Takuji Ogawa

Synthesis and characterization of N-confused porphyrinatoantimony(V): toward a low energy gap molecular wire

N-Confused tetraarylporphyrinatoantimony(V) dimethoxides were synthesized and their X-ray crystallographic structure, absorption spectra and voltammetric spectra were studied. X-ray crystallographic structure revealed neutral molecules with no counter anion. From the absorption spectra and voltammetric studies we estimated their energy gaps to be about 0.2 eV less than the corresponding porphyrinatoantimony(V). The axial ligands could easily be exchanged in solvent alcohol by acid promotion. These characteristics of N-confused porphyrinatoantimony(V) indicate that they are good candidates for the molecular wire component.

The first preparation of crown ether-annulated porphyrin

Abstract Pyrroles fused with crown ethers are prepared by the reaction of 3,4-dihydroxy pyrrole 1 and polyethylene glycol ditosylate 2 in the presence of cesium fluoride using a convenient high dilution method. These pyrroles can be converted into the corresponding porphyrins with four crown ether moieties, which are expected to form ion channels.

Halide Anion Mediated Dimerization of a meso‐Unsubstituted N‐Confused Porphyrin

The new N-confused porphyrin (NCP) derivatives, meso-unsubstituted beta-alkyl-3-oxo N-confused porphyrin (3-oxo-NCP) and related macrocycles, were synthesized from appropriate pyrrolic precursors by a [3+1]-type condensation reaction. 3-Oxo-NCP forms a self-assembled dimer in dichloromethane that is stabilized by complementary hydrogen-bonding interactions arising from the peripheral amide-like moieties. The protonated form of 3-oxo-NCP was observed to bind halide anions (F(-), Cl(-)) through the outer NH and the inner pyrrolic NH groups, thus affording a dimer in dichloromethane. The structure of the chloride-bridged dimer in the solid state was determined by X-ray diffraction analysis.

An Alternative Method for the Stereospecific Synthesis of Conjugated Alkenynes Via the Copper (I) Iodide Assisted Cross-Coupling Reaction of 1-Akyens with Haloalkenes

Abstract Conjugated alkenynes were prepared stereospecifically in moderate to good yields by heating haloalkenes with 1-alkynes in the presence of copper(I) iodide in hexamethylphosphoric triamide (HMPA).

A new synthesis of pyrroles and porphyrins fused with aromatic rings

Pyrroles fused with aromatic rings (isoindole derivatives) have been readily prepared by the reaction of aromatic nitro compounds with ethyl isocyanoacetate in the presence of DBU. The ease of this reaction depends on the aromaticity of the starting nitro aromatics. Polycyclic aromatic nitro compounds such as 1-nitroacenaphthylene or 9-nitrophenanthrene are more reactive than simple nitro aromatics such as nitrobenzene or nitronaphthalenes and give the corresponding pyrroles in good yields. Pyrroles prepared by this method have been converted into porphyrins fused with various aromatic rings by the reduction with LiAlH4 followed by treatment with an acid catalyst and oxidation with chloranil or oxygen. Tetra-1,2-naphthoporphyrin has been prepared by the reaction of 2-nitro-3,4-dihydronaphthalene or 1-nitronaphthalene with ethyl isocyanoacetate followed by reduction, tetramerization and oxidation. Thus, highly conjugated porphyrins are readily prepared starting from aromatic nitro compounds, and their electronic and optical properties can be controlled by choice of the starting aromatic nitro compound.

Synthesis of 3,4-diarylpyrroles and conversion into dodecaarylporphyrins; a new approach to porphyrins with altered redox potentials

3,4-Diarylpyrroles (1) have been directly prepared in 20–50% yield by the reaction of β-nitrostyrenes with aqueous TiCl3 in 1,4-dioxane. Pyrroles 1 were also prepared via Barton–Zard pyrrole synthesis using the reaction of α-nitrostilbenes with ethyl isocyanoacetate followed by de-ethoxycarbonylation. 3,4-Diarylpyrroles have been converted into dodecaarylporphyrins by reaction with aromatic aldehydes. Various aryl groups are readily introduced at the periphery of porphyrins by this method. Phenyl substitution at any of the positions of pyrroles decreases Eox1/2, while E1/2red is almost unchanged. On the other hand, substitution of the 2-thienyl group affects both the HOMO and LUMO energies, and the UV-vis spectra of dodeca-2-thienylporphyrins (4f or 4i) are extremely red-shifted.

A new synthesis of π-electron conjugated phosphonates and phosphonic bis(diethylamides) and their SHG activities

A series of vinylic and arylic phosphonates and phosphonic bis(diethylamides) were prepared by copper promoted substitution of the corresponding bromides. These π-electron conjugated phosphonates and phosphonic bis(diethylamides) were investigated to elucidate their optical and second harmonic generation (SHG) properties; it was found that diphenyl 2-(4-dimethylaminophenyl)ethenylphosphonate exhibited strong SHG activity, the efficiency being 13 times greater than that of urea.

Selective activation of primary carboxylic acids by electron-rich triarylbismuthanes. Application to amide and ester synthesis under neutral conditions

On being heated in benzene in the presence of tris(methoxyphenyl)bismuthanes 1b–1e, primary carboxylic acids are selectively activated to couple with amines and alcohols to produce the corresponding amides and esters in satisfactoy yields, while secondary, tertiary and aromatic carboxylic acids remain unaffected. 2-Benzylmalonic acid is similarly converted into its corresponding diamides and diesters, but 2,2-dibenzylmalonic acid suffers extensive decarboxylation and, in the presence of aromatic olefins, it undergoes a novel [3 + 2]-type cycloaddition reaction to form 4-substituted 2,2-dibenzyl-4butanolides in low to fair yields.

Tris(2-methoxyphenyl)bismuthane as a dehydrating agent with high template ability: an efficient single-step synthesis of macrocyclic diesters from diacid anhydrides and glycols

Tris(2-methoxyphenyl)bismuthane works as both a mild dehydrating agent and a good template for macrocyclic ester synthesis; prolonged heating of the bismuthane with a dicarboxylic acid anhydride and a glycol in toluene under reflux afforded the corresponding macrocyclic 1:1 diester in moderate to good yields, together with a small amount of a macrocyclic 2:2 tetraester.

3-Nitrochromenes for second order nonlinear optical applications

3-Nitrochromenes bearing various substitutents have been prepared by the reaction of substituted salicylaldehydes with nitrostyrenes; some of these compounds have been found to display efficient optical second harmonic generation.