NMR spectroscopic structure elucidation of the products of the reaction of 3-(3-aryl-3-oxopropenyl)- chromen-4-ones with 1,2-phenylenediamine

The reaction of 3-(3-aryl-3-oxopropenyl)chromen-4-ones with 1,2-phenylenediamine resulted in the unexpected formation of 10a-aryl-1,2,10,10a-tetrahydrobenzo-[4,5]-imidazo[1,2-a]pyridin-3-yl(2-hydroxyphenyl)-1-methanones. Their structure elucidation and complete 1H and 13C assignments have been performed by a combination of various one- and two-dimensional NMR experiments.     

Fused Mesoionic Heterocycles Analogues of Heptafulvene: Synthesis of 1, 3, 4-Thiadiazolo[3, 2-a]Pyridylium-2-Methylides

A number of 1, 3, 4-thiadiazolo[3, 2-a]pyridylium-2-methylides have been prepared either from 1-amino-4, 6-diphenylpyridine-2-thione and 3,3-bis(methylthio) acrylonitriles or by the reaction of the conjugate anion of active methylene compounds with 2-methylthio-1, 3, 4-thiadiazolo[3, 2-a]pyridinium cations.     

Application of n-Bu4NHF2 as a fluorinating agent for the preparation of fluoroanions: synthesis and crystal structure of the anions [t-BuPO3AlF2]2(2-), [PhPO3AlF2]2(2-), and [(O-i-Pr)3Ti(mu-F)2(mu-O-i-Pr)Ti(O-i-Pr)3]-

The first phosphonate anions of aluminum-containing fluorine and an anionic bridged fluoroalkoxy derivative of titanium have been realized using n-Bu4NHF2 as a fluorinating agent in organometallic synthesis. Reactions of [RPO3AlMe]4 [R = Ph (1), t-Bu] with n-Bu4NHF2 yield organic-soluble compounds of the type [n-Bu4N]2[RPO3AlF2]2 [R = Ph (2), t-Bu (3)], whereas the reaction of Ti(O-i-Pr)4 with n-Bu4NHF2 results in the formation of [n-Bu4N][O-i-Pr)3Ti(mu-F)2(mu-O-i-Pr)Ti(O-i-Pr)3] (4). These compounds have been obtained in high yields and have been adequately characterized through spectroscopic techniques and X-ray diffraction studies.     

Synthesis of ethyl 3-aryl-1-methyl-8-oxo- 8H-anthra[9,1-gh]quinoline-2-carboxylates as dyes for potential application in liquid crystal displays

[reaction: see text] Two new fluorescent ethyl 3-aryl-1-methyl-8-oxo-8H-anthra[9,1-gh]quinoline-2-carboxylates have been synthesized for the first time by cyclization of 3-(arylidene-amino)-benzo[de]anthracen-7-ones with 3-oxo-butyric acid ethyl ester. The cyclization reaction was investigated with and without concentrated hydrochloric acid as a catalyst. New dyes have shown a very good orientation parameter (S(A)) in nematic liquid crystal, indicating a high potential for application in liquid crystal displays.     

Kinetics of base hydrolysis of [Co(tetren)dmf]3+ and [Co(tetren)-dmso]3+ (tetren=1,11-diamino-3,6,9-triazaundecane)

The complexes [Co(tetren)dmf](ClO4)3 and [Co(tetren)-dmso](ClO4)3 have been prepared from alpha alpha-[Co(tetren)-Cl](ClO4)Cl (tetren=1,11-diamino-3,6,9-triazaundecane). 1H-n.m.r. and i.r. measurements confirm that the complexes contain O-bonded dmf and dmso. A biphasic reaction is observed in the base hydrolysis of the dmf derivative, monitored by the pH-stat method, with the fast reaction having kOH=1.2*104dm3mol-1s-1 and the slower reaction kOH=1.9*102dm3mol-1s-1 at 25degC and I=0.1moldm3. The fast reaction is assigned to the hydrolysis of the alpha beta(R)-[Co(tetren)dmf]3+ and the slower reaction to that of the alpha The reaction appears to proceed predominantly by a DCB pathway without parallel hydrolysis of coordinated dmf, which has been observed in the hydrolysis of [Co-(NH3)5dmf]3+. Base hydrolysis of [Co(tetren)dmso]3+ was monitored spectrophotometrically over the pH range 4.2 to 5.0. A single reaction was observed with kOH=1.9*106dm3mol-1 s-1 at 25°C and I=0.1 moldm-3. The rapid base hydrolysis is attributed to hydrolysis of the alpha beta(R)- or the alpha beta(S)-[Co(tetren)-dmso]3+ isomer rather than the alpha alpha-isomer. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis and biological activities of novel furo[2,3,4-jk][2]benzazepin-4(3H)-one derivatives

