Photochromic dihetarylethenes

The structures of two hetarylethene photochromes,viz., 1,2-bis(2-ethyl-5-ethylsulfonylthien-3-yl)perfluorocyclopentene and 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene, were established by X-ray diffraction analysis. The conformational parameters of the title compounds are considered. The cyclopentene ring in the former compound is planar and this ring in the latter compound adopts an envelope conformation. There are no overall conjugated systems in the molecules under study. In both structures, the dihetaryl fragments are rotated with respect to the perfluorocyclopentene fragments by ∼55°. The thiophene and benzoxazole rings in 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene are coplanar. For Part 3, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 74–77, January, 2000.     

Substituent effects on some physicochemical properties of chalcones and their vinylogues

Carbonyl stretching frequencies (ν_CO), dipole moments (μ), longwave maxima (λ_max), half-wave potentials (°_1/2), and relative intensities (Z/Z₀) of benzoyl-ion in mass-spectra oftrans chalcones and their vinylogues of the general type PhCO(CH=CH)_nC₆H₄R-p (I) were measured. Contrary to the previously investigated polyenes of the type R(CH=CH)_nR′ (R′ = CHO or COOEt) variation of the substituent R in compounds I has little influence on properties of I in the ground state and a satisfactory linear relationship between (ν_CO) or μ and σ constants exists only in the case of I (n = 0, 1); the best correlation with σ⁺ indicates that the mesomeric mechanism plays a great part in the transmission of electronic effects. λ_max.,E_1/2, orZ/Z₀ of all series I (n = 0–3) correlate with σ_p or σ⁰ constants, and the separation of mesomeric and inductive effects by multiparametric correlation reveals that in this case inductive effect is of great importance in the transmission of electronic effects. These features were accounted for by the non-planar structure of molecules of I, which was confirmed by X-ray analysis of I (R = Br). The Pariser-Parr-Pople method has also been applied to the calculation of π-electronic density in molecules I and it was found that the introduction of various substituents in para position of I exercises a very little influence on the electronic distribution in compounds I.     

The molecular and crystal structure of stable 5-methyl-2-methylsulfonyl-3-thiophenecarbonitrile oxide

A stable thiophene derivative, 5-methyi-2-methylsulfonyl-3-thiophenecarbonitrile oxide, which is active in reactions with dipolarophiles, was studied by means of X-ray structural analysis. In the crystalline state the structure includes two independent molecules with similar values of geometric and conformation parameters. The bond angle at the C atom of the nitrile oxide group is significantly different from 180°. The intramolecular distances between the C and S atoms in the nitrile oxide and sulfonyl groups are well below the equilibrium distance. The stability of the molecule is thought to be increased by electrostatic or donor-acceptor interactions between the atoms of these groups. The mutual orientation of the two independent molecules in the crystal is nearly orthogonal.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–727, April, 1993.     

Synthesis and Structure of 4-Indolyl-5-(thieno[3,2-<Emphasis Type="Italic">b</Emphasis>]pyrrol-6-yl)imidazoles

A procedure was proposed for regioselective acylation of methyl 2-methyl-4H-thieno[3,2-b]-pyrrole-5-carboxylate with 2-(3-indolyl)-2-oxoacetyl chloride. Reactions of the resulting methyl 6-[2-(3-indolyl)-1,2-dioxoethyl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate with aromatic aldehydes and ammonium acetate in acetic acid afforded the corresponding methyl 6-[2-aryl-4-(3-indolyl)imidazol-5-yl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylates. The structure of methyl 6-[2-(4-chlorophenyl)-4-(3-indolyl)imidazol-5-yl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate was studied by X-ray analysis.     

Conformational peculiarities of a new heterocyclic dihydrothienothiopyranoisoxazole system

The crystalline and molecular structures of 3H-3a,4-dihydro-7-methylthieno[3,2:5,6]thiopyrano[4,3-c]isoxazole and 3H-3a,4-dihydro-3-isopropoxycarbonyl-3a,7-dimethylthieno[3,2:5,6]thiopyrano[4,3-c]isoxazole are determined by X-ray analysis. The effect of steric factors on intramolecular 1,3-dipolar cycloaddition is shown.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 302–304, February, 1995.This work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-18461).     

