Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 68 , Issue 5
Showing 1-32 articles out of 32 articles from the selected issue
  • Hiroshi Sugimoto, Takuzo Aida, Shohei Inoue
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1239-1246
    Published: 1995
    Released: July 06, 2006
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    The living polymerization of methacrylic esters initiated with aluminium porphyrins was found to be dramatically accelerated upon the addition of organoaluminium or organoboron compounds as a Lewis acidic monomer activator (high-speed living polymerization). Under appropriate conditions, high-molecular-weight poly(methyl methacrylates) (Mn > 500000) having a narrow molecular-weight distribution (Mw/Mn = 1.1—1.2) were synthesized. The key concept of the high-speed living polymerization is the coexistence of nucleophilic growing species and a Lewis acid without a degradative direct reaction.
  • Hisao Nishiyama, Yoshiki Itoh, Yuji Sugawara, Hideki Matsumoto, Katsuy ...
    1995 Volume 68 Issue 5 Pages 1247-1262
    Published: 1995
    Released: July 06, 2006
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    A chiral ruthenium(II)–bis(2-oxazolin-2-yl)pyridine catalyst prepared in situ from optically active bis(2-oxazolin-2-yl)pyridine (Pybox-ip) (2) and [RuCl2(p-cymene)]2 (1) exhibited efficient activity for the asymmetric cyclopropanation (ACP) of styrene and several diazoacetates to give the corresponding trans- and cis-2-phenylcyclopropane-1-carboxylates (3 and 4) in good yields (66—87%). A mixture of 1 and 2 in an atmosphere of ethylene produced the trans-RuCl2(Pybox-ip)(ethylene) complex (5), which also proved to be a powerful catalyst for ACP. The stereoselectivity of the trans- and cis-cyclopropanes were from 90 : 10 up to 98 : 2, and their enantioselectivities reached 97%. A catalytic system with 5 could be used for several olefins and internal olefins. A concerted mechanism of ACP with the Ru–Pybox catalyst was postulated on the basis of the stereospecificity with deuterated styrene. Other substituents, such as ethyl, s-butyl, benzyl, and phenyl on the oxazoline rings of Pybox in place of the isopropyl group were also examined, and were found to exhibit a similar high trans-stereoselection and a high enantioselectivity of the cyclopropane products; ex. with Ru–Pybox-ethyl 91 : 9 of 3 : 4 and 82% ee for 3. The non-chiral Ru–Pybox-dihydro catalyst exhibited asymmetric induction with 39% ees of 3 with d- and l-menthyl diazoacetates, and kept a high trans- and cis-stereoselection of 97 : 3.
  • Akira Yanagisawa, Hiroaki Hibino, Shigeki Habaue, Yoshiyuki Hisada, Ka ...
    1995 Volume 68 Issue 5 Pages 1263-1268
    Published: 1995
    Released: July 06, 2006
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    The highly α,α′ selective and stereocontrolled homocoupling reaction of allylic halides was achieved using barium reagent. The double-bond geometry of the starting allylic chloride was completely retained. The α,α′ cross-coupling products were also prepared stereospecifically and regioselectively by this method.
  • Debajyoti Bhattacharjee, Anusree Ghosh (Purkayastha), T. N. Misra
    1995 Volume 68 Issue 5 Pages 1269-1273
    Published: 1995
    Released: July 06, 2006
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    The Raman band of the C=O stretching vibration of benzaldehyde has been recorded as a function of the concentration in a number of solvents. The experimental results suggest that dispersion forces are responsible for the observed frequency shift. The variation in the band-shape parameters have been interpreted using microviscosity theory.
  • Satoshi Suzuki, Naoaki Tokou, Toshiaki Mabuchi, Tsuyoshi Nakajima, Jui ...
