I. Tabushi

Stereospecific deoxydichlorocyclopropanation of expoxides by dichlorocarbene generated in an emulsifying system

Abstract The reaction of epoxides with dichlorocarbene generated in an emulsifying system was investigated. The products were the corresponding dichlorocyclopropane derivatives. The reaction of cis - and trans -β-methylstyrene oxides showed the reaction was completely stereospecific. Styrene oxide gave the corresponding dichlorocyclopropane and styrene, where the concentration of the latter was kept in the nearly stationary state during the reaction. Further the competitive reaction of α- and β-methylstyrene oxide showed that introduction of an additional Me group at the α-position accelerated the reaction only 12 times. From these observations the reaction was concluded to involve the two step process, namely, the deoxygenation process and dichlorocyclopropanation process, both of which were stereospecific and practically concerted.

Electronic structures and charge-transfer spectra of tris[2.2.2]paraxylylene and related compounds

Abstract Electronic spectra of tris [2.2.2]paraxylylene (3°-PX) and some related compounds were measured in order to investigate the electronic interaction (pπ-pπ and pσ-pσ type) between “normal” (undistorted) benzene rings. 3°-PX showed a large hypochromic effect, i.e., its oscillator strength was observed to be 0·61 times of that of the corresponding linear polyparaxylylene. Charge-transfer (CT) spectra between these compounds and some electron acceptors were also studied. MO calculations (the VI/1, CNDO/2 and CI methods) were carried out in order to elucidate the electronic structure of 3°-PX and also the CT interactions between tetracyanoethylene and 3°-PX, benzene, toluene or p -xylene.

The extrusion reaction of sulfur dioxide from strained sulfolene

Similar extrusion of sulfur atom4 or sulfur monooxide 4c has also been reported for 7-thiabicyclo[2.2.1lhepta-2,5-diene or corresponding sulfoxide, respectively. The facts of the enol form participation in the solvolyses of anti-7tosyloxybicyclo[2.2.llheptan-2-one5 and 3-(2-tosyloxyethyl)cyclopentanone 6 and the facile SO 2 extrusion of 1 stimulated us to investigate the behavior ?J of 2-0x0-(2) and 2,5-dioxo-7-thiabicyclo[2,2.llheptane-7,7-dioxide 7 (3).

Preparations and properties of pseudo-geminal ketones of tris-[2.2.2]- and tetrakis[2.2.2.2]parazylylene

Abstract Pseudo-geminal bridged ketones of tris[2.2.2]paraxylylene, 1, and of tetrakis[2.2.2.2]paraxylylene, 2, were prepared and their spectral properties were investigated in comparison with those of dibenzosuberone, 3. The CO stretching band of 1 was observed at abnormally high frequency region (by ca. 50 cm−1) compared with that of 3, while that of 2 was at a position similar to that of 3. The electronic spectrum of 1 showed that 1 has enormous loss of conjugation due to lack of coplanarity between CO and aromatics. The chemical shift of H0, ortho to CO, of 1 also supported this structural characteristic.

Temperature dependent chemical shift change in 4-substituted[2.2.2.2]paracyclophanes

Abstract Temperature dependent NMR spectra of 4-substituted tetrakis[2.2.2.2]paracyclophane (4°-PCP) were measured at low temperature. The high field shift at low temperature was remarkable for the protons meta and para to an electron withdrawing and/or bulky substituent. While the chemical shift change was very small for the aromatic protons of 4°-PCP bearing a not so bulky and electron donating substituent. From these observations it is concluded that the rotation or vibration of a benzene bearing an electron withdrawing and/or bulky substituent around C 2 -C 3 -C 6 -C 9 axis was increasingly frozen as the temperature decreased to a more stable “lateral” (or half “lateral”, the intermediary state between “face” and “lateral” 4 ) conformation, in an interesting contrast to the favored face conformation of unsubstituted 4°-PCP at low temperature as well as at room temperature.

Synthesis of a bridged homo[15]annulenium ion

Aus dem Annulenon (I) erhalt man mit Dimethylsulfoniummethylid das Homoannulenon (II), das durch Decarboxylierung und Reduktion mit Boranat in das Diol (III) ubergefuhrt wird.