Azulene, structure

The stereochemistry of a thermally induced 10e electrocyclization (predicted to be disrotatory) has not been firmly established and the main synthetic application is found in the formation of azulenes and ring-fused azulenes as in the transformation (452) to (453). Thermolysis of (454) with spontaneous elimination of dimethylamine from intermediate (455) afforded the fused azulene structure (456). The chemistry of even higher order (12e to 20e") pericyclic processes has been recently reviewed. An example of an unusual sequence of pericyclic processes is the transformation of heptahendecafulvadiene (457) to the pentacyclic hydrocarbons (462) and (463) in a 2 1 ratio. The pathway for this transformation can be viewed as an initial conrotatory 20e electrocyclization followed by a cascade of 10e and 6e pericyclic processes. ... 

A new zoanthoxanthin, containing the tetra-azacyclopent[ ]azulene structure... 

At MP2 and MR-SDCI>32 and B3LYP/6-311-EG levels of theory, the delocalized azulene structure is the energy minimum with the localized structure about 11—17 kJ/mol higher. Both structures are deemed aromatic on the basis of their NICS values for the five- and seven-membered rings —21.5—8.3 for the delocalized structure and —18.1 and —5.9 for the localized structure. 

Outline the plausible electrochemical polymerization mechanism for the monomer azulene (structure below). Outline a possible chemical polymerization method for this monomer, and identify mechanistic differences between the chemical and electrochemical methods. 

Poly(azulenes) (structure, Eo. 14.121. and a variety of derivatives, have been synthesized and studied in detail by the Bargon group at IBM [443, 577], who have studied the parent CP as well as the 1-Me-, 1-Phe-, 4,6,8-TriMe-, 4,6,8-TriMe-l-aldehyde, l-(Phe-acetylenenyl)-, and the 1,3,-Di(trimethylsilylacetyleneyl)-derivatives. 

The cyclic 2,4-dienoate 184, formed by the Pd-catalyzed cyclization of the 1,6-enyne 183, reacted with 154 to form the azulene derivative 185[118], The 3-methylenepyrrolidine 188 is formed by the reaction of the Zn reagent 186 with the chiral imine 187 with high diastereomeric excess. The structure of the allylic ethers is important for obtaining high diastereoselectivity[l 19],... 

Azulene does have an appreciable dipole moment (0.8 The essentially single-bond nature of the shared bond indicates, however, that the conjugation is principally around the periphery of the molecule. Several MO calculations have been applied to azulene. At the MNDO and STO-3G levels, structures with considerable bond alternation are found as the minimum-energy structures. Calculations which include electron correlation effects give a delocalized n system as the minimum-energy structure. ... 

Azulene, an isomer of naphthalene, lias a remarkably large dipole moment for a hydrocarbon (/i = 1.0 D). Explain, using resonance structures. 

Azulene, dipole moment of. 54 electrostatic potential map of, 541 structure of, 533... 

In contrast to the other measurements, the X-ray crystal analysis of thieno[3,4-d]thiepin shows an azulene-like, planar structure.30... 

Pariser, R., J. Chem. Phys. 25, 1112, "Electronic spectrum and structure of azulene."... 

Of the fundamental nonalternant hydrocarbons, only two prototypes were known about fifteen years ago azulene (XI, Fig. 5), the molecular structure of which was determined by Pfau and Plattner and fulvene (XIX) synthesized by Thiec and Wiemann. Early in the 1960 s many other interesting prototypes have come to be synthesized. Doering succeeded in synthesizing heptafulvene (XX) fulvalene (XXI) and heptafulvalene (XXIII). Prinzbach and Rosswog reported the synthesis of sesquifulvalene (XXII). Preparation of a condensed bicyclic nonalternant hydrocarbon, heptalene (VII), was reported by Dauben and Bertelli . On the other hand, its 5-membered analogue, pentalene (I), has remained, up to the present, unvanquished to many attempts made by synthetic chemists. Very recently, de Mayo and his associates have succeeded in synthesizing its closest derivative, 1-methylpentalene. It is added in this connection that dimethyl derivatives of condensed tricyclic nonaltemant hydrocarbons composed of 5- and 7-membered rings (XIV and XV), known as Hafner s hydrocarbons, were synthesized by Hafner and Schneider already in 1958. 

Kozlowski, P. M., Rauhut, G., Pulay, P., 1995, Potential Symmetry Breaking, Structure and Definite Vibrational Assignment for Azulene Multiconfigurational and Density Functional Results , J. Chem. Phys., 103, 5650. 

The thiepin 13 (X = S) was found to be inert toward catalytic hydrogenation. The authors ascribe the stability of 13 (X = S) to a contribution of the charge-separated structures 13a and 13 b to the ground state of 13 (X = S) 71). An X-ray structural determination showed that 13 (X = S) is nearly planar with a disordered crystal structure similar to that of azulene 73). 

Some allelochemicals such as sesquiterpene lactones or alkaloids penetrate into a cell, binding with various cellular compartments, and changing the cellular fluorescence excited by ultra-violet or violet light. This makes clear cellular mechanisms of actions for the allelochemicals. Sesquiterpene lactones azulene and proazulenes binds DNA-containing structures such as nuclei and chloroplasts, which fluoresce in blue (Roshchina, 2004). 

When light from all three channels excites the fluorescence of crystalline individual compounds such as allelochemicals flavonoids quercetin and rutin or pigments of plant cells - azulene, chlorophyll and carotenoids fluoresce in different regions of the spectra in yellow and red or blue, red and yellow-orange, respectively (Fig. 7). It compares the light emission of the substances within cellular structures. 

The structures of several compounds containing the pyrrolo[l,2,4]triazine moiety have been established by X-ray crystallography, as for example pyrrolo[l,2- ][l,2,4]triazine 13 <1997J(P1)1829>, 4-acetyl-l-phenyl-2a,3,5-triaza-benz[r-,<7]azulene 14 <2000H(53)323>, heterodiquinane 15 <1998CL1135>, cation 16 derived from methylation of 3-phenylcyclohepta[4,5]pyrrolo[l,2- ][l,3,5]triazine-2,4(377)-dione <2005H(65)1629>, 2-phenyl-3-phenyl-... 

We have established the conversion between the two colored species by electrochemical reaction utilizing the concept of a Wurster type violene-cyanine hybrid. Dications 222+ and 232+ showed significant changes in their absorption spectra in different oxidation states. Therefore, dications 222+ and 232+ could function as new violene-cyanine hybrids, in which the four end groups (X and Y) in the general structure are azulenes (Figure 4). 

Flash vacuum pyrolysis of tricyclo[7.1.0.04,6]deca-2,7-diene 544 is accompanied by a long cascade of rearrangements leading to various azulenes (equation 214)266. The structures of these products were determined by using the chlorine atoms as labels for the 13C NMR measurements. 

Clar, E. Aromatic Hydrocarbons. Part LVIII. The Structure of Azulene. 

Shifts on Alkyl Substitution. Structure and Color of Methylated Derivatives of Azulene. J. chem. Physics 18, 257 (1950). 

Medel. vlaamsche chem. Vereen. 13, 99 (1951) C. A. 47, 365 (1953).. Electronic structure of azulene. Abstr. XIIItl1 Int. Congr. of pure and applied Chem. Stockholm 1953. 

Figure 16.9. Calculated structures of azulene 135 and 1,3-azulyne 136 compared to naphthalene 60 and 1,4-naphthyne 52." ...

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