851-51-4Relevant academic research and scientific papers
Photochemical Cis to Trans One-Way Isomerization of Styrylazulenes on Their Triplet Excited State. Examination of Ethylenes with Non-Benzenoid Substituents of Low Triplet Energies
Karatsu, Takashi,Kitamura, Akihide,Arai, Tatsuo,Sakuragi, Hirochika,Tokumaru, Katsumi
, p. 1674 - 1679 (2007/10/02)
1-Styrylazulene and 7-isopropyl-1,4-dimethyl-3-styrylazulene (3-styrylguaiazulene) underwent one-way isomerization from the cis to the trans isomer on triplet sensitization.Their triplet states as intermediates of the isomerization were observed by laser flash photolysis.However, their excitation to either the lowest excited single state (S1) or the second excited singlet state (S2) by direct irradiation afforded photostationary mixtures comprising 98percent of the trans and 2percent the cis isomers, which implies the participation of a singlet isomerization path.
New Results in the Synthesis of Styrylazulene Derivatives: Application of the 'Anil Synthesis' to the Preparation of Azulenes Substituted with Styryl Groups at the Seven-Membered Ring
Briquet, Anne Andree Sophie,Hansen, Hans-Juergen
, p. 1921 - 1939 (2007/10/02)
The synthesis of 4,6,8-trimethyl-1-azulenes 5 (R=H, MeO, Cl) has been performed by Wittig reaction of 4,6,8-trimethylazulene-1-carbaldehyde (1) and the corresponding 4-(R-benzyl)(triphenyl)phosphonium chlorides 4 in the presence of EtONa/EtOH in boiling toluene (see Table 1).In the same way, guaiazulene-3-carbaldehyde (2) as well as dihydrolactaroviolin (3) yielded with 4a the corresponding styrylazulenes 6 and 7, respectively (see Table 1).It has been found that 1 and 4b yield, in competition to the Wittig reaction, alkylation products, namely 8 and 9, respectively (cf.Scheme 1).The reaction of 4,6,8-trimethylazulene (10) with 4b in toluene showed that azulenes can, indeed, be easily alkylated with the phosphonium salt 4b. 4,6,8-Trimethylazulene-2-carbaldehyde (12) has been synthesized from the corresponding carboxylate 15 by a reduction (LiAlH4) and dehydrogenation (MnO2) sequence (see Scheme 2).The Swern oxidation of the intermediate 2-(hydroxy-methyl)azulene 16 yielded only 1,3-dichloroazulene derivatives (cf.Scheme 2).The Wittig reaction of 12 with 4a and 4b in the presence of EtONa/EtOH in toluene yielded the expected 2-styryl derivatives 19a and 19b, respectively (see Scheme 3).Again, the yield of 19b was reduced by a competing alkylation reaction of 19b with 4b which led to the formation of the 1-benzylated product 20 (see Scheme 3).The 'anil synthesis' of guaiazulene (21) and the 4-R-benzanils 22 (R=H, MeO, Cl, Me2N) proceeded smoothyl under standard conditions (powered KOH in DMF) to yield the corresponding 4-azulene derivatives 23 (see Table 4).In minor amounts, bis(azulen-4-yl) compounds of type 24 and 25 were also formed (see Table 4).The 'anil reaction' of 21 and 4-NO2C6H4CH=NC6H5 (22e) in DMF yielded no corresponding styrylazulene derivative 23e.Insteed, (E)-1,2-bis(7-isopropyl-1-methylazulen-4-yl)ethene (27) was formed (see Scheme 4).The reaction of 4,6,8-trimethylazulene (10) and benzanil (22a) in the presence of KOH in DMF yielded the benzanil adducts 28 to 31 (cf.Scheme 5).Their direct base-catalyzed transformation into the corresponding styryl-substituted azulenes could not be realized (cf.Scheme 6).However, the transformation succeeded smoothly with KOH in boiling EtOH after N-methylation (cf.Scheme 6).
