Algebraic characterization of bridged polycyclic compounds

An approach based on the topological distance matrix is used for algebraic characterization of bridged polycyclic compounds. The classical bridged structures which have external bridges between cycles were examined together with the more complicated three-dimensional polycyclic systems regarded as containing internal bridges. Thirteen rules are given for characterizing the main types of structural rearrangements in these compounds. The important topological characteristic of (poly)cyclic systems, the molecular cyclicity, is examined in the polycyclic condensed, spiro- and bridged structures, respectively.     

Structure and magnetic properties of a non-heme diiron complex singly bridged by a hydroxo group

The synthesis of the first singly bridged non-heme diiron complex with a mu-hydroxo bridging ligand, [{(salten)Fe}2(OH)][B(C6H5)4].(CH3CN)x.(H2O)y (1) [H2salten = 4-azaheptane-1,7-bis(salicylideneiminate)], is reported. The complex has been characterized with X-ray crystallography, FTIR, magnetic susceptibility measurements, and M?ssbauer spectroscopy. The data have been compared with the results of DFT calculations on both 1 and a model with an unsupported mu-oxo bridge (2) to verify the formulation of the complex as a mu-hydroxo-bridged species. The X-ray structure [Fe-O(H) = 1.997(1) A and Fe-O(H)-Fe = 159 degrees ] is consistent with the DFT-optimized geometry of 1 [Fe-O(H) = 2.02 A and Fe-O(H)-Fe = 151 degrees ]; the Fe-O(H) distance in 1 is about 0.2 A longer than the Fe-O separations in the optimized geometry of 2 (1.84 A) and in the crystallographic structures of diiron(III) compounds with unsupported mu-oxo bridges (1.77-1.81 A). The formulation of 1 as a hydroxo-bridged compound is also supported by the presence of an O-H stretch band in the FTIR spectrum of the complex. The magnetic susceptibility measurements of 1 reveal antiferromagnetic exchange (J = 42 cm(-1) and H(ex) = JS(1).S(2)). Nearly the same J value is obtained by analyzing the temperature dependence of the M?ssbauer spectra (J = 43 cm(-1); other parameters: delta = 0.49 mm s(-1), DeltaE(Q) = -0.97 mm s(-1), and eta = 0.45 at 4.2 K). The experimental J values and M?ssbauer parameters agree very well with those obtained from DFT calculations for the mu-hydroxo-bridged compound (J = 46 cm(-1), delta = 0.48 mm s(-1), DeltaE(Q) = -1.09 mm s(-1), and eta = 0.35). The exchange coupling constant in 1 is distinctly different from the value J approximately 200 cm(-1) calculated for the optimized mu-oxo-bridged species, 2. The increased exchange-coupling in 2 arises primarily from a decrease in the Fe-O bond length.     

Mesoionic compounds with a bridged nitrogen atom.

The cyclization of (4-quinazolinylthio)phenylacetic and acetic acids gives extremely reactive thiazolo[3,2-c]quinazolinium 3-oxides, which, depending on the structure of the mesoionic ring, react with either electrophilic or nucleophilic reagents.See [1] for Communication 16.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 408–412, March, 1989.     

3,6-dioxypyridazine bridged tungsten-tungsten quadruple bonds. Comparisons of electron delocalisation with oxalate bridged compounds

The preparation and characterisation of the tungsten-tungsten quadruply bonded, 3,6-dioxypyridazine bridged complex [((t)BuCO(2))(3)W(2)](2)([micro sign]-H(2)C(4)N(2)O(2)) and its single electron oxidised radical cation are reported and, when compared with related bridged dimolybdenum complexes, reveal a different mechanism of electronic coupling from that seen in related oxalate bridged systems.     

Synthesis and structure of singly bridged and doubly bridged [MoFe(3)S(4)] double cubanes with bidentate phosphine ligands

The reactions of the (Et(4)N)(2)[(Cl(4)-cat)(MeCN)MoFe(3)S(4)Cl(3)] (I) cluster with Fe(pp)(2)Cl(2) (pp = depe (bis(1,2-diethylphosphino)ethane) or dmpe (bis(1,2-dimethylphosphino)ethane)) produced the [(Cl(4)-cat)MoFe(3)S(4)(pp)(2)Cl](2)(mu-pp) (pp = depe (III) or dmpe (V)) singly bridged double cubanes. The reactions of I with the same bidentate phosphine ligands in the presence of NaBPh(4) also produced III and the [(Cl(4)-cat)MoFe(3)S(4)(dmpe)(2)](2)(mu-S)(mu-dmpe) (VI) doubly bridged double cubane, respectively. The byproduct (BPh(4))[Fe(dmpe)(2)(MeCN)Cl] (VII) has been isolated from the reaction mixture and crystallographically characterized. The depe analogue of VI, [(Cl(4)-cat)MoFe(3)S(4)(depe)(2)](2)(mu-S)(mu-depe) (IV), has been successfully prepared from III in the presence of excess Li(2)S. Similar reactions with (Et(4)N)(2)[Fe(4)S(4)(SPh)(4)] (VIII) have resulted in the formation of the neutral Fe(4)S(4)(depe)(2)(SPh)(2) (IX) cluster. The chloride analogue of IX, Fe(4)S(4)(depe)(2)Cl(2) (XI), has been obtained by a reaction of IX with benzoyl chloride. The crystal and molecular structures of III, VI, VII, and XI have been determined by single-crystal X-ray crystallography. The electrochemical and spectroscopic properties, including the Mossbauer spectra of the new clusters, have been determined and analyzed.     