    1995 Volume 68 Issue 5 Pages 1275-1279
    Published: 1995
    Released: July 06, 2006
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    The method of liquid phase deposition (LPD) is a wet process forming hard and transparent silica thin films on glass surfaces and has interesting features, such as some organic molecules can be directly doped inside silica phases. The pH indicator dyes methyl yellow and methyl orange were doped in silica thin films by the LPD method and the absorption spectra of the samples were observed. The comparison with the corresponding spectra of the pH indicator dyes in pH-controlled buffer solutions leads to the conclusion that the doped organic dye molecules in the LPD silica solid phase are in an acidic environment equivalent to pH = 3.7. The acidity of the interior of LPD silica is high compared with surface acidity of other silicas such as silica gel. The origin of the high acidity of LPD silica has been attributed to the existence of Si–F bonds inducing an electron-attracting tendency.
  • Hitoe Iki, Kayako Hori
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1281-1288
    Published: 1995
    Released: July 06, 2006
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    Single crystal X-ray analysis has been done for two isomeric series, 4-cyanophenyl 4-n-alkoxybenzoates (CPnOB, n = 6, 7, and 8) with a phase sequence of crystal–nematic–isotropic and 4-n-alkoxyphenyl 4-cyanobenzoates (nOPCB, n = 6, 7, and 8), which have the smectic A phase as well as the nematic phase for n = 7 and 8. In the crystals of CP6OB and CP8OB, close arrangements between CN groups of a pair of molecules are observed, though in the latter crystal two carbonyloxy groups between another pair of molecules are also closely arranged. For CP7OB and 6OPCB, CN and carbonyloxy groups come close to each other between a pair of molecules. These pairs of molecules have half-and-half overlappings (imbricate structures), being closely related to the nematic structure. On the other hand, the crystal of 7OPCB has a distinct smectic-like layer structure with infinite networks of close arrangement of the CN groups, while in the crystal of 8OPCB dimers formed by association of the CN and carbonyloxy groups are arranged in an alternate stacking of core moieties and chains, also closely related to a smectic-like layer structure. The different features of the two series are discussed in terms of the different magnitudes of the overall dipole moments along the molecular long axes caused by opposite directions of the carbonyloxy groups between the two series.
  • Kô Takehara, Hiroyuki Takemura
    1995 Volume 68 Issue 5 Pages 1289-1296
    Published: 1995
    Released: July 06, 2006
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    Self-assembled monolayers of 11-mercapto-1-undecanol (MUO), 11-mercaptoundecanoic acid (MUA), and 11-amino-1-undecanethiol (AUT) were formed on a gold disk electrode. The effects of the terminal charges of these monolayers on the redox responses of 1,1′ -ferrocenedimethanol (FcDM), (ferrocenylmethyl)trimethylammoniun bromide (FcMA) and ammonium ferrocenesulfonate (FcSA) were evaluated by using voltammetric (CV) techniques. The CV responses of FcDM and FcMA decreased in the order of MUA/Au (MUA modified gold electrode), MUO/Au, and AUT/Au. In contrast, the CV response of FcSA increased in the order of MUA/Au, MUO/Au, and AUT/Au. From these results, the effects of the terminal charges on the CV responses were measured in relation to the diffuse layer potential and the electrostatic interaction between the terminal unit and redox species.
  • Toshiyuki Momma, Shin-ichi Komaba, Tetsuya Osaka, Sadako Nakamura, Yos ...
    1995 Volume 68 Issue 5 Pages 1297-1304
    Published: 1995
    Released: July 06, 2006
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    Polypyrrole (PPy)/polyanion composite films were formed electrochemically in coexistence with a polymer electrolyte (poly(sodium 4-styrenesulfonate) (PSS) or poly(acrylic acid) (PAA)) in the polymerizing solution. The potential response behaviors of the PPy/PSS and PPy/PAA composites to cation activities were investigated, and the PPy/PSS electrode showed a better Nernstian response than that of the PPy/PAA electrode. The selection of incorporated polyanions and the polymerizing conditions, which were determined in this paper, affected the response behavior. The resultant PPy/PSS electrode showed a good Nernstian response only to monovalent cations with 58 mV/decade. The electrode indicated the equilibrium potential in a few seconds at the change of cation activity. It was found that the potential response was influenced by both the electroactivity of PPy and the PSS content in the PPy matrix.
