Radical cation of dibenzothiophene fully annelated with bicyclo[2.2.2]octene units: X-ray crystal structure and electronic properties

New dibenzothiophene 2 fully annelated with bicyclo[2.2.2]octene units was synthesized and oxidized to stable radical cation salt 2(*+)SbCl(6)(-), whose structure was determined by X-ray crystallography. Although the intrinsic electronic structure of 2(*+) is predicted to be close to structure A, an interaction with the counteranion makes structure B contribute significantly. A part of the salt 2(*+)SbCl(6)(-) underwent rearrangement to arenium ion 6(+), whose structure was also clarified by X-ray crystallography.     

Synthesis of a pericosine analogue with a bicyclo[2.2.2]octene skeleton

A new analogue of the antitumor pericosines possessing a bicyclo[2.2.2]octene skeleton has been synthesized from methyl gallate using oxidative dearomatization and regio- and diastereoselective Diels-Alder reaction as the key steps.     

Formation of a novel arenium ion from the radical cation of a twisted triphenylene fully annelated with bicyclo[2.2.2]octene units

[reaction: see text]. Triphenylene 1 was synthesized by palladium-catalyzed cyclotrimerization of a benzyne annelated with two bicyclo[2.2.2]octene (BCO) units. Theoretical calculations indicated that 1 is constrained to a twisted conformation with a C2 symmetry as a result of steric repulsion between the BCO units. The one-electron oxidation of 1 with SbCl5 gave the corresponding radical cation 1*+, which abstracted a chlorine atom in the medium with the concomitant rearrangement to form novel arenium ion 2+.     

Radical cation and dication of fluorene fully annelated with bicyclo[2.2.2]octene units: importance of the quinoidal resonance structure in the cationic fluorene

Fluorene 1 fully annelated with bicyclo[2.2.2]octene units was newly synthesized and oxidized to stable cationic species. The structure of radical cation salt 1(.+)SbCl(6)(-) was determined by X-ray crystallography, while the first fluorene dication 1(2+) was characterized by (1)H and (13)C NMR at -80 degrees C. Combined with the results of theoretical calculations, an important contribution of a quinoidal structure to the resonance hybrid was demonstrated in both 1(.+) and 1(2+). [structure: see text]     

1,2-dithiin annelated with bicyclo[2.2.2]octene frameworks. One-electron and two-electron oxidations and formation of a novel 2,3,5,6-tetrathiabicyclo[2.2.2]oct-7-ene radical cation with remarkable stability owing to a strong transannular interaction

A stable derivative of 1,2-dithiin annelated with bicyclo[2.2.2]octene frameworks 4 was synthesized as red crystals by the reaction of a dilithiated dimer of bicyclo[2.2.2]octene with elemental sulfur in 59% yield. The cyclic voltammetry of 4 in CH(2)Cl(2) at -78 degrees C showed two reversible oxidation waves at E(1/2) +0.18 V and +0.72 V versus Fc/Fc(+), indicating that the radical cation and dication of 4 are stable under these conditions. Upon chemical one-electron oxidation of 4 in a rather low concentration (4.0 x 10(-4) M) with a 1.5 equiv of SbCl(5) in CH(2)Cl(2), a radical cation 4.+ was formed, whose spin distribution was determined by ESR spectroscopy and by the results of theoretical calculations (UB3LYP/6-31G). The electronic absorption spectrum of 4.+ in CH(2)Cl(2) exhibited a maximum absorption at 428 nm (epsilon = 2.3 x 10(3)), which was hypsochromically shifted from that of neutral 4 (469 nm). When the radical cation 4.+ was produced in higher concentration (0.06 M) in CH(2)Cl(2), a disproportionation was found to take place to give a SbCl(6)(-) salt of remarkably stable radical cation 5.+ having a novel 2,3,5,6-tetrathiabicyclo[2.2.2]oct-7-ene structure. In the X-ray structure of 5.+SbCl(6)(-), the transannular distance (2.794(3) A) between the sulfur atoms was found to be less than the sum of the van der Waals radii of a sulfur atom (3.70 A), suggesting the existence of a bonding interaction between the two disulfide linkages. The theoretical calculations (UB3LYP/6-31G) suggested that this transannular interaction could be described as the resonance between the limiting structures, each of them having a two-center three-electron bond between two sulfur atoms belonging to two different disulfide linkages: thus, both the spin and positive charge are equally delocalized to the four sulfur atoms, causing a great stabilization of 5.+. On the other hand, the 1,2-dithiin radical cation 4.+ was found to readily react with triplet oxygen with subsequent rearrangement to give the 1,2-dithiolium derivative 6+ having a carboxyl group. Finally, the reaction of 4 with an excess amount of SbF(5) gave the corresponding dication 4(2+), which was found to be a 6pi aromatic system on the basis of the results of NMR measurement and theoretical calculations.     

