Ikuo Iida

First Preparation of Dibenzo(bc,fg)(1,4)dithiapentalene and Determination of the Structure by X-Ray Analysis.

Abstract New stable dibenzo[ bc,fg ][1,4]dithiapentalene ( 1 ) was prepared by heating 1,9-bis(methylthio)-dibenzothiophene in a glass tube. The X-ray analysis of 1 reveals clearly that it has a completely planar structure. Repeated scanning of cyclic voltammetry of 1 shows an analogous voltammogram with that of polythiophene.

First preparation of a sulfurane with four carbon–sulfur bonds: synthesis and molecular structure of bis(2,2′-biphenylylene)sulfurane

The first stable pentacoordinated sulfur compound with four carbon–sulfur bonds, bis(2,2′-biphenylylene)sulfurane 1, is prepared and its molecular structure is determined by X-ray crystallographic analysis.

Photoaddition of benzoxazole-2-thiones with alkenes

The photochemical reactions of the benzoxazole-2-thiones 6 have been examined. Irradiation of 3-unsubstituted benzoxazole-2-thione 6a in the presence of alkenes 2 gave 2-alkylated benzoxazoles 7, 9–15 and 8 (in the case of 2a). Irradiation of 3-substituted benzoxazole-2-thiones 6b–e and acrylonitrile 2f yielded the 2-alkylidenebenzoxazoles 17, 22 and 24–25. Irradiation of 6b–e in the presence of 1,1-di-and tetra-substituted alkenes 2a,c and e gave the amide derivatives 18–20, 23 and 26. The 3-(alk-ω-enyl)-benzoxazole-2-thiones 6g–i gave the lactam derivatives 28g–i upon irradiation. The formation of these photoproducts can be explained in terms of the intermediacy of amino spiro-thietanes, which are derived by [2 + 2] photocycloaddition of the CS bond of benzoxazole-2-thiones and the CC bond of alkenes.

Photochemical reactions of N-acylbenzoxazole-2-thiones

The photochemical reactions of N-acylbenzoxazole-2-thiones 1 are examined. Irradiation of N-acylbenzoxazole-2-thiones 1 in the presence of a variety of alkenes 2 yields 2-substituted benzoxazoles 3–20 and/or the unexpected products, iminothietanes 21–29 by intramolecular trapping of the acyl group by thiolate anion of the zwitterionic intermediate I and by the phenolate anion of the zwitterionic intermediate II, respectively, derived from the spirocyclic aminothietanes AT which are formed by regioselective [2+2] cycloaddition of the carbon–sulfur double bond of 1 to the alkene double bond.

Inter- and intra-molecular selectivity in the cyclisation of N-cinnamoyl-1-naphthamides in solid-state photochemistry and peri selectivity in their photocyclisation in solution

The photocyclisation of N-cinnamoyl-1-naphthamides 1a–f was examined in the solid state and in solution. Three types of cyclisation, intramolecular 2π+ 2π and 4π+ 2π, and intermolecular 2π+ 2π cyclisations were observed in the solid state. The ratios of these products were largely dependent on the substituents at the para-position of the cinnamoyl moiety. Single-crystal X-ray crystallographic analysis of 1b showed that the intermolecular distance between the two double bonds was 4.34 A. Amides with bulky substituents preferred intramolecular 2π+ 2π cyclisation. In contrast to the solid-state photochemistry, only intramolecular cyclisation was observed in solution. The ratios of 2π+ 2π and 4π+ 2π cyclisation products were irradiation time dependent. It was found that the 2π+ 2π cycloreversion and rearrangement from the 2π+ 2π product to the endo 4π+ 2π isomer were the cause of this dependency.

Conformation of acylureas. Solvent polarity dependent specific rotation and the formation of molecular complexes with solvent molecules possessing a carbonyl or epoxy functionality

In order to elucidate the conformation of acylurea which possesses intramolecular hydrogen bonding between the carbonyl and NH groups, the relation between solvent polarity [ET(30)] and specific rotation of 2,6-bis(ureidocarbonyl)naphthalene 1 was examined. A good linear relationship was observed, except for solvents with a carbonyl functionality. Some of these solvents formed molecular complexes with 1(molar ratio of 1: solvent, 1:2). Single crystal X-ray diffraction analysis of the molecular complex of 1 with ethyl acetate disclosed that the intramolecular hydrogen bonding was absent due to the intermolecular hydrogen bonding with ethyl acetate. In contrast, 2,4′-bis(ureidocarbonyl)benzophenone 2 formed 1:1 complexes with carbonyl compounds, and the bulkier -2,6-bis(ureidocarbonyl)naphthalene 3 could not form complexes with them.

Conformation of N-cyclopropylcarbonylureas. Solvent polarity dependent chemical shifts

The relation between solvent polarity and the chemical shifts of two diastereoisomeric N-cyclopropylcarbonylureas 1 and 2 was examined to elucidate their conformations in solution. In non-polar solvents, where intramolecular hydrogen bonding was playing an important role, their conformations were estimated to be similar to that of 1 in its crystalline state.