Showing papers by "Chizuko Kabuto published in 1988"
62 citations
TL;DR: A-alkoxyorganostannanes, by reaction through the derived a-alk Oxyorganocuprate, can be considered as a synthetic equivalent to a carbonyl ylide and highly substituted tetrahydrofurans are generated in good yields from cyclic and acyclic enones.
Abstract: 9, and 10 could not be unambiguously assigned by N M R since the isomers were inseparable by chromatography. Only three of the four possible isomers of 12 were isolated. The major isomer of which bears a cis relationship between the isopropyl and phenyl substituents. To illustrate the potential synthetic utility of this approach to tetrahydrofuran synthesis, a short total synthesis of the hop ether 169 was carried out as shown in Scheme I. The required a-alkoxystannane 13 was readily prepared from acetone by a condensation reaction with Bu3SnLila and subsequent protection of the a-hydroxystannane intermediate with chloromethyl methyl ether. Transmetalation of 13 was accomplished in DME" at -78 "C and cuprate formation2b*d proceeded smoothly. The cuprate reagent 14 underwent clean regiospecific addition to cyclopentenone in the presence of trimethylsilyl chloride to afford the silyl enol ether 15 after quenching the reaction mixture with triethylamine. The crude silyl enol ether 15 was obtained in nearly quantitative yield (GC). Without further purification, 15 was treated with titanium tetrachloride in methylene chloride to provide the annelated tetrahydrofuran 11 in 73% overall yield from cyclopentenone. Methenylation, following the procedure of Lombardo,I0 provided the natural product 16 in good yield (91%). In summary, a-alkoxyorganostannanes, by reaction through the derived a-alkoxyorganocuprate, can be considered as a synthetic equivalent to a carbonyl ylide. Highly substituted tetrahydrofurans are generated in good yields from cyclic and acyclic enones. Further studies are in progress to evaluate the use of other acetal protecting groups (other than MOM) in the final closure step.
45 citations
TL;DR: The intramolecular conjugate addition of carbamoyloxy nitrogen to chiral vinyl sulfoxides displays diastereoselectivity governed by cooperation or competition of two controlling factors.
27 citations
TL;DR: In this paper, anion radical salts of bis[1,2,5]thiadiazolotetracyanoquinodimethan (BTDA) containing forty kinds of alkylammonium ions were prepared whose molar ratios are unique for each cation and changed from 1:1 (2A-2L) to 2:3 (2M-2Z), 1:2 (2a-2m), and 2:5 (2n) with elongation of the side chains.
Abstract: Anion radical salts of bis[1,2,5]thiadiazolotetracyanoquinodimethan (BTDA) containing forty kinds of alkylammonium ions were prepared whose molar ratios are unique for each cation and changed from 1:1 (2A–2L) to 2:3 (2M–2Z), 1:2 (2a–2m), and 2:5 (2n) with elongation of the side chains. The electrical conductivities of the salts are largely affected by the molar ratio and the spatial requirement of cations (ρRT 3.1 Ω cm for 2a and 4.2×106 Ω cm for 2L), and some of the salts exhibit high electrical conductivities (ρRT 3.1–8.3 Ω cm for 2a–2e) with small anisotropy (ρ⁄⁄ 1.7 Ω cm, ρ⊥ 21.6 Ω cm for a single crystal of 2g). Three salts (2A, 2M, and 2g) showed semiconducting temperature dependence of electrical conductivity with the activation energies of 0.12–0.20 eV. The X-ray study of three kinds of the salts (2A, 2g, and 2m) revealed that two-dimensional networks are formed by S–N≡C interactions (3.12–3.33 A) of BTDA anion radicals. The crystals of 2A and 2g showing higher conductivities consist of two-dimens...
27 citations
25 citations
17 citations
TL;DR: In this article, the structures of the most twisted and untwisted olefins were determined by X-ray diffraction using X-Ray diffraction techniques, and tetrakis(dimethylsilyl)ethylene was used.
Abstract: Tris(t-butyldimethylsilyl)trimethylsilylethylene and tetrakis(dimethylsilyl)ethylene were prepared. Structures of these most twisted and untwisted olefins are determined by X-ray diffraction.
