bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Family of Dinuclear Vanadium(V) Complexes Containing the {OV(μ-O)VO}4+ Core: Syntheses, Structures, and Properties
Authors: Sangeetha Nimma Rajaiah , Pal Samudranil 
Published: September 2002

Abstract
Dark-brown complexes of {OV(μ-O)VO}4+ with the general formula [(VOL)2O] were isolated from reactions of bis(acetylacetonato)oxovanadium(IV) and aroylhydrazones of salicylaldehyde or of 5-methoxysalicylaldehyde (H2L, two H stand for the dissociable protons at the phenol and the amide functionalities) in acetonitrile. The infrared spectra of these complexes are consistent with the dianionic form of the ligands. The electronic spectral profiles are very similar and display strong absorptions in the range 425—263 nm due to ligand-to-metal charge transfer and intraligand transitions. The proton NMR spectra suggest that in solution the two ligands in each complex are magnetically equivalent. The complexes are redox active and display a reduction response in the potential range -0.28—0.47 V (vs. Ag/AgCl). The molecular structures of the complexes were determined by X-ray crystallography. The deprotonated dianionic planar ligands coordinate the metal ions through the phenolate-O, the imine-N, and the amide-O atoms forming a six-membered and a five-membered chelate ring. The metal ions in each complex are essentially in a square-pyramidal O4N coordination sphere. The O, N, O-donor ligand and the bridging oxygen atom constitute the square plane and the oxo group occupies the apical position. The metal center is displaced from the basal plane towards the apical oxo group by 0.44—0.57 Å. The V-O-V bridge angles in the complexes are very similar and within the range 112.86(13) to 115.89(12)°.
Observation of Molecular Alignments and Dimer Formation of Bis(5-alkylsalicylidene)ethylenediaminatonickel(II) in a Monolayer
Authors: Fujii Takashi , Miyamura Kazuo 
Published: September 2002

Abstract
A monolayer of bis(5-butylsalicylidene)ethylenediaminatonickel(II), prepared on highly oriented pyrolytic graphite by the Langmuir-Blodgett method, was observed by scanning tunnelling microscopy. The image revealed that one of the monolayers was comprised dimers of complexes, similar to that observed in the crystalline phase. The π-A isotherms of the analogues of various alkyl chain lengths were measured, and the critical area of the monolayer was found to decrease by 20% when the alkyl chain length decreased from 3 (propyl) to 2 (ethyl). This decrease of the critical area is explained by the presence of CH-π interactions between the π conjugated system of the salen moiety, and α- and γ-methylenes of the alkyl side chain.
Thermal Dehydrogenation Reacton of [N,N′-Bis(3-ethoxysalicylidene)-1,2-diphenyl-1,2-ethanediaminato]nickel(II) with [VO(salen)]NO3 in the Solid State
Authors: Hoshina Gakuse , Tsuchimoto Masanobu , Ohba Shigeru 
Published: September 2002

Abstract
A dehydrogenation reaction of the red-brown powder of [Ni(3-EtOsal-meso-stien)] (H2(3–EtOsal–meso–stien) = N,N′-bis(3-ethoxysalicylidene)-(R,S)(S,R)-1,2-diphenyl-1,2-ethanediamine) did not occur by heating solely in the air up to 210 °C. However, the reaction occurred upon heating together with [VO(salen)] (H2(salen) = N,N′-disalicylidene-1,2-ethanediamine) in the air at 190 °C, and a red powder of [Ni(3-EtOsalton)] (H2(3-EtOsalton) = N,N′-bis(3-ethoxysalicylidene)-1,2-diphenyl-1,2-ethenediamine) was obtained. The dehydrogenation reaction could also be carried out under Ar at 160 °C by mixing with [VO(salen)]NO3. These facts revealed that the oxidants in solid state dehydrogenation in air are the VV species originating from the VIV=O complex. The crystal structures of [Ni(3-EtOsal-meso-stien)]·CH3CN·H2O, (1); [Ni(3-EtOsal-rac-stien)]·0.5H2O, (2); and [Ni(3-EtOsalton)]·CH3OH·1.33H2O, (3) were determined by X-ray analyses. [Ni(3-EtOsalton)] was prepared in a dioxane solution of [Ni(3-EtOsalstien)] using DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) as an oxidant. The rac complex, [Ni(3-EtOsal-rac-stien)] (H2(3–EtOsal–rac–stien) = N,N′-bis(3-ethoxysalicylidene)-(R,R)(S,S)-1,2-diphenyl-1,2-ethanediamine), is less reactive in dehydrogenation than the meso in the solid state as well as in solution. The molecular structures in (1) and (2) indicate that the benzylic H atoms are sterically protected by phenyl groups in the rac complex, but are exposed to the oxidant in the meso complex.
A CIDEP Study on the Photosensitized Reaction of Maleimide with Xanthone: Addition Effect of Hydrochloric Acid
Authors: Ohara Keishi , Nagaoka Shin-ichi , Mukai Kazuo 
Published: September 2002