  • Midori Goto, Yoshimitsu Yamazaki, Kazumasa Honda, Atsushi Masaki
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1305-1308
    Published: 1995
    Released: July 06, 2006
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    (−)-1-[4-(Nitrophenylthio)ethyl]ferrocene, (+)-1-[4-(nitrophenyl)thioethyl]ruthenocene, and (+)-1-[4-(nitrophenylthio)ethyl]osmocene all have the absolute configuration of R. These compounds were prepared by substitution of (R)-(−)-1-(hydroxyethyl)ferrocene, -ruthenocene, and -osmocene with 4-nitrobenzenethiol, showing that the substitution proceeded with retention of configuration.
  • Yasuyuki Takeda, Atsuhiro Kawarabayashi, Keiko Takahashi, Yoshihiro Ku ...
    1995 Volume 68 Issue 5 Pages 1309-1314
    Published: 1995
    Released: July 06, 2006
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    For the determination of the actual overall extraction equilibrium constant (Kex) and the ion-pair formation constant (KMLA) in water of a crown ether–metal salt 1 : 1 : 1 complex, a more completed method is established by considering the concentration of the resulting 1 : 1 : 1 crown ether complex and ion-pair formation between the uncomplexed metal ion and the anion in the aqueous phase. The theoretical predictions were verified experimentally by solvent extraction with benzo-18-crown-6 (B18C6), alkali metal (Na, K, Rb) picrates, and various diluents of low dielectric constant. The actual log KMLA values in water at 25 °C of the 1 : 1 : 1 B18C6-alkali metal picrate complexes are 1.54 ± 0.16 for Na, 3.30 ± 0.20 for K, and 3.11 ± 0.24 for Rb. The distribution constants of the 1 : 1 : 1 B18C6 complexes were calculated from the partition constants of B18C6, the formation constants in water of the B18C6-alkali metal-ion complexes, and the actual Kex and KMLA values obtained in this study. The distribution behavior of the 1 : 1 : 1 B18C6 complexes is explained based on regular solution theory. The molar volumes and solubility parameters of the complexes were determined. Moreover, the fundamental equilibria which govern the highest extraction selectivity of B18C6 for K+among the alkali metal ions were completely elucidated.
  • Natsuo Ishiwata, Hisao Murai, Keiji Kuwata
    1995 Volume 68 Issue 5 Pages 1315-1322
    Published: 1995
    Released: July 06, 2006
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    The CIDEP (chemically induced dynamic electron polarization) spectra of quasi-stable radical pairs formed in the laser flash photolysis of xanthone and several phenol derivatives in SDS (sodium dodecyl sulfate) micellar solutions were studied. In consideration of the spectral patterns of CIDEP and the results of the magnetic-field effects on the reaction, it is concluded that the steric bulkiness of phenol derivatives obstructs the free diffusion of the reactants and the intermediate radical pairs in the micelle. The dependence of the number and position of the t-butyl substituents upon the kinetic parameters and the interaction as the radical pairs in the micellar environment are presented.
  • Kikujiro Ishii, Masako Nukaga, Yukinobu Hibino, Shohgo Hagiwara, Hidey ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1323-1330
    Published: 1995
    Released: July 06, 2006
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    Structural relaxation in amorphous tetracosane n-C24H50 was studied by infrared and Raman spectroscopies. Samples were prepared by vacuum deposition onto cold substrates and the spectral changes were monitored as the temperature was raised stepwise. Several distinguishable relaxation processes were found to take place similarly to the case of amorphous states of other hydrocarbons. However, in contrast to the previous study, we arrived at a conclusion that the initial relaxation of the disordered molecules does not take place in a single step. In the later part of the relaxation, metastable orthorhombic-type subcells were found to appear. They disappear finally when the adjustment of the mutual position of extended molecules occurs to attain the lateral molecular packing of the stable triclinic crystal. The intermolecular interactions along the chain direction are also discussed.