The stable radical cation of thiophene annelated with bicyclo[2.2.2]octene and its reaction with triplet oxygen to give a protonated cation of 2-butene-1,4-dione derivative

The first isolable salt of the thiophene radical cation was prepared from the derivative annelated with two bicyclo[2.2.2]octene units, and its reaction with triplet oxygen was found to give a novel cation of a proton-chelating 2-butene-1,4-dione derivative with remarkable stability.     

Synthesis and conformational study of 1,3,2-oxazaphosphorino[4, 3-a]isoquinolines: a new ring system

A set of 1,3,2-oxazaphosphorino[4,3-a]isoquinolines 6a,b-9a,b, a new ring system, was synthesized, and their stereochemical and conformational analyses were performed by (1)H, (13)C, and (31)P NMR methods. X-ray measurements were also carried out to confirm the stereochemical assignments and conformational results obtained by means of NMR. Intermediate coupling constants (3)J(P,H) were found for compounds 7 and 9; these do not relate to equilibria between previously reported conformers, but are indicative of new distorted conformational states in solution. The connecting isoquinoline and the steric interaction between the aromatic moiety and the Me-1 substituent can block the oxazaphosphorinane ring. The conformational behavior of compounds 6 and 8 was characterized by the usual chair-twist equilibrium.     

Diazabicycloalkanes with nitrogen atoms in nodal positions. 14. Synthesis of dibenzo[1′,2′-b,e]-1,4-diazabicyclo[2.2.2]octadienes containing a tertiary amino group in the aromatic ring

The corresponding 2-amino derivatives of phenazinium salts were obtained by the action of dimethylamine and morpholine on N-(2-hydroxyethyl)phenazinium chloride. The subsequent exchange of the hydroxyl group for chlorine and the reductive cyclization of 2-amino derivatives of N-(2-chloroethyl)phenazinium salts leads to 4-aminodibenzo[1,2-b,e]-1,4-diazabicyclo[2.2.2]octadienes, together with unsubstituted dibenzo-[b,e]-1,4-diazabicyclo[2.2.2]octadiene and the corresponding 2-aminophenazines.For Communication 13, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1658–1661, December, 1986.     

Synthesis,structure and electrocatalytic H2-evoluting activity of a dinickel model complex related to the active site of [NiFe]-hydrogenases

Structural and functional biomimicking of the active site of [NiFe]-hydrogenases can provide helpful hints for designing bioinspired catalysts to replace the expensive noble metal catalysts for H₂ generation and uptake. Treatment of dianion [Ni(phma)]²⁻ [H₄phma = N,N'-1,2-phenylenebis(2-mercaptoacetamide)] with [NiCl₂(dppp)] (dppp = bis(diphenylphosphino)propane) yielded a dinickel product [Ni(phma)(μ-S,S')Ni(dppp)] (1) as the model complex relevant to the active site of [NiFe]-H₂ases. The structure of complex 1 has been characterized by single-crystal X-ray analysis. From cyclic voltammetry and controlled potential electrolysis studies, complex 1 was found to be a moderate electrocatalyst for the H₂-evoluting reaction using ClCH₂COOH as the proton source.     

Synthesis and properties of 5-(2,3-diphenylcyclopropenylidene)-1,6-methano-2(5h)-[10]- annulenone (or 10,11-diphenyl-4,9-methano[3.10]quinaren-3-one). Contribution of a homobenzene structure annelated on [3.6]quinaren-3-one

The title quinarenone 2 has been prepared and proved that the three-membered ring possesses a larger diatropicity than diphenylcyclopropenone and the seven-membered ring exists in a cycloheptatriene (not norcaradiene) tautomer having a contribution of a homobenzene structure. The rotational barrier about the intercyclic bond of 2 is 13.3 Kcal/mol.     

Research on nitrogen containing heterocyclic compounds. XVIII. Synthesis of 9H-pyrrolo[2,1-c]-s-triazolo[4,3-a][1,4]benzodiazepine,a novel tetracyclic ring of pharmaceutical interest

Reaction of di-4-morpholinylphosphinic chloride on 5,10-dihydro-9H-pyrrolo[2,1-c][1,4]benzodiazepin-11-one 9 afforded 11-(di-4-morpholinylphosphinyloxy)-5H-pyrrolo[2,1-c][1,4]benzodiazepine 10 . Displacement of di-4-morpholinylphosphinyloxy group of 10 by formylhydrazine with concomitant intramolecular cyclization led directly to 9H-pyrrolo[2,1-c]-s-triazolo[4,3-a][1,4]benzodiazepine 7, a novel nitrogen heterocyclic ring of pharmaceutical interest. A new procedure for the synthesis of 9 is also described.     

Synthesis, crystal structure, and nonlinear optical properties of Li6CuB4O10: a congruently melting compound with isolated [CuB4O10]6- units

Single crystals of Li(6)CuB(4)O(10) have been synthesized, and its crystal structure has been determined. Li(6)CuB(4)O(10) crystallizes in the non-centrosymmetric triclinic space group P1 (No. 1). The structure consists of isolated [CuB(4)O(10)](6)(-) polyanions that are bridged by six LiO(4) tetrahedra. Li(6)CuB(4)O(10) is a congruently melting compound. It produces SHG intensity similar to that produced by KH(2)PO(4) and is phase-matchable.     

