liquid crystals. Cotrimerization of benzyne and electron-deficient alkenes selectively affords dihydrophenanthrenes or ortho-olefinated biaryls depending on the catalytic system employed. The use of 2,2'-bis(diphenylphosphino)-1,1'-binophythyl (BINAP)-based palladium(0) catalysts in the cocyclotrimerization of 7-methoxynaphthalyne and dimethyl acetylenedicarboxylate affords an enantiomerically enriched tetrasubstituted pentahelicene, the first example of a metal-catalyzed enantioselective reaction involving arynes. Strained cyclic alkynes can also participate in the palladium-catalyzed cyclotrimerization reactions, which again lead to structurally interesting products.     

Asymmetric Synthesis of a Fused Tricyclic Hydronaphthofuran Scaffold by Desymmetric [2+2+2] Cycloaddition

A rhodium(I)‐BINAP‐catalyzed highly enantioselective [2+2+2] cycloaddition of enynes with alkynes has been developed. Diverse fused tricyclic hydronaphthofuran scaffolds with three consecutive stereogenic centers were constructed in one step from easily available materials with excellent chemo‐, regio‐, diastereo‐, and enantioselectivity. Notable features of these reactions include 100 % atom economy, very broad scope, and mild reaction conditions.     

An unexpected possible role of base in asymmetric catalytic hydrogenations of ketones. Synthesis and characterization of several key catalytic intermediates

The dihydrogen compound trans-[Ru((R)-BINAP)(H)(eta2-H2)((R,R)-dpen)]+ (2', BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl, dpen = 1,2-diphenylethylenediamine) is a proposed intermediate in asymmetric ketone hydrogenations. It quickly reacts at -80 degrees C with 1 equiv of the base KOtBu in 2-PrOH-d8/CH2Cl2-d2 under H2 to generate trans-Ru((R)-BINAP)(H)(2-PrO)((R,R)-dpen) (4). The alkoxide 4 does not react with H2 after hours under ambient conditions. Addition of 1 equiv of KOtBu to 4 produces a hydrogen bonded species 10 that reacts readily with H2 at -80 degrees C to generate the dihydride catalytic intermediate trans-[Ru((R)-BINAP)(H)2((R,R)-dpen)] (3'). Addition of 1 equiv of ((CH3)3Si)2NK to the alkoxide 4 produces the amide catalytic intermediate 5. Compound 5 reacts reversibly with H2 to generate 3'.     

Construction of monomeric and polymeric porphyrin compartments by a Pd(II)-pyridine interaction and their chiral twisting by a BINAP ligand

The construction of chirally twisted porphyrin-based molecular capsule 6 and polymeric capsule 8 was investigated by means of scanning electron microscopy (SEM) and (1)H NMR, UV-visible, and CD spectroscopic observations. Molecular capsule 6 and polymeric capsule 8 were constructed by the reaction of chiral cis-Pd(II) complex 4 bearing a (R)-(+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) ligand with porphyrin 1 bearing four pyridyl groups and porphyrin 2 bearing eight pyridyl groups, respectively. The peak-splitting pattern of the beta-pyrrole protons in the (1)H NMR spectrum and the specific CD spectral pattern bearing an exciton coupling band indicate that both molecular capsule 6 and polymeric capsule 8 are chirally twisted. Moreover, it was found that the CD intensity of the polymeric capsule plotted against [4]/([4] + [3]) shows a sigmoidal curvature, reflecting a unique cooperativity among the ligand groups; that is, the ligand existing in excess over the other dominates the twisting direction. These results consistently demonstrate that "chirality" in these molecular assembly systems is conveniently controlled by the use of chiral ligands.     

Asymmetric synthesis of 5-arylcyclohexenones by rhodium(I)-catalyzed conjugate arylation of racemic 5-(trimethylsilyl)cyclohexenone with arylboronic acids

[reaction: see text] A catalytic asymmetric conjugate arylation of racemic 5-(trimethylsilyl)cyclohex-2-enone with arylboronic acids was catalyzed by 3 mol % chiral amidophosphane- or BINAP-Rh(I) in dioxane-water (10:1) to afford trans- and cis-3-aryl-5-(trimethylsilyl)cyclohexanones in high enantioselectivity. Dehydrosilylation of the product mixture with cupric chloride in DMF gave 5-arylcyclohex-2-enones with up to 93% ee in good yield. Enantiofacial selectivity with chiral phosphane-Rh(I) exceeds the trans-diastereoselectivity that is maintained in the achiral or racemic phosphane-Rh(I)-catalyzed conjugate arylation of 5-(trimethylsilyl)cyclohexenone.     

Facile preparation of a new BINAP-based building block, 5,5'-diiodoBINAP, and its synthetic application

[reaction: see text] Bis(pyridine)iodonium tetrafluoroborate was successfully used for regioselective iodination of BINAP dioxide to give 5,5'-diiodoBINAP dioxide in an excellent yield of 92%, with no observed formation of 4,4'-diiodoBINAP dioxide. A Sonogashira cross-coupling reaction with 5,5'-diiodoBINAP dioxide gave the desired bis(trimethylsilylethynyl) product in 86% yield. The resulting 5,5'-disubstituted BINAP dioxides were reduced to the corresponding phosphines, which were used as chiral ligands for rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid to 2-cyclohexenone to give 3-phenylcyclohexanone in excellent yield with high enantioselectivity.