  • Takashi Yokoyama, Tohru Masuo, Haruo Akashi, Michio Zenki
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1331-1336
    Published: 1995
    Released: July 06, 2006
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    The structures of both 2-perimidinylammonium ethyl sulfate (PDAEtSO4) and 2-perimidinylammonium bromide (PDABr) were determined by single-crystal X-ray diffractometry. PDAEtSO4 crystallized in the monoclinic system, space group P21/c, with a = 7.229(2), b = 8.329(1), c = 22.404(1) Å, β = 91.94(1)°, V = 1348.1(3) Å3, Z = 4. PDABr crystallized in the orthorhombic system, space group Pbca with a = 15.441(1), b = 23.877(1), c = 7.468(1) Å, V = 2754.9(4) Å3, Z = 8. The dimer of PDA was observed in both of the crystals. Also, four hydrogen bonds between the PDA ions and the ethyl sulfate ions for PDAEtSO4 were observed. The ions pack in the crystal held together by the dimer of PDA and strong hydrogen bonds between the oxygen atoms of the ethyl sulfate ion and the hydrogen atoms of the amino groups of the PDA ions. The results are discussed along with giving a reason why PDA is an excellent precipitant for the sulfate ion.
  • Masayasu Iida, Yuri Mizuno, Norio Koine
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1337-1344
    Published: 1995
    Released: July 06, 2006
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    Formation of diastereomers of Δ- and Λ-[Co(en)3]3+ was investigated in aqueous chiral-electrolyte solutions using 59Co NMR spectroscopy. The chiral electrolytes used were alkali salts for L- and D-tartrates, bis(μ-(−)589-tartrato)diantimonate(III), N-dodecanoyl-L-(and D-)alaninate, N-dodecanoyl-L-threoninate, and N-hexadecanoyl-L-prolinate. The 59Co NMR parameters for the [Co(en)3]3+ group were different between the enantiomers in most cases. The NMR parameters used for chiral discrimination were chemical shifts (in simple electrolyte and micellar solutions), relaxation rates (in simple electrolyte and micellar solutions), peak areas (in micellar solutions), and quadrupole splittings (in liquid crystalline solutions). The larger values of the relaxation rates suggest stronger interactions. On the other hand, the magnitude of the chemical shift change was not simply related to the extent of the interactions. For a chemical shift, the contribution of a geometrical factor seems to be dominant in systems having local anisotropy in the interaction.
  • Shinji Toyota, Michinori Oki
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1345-1351
    Published: 1995
    Released: July 06, 2006
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    Kinetic parameters for the sulfur inversion in various gold chloride complexes of alkyl benzyl sulfides were measured by the dynamic NMR method in order to obtain conclusive evidence for the inversion mechanism. A feature of kinetic data is that entropies of activation are nearly zero both in the gold(III) and gold(I) complexes, this suggesting that the sulfur inversion takes place via pyramidal inversion mechanism without breakage of the Au–S coordination bonds but not the dissociative mechanism. The negligible solvent effect on the inversion rates in the gold(III) and gold(I) complexes supports this mechanism as well. The barrier to sulfur inversion is higher by 2.9 kcal mol−1 in the gold(III) complexes than in the corresponding gold(I) complexes. The formal gold(II) complex exists as 1 : 1 mixture of gold(I) and gold(III) complexes in solution, each of them showing the dynamic behavior independently. The effect of oxidation state of the central gold atom on the sulfur inversion is discussed on the basis of MO calculation.