9 citations
TL;DR: Le compose du titre cristallise avec le groupe d'espace P2 1 /n. Affinement de la structure jusqu'a 0,063
Abstract: Le compose du titre cristallise avec le groupe d'espace P2 1 /n. Affinement de la structure jusqu'a 0,063
9 citations
TL;DR: The molecular structure of tris(acetylacetonato)technetium(III) was determined by means of the single crystal X-ray diffraction method in this paper, and the complex has a typical octahedral coordination and the average ∠O-Tc-O is 90.2°.
Abstract: The molecular structure of tris(acetylacetonato)technetium(III) was determined by means of the single crystal X-ray diffraction method. The complex has a typical octahedral coordination and the average ∠O–Tc–O is 90.2°. The average Tc–O distance is 2.025 A.
7 citations
TL;DR: The photochemical reaction of an electron donoracceptor complex of a cage ketone containing a cyclobutane ring with tetracyanoethylene (TCNE) gave an unusual 1:1 adduct which was considered to be formed by interception of a 1, 4-radical cation by TCNE.
4 citations
TL;DR: In this paper, the molecular structure of conformationally stable 1-(p-bromophenyl)-4-t-butyl-1-methyl 1-silacyclohexane was determined by an X-ray diffraction study.
TL;DR: In this paper, 1,4-Radical cations, produced from a cage ketone containing a cyclobutane ring by a reaction with an aminium salt or photochemical reaction of an electron donor-acceptor complex with TCNE, were intercepted by molecular oxygen to give novel oxygenated products.
Abstract: 1,4-Radical cations, produced from a cage ketone containing a cyclobutane ring by a reaction with an aminium salt or photochemical reaction of an electron donor–acceptor complex with TCNE, were intercepted by molecular oxygen to give novel oxygenated products.
TL;DR: In this article, a tricarbonyl complex whose structure was determined by X-ray crystallographic analysis was determined. But the structure of the tricarboxylic acid is unknown.
Abstract: The reaction of 3,3,5,5,8,8,10,10-octamethyl-4,9-dioxa-3,5,8,10-tetrasilacyclodeca-1,6-diyne with diiron nonacarbonyl gave a (trimethylenemethane)iron tricarbonyl complex whose structure was determined by X-ray crystallographic analysis.
TL;DR: An X-ray structural analysis of the title charge transfer complex revealed an unusual cage-like network formed by SNC interactions of bis[1,2,5]thiadiazolotetracyanoquinodimethane (BTDA) in which benzene was tightly included as mentioned in this paper.
Abstract: An X-ray structural analysis of the title charge-transfer complex revealed an unusual cage-like network formed by S––NC interactions of bis[1,2,5]thiadiazolotetracyanoquinodimethane (BTDA)(1) in which benzene was tightly included; the stabilization observed may be attributed to this inclusion behaviour.
TL;DR: In this article, the origin of the σ(Si−Si)-π CT interaction was ascribed to the through-bond orbital interaction, and the trisilane analog was shown to have the same properties as the trimethylsilylsilacyclohexane analog.
Abstract: 4-Dicyanomethylene-1-trimethylsilylsilacyclohexane (2a) and the trisilane analog (2b) showed the intramolecular CT bands in the absorption spectra. In combination with the results of the X-ray structure analysis of 2a, the origin of the σ(Si–Si)-π CT interaction was ascribed to the through-bond orbital interaction.
TL;DR: In this article, the title electron acceptors, TSDA (2) and BSDA (3), were prepared which crystallize isomorphously with the sulfur analogue, BTDA (1).
Abstract: The title electron acceptors, TSDA (2) and BSDA (3), were prepared which crystallize isomorphously with the sulfur analogue, BTDA (1). The molecular interactions are enhanced in 2 and 3 compared with 1, which connect the molecules to form two-dimensionally expanded “sheet-like” networks and their infinite layers.
TL;DR: The intramolecular conjugate addition of carbamoyloxy nitrogen to chiral vinyl sulfoxides displays diastereoselectivity governed by cooperation or competition of two controlling factors as discussed by the authors.
Abstract: The intramolecular conjugate addition of allylically situated carbamoyloxy nitrogen to chiral vinyl sulfoxides displays diastereoselectivity governed by cooperation or competition of two controlling factors. These factors have been evaluated.