Kahei Takase

The formation of azulene derivatives from 2H-cyclohepta[b]furan-2-one derivatives

Abstract 3-Ethoxycarbonyl- and 3-acetyl-2H-cyclohepta[b]furan-2-ones react easily with malonitrile. cyanoacetamide, ethyl cyanoacetate and diethyl malonate, in the presence of sodium ethoxide or t-butyl-amine, giving the corresponding 1,2,3-trisubstituted azulene derivatives, respectively. The structures of these azulene derivatives are determined on the basis of chemical evidence, and spectral data. Considering the structural correlation between the starting 2H-cyclohepta[b]furan-2-ones and the azulene derivatives obtained, a reasonable reaction course, involving the heptafulvene-type and dihydroazulene-type intermediates, is presented for the formation of azulene derivatives from 2H-cyclohepta[b]furan-2-ones.

New extended donors, 2,2'-(2,5-dihydrothiophene-2,5-diylidene)bis(1,3-benzodithiole)s and their electroconductive complexes with electron acceptors

New extended donors, 2,2′-(2,5-dihydrothiophene-2,5-diylidene)bis(1,3-benzodithiole) and its di- and tetra-methyl derivatives having a chalcogen atom and four additional sp2 carbons at the central part of dibenzotetrathiafulvalene (DBTTF) molecule have been synthesized. The electrochemical properties and conductivities of their complexes have been demonstrated characterizing a good coplanar conformation in the oxidized states.

Studies in the syntheses of sesquiterpene lactones—II : Chemical transformation of α-santonin into reynosin, santamarine, epoxysantamarine and 1β-hydroxyarbusculin A

Abstract Eudesmane type α-methylene-γ-lactones, reynosin ( 1 ), santamarine ( 2 ), epoxysantamarine ( 3 ) and 1β-hydroxyarbusculin A ( 4 ) have been synthesized from α-santonin.

The total synthesis of (±)-cycloeudesmol

Abstract The highly stereoselective total synthesis of (±)-cycloeudesmol was achieved by the stereoselective cyclopropane ring formation of an epoxy alcohol ( 7 ) as a key reaction.

The reaction of 2-arylsulfonyloxytropones and active methylene compounds: The formation of 8-hydroxy-2H-cyclohepta[b]furan-2-one and 2-amino-8H-cyclohepta[b]furan-8-one derivatives

Abstract Reaction of 2-arylsulfonyloxytropones (IV) and active methylene compounds, diethyl malonate, ethyl acetoacetate, ethyl cyanoacetate, malononitrile or cyanoacetamide, in the presence of NaOEt give 8-hydroxy-2H-cyclohepta[b]furan-2-one derivatives (V) and/or 2-amino-8H-cyclohepta[b]furan-8-one derivatives (VII), in addition to azulene derivatives (1) or 2H-cyclohepta(b]furan-2-one derivatives (II), known to be obtained by the reaction of 2-chlorotropones or 2-methoxytropones with active methylene compounds. Relative yields of products are influenced markedly by conditions, e.g. base type or molar ratios. The formation of V and VII is characteristic of 2-arylsulfonyloxytropones, not being observed with 2-chlorotropones or 2-methoxytropones. A reaction course involving elimination of the arylsulfonyl group as arenesulfinate ion is presented.

Electronic structure and kinetic behavior of 4-(cycloheptatrienylidene)cyclohexa-2,5-dienone (or [6.7]Quinaren-9-one) and its derivatives)

Abstract The conjugative interaction between the two terminal groups in title quinarenone 2 and its chloro- and methoxy-derivatives were evaluated, proving that the diatropicity of the seven-membered ring is a little larger in 2 than in tropone. Some of these quinarenones are also found to exist in equilibrium with their oligomers and show unexpectedly low barriers of rotation about the intercyclic bond.

Characterization of 4-(2,3-diphenylcyclopropenylidene)cyclohexa-2,5-dienone. Highly polarized 6,7-diphenyl[3.6]q́uinaren-3-one

Abstract The title quinarenone 2 has a pronounced contribution of the dipolar resonance structure to the ground state, and the three-membered ring of 2 is more diatropic than that of diphenylcyclopropenone. The quinarenone 2 exists in equilibrium with its oligomer in solution. The excited state properties of 2 have also been described.

5-(2,3-diphenylcyclopropenylidene)-2(5H)-thiophenone characterization of a thiophene-inserted type compound of diphenylcyclopropenone☆

Abstract The title compound 6 has been synthesized and the effect of cyclic π-system insertion into diphenylcyclopropenone 1 has been discussed. The distribution of positive charge over the 3-membd. ring and phenyl groups slightly predominates in 6 than in parent annulenone 1 , in contrast to 5-cycloheptatrienylidene-2(5H)-thiophenone 5 whose 7-membd. ring is more olefinic than parent tropone 2 . Electronic spectrum of 6 exhibits a broad absorption band having a C-T character.

The synthesis of cyclohept[a]azulenylium ion: A new 14π electron system

Abstract Cyclohept[a]azulenylium ion and its 11-methoxycarbonyl derivative were synthesized as very stable crystalline tetrafluoroborates by the hydride abstraction of 3-H-cyclohept[a]azulenes.

A novel reaction of 5H-cyclohept[a]azulen-5-ones with haloketenes: facile synthesis of dicyclohepta [cd,gh] pentalene

Abstract 5H-Cyclohept[a]azulen-5-ones were found to react with haloketenes in a novel manner to form some derivatives of dicyclohepta[cd,gh]pentalene.