Abstract
The photosensitized reaction of maleimide (MI) with xanthone (Xn) in 2-propanol was investigated by the time-resolved EPR method. The emissive CIDEP spectrum observed in neat 2-propanol is predominantly assigned to two kinds of MI alkyl-type radicals. On the other hand, the absorptive spectrum of the MI anion radical has been newly observed in 2-propanol including hydrochloric acid. The addition effect of hydrochloric acid indicates the existence of two mechanisms for the photosensitization of MI by Xn. One is a typical triplet-triplet energy transfer followed by hydrogen abstraction by the triplet state of MI from the solvent. The other is an electron-transfer process to MI from the Xn ketyl radical produced primarily by a fast reaction of the triplet Xn with HCl. The spin-polarization transfer mechanism based on these photosensitization processes can successfully explain the present CIDEP results. The effect of water and the sensitizer dependence on the above reaction were also investigated.
A Novel-Type Mixed-Ligand Polyoxotungstolanthanoate, [Ln(BW11O39)(W5O18)]12- (Ln = Ce3+ and Eu3+)
Authors: Naruke Haruo , Yamase Toshihiro 
Published: September 2002

Abstract
Two isostructural anions, [Ln(BW11O39)(W5O18)]12- (Ln = Ce and Eu), were isolated as K+ salts from aqueous solutions containing tungstate, Ln3+, and BO33-, at pH = 7. An X-ray crystallographic analysis showed that the Ln3+ center in the anion is chelated by two kinds of tetradentate polyoxotungstate ligands, [W5O18]6- and α-[BW11O39]9- with a square antiprismatic LnO8 configuration, which are monovacant derivatives of [W6O19]2- and α-[BW12O40]5-, respectively. The anion is of approximate Cs symmetry, and the observable asymmetry of K-O bonding between two different K+ cations and the anion causes the two mirror planes within [(W5O18)Ln]3- and [(BW11O39)Ln]6- moieties to be canted to each other by 5.2° for Ln = Ce and 4.1° for Ln = Eu.
Reversibility in the Formation of Oxo(peroxo)porphyrinatomolybdenums
Authors: Fujihara Tetsuaki , Hoshiba Koji , Sasaki Yoichi , Imamura Taira 
Published: September 2002

Abstract
Reversibility in the formation reaction of a series of the oxo(peroxo)porphyrinatomolybdenums, [MoVIO(tmp)(O2)] 1, [MoVIO(tdcpp)(O2)] 2, [MoVIO(ttp)(O2)] 3, [MoVIO(tdmpp)(O2)] 4, and [MoVIO(tpp)(O2)] 5, was studied. In these dioxygen complexes with various porphyrin rings, two complexes, 2 and 4, were newly prepared by the solid-state reactions of corresponding Mo(IV) complexes with O2. All the complexes were characterized by IR, 1H NMR, and UV-vis spectroscopic measurements. In the reaction of O2 with [MoIVO(tdcpp)] 2r, which has bulky substituents with an electron-withdrawal character, the association rate constant was determined to be 1.2 × 10-2 dm3 mol-1 s-1 in toluene at 20 °C. The value of the rate constant is about one thirtieth of that for [MoIVO(tmp)] 1r, which also has bulky substituents. The result indicates that the electronic effects of the porphyrin rings, which reflect on the redox potentials of the central molybdenum ion, are important in determining kinetic and thermodynamic stability of the dioxygen complexes. All the dioxygen complexes undergo deoxygenation upon photoirradiation to give corresponding [MoIVO(por)]. The redioxygenation profiles of [MoIVO(por)] in the dark were also significantly affected by the steric bulkiness of the porphyrin ligands. While the bulky porphyrin complexes of 1 and 2 gave full recovery of the dioxygen complexes in the dark, less bulky porphyrin complexes of 3, 4, and 5 undergo some side reactions to Mo(V) species. The rate and extent of the Mo(V) complex formations increase with decreasing steric bulkiness.
Unsymmetrical Oxygenation Products of [Pd(mnt)2]2-: Syntheses and Crystal Structures of (Bu4N)2[Pd(mnt){O2S2C2(CN)2}] and One-Dimensional Coordination Polymer (Bu4N)2[AgPd(mnt) {O2S2C2(CN)2}]2 (mnt = 1,2-Dicyano-1,2-ethylenedithiolato)
Authors: Sugimoto Kunihisa , Kuroda-Sowa Takayoshi , Maekawa Masahiko , Munakata Megumu 
Published: September 2002