Synthesis, structure, and magnetic behavior of a new gadolinium thiosilicate: Gd4[SiS4]3

Single crystals of the title compound were prepared from the elements by a solid state reaction in an iodine atmosphere. Data collection were carried out using a STOE image plate detector at 293 K. The compound crystallizes in the space group P2₁/n of the monoclinic system isotypically to Tb₄[SiS₄]₃ with four formular units in cells of dimensions: a=986.7(2) pm, b=1099.69(19) pm, c=1646.2(4) pm, β=102.67(3)°. The corresponding residual (all data) for the refined structure is 3.09%.The magnetic behavior of the compound was investigated on powdered samples in a temperature range between 1.7 and 300 K. The deviations from the Curie-behavior could be interpreted by the molecular field approach.     

The effect of polyether ligands on the solution structure of [Li]-α-(phenylthio)benzyllithium in tetrahydrofuran: A H,Li-HOESY NMR study

[⁶Li]-α-(phenylthio)benzyllithium 1-⁶Li was studied in THF/[D₈]THF solution (1:1) in the presence of several acyclic and cyclic polyether ligands by ¹H,⁶Li-HOESY, ¹H and ¹³C NMR spectroscopy. The question whether these ligands are bonded to lithium or not is important for physical–organic investigations as well as for studies of the ground state of (stereoselective) reactions of organolithium compounds in the presence of such ligands. Dimethoxyethane is not bonded to lithium under these conditions. The acyclic ethers diglyme and triglyme coordinate only weakly to the organolithium compound and form contact ion pairs (CIPs) at 25°C. At −80°C, CIPs are in equilibrium with separated ion pairs (SIPs). Very stable complexes of 1-⁶Li are obtained with crown ether ligands. Addition of 12-crown-4 and 15-crown-5, respectively, results in the exclusive formation of SIPs at 25°C and −80°C. With 18-crown-6, a CIP–SIP equilibrium is observed at 25°C which is shifted entirely to the SIP side at −80°C. Graphical analyses of the ¹H and ¹³C NMR spectra of the polyether complexes of 1-⁶Li revealed correlations between the chemical shifts of the para phenyl carbon C-5, the para phenyl proton H-5, the benzylic carbon C-1, and the proton–carbon coupling constant J(C-1,H-1) of 1-Li, which are useful probes for the charge distribution within the carbanionic moiety of 1-⁶Li in the respective complexes, and thus for the ion pair character as a function of the polyether complexation of lithium.     

Synthesis and structure of fused ring containing phosphorus compound—pyridinium 8, 9, 16,-17-tetradehydro-6,14-dithiono-7,8,15,16-tetraza-5,13-dioxa-6,14-diphospha-dibenzo [a,h] tetradecahydroanthracene-6,14-dithiolate and its derivatives

The syntheses of pyridinium of 8,9,16,-17-tetradehydro-6,14-dithiono-7,8,15,16-tetraza-5,13-dioxa-6,14-diphospha-dibenzo [a,h] tetradecahydroanthracene-6,14-dithiolate and its eleven derivatives were described. The crystal and molecular structures of the pyridinium compound and its several derivatives were also determined.     

Gas-phase thermolysis of benzotriazole derivatives. Part 2: Synthesis of benzimidazo[1,2-b]cinnolines, a novel heterocyclic ring system, by pyrolysis of benzotriazole derivatives. Kinetic and mechanistic study

Gas-phase pyrolysis of benzotriazolyl ketones and their arylhydrazones gave indole, benzimidazole and benzimidazo[1,2-b]cinnoline derivatives via interesting novel routes. The homogeneous first-order gas-phase pyrolysis of 10 arylhydrazono derivatives of α-benzotriazol-1-yl ketones was investigated over the temperature range 420-530 K. Five of these substrates were 2-(arylhydrazono)-2-(benzotriazol-1-yl)-1-phenylethanone derivatives (Series 1), and the remaining five were the corresponding acetone analogues (Series 2). The values of the Arrhenius frequency factor (log A/s⁻¹) for the pyrolysis of the compounds of Series 1 and 2 were, respectively, 12.27±1.44 and 9.07±1.20, while the values of the Arrhenius activation energy (E_a/kJ mol⁻¹) were 132.8±8.4 and 123.2±23.0, respectively. Besides, reaction pathways are offered to rationalize the kinetic results and to account for the products of pyrolysis of the substrates under study, namely: (i) extrusion of N₂ and formation of a 1,3-biradical reactive intermediate leading to substituted imidazoles (Series 1); (ii) intramolecular nucleophilic addition, cyclization and subsequent fragmentation with or without loss of H₂O/N₂ fragments (Series 1 and 2).