Diastereodifferentiating the [2+2] Photocycloaddition of Ethylene to Arylmenthyl Cyclohexenonecarboxylates: Stacking‐Driven Enhancement of the Product Diastereoselectivity That Is Correlated with the Reactant Ellipticity

Upon diastereodifferentiating the [2+2] photocycloaddition of ethylene to a series of p‐substituted (?)‐8‐phenylmenthyl cyclohexenonecarboxylates, the diastereoselectivity was critically controlled by the nature of the substituent introduced to the chiral auxiliary, and the p‐nitro‐substituted substrate afforded the cycloadducts in 90 % diastereomeric excess (de) and with 97 % isolated yield. Detailed experimental and theoretical conformation analyses revealed that the stacking interaction of the aromatic auxiliary with the cyclohexenone moiety plays the decisive role in determining the substrate conformation and is, therefore, responsible for the dramatic enhancement of the de. Of particular interest, the product de was directly related to the ellipticity of the substrate, enabling us to “predict” the de prior to photoirradiation.     

Quantization of the Geodesic Flow on Quaternion Projective Spaces

We study a problem of the geometric quantization for the quaternionprojective space. First we explain a Kähler structure on the punctured cotangent bundleof the quaternion projective space, whose Kähler form coincides withthe natural symplectic form on the cotangent bundle and show thatthe canonical line bundle of this complex structure is holomorphicallytrivial by explicitly constructing a nowhere vanishing holomorphicglobal section. Then we construct a Hilbert space consisting of acertain class of holomorphic functions on the punctured cotangentbundle by the method ofpairing polarization and incidentally we construct an operatorfrom this Hilbert space to the L ₂ space of the quaternionprojective space. Also we construct a similar operator between thesetwo Hilbert spaces through the Hopf fiberation.We prove that these operators quantizethe geodesic flow of the quaternion projective space tothe one parameter group of the unitary Fourier integral operatorsgenerated by the square root of the Laplacian plus suitable constant.Finally we remark that the Hilbert space above has the reproducing kernel.     

Photochemistry of host-guest complexes. VIII. The photoreaction of pyrazinedicarbonitrile derivatives having a crown ether moiety in the presence of an ω-diethylamino-1-alkanaminium salt

Irradiation of 5-[(benzo-18-crown-6)-4′-yl]pyrazine-2,3-dicarbonitrile and 5-(3,4-dimethoxyphenyl)pyrazine-2,3-dicarbonitrile in the presence of ω-diethylamino-l-alkanaminium ion caused the reductive decyanation to give pyrazinemonocarbonitrile derivatives. The reaction is initiated by a single electron transfer from the tertiary amino group of the diamine. The complex formation between the crown ether moiety and the ω- diethylamino-l-alkanaminium ion enhances the photoreaction.     

Nodal expansions for strongly coupled classical plasmas

The canonical equilibrium properties of classical Coulomb systems are investigated in 2 + ? dimensions for any value of the plasma parameter $\text{Λ}{}_{\mathrm{?}}\text{=}\text{e}{}^2\text{k}{}_{\mathrm{B}}\text{Tλ}{}^{\mathrm{?}}{}_{\mathrm{D}}$, through the nodal expansion of the two-particle correlation function g₂(r), wh ere e is the electronic charge, k_B the Boltzmann constant, T the absolute temperature and λ_D the Debye length. We first consider the one-component plasma (OCP) model. An attention is especially paid on the higher order bridge (non-convolution type) graphs. The long-ranged resummations of the convolution-like geometric series which build up the hypernetted chain (HNC) approximation are considered at length. The short-range resummations are also performed in view of their specific interest for evaluating the enhancement rates of nuclear reactions in Astrophysics and Fusion Physics. Next, we shall extend the classical nodal expansions to high-temperature OCP models in which the short distance interactions have to be corrected for the ? ≠ 0 diffract ion effects. A second generalization concerns the high-temperature two-component plasma(TCP) model of point charges of opposite signs at high temperatures. In both cases, the bare Coulomb interaction is modified by a temperature-dependent effective interaction which allows for an entirely classical treatment of the small quantum corrections. Finally, the equilibrium properties of the TCP are used to work out the density corrections to the hydrodynamic (Bohm) diffusion transverse to an arbitrarily strong and static magnetic field.     

Electronic structure of the valence band for perovskite-type titanium double oxides studied by XPS and DV-Xα cluster calculations

XPS spectra of the valence bands for the perovskite-type titanium double oxides BaTiO₃, SrTiO₃ and CaTiO₃ have been measured and analyzed by means of DV-Xα calculations for the TiO₆ embedded cluster model. The theoretical photoelectron spectra modulated by the photoionization cross-sections are in good agreement with experiment. The XPS results show that the O 2p valence band is constructed of two peaks whose spacing becomes larger in the order BaTiO₃ < SrTiO₃ < CaTiO₃. The DV-Xα results indicate that the greater part of the lower-energy peak is attributed to the levels which have O 2p orbitals pointing to Ti cations and are thus stabilized by the electrostatic potential concomitant with a decreased TiO bond distance. The electrostatic potential also reduces the O 2p-Ti 3d mixing and, together with the repulsion of the electron cloud between the Ti and O ions, makes the TiO bond more ionic.     

Efficient preparation of c(2)-symmetrical chiral ferrocenyl diols by catalytic enantioselective reduction of diacylferrocenes

[reaction: see text] Enantioselective borohydride reduction, catalyzed by the optically active beta-ketoiminato cobalt(II) complex, was successfully applied to the 1,1'-dialkanoyl- and 1,1'-dibenzoylferrocenes to afford the corresponding C(2)-symmetrical chiral ferrocenyl diols with high diastereoselectivity and excellent enantioselectivity.     

A practical procedure for the large-scale preparation of methyl (2R,3S)-3-(4-methoxyphenyl)glycidate,a key intermediate for diltiazem

A practical synthesis of methyl (2R,3S)-3-(4-methoxyphenyl)glycidate (-)-2, a key intermediate for diltiazem (1), was developed. Treatment of methyl (E)-4-methoxycinnamate 3 with chiral dioxirane, generated from chiral ketone 4, provided (-)-2 in 77% ee and 89% yield. The crude mixture of (-)-2 and 4 was efficiently separated by the use of novel and simple equipment performing a lipase-catalyzed transesterification and a continuous dissolution and crystallization to furnish the optically pure (-)-2 and recovery of 4 in 74% and 91% yield, respectively.