Abstract
Oxidation of [Pd(mnt)2]2- by H2O2 produces a sulfonyl-containing [Pd(mnt){O2S2C2(CN)2}]2- (12-). Addition of AgClO4 to 12- results in the formation of [AgPd(mnt){O2S2C2(CN)2}]22- (22-). Both compounds crystallize with a bulky cation Bu4N+ to form (Bu4N)21 and (Bu4N)22, which are characterized by single crystal X-ray analyses. 12- retains a planar structure except for the sulfonyl oxygen atoms. The electronic absorption band observed at 387 nm (sh) is assigned to d-d transition. 22- has a double-decker structure consisting of two [Pd(mnt){O2S2C2(CN)2}]2- anions bridged by two Ag(I) ions through Ag-S bonds. Two terminal CN groups in 22- coordinate to the neighboring Ag(I) ions, forming a one-dimensional chain structure. Crystallographic data are as follows. (Bu4N)21: PdS4O2N6C40H72, triclinic, P1-, a = 12.145(2), b = 10.991(3), c = 10.156(2) Å, α = 65.09(2), β = 88.93(2), γ = 84.97(2)°, Z = 1. (Bu4N)22: Ag2Pd2S8O4N10C48H72, monoclinic, P21/c, a = 9.649(2), b = 13.235(2), c = 25.107(2) Å, β = 91.03(1)°, Z = 2.
Competitive [3+2] and [4+2] Cycloaddition Reactions of 2-Furaldehyde Phenylhydrazone with Alkenes
Authors: Amarasekara Ananda S , Pathmasiri W Wimal 
Published: September 2002

Abstract
Maleimides react with 2-furaldehyde phenylhydrazone 1 at the furan ring to give 4-(phenylhydrazono)methyl-1H-isoindole-1,3(2H)-diones when equimolar mixtures are refluxed in benzene for shorter reaction times. Excess maleimides and longer reaction times give mixtures of 4-(phenylhydrazono)methyl-1H-isoindole-1,3(2H)-diones and 3-(1,3-dihydro-1,3-dioxo-4-isoindolyl)-1,6a-dihydropyrrolo[3,4-c]pyrazolo-4,6(3aH,5H)-diones resulting from [4+2] and [3+2] double-cycloaddition. Reactions of 1 with dimethyl acetylene dicarboxylate give the double-cycloaddition product dimethyl-3[4-hydroxy-2,3-bis(methoxycarbonyl)phenyl]-1-phenylpyrazole-4,5-dicarboxylate. Methyl acrylate and acrylonitrile gives only the [3+2] cycloaddition products, 3-(2-furyl)-1-phenyl-4,5-dihydropyrazole-4-carboxylic methyl ester and 3-(2-furyl)-1-phenyl-4,5-dihydropyrazole-4-carbonitrile, respectively.
Two-Step Concerted Mechanism for the Hydrocarbon Hydroxylation by Cytochrome P450
Authors: Yoshizawa Kazunari , Ohta Takehiro , Eda Masataka , Yamabe Tokio 
Published: September 2002

Abstract
A possible two-step mechanism for the hydrocarbon hydroxylation by the oxoferryl active species of cytochrome P450 is discussed. We propose that the catalytic reaction is initiated by the formation of a reactant complex involving a five-coordinate carbon species or a σ-complex, followed by concerted hydrogen and alkyl migrations which lead to the formation of a product complex involving alcohol as a ligand. The porphyrin ring is predicted from molecular mechanics and extended Hückel calculations to be significantly bent in the reactant complex and in the hydroxy intermediate to form an energetically preferred octahedral environment at the iron active center. Such bent structures for the porphyrin ring are consistent with observed cis-coordination geometries for the M(porphyrin)L2 complexes, in which M is a large transition-metal ion and L is a ligand. We suggest that possible inversion at the five-coordinate carbon species in the reactant complex can occur to lead to partial inversion of stereochemistry at a labeled carbon.
Synthesis of Dictyopterene A: Optically Active Tributylstannylcyclopropane as a Chiral Synthon
Authors: Itoh Toshiyuki , Inoue Hitomi , Emoto Sachie 
Published: September 2002

