Showing papers by "Chizuko Kabuto published in 2005"
TL;DR: X-ray analysis of the first trigermaallene (3) and 1,3-digermasila allene (4) revealed that the trimetallaallene skeletons are not linear but significantly bent, similarly to the corresponding trisilaallene 2.
123 citations
TL;DR: The first stable 2-germadisilaallene was synthesized by the reduction of a 2 ratio 1 mixture of a stable dialkylsilylene and dichlorogermylene-dioxane complex with KC8, and showed dynamic disorder similar to the corresponding trisila allene in the solid state.
72 citations
TL;DR: A new series of azulene derivatives, 1b, 2b, and 19, substituted by a long alkyl chain at the 6-position shows mesomorphism with crystalline polymorphs.
Abstract: This paper describes the cyclotrimerization reaction of di(2-azulenyl)acetylenes (2a,b) catalyzed by Co2(CO)8 to produce hexa(2-azulenyl)benzene derivatives (1a,b). The cyclooligomerization of 2a and 2b utilizing CpCo(CO)2 as a catalyst produced (η5-cyclopentadienyl)[tetra(2-azulenyl)cyclobutadiene]cobalt complexes (3a,b). The redox behavior of hexakis(6-octyl-2-azulenyl)benzene (1b), bis(6-octyl-2-azulenyl)acetylene (2b), and the cobalt complexes 3a and 3b along with 6-octyl-2-phenylazulene (19) was examined by cyclic voltammetry (CV). The reduction of compound 1b exhibited multiple-electron transfers in one step upon CV with a reduction potential similar to that of compound 19. However, the CVs of compounds 2b, 3a, and 3b were characterized by stepwise waves because of the reduction of each azulene ring. The mesomorphic behaviors of 1b, 2b, and 19 were also studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD) techniques. A new series of azu...
66 citations
TL;DR: The stereoselective outcome of Pd(II)- or Ag(I)-catalyzed intramolecular N-alkylation to afford 1,3-disubstituted 1,2,3,4-tetrahydroisoquinolines was examined and it was found that in the absence of additional substituents, Pd
Abstract: The stereoselective outcome of Pd(II)- or Ag(I)-catalyzed intramolecular N-alkylation to afford 1,3-disubstituted 1,2,3,4-tetrahydroisoquinolines was examined. In the absence of additional substituents, Pd(II) allows a facile access to the cis isomers, while Ag(I) favors formation of the trans isomers. The same observation was made for the synthesis of 2,5-disubstituted pyrrolidines. Possible reasons for the observed stereoselectivities are discussed.
37 citations
TL;DR: Enantiomeric discrimination of chiral secondary alcohols was performed by both reversed-phase HPLC and 1H-NMR after labeling with a chiral fluorescent derivatization reagent, 2-(2,3-anthracenedicarboximide)cyclohexanecarboxylic acid.
35 citations
TL;DR: Inherently chiral anti-O,O′-dibenzyl-p-tert-butylcalix[4]arene 1 was resolved as the (S)-2-methoxy-2-(naphthalen-1-yl)propionic ester by flash chromatography as mentioned in this paper.
Abstract: Inherently chiral anti-O,O′-dibenzyl-p-tert-butylcalix[4]arene 1 was resolved as the (S)-2-methoxy-2-(naphthalen-1-yl)propionic ester by flash chromatography. Conversely, the anti-O,O′-dibutyl analogue 2 was resolved as the (Sa)-2′-methoxy-1,1′-binaphthalene-2-carboxylic ester by crystallization combined with flash chromatography. CD analysis of these compounds indicated the absolute stereochemistries to be (Sa)-(+)-1 and (Sa)-(+)-2, respectively, the former of which was confirmed by X-ray crystallographic analysis.
35 citations
TL;DR: In this paper, the alkynyl-bridged W−Si complexes, (η5-C5Me4R)(CO)2W(μ-η1:η2-C⋮CtBu)(SiPh2) (R = Me, Et), whose ligands bridge the tungsten and silicon atoms in an η 1: η 2-coordination mode were fully characterized, including X-ray crystallography.
Abstract: Reactions of (η5-C5Me4R)(CO)2(MeCN)WMe (R = Me, Et) with HPh2SiC⋮CtBu gave the novel alkynyl-bridged W−Si complexes, (η5-C5Me4R)(CO)2W(μ-η1:η2-C⋮CtBu)(SiPh2) (R = Me, Et), whose alkynyl ligands bridge the tungsten and silicon atoms in an η1:η2-coordination mode. The structures of these complexes were fully characterized, including X-ray crystallography. Treatment of (η5-C5Me5)(CO)2W(μ-η1:η2-C⋮CtBu)(SiPh2) with acetone resulted in acetone insertion into the silicon−alkynyl linkage followed by intramolecular C−H activation of the tBu group to give the chelate-type alkyl−alkene complex,
27 citations
TL;DR: The first silacyclobutadiene complex was synthesized as red crystals by the reaction of the corresponding 4-silatriafulvene derivative with (cyclopentadienyl)dicarbonylcobalt at 80 °C in benzene.
18 citations
TL;DR: Phenyloligosilane shows dual fluorescence even in non-polar hexane though the TICT-like mechanism is not applicable and the molecular structure of is determined by X-ray crystallography.
9 citations
TL;DR: A photo-induced electron transfer reaction of 2,2-dianisyl-4-isopropylidene-3,3-dimethylcyclobutanone (5 ) in acetonitrile containing molecular oxygen or water gave 4,4′-dimethoxybenzophenone (7) and 2, 2-diansylmethyl carbonyl subunits in this paper demonstrated the chemical capture of an unprecedented oxatetramethyleneethane-type radical cation intermediate.
5 citations
TL;DR: The preferred conformation of the amide derivative in a solution allows us to exploit (1R,2R)-2-(2,3-anthracenedicarboximido)cyclohexanecarbonyl chloride as a conversion reagent to determine the absolute configuration of chiral amines by 1H-NMR.
Abstract: The crystalline structure of N-(S)-2-heptyl (1R,2R)-2-(2,3-anthracenedicarboximido)cyclohexamide (1), which was crystallized from methanol, was determined by an X-ray analysis and had a different conformation from its preferred one in CD3OD by a 1H-NMR analysis. Inter- and intra-molecular CH-π interaction in a crystal plays a very important role in crystal packing. The preferred conformation of the amide derivative in a solution allows us to exploit (1R,2R)-2-(2,3-anthracenedicarboximido)cyclohexanecarbonyl chloride as a conversion reagent to determine the absolute configuration of chiral amines by 1H-NMR.
TL;DR: A photoinduced electron transfer reaction of 2,2-dianisyl-4-isopropylidene-3,3-dimethylcyclobutanone (1 ) in benzene gave two unexpected CA-adducts.
TL;DR: In this paper, a concerted cyclization mechanism was proposed for isolable dialkylgermylene and -stannylene with a galvinoxyl radical, which gave rather unusual cyclic compounds in high yields via intermediate adduct radicals.
Abstract: The reactions of isolable dialkylgermylene and -stannylene with a galvinoxyl radical were found to give rather unusual cyclic compounds in high yields via intermediate adduct radicals. The structures of the cyclic compounds were determined by X-ray crystallography. We propose a concerted cyclization mechanism in which the abstraction of a hydrogen atom from the tert-butyl group by the galvinoxyl radical is accompanied by the simultaneous attack of the germyl radical center to the tert-butyl carbon atom.