Synthesis and biological evaluation of benzimidazolone bridged triheterocyclic compounds

A new series of benzimidazolone bridged triheterocyclic compounds bearing thiosemicarbazide, thiadiazole, triazole, moieties was synthesized and then screened for their in vitro urease, α-glucosidase, and acetylcholinesterase inhibition properties for the first time. All the synthesized compounds showed an outstanding urease inhibitory effect when compared with standards. Compounds 1 , 4 , 5b , 5d , 6b , 6d , 7b , and 7d showed significant acetylcholinesterase inhibitory activity with IC₅₀ values between 7.32 ± 0.58 and 12.52 ± 0.13 μg/ml comparable to donepezil (15.12 ± 0.20 μg/ml). Compound 5c , having thiosemicarbazide moiety at the positions N-1 and N-3 of benzimidazolone nucleus, showed the highest α-glucosidase inhibitory activity (IC₅₀ = 11.42 ± 0.11 μg/ml).     

Conformational templation in a singly bridged calix[7]arene derivative induced by alkali metal cations

The first examples of alkali metal cation conformational templation of a calix[7]arene derivative were found in the alkali salts of 1,4-calix[7]crown-4, which were obtained by its treatment with the corresponding alkali metal carbonates. Competitive experiments showed that potassium and rubidium cations give the most effective templation, with a slight preference for the former. Experimental results and Monte Carlo conformational searches indicated that the cation interacts with all O-atoms including those of the crown-4 bridge.     

Chiral and Diastereoisomeric Ferrio Phosphanes

Abstract

Deprotonation of the iron salts [Cp(CO)₂FePRH₂] BF₄ (R=alkyl, aryl) (1) yields the ferrio-phosphanes Cp(CO)₂FeP(R)H (2), which are converted in the presence of PMe₃ to the dia-stereomeric derivates Cp(CO)(PMe₃)FeP(R)H (3).     

Synthesis, reactivity and structural studies of selenide bridged carboranyl compounds

Reaction of the lithium salt Li[1-R-1,2-closo-C(2)B(10)H(10)] with selenium under mild conditions, followed by hydrolysis gave the diselenide compound (1-Se-2-R-1,2-closo-C(2)B(10)H(10))(2) in contrast to the well-reported mercapto compounds 1-SH-2-R-1,2-closo-C(2)B(10)H(10) obtained using a similar synthetic procedure. Details for the preparation and X-ray structural characterisation of the new compounds (2-Me-1,2-closo-C(2)B(10)H(10))(2)Se, (1-Se-2-R-1,2-closo-C(2)B(10)H(10))(2) (R = Me, Ph, ) are specified. To further explore the mechanism of the dimerization reaction, the complex [Au(1-Se-2-Me-1,2-closo-C(2)B(10)H(10))(PPh(3))] was synthesized, confirming the existence of the intermediate Li[1-Se-2-R-1,2-closo-C(2)B(10)H(10)] at the early stages of the reaction before selenium oxidation. Theoretical calculations and cyclic voltammetry (CV) studies were carried out to compare the bonding nature of the sulfur and the selenium analog compounds. It was determined that diselenides have a higher tendency to reduce with respect to the disulfides and all chalcogen atoms were found to be positively charged.     

Mesoionic compounds with a bridged nitrogen atom. 13. Thiazolopyrimidoindoles

Derivatives of a new heterocyclic system, viz., thiazolo[3,43,2]pyrimido-[4,5-b]indole, are formed when 4-amino-2-methylthio-5-phenylthiazolium benzenesulfonate is heated with 3-formyloxindole in phosphorus oxychloride.See [1] for communication 12.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 502–504, April, 1985.     

Protolytic Opening of Two Diastereoisomeric Cyclopropanols

Cob(I) alamin ( 1(I) )-catalyzed reduction of the aldehyde 2 led to the two crystalline cyclopropanols 3 and 4 (see Scheme 2). The protolytic ring-opening starting from 3 produced the saturated aldehydes 6 and 7;8 was formed in traces only (see Scheme 3). The protolysis starting from 3 led, therefore, mainly to retention of configuration at the spiro C-atom ( 7 ); ring-opening with inversion was observed in traces only ( 8 ). Starting from 4 , the protolysis produced 9 and 7 ; the absence of 8 showed this protolysis to proceed 9 and 7 ; the absence of 8 showed this protolysis to proceed exclusively with inversion of configuration at the spiro center. Of the p-bromobenzoate 5 (cf. Scheme 2) the structure has been determined by X-ray analysis.     