Abstract
Synthesis of (1S,2R)-1-[(E)-hex-1-en-1-yl]-2-vinylcyclopropane (dictyopterene A), which was isolated from the essential oil of algae of the genus Dictyopteris in Hawaii, has been demonstrated using optically active tributylstannylcyclopropane as a starting chiral synthon.
Synthesis of a Chiral Precursor for No-Carrier-Added (NCA) PET Tracer 6-[18F]Fluoro-L-dopa Based on Regio- and Enantioselective Alkylation of 2,4-Bis(chloromethyl)-5-iodoanisole
Authors: Kuroda Chiaki , Ochi Atsushi , Nakane Noritoshi , Umeyama Takashi , Muto Nobuko , Niimura Nami , Teramoto Yoshiki , Nogami Hiroyuki , Reddy Guvvala N 
Published: September 2002

Abstract
(2S,5S)-5-(3-Formyl-6-iodo-4-methoxybenzyl)-1-t-butoxycarbonyl-2-t-butyl-3-methyl-4-imidazolidinone (11), a chiral intermediate towards NCA PET tracer 6-[18F]fluoro-L-dopa (1), was synthesized from 3-iodoanisole in four steps. 3-Iodoanisole was first bischloromethylated to 2,4-bis(chloromethyl)-5-iodoanisole (14). Regio- and enantio-selective alkylation of 14 with (S)-1-(t-butoxycarbonyl)-2-t-butyl-3-methyl-4-imidazolidinone (12) afforded 33, which was then hydrolyzed and oxidized to the desired intermediate 11.
A Practical Synthesis of Optically Active (R)-2-Propyloctanoic Acid: Therapeutic Agent for Alzheimer's Disease
Authors: Hasegawa Tomoyuki , Yamamoto Hisashi 
Published: September 2002

Abstract
(R)-2-Propyloctanoic acid has been developed as a novel therapeutic agent for Alzheimer's disease. A large-scale synthesis of this candidate was achieved by using Oppolzer's camphorsultam as a chiral auxiliary under improved conditions. It was essential for the successful synthesis of this compound to utilize a new removal method for the chiral source with a combination of tetrabutylammonium hydroxide and hydrogen peroxide. The present process afforded the desired product in high yield with high optical purity.
The γ-Silicon Effect. IV. The Solvolysis Mechanism of 3-(Aryldimethylsilyl)propyl p-Toluenesulfonates
Authors: Nakashima Tohru , Fujiyama Ryoji , Kim Hyun-Joong , Fujio Mizue , Tsuno Yuho 
Published: September 2002

Abstract
Solvolysis rates of 3-(aryldimethylsilyl)propyl p-toluenesulfonates were determined in various solvents. The reaction mechanism of this simple γ-silyl system was clarified based on the solvent effect and the substituent effect analyses. The solvent effect on this system clearly showed the nucleophilic assistance of solvent, but failed to correlate linearly with the extended Winstein-Grunwald equation, substantiating that the reaction should not proceed through either the formation of the cation intermediate or the SN2 mechanism. This suggests that the reaction takes place in competition between γ-silyl-assisted (kSi) and solvent-assisted (ks) pathways, and that the competition ratio varies with solvents and with aryl substituents. Product analysis revealed that the former pathway gave only cyclopropane and the latter gave only the substitution products. The overall kt value could be dissected into the partial rate constants kSi and ks for the two pathways by using product ratios. The effects of aryl substituents at the γ-silyl atom on kSi pathway were correlated with unexalted σ° parameter, giving the ρ values of -1.0 in 60E and -1.32 in 97Tw, and reflecting the delocalization of incipient carbocationic charge by participation of the Si-Cγ bond. The substituent effects on the ks pathway were negligibly small; this is in line with the remote reaction center in the concerted SN2 mechanism.
Theoretical Valence Photoelectron and UV-visible Absorption Spectra of Four Stable Conductive Molecules Obtained by MO Calculations
Authors: Takaoka Kazuchiyo , Maeda Sigehiro , Miura Hidetoshi , Otsuka Takao , Endo Kazunaka , Chong Delano Pun 
Published: September 2002