A novel seven-membered lactam formation method has been established by intramolecular ring closure reaction of 4-bromo-(E)-3-[(2-alkylvinyl)carbonylamino]benzo[b]furans under Heck coupling conditions. A number of furo[2,3,4-jk][2]benzazepin-4(3H)-ones, tricyclicbenzo[b]furans, have been prepared by this method and evaluated for their leukotriene B(4) (LTB(4)) receptor and poly(ADP-ribose)polymerase-1 (PARP-1) inhibitory activities.     

IMPROVED SYNTHESIS OF 3-SPIRO INDOLINES IN DRY MEDIA UNDER MICROWAVE IRRADIATION

An efficient, one-pot synthesis of novel spiro [indole-dipyrrolopyridines] (8) was achieved under microwave irradiation by the interaction of spiro [indole-dipyrrolopyrans] (3) with ammonium acetate (7) in the presence of acetic acid. Spiro [indole-dipyrrolopyrans] (3) were synthesized “in situ” by the reaction of indole-2,3-diones (1) and 2-pyrrolidone (2) in 1:2 molar ratio by microwave induced techniques for the first time. Comparative studies have been made between (a) microwave irradiation of (i) neat reaction of reactants in the absence of any solvent or catalyst (ii) reaction in presence of o-dichlorobenzene and (b) classical heating.     

Synthesis and characterisation of triselenocarbonate [CSe3]2- complexes

[Pt(CSe3)(PR3)2] (PR3= PMe3, PMe2Ph, PPh3, P(p-tol)3, 1/2 dppp, 1/2 dppf) were all obtained by the reaction of the appropriate metal halide containing complex with carbon diselenide in liquid ammonia. Similar reaction with [Pt(Cl)2(dppe)] gave a mixture of triselenocarbonate and perselenocarbonate complexes. [{Pt(mu-CSe3)(PEt3)}4] was formed when the analogous procedure was carried out using [Pt(Cl)2(PEt3)2]. Further reaction of [Pt(CSe3)(PMe2Ph)2] with [M(CO)6] (M = Cr, W, Mo) yielded bimetallic species of the type [Pt(PMe2Ph)2(CSe3)M(CO)5] (M = Cr, W, Mo). The dimeric triselenocarbonate complexes [M{(CSe3)(eta5-C5Me5)}2] (M = Rh, Ir) and [{M(CSe3)(eta6-p-MeC6H4(i)Pr)}2] (M = Ru, Os) have been synthesised from the appropriate transition metal dimer starting material. The triselenocarbonate ligand is Se,Se' bidentate in the monomeric complexes. In the tetrameric structure the exocyclic selenium atoms link the four platinum centres together.     

Quaternary ammonium salts of bis-3-azatricyclo[5,3,0,11,5]undecane

The reaction of the anhydride of exo-cis-bicyclo[3,3,0]octane-2,4-dicarboxylic acid with ammonia followed by the reduction of the resulting imide with lithium aluminum hydride has yielded 3-azatricyclo[5,3,0,1^1,5]undecane, from which a number of quaternary bisammonium salts have been obtained with dihaloalkanes. These salts have also been synthesized from the anhydride of exo-cis-bicyclo[3,3,0] octane-2,4-dicarboxylic acid and polymethylenediamines.     

