Palladium-Catalyzed cross-Benzannulation of Aminoenynes with Diynes. Highly Regioselective Synthesis of Polysubstituted Anilines

Polysubstituted anilines were prepared by the palladium-catalyzed cross-benzannulation of conjugated aminoenynes 1-4 with diynes 8. The reaction proceeded in a highly regioselective manner under mild conditions, and the anilines were obtained as single regioisomers. Our method complements the well-known precedures for the preparation of polysubstituted anilines which are widely used in organic synthesis.     

Surface-potential reversibility of an amino-terminated self-assembled monolayer based on nanoprobe chemistry

Nanoprobe chemistry offers a promising approach for the construction of nanostructures consisting of organic molecules by employing the tip of a scanning probe microscope. In a previous report, we demonstrated that a nitroso-terminated surface on an organosilane self-assembled monolayer could be converted into an amino-terminated surface by applying such a nanoprobe electrochemical technique. This paper reports on surface-potential reversibility originating from a reversible chemical reaction between amino and nitroso groups. In addition, we demonstrate surface-potential memory based on this chemical reversibility. Amino-terminated SAMs were prepared from p-aminophenyl-trimethoxysilane through chemical vapor deposition. Surface potentials were acquired by Kelvin force microscopy. When scanning probe lithography was conducted with a gold tip at positive-bias voltages, the surface potential of the scanned area shifted dramatically in the negative direction. Scanning with negative-bias voltages led to positive shift in the surface potential of the scanned area. The surface potential could be recovered even after multiple scannings with positive and negative applied bias voltages. On the basis of this discovery, we also succeeded in demonstrating surface-potential memory via our nanoprobe electrochemical technique.     

Immobilization of yeast and the function of immobilized yeast.

Hansenula anomala, which catalyzes an asymmetric reduction, was immobilized in bulk or spherical crosslinked polymers. The catalytic activity of the yeast for enantio-selective reduction of 3,8-dioxo-4-methoxycarbonyl-9-methyl-delta 4(10)-octalin (lab) was severely affected by the immobilization conditions, such as the crosslink density, and by hydrophobicity of polymers and other components used for immobilization, oxygen concentration in the medium, etc. In some immobilized systems, the ratio of resulting enantiomers was inverted from that in a free yeast system.     

Effect of Ar/H2 and Kr/H2 mixtures as discharge gas on the ion intensity in dc glow discharge mass spectrometry

 In dc glow discharge mass spectrometry, the addition of small amounts of H₂ to pure Ar as discharge gas has greatly increased the ion intensities of elements compared with the conventional method using pure Ar. This phenomenon was also observed for the addition of H₂ to pure Kr. The reason for the increase of the ion intensities of elements was studied by using a Kr gas mixture containing 0.2% (v/v) H₂. The ion intensities of the elements P, Se and As (whose first ionization potentials are higher than the energy levels of the excited state of Kr) did not increase even if the Kr/H₂ gas mixture was used. The results show that the addition of H₂ significantly contributed to increasing the number of metastable argon or krypton atoms (Penning ionization). Received: 4 November 1995/Revised: 5 January 1996/Accepted: 10 January 1996     

Meerwein-Ponndorf-Verley alkynylation of aldehydes: essential modification of aluminium alkoxides for rate acceleration and asymmetric synthesis

A novel carbonyl alkynylation has been accomplished based on utilization of the Meerwein-Ponndorf-Verley (MPV) reaction system. The success of the MPV alkynylation crucially depends on the discovery of the remarkable ligand acceleration effect of 2,2'-biphenol. For example, the alkynylation of chloral (2c) with the aluminium alkoxide 6(R = Ph), prepared in situ from Me(3)Al, 2,2'-biphenol and 2-methyl-4-phenyl-3-butyn-2-ol (1a) as an alkynyl source, proceeded smoothly in CH(2)Cl(2) at room temperature to give the desired propargyl alcohol 3ca in almost quantitative yield after 5 h stirring. The characteristic feature of this new transformation involving no metal alkynides can be visualized by the fact that the alkynyl group bearing keto carbonyl was transferred successfully to aldehyde carbonyl without any side reactions on keto carbonyl. Although the use of (S)-1,1[prime or minute]-bi-2-naphthol and its simple analogues was found to be unsuitable for inducing asymmetry in this reaction, design of new chiral biphenols bearing a certain flexibility of the biphenyl axis led to satisfactory results in terms of enantioselectivity as well as reactivity.     

Intramolecular catalytic Friedel-Crafts reactions with allenyl cations for the synthesis of quinolines and their analogues

[reaction: see text] This paper describes a novel method to synthesize a quinoline backbone by incorporating allenyl cations into a catalytic intramolecular Friedel-Crafts reaction. The initial products were isomerized and aromatized upon treatment with acid and base, respectively, to give quinolines. The basic concept also proved to be promising for 1-benzazepine, 1-benzazocine, or isoquinoline synthesis.