Abstract
Theoretical valence photoelectron and UV-visible absorption spectra of four stable conductive molecules (N, N′-diphenyl-1,4-phenylenediamine (DPPD), p-quaterphenyl (PQP), 2, 3, 7, 8, 12, 13, 17, 18-octaethyl-21H, 23H-porphyrin (OEP), and 29H, 31H-phthalocyanine (PC)) have been obtained by semiempirical HAM/3 and ZINDO MO calculations, respectively. The Al K α photoelectron spectra were simulated using Gaussian lineshape functions of an approximate linewidth 0.10 Ek (Ek = E′k - WD), where E′k is the vertical ionization potential (VIP) of each MO and WD is a shift to account for sample work function and other energy effects, as stated in previous studies. The theoretical valence spectra of the four conductive compounds are in good accordance with the observed ones. The theoretical UV-visible absorption curves of DPPD, PQP, OEP, and PC were obtained after AM1 calculations with COSMO option to reflect solvent effects. The absorption curves as simulated with Gaussian lineshape functions of a constant linewidth of 0.003 eV. Correspond well to the observed spectra. For PC, the simulated spectrum which consists of 0.5 inner protonation (IP) and 0.5 outer protonation (OP) types for PC-ring shows much better agreement with the experimental spectrum in H2SO4 than the spectrum of either IP or OP type alone.
The Conformation of de Novo Designed Amphiphilic Peptides with Six or Nine L-2-(2,2,2-Trifluoroethyl)glycines as the Hydrophobic Amino Acid
Authors: Arai Toru , Imachi Takashi , Kato Tamaki , Nishino Norikazu 
Published: September 2002

Abstract
Amphiphilic 21-peptides with six and nine L-2-(2,2,2-trifluoroethyl)glycines as the hydrophobic amino acids and lysine and glutamic acid as the hydrophilic amino acids were synthesized. The CD spectra showed that these peptides with L-2-(2,2,2-trifluoroethyl)glycines took a random conformation in H2O. On the contrary, similar amphiphilic 21-peptides with leucine as the hydrophobic amino acids took a helical conformation in H2O. The peptides with L-2-(2,2,2-trifluoroethyl)glycines took a helical conformation in H2O containing a &gt; 20% volume of 2,2,2-trifluoroethanol. These facts suggested the hydrophobic nature of the L-trifluoroethylglycines. The peptide with six L-2-(2,2,2-trifluoroethyl)glycines took a helical structure in methanol, however it slowly changed into the β-structure within 24 h. Interestingly, the peptide with nine L-2-(2,2,2-trifluoroethyl)glycines formed a stable helix under the same conditions. The peptide with nine L-2-(2,2,2-trifluoroethyl)glycines preferred a helical structure, probably because the assembling of the Tfeg side chains was more effective in forming its helix rather than the β-structure.
Catalytic Asymmetric Addition of Dialkylzinc to 3,4-Dihydroisoquinoline N-Oxides Utilizing Tartaric Acid Ester as a Chiral Auxiliary
Authors: Ukaji Yutaka , Shimizu Yuuko , Kenmoku Yuuichi , Ahmed Alauddin , Inomata Katsuhiko 
Published: September 2002

Abstract
The catalytic asymmetric addition of dialkylzinc to a carbon-nitrogen double bond in 3,4-dihydroisoquinoline N-oxides was achieved by utilizing a catalytic amount of 2-magnesium 3-zinc salt of dicyclopentyl (R,R)-tartrate to afford (S)-1-alkyl-2-hydroxy-1,2,3,4-tetrahydroisoquinolines. In order to realize higher enantioselectivity, it was crucial to add the nitrones slowly into dialkylzinc in the presence of a catalytic amount of the 2-magnesium 3-zinc salt of (R,R)-tartrate.
Synthesis and Properties of (η3-1-Methylallyl)palladium(II) Formates as Models of Intermediates in the Palladium-Catalyzed Reductive Cleavage of Allylic Carboxylates and Carbonates with Formic Acid
Authors: Oshima Masato , Sakamoto Toshiaki , Maruyama Yooichiroh , Ozawa Fumiyuki , Shimizu Isao , Yamamoto Akio 
Published: September 2002