Development of a [3+3] cycloaddition strategy toward functionalized piperidines

This paper describes a novel route to functionalized piperidines via a formal [3+3] cycloaddition reaction of activated aziridines and palladium-trimethylenemethane (Pd-TMM) complexes. The cycloaddition reaction generally proceeds enantiospecifically with ring opening at the least hindered site of the aziridine. Therefore, readily available enantiomerically pure 2-substituted aziridines can be utilized to prepare enantiomerically pure 2-substituted piperidines in good to excellent yield. The N-substituent on the aziridine proved to be crucial to the success of this reaction with only 4-toluenesulfonyl (Ts) and 4-methoxybenzenesulfonyl (PMBS) aziridines permitting smooth cycloaddition to take place. Additionally, spirocyclic aziridines have been found to participate in the [3+3] cycloaddition reaction, whereas 2,3-disubstituted aziridines can be applied to provide fused bicyclic piperidines, albeit in low yield.     

Mechanism, regioselectivity, and the kinetics of phosphine-catalyzed [3+2] cycloaddition reactions of allenoates and electron-deficient alkenes

With the aid of computations and experiments, the detailed mechanism of the phosphine-catalyzed [3+2] cycloaddition reactions of allenoates and electron-deficient alkenes has been investigated. It was found that this reaction includes four consecutive processes: 1) In situ generation of a 1,3-dipole from allenoate and phosphine, 2) stepwise [3+2] cycloaddition, 3) a water-catalyzed [1,2]-hydrogen shift, and 4) elimination of the phosphine catalyst. In situ generation of the 1,3-dipole is key to all nucleophilic phosphine-catalyzed reactions. Through a kinetic study we have shown that the generation of the 1,3-dipole is the rate-determining step of the phosphine-catalyzed [3+2] cycloaddition reaction of allenoates and electron-deficient alkenes. DFT calculations and FMO analysis revealed that an electron-withdrawing group is required in the allene to ensure the generation of the 1,3-dipole kinetically and thermodynamically. Atoms-in-molecules (AIM) theory was used to analyze the stability of the 1,3-dipole. The regioselectivity of the [3+2] cycloaddition can be rationalized very well by FMO and AIM theories. Isotopic labeling experiments combined with DFT calculations showed that the commonly accepted intramolecular [1,2]-proton shift should be corrected to a water-catalyzed [1,2]-proton shift. Additional isotopic labeling experiments of the hetero-[3+2] cycloaddition of allenoates and electron-deficient imines further support this finding. This investigation has also been extended to the study of the phosphine-catalyzed [3+2] cycloaddition reaction of alkynoates as the three-carbon synthon, which showed that the generation of the 1,3-dipole in this reaction also occurs by a water-catalyzed process.     

Theoretical studies on the metathesis processes, (Tp(PH3)MR(eta 2-H[bond]CH3)]-->[Tp(PH3)M(CH3)(eta 2-H[bond]R)] (M=Fe,Ru, and Os; R=H and CH3)

Theoretical calculations on the metathesis process, [Tp(PH3)MR(eta 2-H[bond]CH3)] --> [Tp(PH3)M(CH3)(eta 2-H[bond]R)] (M=Fe, Ru, and Os; R=H and CH3), have been systematically carried out to study their detailed reaction mechanisms. Other than the one-step mechanism via a four-center transition state and the two-step mechanism through an oxidative addition/reductive elimination pathway, a new one-step mechanism, with a transition state formed under oxidative addition, has been found. Based on the intrinsic reaction coordinate calculations, we found that the trajectories of the transferring hydrogen atom in the metathesis processes studied are similar to each other regardless of the nature of reaction mechanisms.     