Synthesis and structures of Cu<Superscript>I,II</Superscript> complexes with a 2,2´-bipyridine derivative bearing a (+)-3-carene moiety

The complex salt {[CuL₂][Cu₄I₆]?MeCN}_n (1) and the compound [Cu₄L₃I₄]?3 MeCN (2) (L is a chiral ligand bearing a natural monoterpene (+)-3-carene moiety) were synthesized. The crystal structures of compounds 1 and 2 were determined by X-ray diffraction. The structure of compound 1 consists of complex cations [CuL₂]²⁺ (N₃O₂ polyhedron is a trigonal bipyramid) and Cu^I coordination polymers (CuI₄ polyhedron is a tetrahedron) as anions. The experimental magnetic moment μ_eff at 300 K is 1.90 μ_B, which is consistent with the X-ray diffraction data and the assumption that compound 1 is mixed-valence. The structure of compound 2 comprises a tetranuclear Cu^I complex, in which three Cu atoms are coordinated by two N atoms of the ligand L and two I atoms, and the fourth Cu atom is coordinated by four I atoms (coordination polyhedra are distorted tetrahedra). Compounds L and 2 were found to influence the viability of human laryngeal carcinoma cells (Hep2). The IC₅₀ value for complex 2 (13.0±1.7 μM) is substantially smaller than IC₅₀ for compound L (30.5±0.5 μM).     

Photochromic dihetarylethenes. 17. Synthesis and photochromic properties of dithienylethenes containing new heterocyclic bridging fragments

Procedures were developed for the synthesis of substituted bis(2,5-dimethyl-3-thienyl)ethenes containing the imidazol-2-one, 1,3-dioxol-2-one, or 1,3-oxazol-2-one fragments as ethene bridges. These compounds were demonstrated to exhibit the photochromic properties. The cyclic forms of some imidazolone and oxazolone photochromes possess high thermal stability. The structure of photochromic 4,5-bis(4-acetyl-2,5-dimethyl-3-thienyl)-3-methyl-2,3-dihydro-1,3-oxazol-2-one was established by X-ray diffraction analysis. The molecule adopts an anti-parallel conformation similar to that of perfluorocyclopentene-bridged dithienylethenes.     

The first regioselective double electrophilic substitution of the C2-symmetric pseudo-meta-disubstituted [2.2]paracyclophanes

We report here the first examples of the regioselective double electrophilic substitution of chiral C₂-symmetric pseudo-meta-disubstituted [2.2]paracyclophanes. Thus, the double acylation of 4,15-dihydroxy[2.2]paracyclophane occurs ortho-regioselectively, whereas the double acylation of its respective dimethyl ether is completely para-regioselective. Double bromination of 4,15-dicarbomethoxy[2.2]paracyclophane regioselectively generates the pseudo-gem-substitution pattern. The approaches elaborated allow the synthesis of all three possible types of chiral bis-bifunctional compounds, which have two independent, although chemically and stereochemically equal, functional fragments with pseudo-meta mutual orientation of both pairs of identical substituents.     

Synthesis, structure, and some reactions of 1,2-bis(2-alkylthio-3-thienyl)perfluorocyclopentene

The synthesis of 1,2-bis(2-ethylthio-3-thienyl)perfluorocyclopentene is described. Metallation with n-BuLi and subsequent treatment with DMF or CO₂ gave the corresponding 5,5-diformyl and dicarboxy derivatives. The structure of 1,2-bis(2-ethylthio-3-thienyl)perfluorocyclopentene was studied by x-ray structural analysis. It was established that the unit cell contains two crystallographically independent molecules with geometrical and conformational parameters close to one another. The thiophene rings were inclined at an angle of 60° to the plane of the perfluorocyclopentene fragment, the thioalkyl groups were disposed antiparallel to it.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 927–933, July, 1998.