  • Takumi Konno, Jinsai Hidaka, Ken-ichi Okamoto
    1995 Volume 68 Issue 5 Pages 1353-1359
    Published: 1995
    Released: July 06, 2006
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    The reaction of [CoCl2(en)2]+ with [Ni(aet)2] in water gave an S-bridged CoIIINiIICoIII trinuclear complex, [Ni{Co(aet)2(en)}2]4+ (1), which indicates that the bidentate-N,S ligand aet transfers from the NiII to the CoIII coordination sphere. 1 formed only the racemic compound of Δ(C2-cis(S))Δ(C2-cis(S)) and Λ(C2-cis(S))Λ(C2-cis(S)) isomers, and its crystal structure was analyzed by X-ray diffraction. [Ni{Co(aet)2(en)}2]Cl4·6H2O, chemical formula C12H52N8O6S4Cl4Co2Ni, crystallizes in the monoclinic space group C2/c with a = 14.987(4), b = 19.480(3), c = 12.916(4) Å, β = 113.67(1)°, V = 3454(1) Å3, Z = 4, and R = 0.046. The central NiII atom is situated in an environment markedly distorted from a square-planar to a tetrahedral geometry, coordinated by four thiolato sulfur atoms from two octahedral C2-cis(S)-[Co(aet)2(en)]+ units. The H2O2 oxidation of 1 caused the cleavage of the Ni–S bonds to afford the mononuclear sulfinato complex, [Co(NH2CH2CH2SO2-N,S)2(en)]+ (2), retaining the C2-cis(S) geometry of 1. 1 and 2 were optically resolved and their absorption, CD, and NMR spectral behavior are reported.
  • Giancarlo Verardo, Angelo G. Giumanini, Fausto Gorassini, Paolo Strazz ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1361-1367
    Published: 1995
    Released: July 06, 2006
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    The title compounds were promptly obtained in fair to good yields as distillable liquids by admixing 1,3,5-triarylhexahydro-1,3,5-triazines (1) with n-butyl nitrite (2) in anhydrous CH2Cl2 and were fully characterized by 1H and 13C NMR, IR, and MS. The pure products were invariably made up of geometric isomers which did not interconvert rapidly at room temperature. o-Substituents could cause difficulties in the free rotations of the aryl substituent about the C–N bond as well of the α-butoxymethyl group. The reaction is believed to occur on the monomeric imines derived from the thermal equilibration of their trimeric and dimeric precursors. Aliphatic hexahydrotriazines were found to be unreactive under the present conditions.
  • Yutaka Nakamura, Miki Hirai, Kenji Tamotsu, Yasuchika Yonezawa, Chung- ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1369-1377
    Published: 1995
    Released: July 06, 2006
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    Syntheses of all of the diastereomers of 2,3-diaminobutanoic acids, found in some peptide antibiotics and toxins, were accomplished. The four isomers were derived mainly through two pathways including SN2 inversions of the β-substituent of L- or D-threonine derivatives. The various protecting groups and effective nucleophiles for the SN2 inversion were examined.
  • Toshihiro Kumazawa, Kazuhito Ohki, Mitsuo Ishida, Shingo Sato, Jun-ich ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1379-1384
    Published: 1995
    Released: July 06, 2006
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    The C-glycosylation of 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl fluoride and 2-acetylphloroglucinol 3,5-bis(alkyl ether) in the presence of boron trifluoride etherate as an activator stereoselectively gave the β-C-glucoside in a good yield via OC glycoside rearrangement. Subsequently, aldol condensation of the C-glucoside with benzaldehyde afforded the corresponding β-C-glucosyl chalcone in a good yield.
  • Hideo Tanaka, Masatoshi Taniguchi, Yutaka Kameyama, Marc Monnin, Siger ...
    1995 Volume 68 Issue 5 Pages 1385-1391
    Published: 1995
    Released: July 06, 2006
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    A novel access to 3-hydroxycephems was attained from penicillin G via the C=C bond cleavage of 1-(1-alkoxycarbonyl-2-chloromethyl-2-propenyl)-4-(phenylsulfonylthio)-2-azetidinones by successive treatment with RuCl3/HIO4 and HIO4/CuSO4 and reductive cyclization of 1-(1-alkoxycarbonyl-3-chloro-2-hydroxy-1-propenyl)-4-(phenylsulfonylthio)-2-azetidinones on treatment with a newly devised BiCl3/Sn or TiCl4/Sn bimetal redox couple in DMF containing pyridine.
  • Hirofumi Nakano, Toshikazu Ibata
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1393-1400
    Published: 1995
    Released: July 06, 2006
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    The reaction of allyl α-diazoacetates with di-t-butylthioketene catalyzed by Rh2(OAc)4 gave 4-allyl-2-methylene-1,3-oxathiolan-5-ones through the 1,5-cyclization of a thiocarbonyl ylide intermediate followed by Claisen rearrangement with allene episulfide through the 1,3-cyclization of the intermediate. Other alkenyl and alkynyl diazoacetates also gave similar products through the thiocarbonyl ylide without affording its intramolecular 1,3-dipolar cycloadduct.
