Kazutoshi Yamada

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.

On the mechanism of the rearrangement of 7-vinylnorcaradienes

Thermal rearrangement of diastereomeric 7-vinylnorcaradienes 2 and 3 resulted in the formation of three products, two of which were derived from the vinylcyclopropane-cyclopentene rearrangement and the third from the Cope rearrangement. Almost identical product ratios from 2 and 3 suggested the existence of a common biradical as an intermediacy. The kinetic versus thermodynamic control of the rearrangement was achieved by the choice of the substituent (X) in norcaradienes 9.

Synthesis and stereochemical behavior of 1-aryloctahydroisobenzofuro[7a,1-d]oxazole ring system : new examples of isolable rotamers

Abstract Preparation and stereochemical behavior of new examples of isolable rotamers are described. Reaction of hydroxylactone 2 with isocyanates 3 – 11 gave the corresponding 12 – 20 in good yields. Among them, ortho di-substituted ones gave isolable rotamers. The behavior of ortho mono-substituted derivatives is also discussed.

Acid catalyzed, dehydrative aromatization of 1,7-lactol ring fused and 7-hydroxymethyl norcaradienes: A specific cleavage of the C1C7 bond

Abstract A specific cleavage of the C1C7 bond, one of the three σ-bond of cyclopropane moiety, of norearadienes 1 was accomplished by acid catalyzed, dehydrative aromatization of the corresponding lactols to give 2H-pyran derivatives.

Tetramer formation from methacrylic acid metal salts in solid state

Abstract We have investigated the formation of tetramers of methacrylic acid via the thermal reaction of metallic salts of methacrylic acid salts in the solid state in the temperature range 300°–350°C. N.m.r. and mass spectra and gas chromatography were used in the characterization of the tetramers formed.

Synthesis of 2,5-Dimethylpyrazine-3,6-Dicarboxylic Acid Derivatives

Abstract The general synthetic method of pyrazines1 has been established. The method for synthesizing symmetrically substituted pyrazine derivatives, however, has not been well-studied.2 Especially for synthesis of the title pyrazines, it is only described in a few words by Adkins3 and co-workers that ethyl 2-aminoacetoacetate employed in process to preparing of the threonine synthesis is spontaneously autoxidized to give 2,5-dimethyl-3,6-dicarbetoxy pyrazine as a byproduct. On the basis of this finding of Adkins, we have established a convenient method for the synthesis of 2,5-di-methylpyrazine-3,6-dicarboxylic acid derivatives (D1–5) using the corresponding acetoacetic acid derivatives (A1–4) as the starting materials (Scheme).

Synthesis, hydrophilicity, and oxygen permeability of poly[(trimethylsilyl)propyne]‐gr‐poly(N,N‐dimethylacrylamide)

N,N-dimethylacrylamide (DMAA) was graft copolymerized on poly[(trimethylsilyl)propyne] (PTMSP) by single electron reduction of PTMSP with potassium naphthalenide (K-Naph), followed by anion polymerization of DMAA from the carbanion formed in the reduction. A hard and practically non-water-swelling PTMSP-gr-poly(DMAA) was obtained under the conditions using controlled amount of K-Naph and DMAA. The graft copolymer was characterized with regard to structure, number-averaged molecular weight, and the amount of grafting poly(DMAA) determined by the relative absorbance of the IR absorption band assigned to the CO and SiCH functionalities (ACO/ASiCH). The oxygen permeability and water contact angle (θ) of the graft copolymer were evaluated while varying the amount of grafting poly(DMAA). The graft copolymer proved to be highly oxygen permeable (165 Barrers) and hydrophilic (θ = 27°). Its transparency was also elucidated with UV–vis spectra. This graft copolymer was proposed as a promising candidate for use as a hard contact lens material.

Control of the rotational barrier and spatial disposition of the N-(2′-methylphenyl) group in succinimides by substituent and solvent effects

Both the rotational barrier for the N-(2′-methylphenyl) group in benzylamino-N-(2′-methylphenyl)succinimides 1a–h (X = NEt2, OMe, Me, H, F, Cl, CO2Me and NO2) and the spatial disposition of the N-(2′-methylphenyl) group in N-(4′-substituted 2′ -methylphenyl)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximides 2a–h (X = NEt2, OMe, Me, H, F, Cl, CO2Me and NO2) are controlled by the substituents present and the solvents used. The rotational barrier of 1 decreases with an increase in σp (Hammett’s para substituent constant of X) and increases in proportion to an increase of the solvent parameter [ET(30)]. Clear correlation was observed in the plots of the syn/anti ratio of 2 against σm (Hammett’s meta-substituent constant of X) and the ratios are also controllable by the solvent polarity (µ).

Photolysis of 4,5-diazatetracyclo[6.2.1.13,6.02,7]dodeca-4,9-dienes: a formal homo-Cope rearrangement

The first example of a formal homo-Cope rearrangement in azoalkane chemistry is presented; a double bond in the proximity of a denitrogenation site participates in the rearrangement.

Diastereomeric separation of α-amino acid derivatives using a chiral carbodiimide

Abstract N,N′-Bis[(S)-1-phenylethyl]carbodiimide (1) was found to be an efficient chiral derivatizing agent for the diastereomeric separation of 2-N-benzyloxycarbonylamino acids (2). Diastereomeric acylureas prepared from 1 and 2 showed a large chromatographic selectivity (α). Their capacity factors and selectivity depend on the carbon chain length of the α-alkyl substituents of acylureas.