DABCO and Bu(3)P catalyzed [4 + 2] and [3 + 2] cycloadditions of 3-acyl-2H-chromen-ones and ethyl 2,3-butadienoate

DABCO-catalyzed [4 + 2] and Bu(3)P-catalyzed [3 + 2] cycloadditions between 3-acyl-2H-chromen-ones and ethyl 2,3-butadienoate were developed for the synthesis of dihydropyran-fused and cyclopenten-fused chromen-2-ones with high regio- and stereo-selectivities, respectively. The synthetic procedures have the advantages of mild reaction conditions, convenient handling and good atom economy as well as a wide substrate scope, which make this method useful for the synthesis of potentially biologically active dihydropyran-fused and cyclopenten-fused chromen-2-ones derivatives. Possible reaction mechanisms have also been proposed on the basis of previous literature and our investigation.     

A bicyclo[3.2.0]hept-3-en-6-one approach to prostaglandin intermediates

[reaction:see text] The substituted cyclopentanic structures, 6-benzyloxymethyl-7-hydroxy-2-oxabicyclo [3.3.0]octan-3-one (1), a Corey lactone derivative, and 6-exo-benzyloxymethyl-2-oxabicyclo[3.3. 0]oct-7-en-3-one (2), have been obtained stereoselectively through the bicyclo[3.2.0]hept-3-en-6-one approach via 5-benzyloxymethyl-3-hydroxy-6-heptenoic acid, easily accessible from the inexpensive monoprotected cis-2-butene-1,4-diol.     

R3Al-R'3SiOTf: novel and powerful reagent system for stereospecific alkylation-silylation reactions of epoxides

[reaction: see text] A novel and powerful reagent system R(3)Al-R'(3)SiOTf for the one-pot alkylation-silylation reaction of epoxides was discovered, and the reactions of various epoxides with the new reagent system have been demonstrated to occur stereospecifically giving rise to the corresponding alkylation-silylation products in excellent yields.     

Synthesis and structure of the organometallic MFe2(mu3-S)2 clusters (M = Mo or Fe)

New organometallic clusters with the MFe2(mu3-S)2 core (M = Mo or Fe) have been synthesized from inorganic [MoFe3S4] or [Fe4S4] clusters under high pressure CO. The reaction of (Cl4-cat)2Mo2Fe6S8(PR3)6[R = Et, (n)Pr] with high pressure CO produced the crystalline [MoFe2S2]4+ clusters, (Cl4-cat)Mo(O)Fe2S2(CO)(n)(PR3)6-n[n= 4, Et =I, (n)Pr =II; n = 5, Et =III] after flash column chromatography. The similar [MoFe2S2]4+ cluster, (Cl4-cat)2MoFe2S2(CO)2(depe)(2)(IV), also has been achieved by the reactions of (Cl4-cat)MoFe3S3(CO)6(PEt3)2 with depe by reductive decoupling of the cluster. For the [Fe3(mu3-S)2]4+ cluster, [Fe4S4(PcHex3)4](BPh4) was reacted with high pressure CO to produce a new Fe3S2(CO)7(PcHex)(2)(V) compound. These reactions generalized the preparation of organometallic compounds from inorganic clusters. All the compounds have been characterized by single crystal X-ray crystallography. A possible reaction pathway for the synthesis of the MFe2(mu3-S) clusters (M = Mo or Fe) has also been suggested.     

Magnetism of cyano-bridged Ln3+-M3+ complexes. Part II: one-dimensional complexes (Ln3+ = Eu, Tb, Dy, Ho, Er, Tm; M3+ = Fe or Co) with bpy as blocking ligand

The reaction of Ln(NO3)3(aq) with K3[Fe(CN)6] or K3[Co(CN)6] and 2,2'-bipyridine in water/ethanol led to 13 one-dimensional complexes: trans-[M(CN)4(mu-CN)2Ln(H2O)4(bpy)]n.4nH2O.1.5nbpy (Ln = Eu3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Lu3+; M = Fe3+, Co3+). The structures for [EuFe]n (1), [TbFe]n (2), [DyFe]n (3), [HoFe]n (4), [ErFe]n (5), [TmFe]n (6), [LuFe]n (7), [EuCo]n (8), [TbCo]n (9), [DyCo]n (10), [HoCo]n (11), [ErCo]n (12), and [TmCo]n (13) have been solved: they crystallize in the triclinic space group P and are isomorphous. They exhibit a supramolecular architecture created by the interplay of coordinative, hydrogen bonding, and pi-pi interactions. A stereochemical study of the eight-vertex polyhedra of the lanthanide ions, based on continuous shape measures, is presented. The Ln3+-Fe3+ interaction is antiferromagnetic in [DyFe]n and [TbFe]n. For [EuFe]n, [HoFe]n, [ErFe]n, and [TmFe]n, there is no sign of any significant interaction. The magnetic behavior of [DyFe]n suggests the onset of weak long-range ferromagnetic ordering at 2.5 K.     

