Hiromu Aoyama

Facile and reversible synthesis of an acidic water-soluble poly(amidoamine) fullerodendrimer

Water-soluble fullerodendrimer was obtained by the use of a Diels–Alder reaction of C60 with a newly designed anthryl dendron under an extremely mild condition in 70% yield, which is more than five times as high as the yield described in our previous report.

Highly Cis-Selective Horner-Wadsworth-Emmons (HWE) Reaction of Methyl Bis(2,4-Difluorophenyl) Phosphonoacetate

Abstract Of the previously reported Horner-Wadsworth-Emmons (HWE) reaction, the olefination of methyl bis(2,4-difluorophenyl)phosphonoacetate (la) with various aldehydes gave unsaturated esters in the highest cis-selectivity.

The Horner–Wadsworth–Emmons reaction of mixed phosphonoacetates and aromatic aldehydes: geometrical selectivity and computational investigation

Abstract The substituent effect on the geometrical selectivity in the Horner–Wadsworth–Emmons (HWE) reaction was studied employing several mixed phosphonoacetates. Their reactions with aromatic aldehydes showed a gradual change in Z -selectivity according to the electron-withdrawing ability of the phosphonate substituents, and there was a good correlation between the observed selectivities and 31 P chemical shifts of the phosphonoacetates. Some variables such as the metal cation and crown ether also affected the selectivity. A computational study using ab initio and semi-empirical calculations suggests that the electron-withdrawing substituents stabilize the intermediates as well as the transition states, which reduces the reversibility to increase Z -products. This is in agreement with the experimentally observed selectivity.

Nuclear magnetic resonance spectral study of β-aminoenones

The n.m.r. spectra of the four geometrical isomers of β-aminoenones, trans-s-trans, trans-s-cis, cis-s-trans, and cis-s-cis, are discussed. It was found that the chemical shift of the α-proton of β-aminoenones depends on both anisotropic effects and the electron density: δ=δ0–Δδstruc=ΔδAr+K(q–q0). Thus the conformation of non-rigid β-aminoenones can be determined from the observed and the calculated chemical shifts of the α-proton.

The photochemical reactions of N,N-dialkyl α,β-unsaturated amides

Abstract Upon benzene-sensitized irradiation N,N-dibenzyl α,β-unsaturated amides 1a-1c cyclized to the corresponding 2-azetidinones 2a-2c in good yields via intramolecular hydrogen abstraction by the β-C atom. Under the same conditions N,N-diisopropyl amides 1e and 1f were found to undergo a novel photoreaction to give N-isopropyl saturated amides via the abstraction. Irradiation of N,N-diethyl and dimethyl amides gave neither 2-azetidinones nor N-monosubstituted amides.

Synthesis and Characterization of a Poly(Benzyl Ether) Dendron Sulfenyl Iodide

Abstract A poly(benzyl ether) dendron with a sulfenyl iodide group at the focal point was synthesized and well characterized. Although the molecule showed high stability to chemical reactions, the corresponding den-drimer disulfide was obtained upon photoirradiation quantitatively.

A new synthesis of β-lactams via photochemical γ-hydrogen abstraction of monothioimides

Photochemical reactions of acyclic and semicyclic monothioimides were studied. Photolysis of acyclic monothioimides gave β-lactams (Type II cyclization products) and thioamides (Type II cleavage products). 4-Mercapto-β-lactams were isolated as 4-acylthio-β-lactams by acylation with benzoyt chloride or acetyl chloride in the presence of triethylamine. Irradiation of six- or seven- membered semicyclic monothioimides gave bicyclic β-lactams, but five-membered semicyclic monothioimides gave only Type II cleavage products.

Photochemical reactions of N-alkyl-α-oxoamides

Photolysis of N-alkyl-α-oxoamides gave oxazolidin-4-ones or β-lactams as major products as in the case of NN-dialkyl-α-oxoamides. The formation of cyclohexanone in the photolysis of N-cyclohexylbenzoylformamide in an aqueous acidic medium was most reasonably explained by hydrolysis of an intermediate, N-cyclohexylidenemandelamide.

Acid-catalysed cyclization of α-oxo-anilides to 1,3-dihydro-3-hydroxyindol-2-ones

N-Alkyl-α-oxo-anilides undergo acid-catalysed cyclization at 25 °C to give the corresponding 1,3-dialkyl-1,3-dihydro-3-hydroxyindol-2-ones in high yields. The same anilides give 1,3-dialkyl-3-chloro-1,3-dihydroindol-2-ones, when treated with concentrated hydrochloric acid at 80°C. Reduction of the hydroxyindolones yields 1,3-dialkylindoles.

Photochemical reactions of β-aminovinyl phenyl ketones and related compounds

Photochemical reactions of some β-aminovinyl ketones and related compounds have been examined. Irradiation of the β-NN-dialkylaminovinyl phenyl ketones (1a–g) yielded the corresponding pyrroles (2a–g′), while ketones (1h–m) were inert. Irradiation of the (β-benzoylvinyl)trialkylammonium chlorides (7a and b) afforded the 1,4-diketones (8a and b) respectively. Irradiation of β-ethoxyvinyl phenyl ketone (5) gave an intractable mixture, while the corresponding thioketone (6) was photochemically inactive. Photolysis of the 2-dialkylaminobenzophenones (9a and b) gave the corresponding indoles (10a and b) respectively, accompanied by dealkylation products. The formation of the pyrrole was presumed to occur from the n–π* triplet state. The mechanisms of these photochemical reactions are discussed.