  • Kazuhiro Kobayashi, Masataka Kawakita, Kouichi Yokota, Tohru Mannami, ...
    1995 Volume 68 Issue 5 Pages 1401-1407
    Published: 1995
    Released: July 06, 2006
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    The reactions of sulfoxides with magnesium amides generated in situ from the reaction of ethylmagnesium bromide and secondary amines, such as diisopropylamine (DIPA) or 2,2,6,6-tetramethylpiperidine (TMP) in diethyl ether, were examined. Diaryl sulfoxides were heated with the diisopropylaminomagnesium reagent in diethyl ether to give the corresponding diaryl sulfides in 42—52% yields. Sulfoxides bearing hydrogens at the α-positon only (RSOCH2R1) reacted with the tetramethylpiperidinomagnesium reagent at room temperature to produce the corresponding dithioacetals (RSCHR1SR) in 47—86% yields. The treatment of sulfoxides bearing hydrogens both at the α- and β-positions (RSOCHR1CHR2R3) with the magnesium amides at room temperature afforded the corresponding vinyl sulfides (RSCR1=CR2R3) in 52—72% yields accompanying 2.3—27% yields of the corresponding dithioacetals. The pathways leading to the products involving the formation of the sulfur-stabilized carbonium ion intermediates are discussed.
  • Shunji Ito, Noboru Morita, Toyonobu Asao
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1409-1436
    Published: 1995
    Released: July 06, 2006
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    A series of azulene analogues of triphenylmethyl cation (tri(1-azulenyl)methyl, di(1-azulenyl)phenylmethyl, and (1-azulenyl)diphenylmethyl hexafluorophosphates) were synthesized by hydride abstraction from the corresponding methane derivatives with DDQ. In order to examine the effect of substituents on the cations, and to enhance their stabilities, a series of cations bearing 3-methyl, 3-methoxycarbonyl, 3,6-di-t-butyl, 6-t-butyl, or 3-t-butyl groups on each of the azulene rings were also synthesized. Their pKR+ values showed that the stabilities of these cations dramatically increase with the number of azulene rings. Tris(3,6-di-t-butyl-1-azulenyl)methyl cation showed the highest pKR+ value (14.3) ever observed. The high stabilities of these cations were attributed to a large conjugative effect between the central cation and the azulene ring(s). The dynamic stereochemistry of these cations was also studied based on the temperature-dependent 1H NMR spectra, which were analyzed by a flip mechanism. Low-temperature NMR studies indicated that tri(1-azulenyl)methyl cations exist in two types of propeller conformations (symmetrical and unsymmetrical propellers, which have C3 (A) and C1(B) symmetries, respectively), and at higher temperature the NMR reflect the rapid isomerization. The lower activation energy of the process B (or A), compared with that of B, indicates that the threshold rotation mechanism for the cation is a one-ring flip. This is the first example of a molecular propeller with a threshold rotation mechanism comprising a one-ring flip.
  • Soichiro Watanabe, Takayuki Kawashima, Norihiro Tokitoh, Renji Okazaki
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1437-1448
    Published: 1995
    Released: July 06, 2006
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    Sterically congested thiiranes having a 2,4,6-tri-t-butylphenyl group were synthesized by the reactions of (2,4,6-tri-t-butyl)thiobenzaldehyde with sterically hindered diazo compounds. Thermal desulfurization of the most congested thiirane, 2,2-di-t-butyl-3-(2,4,6-tri-t-butylphenyl)thiirane (15c), did not proceed even upon using highly reactive reagents, such as hexamethylphosphorous triamide or organolithiums. The photo-reaction of 15c did not give the corresponding styrene, but afforded several products containing 2,4,6-tri-t-butylbenzo[b]thiophene and Dewar benzenes, 2,2-di-t-butyl-3-(3,4,6-tri-t-butylbicyclo[2.2.0]hexa-2,5-dien-2-yl)thiirane and 2-t-butyl-3,3-dimethyl-1-(1,3,5-tri-t-butylbicyclo[2.2.0]hexa-2,5-diene-2-yl)-1-butene (24), the latter of which is the first example for a vinyl-substituted Dewar benzene. Compound 24 has a unique reactivity, giving a rearrangement product, 2-t-butyl-3,3-dimethyl-1-(1,3,5-tri-t-butylbicyclo[2.2.0]hexa-2,5-diene-2-yl)-1-butene on thermolysis.
  • Eisuke Kaji, Eiko Matsui, Mie Kobayashi, Shonosuke Zen
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1449-1454
    Published: 1995
    Released: July 06, 2006
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    A practical stereoselective synthesis is described for α-D-ManNAc-(1→4)-α-D-Glc-(1→2)-L-Rha, an anomerically modified trisaccharide component of the capsular polysaccharide of Streptococcus pneumoniae type 19F. The key intermediary disaccharide, 2-(benzoyloxyimino)-2-deoxyglycosyl-α(1→4)-glucoside, was prepared by α-selective glycosylation (AgOTf–TMU/CH2Cl2, 90%) of a suitably blocked p-methoxybenzyl 2,3,6-tri-O-benzyl-β-D-glucopyranoside with 3,4,6-tri-O-benzoyl-2-(benzoyloxyimino)-2-deoxy-α-D-arabino-hexopyranosyl bromide, and converted into an α-D-ManNAc-(1→4)-α-D-Glc-(1→MBn) derivative by means of a manno-selective reduction (BH3·THF → Ac2O, 55%). Consecutive anomeric activation (1-OMBn → 1-OH → 1-F, 45% over 2 steps), glycosylation (SnCl2–AgClO4/CH2Cl2, 71%, α : β = 2 : 1) of 2-OH of benzyl 3,4-di-O-benzyl-α-L-rhamnopyranoside, and deblocking (NaOMe → Pd-C/H2, 90%) gave the target trisaccharide.
  • Takushi Nagata, Kiyomi Imagawa, Tohru Yamada, Teruaki Mukaiyama
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1455-1465
    Published: 1995
    Released: July 06, 2006
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    A novel manganese(III) complex having an optically active N,N′-bis(3-oxobutylidene)diamine ligand with bulky substituents was prepared and characterized crystallographically. In the presence of a catalytic amount of the manganese(III) complex, unfunctionalized olefins were oxygenated to give optically active epoxides with molecular oxygen by the combined use of several aliphatic aldehydes. Cyclic and acyclic cis-β-substituted styrene derivatives, conjugated dienes, and enynes were converted into the corresponding epoxides with moderate-to-good enantioselectivities. The present aerobic and enantioselective epoxidation proceeded with the opposite enantioface selection from those obtained by using terminal oxidants, such as sodium hypochlorite and iodosylbenzene. The key intermediate of the aerobic asymmetric epoxidation is also discussed.
  • Yoo Tanabe, Hitomi Okumura, Masaki Nagaosa, Masanari Murakami
    1995 Volume 68 Issue 5 Pages 1467-1472
    Published: 1995
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    The cyclo-condensation of silyl 2-mercaptoalkanoates and arylmethyleneamines proceeded with high stereoselectivity to give alternatively both the cis- and trans-2,5-disubstituted 4-thiazolidinones, some of which are known as anti-platelet activating factor-active drugs. The use of the piperidine catalyst and no catalyst showed very high cis-stereoselectivity (cis/trans = 10/1—50/1) during the reaction. On the other hand, the trans-selective reaction was promoted by Ti(O-i-Bu)4 and Al(O-s-Bu)3 catalysts (cis/trans = 1/8—1/25). Both reactions were conducted with higher cis- and trans-selectivities as compared with those of the alkyl 2-mercaptoalkanoates under mild conditions. The cyclo-condensation using trimethylsilyl 2-(trimethylsilylthio)propionate and methyl 2-(trialkylsilylthio)propionates proceeded by the action of a catalytic amount (0.02 molar amount) of tetrabutylammonium fluoride with moderate cis-selectivity.