The stepwise formation of mixed-metal coordination networks using complexes of 3-cyanoacetylacetonate

The complexes [Cu(L(1))2] 1, [Fe(L(1))3] 3 and [Al(L(1))3] 4 [L(1) = CH(3)C(O)C(CN)C(O)CH(3)] have been prepared for use as metallo-ligands in mixed-metal coordination networks. Surprisingly, the nature of the copper precursor is important in the synthesis of 1, with the reaction between Cu(NO3)2.3H2O, HL(1) and NEt3 giving [Cu6(micro(3)-OMe)4(micro-OMe)2(L(1))6] 2 instead of the anticipated 1, which was obtained with CuCl2.2H2O under the same conditions. Compound 1 reacts with AgNO3 to form [Cu(L(1))2.AgNO3](infinity) 5, the structure of which contains one-dimensional chains in which Ag+ ions bridge between molecules of 1. These chains are cross-linked into ladders by bridging nitrates. The product obtained from the reaction of 3 and AgNO3 is crucially dependent on the solvent used. The reaction in methanol-acetone gives [Fe(L(1))3.AgNO3](infinity) 6, {[Fe2(micro-OMe)2(L(1))4.2AgNO3].CH(3)C(O)CH(3)}(infinity) 7 and [Fe2(micro-OMe)2(L(1))4.AgNO3](infinity) 8. Compounds 6 and 8 both have one-dimensional chain structures, whereas 7 has a two-dimensional layer structure. The reaction in methanol gives 6 and 8 as the major products and, in addition, small quantities of {[AgFe2(micro-OMe)2(L(1))4]OH.0.4H2O](infinity) 9. Compound 9 has a three-dimensional structure based on doubly interpenetrated PtS nets. Compounds 7-9 contain Fe2(micro-OMe)2(L(1))4 dimers, but the coordination properties of the dimers differ, with all the cyanides coordinated in 7 and 9 but one uncoordinated in 8. The orientation of the cyanide groups depends on the relative chirality of the iron centres. A transmetallation reaction occurs between 4 and AgNO3 to give [Ag(L(1))](infinity) 10, which has a two-dimensional layer structure. Compounds 2, 3 and 5-10 have been characterised by X-ray crystallography.     

Synthesis of [2]- and [3]rotaxanes through Sonogashira coupling

The synthesis of new [2]- and [3]rotaxanes through Sonogashira coupling has been accomplished in the aim to built oligo(phenyleneethynylene) (OPE) encircled by crown ethers. Optimization of the Sonogashira coupling for the formation of the [2]rotaxane (capping reaction) is presented and the best method has been applied for the synthesis of the longer [3]rotaxane.     

Dimerization of Incomplete Cubane-Type Mo3S4(DTP)3 Units Linked by Bridging α, ω-Dicarboxylate

Since the trinuclear molybdenum cluster compound Mo₃S₄(DTP)₃(μ-DTP)(L) (DTP=diethyldithiophosphate, L=loosely-coordinated ligand) was reported^[1],a large number of monomeric trinuclear molybdenum derivatives have been synthesized from it by its diverse substitution reactions^[2]. This reaction provides a useful route to design cluster complexes with specific functions. By the reaction with α, ω-dicarboxylates, we successfully synthesized the first oligomer containing two incomplete cubane-type[Mo₃S₄] cores formulated as[Mo₃S₄(DTP)₃(DMF)]₂[η²-μ-OOC(CH₂)₃COO-μ-η²]) whose molecule structure is as follows: