941-81-1Relevant articles and documents
SYNTHESIS OF 6-HETARYL-SUBSTITUTED AZULENES AND THEIR REACTIONS WITH 2,6-DIPHENYLPYRYLIUM PERCHLORATE
Dorofeenko, G. N.,Koblik, A. V.,Polyakova, T. I.,Murad'yan, L. A.
, p. 807 - 810 (1980)
A method for the synthesis of 4,6,8-trimethyl- and 4,8-dimethyl-6-(2-thienyl, 2-benzothiazolyl)azulenes from 2,6-dimethyl-4-(methyl, 2-thienyl, 2-benzothiazolyl)-pyrylium perchlorates and cyclopentadienyllithium is described.The possibility of direct pyrylation of azulenes with 2,6-diphenylpyrylium perchlorate is demonstrated.Azulenes with a pyrylium ring in the 1 position were synthesized, and their behavior with respect to ammonium acetate was investigated.
Surprising formation of highly substituted azulenes on thermolysis of 4,5,6,7,8-pentamethyl-2h-eyelohepta[b]furan-2-one and heptalene formation with the new azulenes
Lellek, Vit,Hansen, Hans-Juergen
, p. 1712 - 1736 (2007/10/03)
Heating of 4,5,6,7,8-pentamethyl-2H-cyclohepta[b]furan-2-one (1a) in decalin at temperatures > 170° leads to the development of a blue color, typical for azulenes. It belongs, indeed, to two formed azulenes, namely 4,5,6,7,8-pentamethyl-2-(2,3,4,5,6-pentamethylphenyl)azulene (4a) and 4,5,6,7,8-pentamethylazulene (5a) (cf. Scheme 2 and Table 1). As a third product, 4,5,6,7-tetramethyl-2-(2,3,4,5,6-pentamethylphenyl)-1H-indene (6a) is also found in the reaction mixture. Neither 4,6,8-trimethyl-2H-cyclohepta[b]furan-2-one (1b) nor 2Hcyclohepta[b]furan-2-one (1c) exhibit, on heating, such reactivity. However, heating of mixtures 1a/1b or 1a/1c results in the formation of crossed azulenes, namely 4,6,8-trimethyl-2-(2,3,4,5,6-pentamethylphenyl)azulene (4ba) and 2-(2,3,4,5,6-pentamethylphenyl)azulene (4ca), respectively (cf. Scheme 3). The formation of small amounts of 4,6,8-trimethylazulene (5ba) and azulene (5ca), respectively, besides 1H-indene 6a is also observed. The observed product types speak for an [8 + 2]-cycloaddition reaction between two molecules of la or between 1b and 1c, respectively, with 1a, whereby la plays in the latter two cases the part of the two-atom component (cf. Figs. 5-7 and Schemes 4-6). Strain release, due to the five adjacent Me groups in 1a, in the [8+2]cycloaddition step seems to be the driving force for these transformations (cf. Table3), which are further promoted by the consecutive loss of two molecules of CO2 and concomitant formation of the 10π-electron system of the azulenes. The new azulenes react with dimethyl acetylenedicarboxylate (ADM) to form the corresponding dimethyl heptalene-4,5-dicarboxylates 20, 22, and 24 (cf. Scheme 7), which give thermally or photochemically the corresponding double-bond-shifted (DBS) isomers 20′, 22′, and 24′, respectively. The five adjacent Me groups in 20/20′ and 24/24′ exert a certain buttressing effect, whereby their thermal DBS process is distinctly retarded in comparison to 22/22′, which carry 'isolated' Me groups at C(6), C(8), and C(10). This view is supported by X-ray crystal-structure analyses of 22 and 24 (cf Fig. 8 and Table 5).
Synthesis of an Isotopically Isomeric Mixture of 1,4,6,8-Tetramethyl2>azulene and Its Thermal Reaction with Dimethyl Acetylenedicarboxylate
Fallahpour, Reza-Ali,Hansen, Hans-Juergen
, p. 1419 - 1436 (2007/10/02)
Sodium 2>cyclopentadienide in tetrahydrofuran (THF) has been prepared from the corresponding labelled 2>cyclopentadiene which was synthesized from 13CO2 and (chloromethyl)trimethylsilane (cf.Scheme 10) according to an established procedure.It could be shown that the acetate pyrolysis of cis-cyclopentane-1,2-diyl diacetate (cis-22) at 550 +/- 5 deg under reduced pressure (60 Torr) gives five times as much cyclopentadiene as trans-22.The reaction of sodium 2>cyclopentadienide with 2,4,6-trimethylpyrylium tetrafluoroborate in THF leads to the formation of the statistically expected 2:2:1 mixture of 4,6,8-trimethyl2>-, -2>-, and -2>azulene (20; cf.Scheme 7 and Fig. 1).Formylation and reduction of the 2:2:1 mixture 2>-20 results in the formation of a 1:1:1:1:1 mixture of 1,4,6,8-tetramethyl2>-, -2>-, -2>-, -2>-, and -2>azulene (5; cf.Scheme 8 and Fig. 2).The measured 2J(13C,13C) values of 2>-20 and 2>-5 are listed in Tables 1 and 2.Thermal reaction of the 1:1:1:1:1 mixture 2>-5 with the four-fold amound of dimethyl acetylenedicarboxylate (ADM) at 200 deg in tetralin (cf.Scheme 2) gave 5,6,8,10-tetramethyl-2>heptalene-1,2-dicarboxylate (2>-6a; 22percent), its double-bond-shifted (DBS) isomer 2>-6b (19percent), and the corresponding azulene-1,2-dicarboxylate 7 (18percent).The isotopically isomeric mixture of 2>-6a showed no 1J(13C,13C) at C(5) (cf.Fig. 3).This finding is in agreement with the fact that expected primary tricyclic intermediate 2>-8 exhibits at 200 deg in tetralin only cleavage of the C(1)-C(10) bond and formation of a C(7)-C(10) bond (cf.Schemes 6 and 9), but no cleavage of the C(1)-C(11) bond and formation of a C(7)-C(11)-bond.The limits of detection of the applied method is Y>/= 96percent for the observed process, i.e., 2>-5 + ADM -> 2>-8 -> 2>-9 -> 2>-6a (cf.Scheme 6).
