Subporphyrins with an axial B-C bond.

Axial fabrications of subporphyrins have been conveniently accomplished by the reaction of B(methoxo)triphenylsubporphyrin with Grignard reagents such as aryl-, heteroaryl-, ferrocenyl-, ß-styryl-, phenylethynyl-, and ethylmagnesium bromides. The axial groups thus introduced are not conjugated with the subporphyrin core. This situation leads to effective fluorescence quenching of subporphyrins when the axial group is strongly electron donating such as 4-dimethylaminophenyl and ferrocenyl groups.

Facile synthesis of meso-arylamino- and alkylaminosubporphyrins.

Newcomers: meso-Arylamino- and meso-alkylaminosubporphyrins have been synthesized by the Pd-catalyzed aminations of meso-bromosubporphyrin 1 as the first example of subporphyrins containing heteroatom substituents at the meso-position. The X-ray structural analyses have revealed significant structural distortions of meso-aminosubporphyrins 2 due to the effective electronic interaction (see scheme).

Rational synthesis of A2B-type meso-triarylsubporphyrins.

Rational synthesis of A(2)B-type meso-arylsubporphyrins has been accomplished by the condensation of triethylamine-tri-N-tripyrromethene-borane with acid chlorides. These subporphyrins are useful for evaluations of the intrinsic substituent effects and the influences of substitution patterns, A(3)-type versus A(2)B-type substitution.

Planar subporphyrin borenium cations.

Subporphyrin borenium cations with a carborane counterion have been prepared by treatment of B-methoxy subporphyrins with the silylium reagent Et(3)Si(CH(6)B(11)Br(6)). In contrast to the distinctly domed subphthalocyanine borenium cation, a nearly planar structure with sp(2) hybridized boron is found in the X-ray structure of the triphenylsubporphyrin borenium cation. The cations exhibit absorption and fluorescence spectra that are quite similar to those of B-methoxy subporphyrins. B-phenyl subporphyrins were prepared in good yield by reaction of subporphyrin borenium cations with phenyllithium.

Synthesis and properties of boron(III)-coordinated subbacteriochlorins.

Subbacteriochlorins, which were prepared via hydrogenation of subporphyrins with Raney nickel, are modestly aromatic due to 14π-diazaannulenic circuit and exhibit characteristic blue-shifted Soret-like bands, intensified fluorescence spectra, and high oxidation potentials.

meso-Tris(oligo-2,5-thienylene)-substituted subporphyrins.

meso-Tris(oligo-2,5-thienylene)-substituted subporphyrins exhibit remarkably red-shifted and intensified absorption bands with increasing number of thienyl subunits. A dimeric subporphyrin obtained from homocoupling of a monobrominated tris(2-thienyl)-substituted subporphyrin exhibits a split Soret-like band due to the exciton coupling.

Stereoselective synthesis of spirooxindoles by palladium-catalyzed decarboxylative cyclization of gamma-methylidene-delta-valerolactones with isatins.

A new synthetic method of spirooxindole derivatives has been developed by way of a palladium-catalyzed decarboxylative cyclization of gamma-methylidene-delta-valerolactones with isatins. By employing a newly prepared phosphoramidite ligand, the reaction proceeds smoothly with excellent diastereoselectivity. Preliminary results of its application to asymmetric catalysis using a chiral phosphoramidite ligand are also described.