Remarks on unit indices of imaginary abelian number fields II

Satz 41 in Hasse's monograph [4] is modified because of the incorrectness of Satz 29. We investigate unit indices of imaginary abelian number fields of type (2,2) and (2,2, 2), some of which give counterexamples to Satz 41. We moreover give a relation between unit indices of certain imaginary fields of type (2,2²) and those of their real cyclic subfields.     

Buchsbaum homogeneous algebras with minimal multiplicity

In this paper we first give a lower bound on multiplicities for Buchsbaum homogeneous k-algebras A in terms of the dimension d, the codimension c, the initial degree q, and the length of the local cohomology modules of A. Next, we introduce the notion of Buchsbaum k-algebras with minimal multiplicity of degree q, and give several characterizations for those rings. In particular, we will show that those algebras have linear free resolutions. Further, we will give many examples of those algebras.     

Ruthenium-catalyzed one-pot hydroformylation of alkenes using carbon dioxide as a reactant

A new hydroformylation of alkenes using carbon dioxide as a reactant is shown to take place in the presence of ruthenium cluster complexes and halide salts. Similar or even better yields of alcohols were formed as compared to the conventional hydroformylation with CO under the same reaction conditions. The reaction proceeded in three steps: CO₂ is first converted to CO; then it is used as a reagent for hydroformylation to give aldehyde; subsequently, it is hydrogenated to alcohol. ESI-mass spectrometric analyses of the reaction solutions indicated formation of four kinds of ruthenium anionic complexes including tetra-, tri-, and mononuclear species. On the basis of experimental findings, possible roles of these complexes are discussed.     

Ligand Substitution Reaction of Bis(ethylenediamine)glycinatocobalt(III) Complex with Ethylenediamine Catalyzed by the Photo-excited Tris(2,2′-bipyridine)ruthenium(II) Complex

Substitution reaction with ethylenediamine of coordinated glycinate ligand in bis(ethylenediamine)-glycinatocobalt(III) complex has been studied in the presence of photo-excited tris(2,2′-bipyridine)ruthenium(II) complex in alkaline aqueous solution (buffered around pH 12) containing 1.0M chloride ion at 25°C. VIS absorption and CD spectra were used for the racemate and the optically active isomers of the Co(III) complexes, respectively. The reaction was catalyzed by the excited Ru(II) complex to give tris(ethylenediamine)cobalt(III) complex. Mechanism of the ligand-substitution reaction and role of the excited Ru(II) complex were discussed.     

Chiral ligand-controlled asymmetric conjugate addition of lithium amides to enoates

The external chiral ligand-controlled asymmetric conjugate addition reaction of lithium amides with alpha,beta-unsaturated esters provided beta-amino esters in high yields and high enantioselectivities.     

A practical procedure for the synthesis of esonarimod, (R,S)-2-acetylthiomethyl-4-(4-methylphenyl)-4-oxobutanoic acid,an antirheumatic agent (part 1)

An efficient and practical procedure for the synthesis of esonarimod, (R,S)-2-acetylthiomethyl-4-(4-methylphenyl)-4-oxobutanoic acid (1), a new antirheumatic drug, has been developed. The intermediate, 2-methylene-4-(4-methylphenyl)-4-oxobutanoic acid (2), was prepared by Friedel-Crafts acylation of toluene with itaconic anhydride (3) in the presence of aluminum trichloride and nitrobenzene in 63% yield without silica gel column purification. Compound 1 was prepared by Michael addition of 2 with thioacetic acid (4) in 74% yield. Overall, 1 was obtained in 47% yield from 3. The structures and synthetic mechanisms of by-products (five compounds) of 2 were also clarified.     

Crystal habit of fcc metal particles controlled by electrode potential in solution

The crystal habit of fcc metal particles formed on an amorphous carbon film electrode in solution at different electrode potentials is discussed. The fcc metal particles have different crystallographic habits depending on applied electrode potential; that is, icosahedral and/or decahedral particles are formed at lower potentials, and fcc single-crystalline or polycrystalline particles at higher potentials. It was found that decahedra and icosahedra of Cu-Au alloy particles are formed in the potential region of underpotential deposition (UPD) of Cu at which only fcc Au single-crystalline particles and Au polycrystalline particles appear. This is attributed to the charge transfer from the UPD Cu ions to the Au overlayer of Cu-Au alloy particles. The formation of decahedral and icosahedral Cu-Au alloy particles depends on the composition of the Cu-Au alloy. On the basis of these results it was deduced that the contraction of the surface lattice of the growing particles is responsible for the formation of icosahedral and decahedral particles. Received: 25 February 1997 / Accepted: 21 April 1997     

A novel reaction of allylic alcohols with hexafluoropropene-diethylamine adduct (PPDA) to form 2-fluoro-2-trifluoromethyl-4-alkenamide

Treatment of allylic alcohols with hexafluoropropene-diethylamine adduct (PPDA) afforded N,N-diethyl-2-fluoro-2-trifluoromethyl-4-alkenamides which were formed by the Claisen rearrangement of intermediary 2-alkenyl-1-diethylamino-2,3,3,3-tetrafluoro-1-propenyl ethers. Although (E)-allylic alcohols gave two diastereomeric products in about 1:1 ratio, (Z)-allylic alcohols gave the corresponding product as a single diastereomer.