102435-38-1Relevant academic research and scientific papers
Preparation and Stille cross-coupling reaction of the first organotin reagents of azulenes. An efficient Pd(0)-catalyzed synthesis of 6-aryl- and biazulenes
Okujima, Tetsuo,Ito, Shunji,Morita, Noboru
, p. 1261 - 1264 (2002)
The first versatile organometallic reagents of azulenes, 6-(tri-n-butylstannyl)azulenes, have been prepared by a Pd(0)-catalyzed direct stannylation of 6-bromoazulenes with bis(tri-n-butyltin). We demonstrate herein the utility of the reagents in the Stille cross-coupling reaction with aryl and azulenyl halides to afford 6-aryl- and biazulenes in good yield.
Preparation and Stille cross-coupling reaction of the first organotin reagents of azulenes. Easy access to poly(azulen-6-yl)benzene derivatives
Ito, Shunji,Okujima, Tetsuo,Morita, Noboru
, p. 1896 - 1905 (2007/10/03)
The first versatile organometallic reagents derived from azulenes, i.e., 6-(tri-n-butylstannyl)azulene (1a) and its 1,3-diethoxycarbonyl derivative (1b), have been prepared by Pd(0)-catalyzed direct stannylation of 6-bromoazulenes with bis(tri-n-butyltin). We demonstrate the utility of the reagents in the Stille cross-coupling reaction with aryl, acyl and azulenyl halides to afford 6-aryl-, 6-acyl- and bi-azulenes in good yield. Furthermore, the methodology was applied to the synthesis of poly(azulen-6-yl)benzene derivatives. The reaction of 1b with 1,4-di-, 1,3,5-tri-, 1,2,4,5-tetra- and hexabromobenzenes afforded 1,4-di-, 1,3,5-tri-, 1,2,4,5-tetra-, 1,2,4-tri- and 1,2,3,5-tetra(azulen-6-yl)benzene derivatives (18, 20, 22, 24 and 25). The redox behavior of 18 and 22 was examined by cyclic voltammetry (CV) and compared with those of 20 and 24 reported previously. In contrast to the three-step reduction of 20, the compound 18 exhibited a reversible one-step two-electron reduction wave at - 1.30 V upon CV, which revealed the formation of a closed-shell dianion. The four azulen-6-yl substituents on benzene in a 1,2,4,5 relationship increased electron-accepting properties because of the formation of a closed-shell dianion stabilized by four azulen-6-yl groups. As expected, the compound 22 exhibited a color change during the electrochemical reduction. However, the reverse oxidation did not regenerate the spectrum of 22 due to the low stability of the presumed dianionic species under the conditions of the UV-vis measurement.
ARYLATION OF AZULENE
Nefedov, V. A.,German, N. A.,Lutsenko, A. I.,Nikishin, G. I.
, p. 154 - 162 (2007/10/02)
In the reaction of azulene with phenylhydrazine and an oxidizing agent (Cu(2+)) a mixture of 1-phenylazulene (28percent) with 2-, 4-, and 6-phenylazulenes (27percent in total) is formed; a series of para-substituted phenylazulenes and α-naphthylazulenes were obtained in a similar way.If p-nitrophenylhydrazine is used, selective arylation of azulene (at position 1) and also of dimethylaniline (at the ortho and para positions) occurs.An excess of the oxidizing agent (Cu(2+)) increases and an excess of the reducing agent (arylhydrazine) reduces the selectivity of arylation.Some of the obtained arylazulenes can be used as dichroic coloring additives for liquid crystals.
Novel 2,6-Disubstituted Azulenes
Balschukat, Dietmar,Dehmlow, Eckehard V.
, p. 2272 - 2288 (2007/10/02)
Methods are described to introduce varying residues into 2- and 6-positions of azulene, starting from diethyl 6-bromo-2-methoxy-1,3-azulenedicarboxylate (1). 2-Substitution is achieved by Grignard reaction or exchange of the alkoxy group and by aldol condensation of 2-methyl compounds whereas 6-substitution is conducted by nucleophilic displacement and by homo- and hetero-aromatic coupling.Consecutive dealkoxycarbonylation yields azulenes 20 with free 1,3-positions.Biazulenes 9a - c and 20l, 20m, styryl- and bis(styryl)azulenes 15 - 18 and 20i - k, and finally the azulenedialdehyde 19 are novel compounds which were difficult to prepare or were inaccessible so far.