Targeted application of bridged fragments in the design of physiologically active compounds

The present review comprises the examples of targeted application of bridged groups in drug design for the purposes of bioisosteric replacement, conformational restriction, or enhancement of lipophilicity of the lead-compound and as the scaffolds securing a proper orientation of the binding groups.     

Synthesis of bridged heteroaromatic compounds as reference standards for coal degradation products

The synthesis of 2-naphthyl 2′-dibenzothienyl ether, 1-(1′-naphthyl)-2-(4″-acridinyl)ethane and a series of naphthylethyldibenzothiophenes is reported.     

基于半夹心Cp*Rh单元的超分子桥环和螺环化合物的构筑策略

桥环和螺环化合物是有机化学中常用的概念而在其他领域鲜有提及。在本研究中,我们将桥环和螺环的概念拓展至超分子化学领域中并提出了相应的构筑策略。在刚性直线型配体中引入额外的螯合位点,通过配位驱动、分步组装的方法合成了复杂的3个有机金属超分子桥环化合物[(Cp*Rh)₆(μ-η²-η²-C₂O₄)₂(μ-C₂O₄)(L^A)₂](OTf)₆(1)、[(Cp*Rh)₆(dhbq)₂(pyrazine)(L^A)₂](OTf)₈(2)和[(Cp*Rh)₆(tpphz)₂(bpea)(L^A)₂](OTf)₁₂(3),以及一个超分子螺环化合物(Cp*Rh)₁₂(bibzim)₃Ru(L^A)₃(L^B)₃](OTf)₁₀(PF₆)₄(4),其中L^A=3,3''-di (pyridin-4-yl)-2,2''-bipyridine,OTf-=CF₃SO₃^-,dhbq=2,5-dihydroxy-1,4-benzoquinone,tpphz=tetrapyrido[3,2-a∶2'',3''-c∶3″,2″-h∶2‴,3‴-j]phenazine,bpea=1,2-di (pyridin-4-yl) ethane,bibzim=2,2''-bisbenzimidazole,L^B=4,4''-di (pyridin-4-yl)-1,1''-biphenyl。并通过单晶X射线衍射的方法一一表征了它们的单晶结构。     

基于半夹心Cp*Rh单元的超分子桥环和螺环化合物的构筑策略

桥环和螺环化合物是有机化学中常用的概念而在其他领域鲜有提及。在本研究中,我们将桥环和螺环的概念拓展至超分子化学领域中并提出了相应的构筑策略。在刚性直线型配体中引入额外的螯合位点,通过配位驱动、分步组装的方法合成了复杂的3个有机金属超分子桥环化合物[(Cp*Rh)₆(μ-η²-η²-C₂O₄)₂(μ-C₂O₄)(L^A)₂](OTf)₆(1)、[(Cp*Rh)₆(dhbq)₂(pyrazine)(L^A)₂](OTf)₈(2)和[(Cp*Rh)₆(tpphz)₂(bpea)(L^A)₂](OTf)₁₂(3),以及一个超分子螺环化合物(Cp*Rh)₁₂(bibzim)₃Ru (L^A)₃(L^B)₃](OTf)₁₀(PF₆)₄(4),其中L^A=3,3′-di (pyridin-4-yl)-2,2′-bipyridine,OTf^-=CF₃SO^3-,dhbq=2,5-dihydroxy-1,4-benzoquinone,tpphz=tetrapyrido[3,2-a∶2′,3′-c∶3″,2″-h∶2'',3''-j]phenazine,bpea=1,2-di (pyridin-4-yl) ethane,bibzim=2,2′-bisbenzimidazole,L^B=4,4′-di (pyridin-4-yl)-1,1′-biphenyl。并通过单晶X射线衍射的方法一一表征了它们的单晶结构。     

High yield syntheses of stable, singly bonded Pd2(6+) compounds

A general method for the syntheses of dipalladium compounds having a singly bonded Pd26+ core and the formula R,S-cis-Pd2(C6H4PPh2)2(O2CR)2Cl2 is described. When the alkyl group in the carboxylate ligands is an electron donating group, the compounds are stable and the yields high. The Pd-Pd distances for the diamagnetic compounds with R = CF3 and CMe3 are 2.5434(4) and 2.5241(9) A, respectively. Calculations at the DFT level suggest that the electronic configuration is sigma2pi4delta2delta*2pi*4. These represent rare examples of palladium(III) compounds.