Kazuhiro Hattori

Generation and alkylation reaction of 1-bromoalkenylzincate

Abstract 1-Bromoalkenylzincates (R 1 R 2 C=CBrZnR 3 2 Li) which are generated by the reaction of 1,1-dibromoalkenes with a lithium triorganozincate (R 3 3 ZnLi)at −85 °C undergo alkylation reaction at temperatures from −85 °C to 0 °C to give alkenes R 1 R 2 C=CHR 3 .

Generation and alkylation reaction of lithium 1-halocyclopropylzincate

Abstract Lithium dialkyl(1-halocyclopropyl)zincates which are generated from 1,1-dibromocyclopropanes undergo intramolecular alkylation to give 1-alkylcyclopropanes stereoselectively.

Stereochemistry in carbenoid formation by bromine/lithium and bromine/zinc exchange reactions of gem-dibromo compounds

Abstract Stereochemistry in generation of lithium and zincate carbenoids by bromine/metal exchange reactions of gem -dibromo compounds with BuLi and lithium triorganozincates, respectively, has been investigated. Both lithium and zincate carbenoids derived from 1,1-dibromoalkenes are demonstrated to be configurationally stable at low temperatures whereas, in the presence of the unreacted starting dibromoalkenes, the lithium carbenoids, but not the zincate carbenoids, undergo facile isomerization at the carbenoid carbons. Zincate carbenoids derived from 1,1-dibromocyclopropanes undergo isomerization slowly at the carbenoid carbons in the presence of the starting dibromocyclopropanes. The isomerization reactions of the lithium and zincate carbenoids are proved to proceed through a mechanism involving a bromine/metal exchange between the carbenoids and the starting dirbromo compounds. Highly stereoselective formation of the lithium carbenoids is observed in the reaction of 1,1-dibromoalkenes under the thermodynamic conditions. Under kinetically controlled conditions, both the bromine/lithium and bromine/zinc exchange reactions take place preferentially at the sterically more hindered bromine atom of the starting gem -dibromo compounds. The observation is rationalized by an exchange mechanism involving a linear transition state of either an ate complex formation or an S N 2 reaction at the more hindered bromine atom where strain relief due to the elongation of the carbon-bromine bond is expected.

Stereoselective synthesis of gem-disubstituted cyclopropanes from gem-dibromocyclopropanes

Abstract The title reaction is realized by utilizing an intramolecular alkylation reaction of zincate carbenoids followed by a Pd(0)-catalyzed coupling reaction with acyl, aryl, and alkenyl halides.

Diffraction Amplitudes from Periodic Neumann Surface: Low Grazing Limit of Incidence (II)

This paper deals with the singular behavior of the diffraction of transverse magnetic (TM) waves by a perfectly conductive triangular periodic surface at a low grazing limit of incidence. The wave field above the highest excursion of the surface is represented as a sum of Floquet modes with modified diffraction amplitudes, whereas the wave field inside a triangular groove is written as a sum of guided modes with unknown mode amplitudes. Then, two sets of equations are derived for such amplitudes. From the equation sets, all the amplitudes are analytically shown to vanish at a low grazing limit of incidence. From this fact, it is concluded analytically that no diffraction takes place and only reflection occurs at a low grazing limit of incidence for any period length and any triangle height. This theoretical result is verified by a numerical example.

Diffraction and scattering of TM plane waves from a binary periodic random surface

This paper deals with the diffraction and scattering of a TM plane wave from a binary periodic random surface generated by a stationary binary sequence using the stochastic functional approach. The scattered wave is represented by a product of an exponential phase factor and a periodic stationary process. Such a periodic stationary process is regarded as a stochastic functional of the binary sequence and is expressed by an orthogonal binary functional expansion with band-limited binary kernels. Then, hierarchical equations for the binary kernels are derived from the boundary condition without approximation. We point out that binary kernels obtained by a single scattering approximation diverge unphysically when the periodic random surface is zero on average, thus the effects of multiple scattering should be taken into account. The expressions of such binary kernels are obtained using the multiply renormalizing approximation. Then, statistical properties such as differential scattering cross-section and the optical theorem are numerically calculated with the first two order binary kernels and illustrated in the figures. It is found that the incoherent Woods anomaly appears in the angular distribution of scattering even when the surface has zero average.

Scattering of TM Plane Wave from Periodic Grating with Single Defect

This paper deals with the scattering of a TM plane wave from a periodic grating with single defect, of which position is known. The surface is perfectly conductive and made up with a periodic array of rectangular grooves and a defect where a groove is not formed. The scattered wave above grooves is written as a variation from the diffracted wave for the perfectly periodic case. Then, an integral equation for the scattering amplitude is obtained, which is solved numerically by use of truncation and the iteration method. The differential scattering cross section and the optical theorem are calculated in terms of the scattering amplitude and are illustrated in figures. It is found that incoherent Woods anomaly appears at critical angles of scattering. The physical mechanisms of Woods anomaly and incoherent Woods anomaly are discussed in relation to the guided surface wave excited by the incident plane wave. It is concluded that incoherent Woods anomaly is caused by the diffraction of the guided surface wave.

Low Grazing Scattering from Periodic Neumann Surface with Finite Extent

Low grazing scattering from rough surface is an important problem in the study if sea observation by a fround based radar. This is an interesting problem, because singularity appears in case of the Nenmann surface. When the rough surface is inflnite in extent, only re- ∞ection but no difiraction or no scattering take place at a low grazing limit of incidence (LGLI). Such singular behavior is predicted analytically in case of a homogenous random surface with slight roughness (1,2). It was also demonstrated analytically and numerically for periodic Neu- mann surfaces (3,4). On the other hand, it is pointed out theoretically that scattering takes place at LGLI, if the rough surfaces is flnite in extent (5). This fact is supported by numerical calculations (6). One says only re∞ection takes place but the other insists the scattering may occur at LGLI. Obviously,there is a wide gap. To bridge over the gap, this paper presents a simple numerical example. We deal with the scattering from a periodic array of flnite number of rectangular grooves as is shown in Figure 1. By the modal expansion method, the total scattering cross section is numerically calculated for several difierent numbers of grooves. Generally, the total scattering cross section pc increases linearly proportional to the corrugation width Wc = (2Ng + 1)L, where L is the period and (2Ng + 1) is the total number of groves. However, we newly flnd that an exception takes place at LGLI, where pc is roughly proportional to W fi c with the exponent fi less than 1. From this fact, it is concluded that the total scattering cross section pc must diverge but the total scattering cross section per unit surface pc=Wc must vanish at LGLI as the number of grooves goes to inflnity. Thus, the total difiraction cross section vanishing at LGLI, because it is given as the total scattering cross section per unit surface.