  • Akikazu Kakehi, Suketaka Ito, Shuichi Fujita
    1995 Volume 68 Issue 5 Pages 1473-1483
    Published: 1995
    Released: July 06, 2006
    JOURNALS RESTRICTED ACCESS
    The title compounds, dimethyl 6-thia-3-azatricyclo[5.3.1.03,8]undeca-4,9-diene-7,11-dicarboxylates, were smoothly prepared in variable yields by the reactions of some (1-pyridinio)thiocarbonylmethylides with dimethyl acetylenedicarboxylate (DMAD) in chloroform, including various alcohols at room temperature. The mechanistic consideration for these reactions clarified the intervention of primary 1 : 1 zwitterionic intermediates between the ylides and DMAD, which were previously proposed by us, and their traps by alcohol molecules. Some of these dimethyl 6-thia-3-azatricyclo[5.3.1.03,8]undeca-4,9-diene-7,11-dicarboxylates were hydrolyzed by hydrochloric acid to afford dimethyl 7-formyl-4a,5,8,8a-tetrahydro-4H-benzo-1,4-thiazine-8,8a-dicarboxylates or tetramethyl 2,2′-oxydi(6-thia-3-azatricyclo[5.3.1.03,8]undeca-4,9-dien-7,11-dicarboxylate)s.
  • Michinori Oki, Yasushi Taguchi, Tsutomu Miyasaka, Mika Kitano, Shinji ...
    1995 Volume 68 Issue 5 Pages 1485-1496
    Published: 1995
    Released: July 06, 2006
    JOURNALS RESTRICTED ACCESS
    The title amine rotamers were prepared from the corresponding carboxylic acids and were diazotized with isopentyl nitrite in the presence of acetic acid in benzene. The ap rotamer affords, as main products, olefins that are derived by deprotonation after rearrangement of the intervening carbocation and small amounts each of the corresponding acetate and a cyclized product, both of which are derived from the unrearranged cation. By contrast, the olefins are minor products and a cyclized product, which is formally derived by insertion of the intervening cation to a C–H bond of the 1-methyl group before rearrangement, is main in the case of the sc isomer. This cyclic product was synthesized independently. The yield of the corresponding acetate is increased to a considerable extent in the case of the sc relative to the ap. These results in the reaction of the sc are discussed in terms of stabilization of the intervening cation by the C–H bond.
  • Yasufumi Dan-oh, Hirokazu Matta, Junko Uemura, Hisayuki Watanabe, Kenj ...
    1995 Volume 68 Issue 5 Pages 1497-1507
    Published: 1995
    Released: July 06, 2006
    JOURNALS RESTRICTED ACCESS
    N-Aryltrifluoroacetimidoyl radicals have been generated by three different methods: the tin-radical promoted deiodination and photochemical homolysis of imidoyl iodides and the thermal homolysis of imidoyl azo-compounds. N-[2-(1-alkynyl)phenyl]trifluoroacetimidoyl iodides have been converted to trifluoromethylated indoles by the tin-radical promoted homolysis of the carbon–iodine bond followed by intramolecular cyclization. The photolysis of trifluoroacetimidoyl iodides enabled both intra- and intermolecular cyclization to indoles and quinolines. Likewise, thermal reactions of N-(2,2,2-trifluoro-1-tritylazoethylidene)anilines provided trifluoromethylated quinolines and indoles.
  • Shigeo Niihata, Takashi Ebata, Hiroshi Kawakami, Hajime Matsushita
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 5 Pages 1509-1512
    Published: 1995
    Released: July 06, 2006
    JOURNALS RESTRICTED ACCESS
    2,3-Dideoxy-2-fluoro-D-erythro-pentofuranose was easily prepared from 3-DPA lactone. The condensation reaction between 1-O-acetyl derivative of this sugar and silylated thymine in the presence of TMSOTf proceeded in a poorly stereoselective manner.
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