Abstract
In order to gain insight into the mechanism of the regioselective formation of alkenes in the palladium-catalyzed reductive cleavage of allylic carboxylates or carbonates with formic acid, two types of (η3-1-methylallyl)palladium formates (P1 and P2 types) have been prepared as simple models of catalytic intermediates. The P1 type is a neutral complex coordinated with one tertiary phosphine ligand and a formato ligand: [Pd(η3-MeCHCHCH2)(O2CH)(L)] (L = PMePh2, PMe2Ph, PMe3, P(o-tolyl)3); the P2 type is a cationic complex bearing two tertiary phosphine ligands and a formate counter anion: [Pd(η3-MeCHCHCH2)L2]+CO2H- (L = PMePh2, PMe2Ph, PMe3). The structures and dynamic behavior of the complexes in solution have been examined in detail by NMR spectroscopy. Studies on the thermolysis of the P1 and P2-type complexes have clearly provided the following mechanistic viewpoints: (1) 1-butene and 2-butene are formed from the P1 species; (2) butadiene is liberated from the P2 species; (3) the ratio of 1-butene to 2-butene increases as the bulkiness of phosphine ligand increases. A mechanism involving two geometrical isomers of [Pd(η3-MeCHCHCH2)(H)(L)], which are formed by decarboxylation of the P1-type complexes, has been proposed for the formation of butenes.
Synthesis, Chemi- and Bioluminescence Properties, and Photolysis of a Coelenterazine Analogue Having a Photoreactive Azido Group
Authors: Zheng Jing Ling , Chen Feng Qi , Hirano Takashi , Ohmiya Yoshihiro , Maki Shojiro , Niwa Haruki , Ohashi Mamoru 
Published: September 2002

Abstract
A photoreactive analogue of coelenterazine having an azido group was synthesized. The analogue showed similar chemi- and bioluminescence properties to those of the natural coelenterazine. Photolysis of the analogue in the presence of diethylamine gave a derivative azepine as the major product.
A Convenient Synthesis of Trifluoromethyl Ethers by Oxidative Desulfurization-Fluorination of Dithiocarbonates
Authors: Kanie Kiyoshi , Tanaka Yoichiro , Suzuki Kazundo , Kuroboshi Manabu , Hiyama Tamejiro 
Published: September 2002

Abstract
Trifluoromethyl ethers R-OCF3 are easily synthesized from the corresponding dithiocarbonates R-OCS2Me (R = aryl or primary alkyl) by a reagent system consisting of 70% HF/pyridine and an N-halo imide. When the reaction is applied to R-OCS2Me wherein R = secondary alkyl, tertiary alkyl, or benzylic group, fluorination leading to the corresponding alkyl fluorides R-F is achieved, whereas a combination of 50% HF/pyridine and N-bromosuccinimide affords the corresponding trifluoromethyl ethers R-OCF3 (R = secondary).
Asymmetric Hydrosilylation of Ketones Using Trans-Chelating Chiral Peralkylbisphosphine Ligands Bearing Primary Alkyl Substituents on Phosphorus Atoms
Authors: Kuwano Ryoichi , Sawamura Masaya , Shirai Junya , Takahashi Masatoshi , Ito Yoshihiko 
Published: September 2002

Abstract
Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001—0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)-secondary alcohols with up to 97% ee. The asymmetric hydrosilylation using TRAP ligands with bulkier P-substituents resulted in much lower enantioselectivities. The EtTRAP-rhodium catalyst was also effective for asymmetric hydrosilylation of keto esters with a coordination site for a rhodium atom (up to 98% ee). Optically active symmetrical diols were obtained with up to 99% ee from the corresponding diketones via the asymmetric reduction using 2.5 molar amounts of diphenylsilane.
An Efficient Method to Construct the A,B-Rings Component toward Total Syntheses of Phycocyanobilin and Its Derivative as a Photoprobe
Authors: Jayasundera Krishanthi Padmarani , Kinoshita Hideki , Inomata Katsuhiko 
Published: September 2002

Abstract
Total syntheses of phycocyanobilin and its derivative bearing a photoreactive group at the D-ring were accomplished by developing a new and efficient method for the construction of A,B-rings component, which consists of the Wittig-type new coupling reaction of 4-(1-methoxyethyl or 1-tosylethyl)-3-methyl-5-tosyl-1,5-dihydro-2H-pyrrol-2-one and a 2-formyl pyrrole derivative in the presence of nBu3P and a base, followed by reduction with aluminum amalgam and a subsequent acid or base treatment.