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[structure: see text] The role played by the electronic properties and the steric features of bis(oxazoline) ligands in the Cu(I)-catalyzed cyclopropanation of styrene effected with ethyl diazoacetate was investigated. Two pairs of new bis(oxazolines) displaying flexible and atropisomeric 3,3'-bithiophene backbones were synthesized and structurally and electronically characterized. For the first time, the electrochemical oxidative potential was used as a reliable index of the electronic density on the nitrogen atom of the chelating groups of new and, for comparative purposes, of already known bis(oxazolines). The Cu(I) complexes of the new ligands were prepared, and their enantioselection ability and catalytic efficiency were tested. This investigation suggests that steric factors and catalyst geometrical features are clearly more important than any consideration of the electronic properties of the chiral ligands.

The electrochemical polymerization of bis(2-thienyl)methanes carrying substituents either on the methylene carbon or on the thiophene rings is reported. Poly(dithienylenemethylene)s are formed which undergo in-situ dehydrogenation to poly(dithienylenemethine)s. Bis(3,4-ethylenedioxythienyl)methane gave a very low-gap material (0.4 V onset-based bandgap). This value is much lower than those previously reported for chemically prepared materials having the same conjugated backbone but carrying different substituents. The unsubstituted bis(2-thienyl)methane gives a similar low-gap polymer as well, but overoxidation and probably misjunction defects are present. No polymer was formed in the case of 2,2‘-bis(2-thienyl)propane, for which the possibility of producing a conjugated polymer is precluded by the lack of at least one hydrogen atom on the carbon bridging the thiophene units. Full electrochemical and optical characterization data for the polymers are reported, and the polymerization and p- and n-doping pr...

The Pd(II) and Pt(II) complexes (perchlorates and hexafluoroantimoniates, respectively) of a series of C2 symmetric biheteroaromatic diphosphines differing in their electronic properties at phosphorus have been tested as catalysts in [4+2]-cycloaddition reactions of cyclopentadiene and N-2-alkenoyl-1,3-oxazolidine-2-ones. The best stereoselection results were obtained with the complexes produced from electron-rich ligands, which were found to give also the kinetically most active catalysts.

Racemic (+/-)-3,3'-bis(diphenylphosphinyl)-1,1'-dimethyl-2, 2'-biindole (1c) (N-Me-2-BINPO) and (+/-)-3, 3'-bis(diphenylphosphinyl)-1,1'-bis(methoxymethyl)-2,2'-biindole (1d) (N-MOM-2-BINPO) were synthesized in satisfactory yields following a three-step reaction sequence, starting from indole. Resolution of racemic 1c and 1d was achieved through fractional crystallization of their diastereomeric adducts with optically active dibenzoyl tartaric acids, followed by alkaline decomplexation of the diastereomerically pure salts. Their trichlorosilane reduction gave enantiopure phosphines (+)- and (-)-(1a) (N-Me-2-BINP) and (+)- and (-)-(1b) (N-MOM-2-BINP). The electrochemical oxidative potential of 1a and 1b was found to be 0. 52 and 0.60 V, respectively. Both the enantiomers of (1a) were tested as ligands of Ru(II) in asymmetric hydrogenation reactions of alpha- and beta-oxoesters. Reactions were found to be outstandingly fast and enantioselection quite good. Comparative kinetic experiments on the hydrogenation reaction of methyl acetoacetate carried out with 1a, 1c, BINAP, and other biheteroaromatic diphosphines as ligands of Ru(II) demonstrated that all the reactions follow a first-order kinetic. A linear relationship was found between the kinetic constant log and the electrochemical oxidative potential of the diphosphine ligand.

The effects of N- and C-methyl substitution on electrical and spectral properties of pyrrole, 2,2¢-bipyrrole, and the corresponding polymers were investigated. The whole series of monomethyl and N- or Câ-dimethyl-substituted 2,2¢-bipyrroles was synthesized, and the electrochemical and spectral properties of all the compounds were investigated under identical testing conditions. The corresponding polymers were prepared by electrochemical anodic oxidation under comparable experimental conditions and their spectroscopic and conductivity properties evaluated for comparison. The higher degree of efficiency in transmission of electronic effects associated with methyl substitution at Câ with respect to substitution at N was clearly demonstrated. The influence of the symmetry of the starting monomer (C2v or Cs) on the electrical properties of the resulting polymers is discussed.

The effects of N- and Cβ-methyl substitution in pyrrole and 2,2‘-bipyrrole were investigated through ab initio calculations and Atoms in Molecules analysis of the resulting wave functions. Replacem...

2,2'-Bis(diphenylphosphino)-1,1'-bibenzimidazole BIMIP) was resolved in an enantiomerically pure state through a kinetic resolution process effected by complexation of the racemate with half of the stoichiometric amount of a chiral aminopalladium complex. The enantiopure diphosphine was fully characterized by X-ray diffractometric analysis.

Functionalized cyclopentadithiophenes 2 and 3 were synthesized and polymerized by anodic coupling, in acetonitrile solution, in the presence of 0.1 M tetraethylammonium perchlorate as supporting electrolyte. The former carries a 16-crown-5-ether ring coplanar to the bithiophene moiety, while a perpendicular 15-crown-5-ether ring is present in the latter. The cyclic voltammogram of poly-2 shows two redox processes at E° = −0.3 and +0.3 V, whereas that of poly-3 consists of a single response at E° = 0.0 V. The difference in electrochemical behavior is attributed to the occurrence of strong polaron π-dimerization in poly-2. The redox potential (E°) of this polymer moves toward more positive values passing from lithium to sodium salts as supporting electrolytes in acetonitrile solution. The redox cycle of poly-3 is instead completely insensitive to the change of the cationic species in solution. EQCM analysis shows that (i) both neutral polymers incorporate one alkaline ion per crown ring, (ii) the p-doping p...

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most widely prescribed medications, but their use continues to be limited by significant toxicity, particularly in the gastrointestinal tract and kidney. Better understanding of the pathogenesis of these adverse effects has led to the development of a series of derivatives of standard NSAIDs that are not only less toxic but more efficacious. The coupling of a nitric oxide-releasing moiety to a range of NSAIDs greatly reduces their ability to induce gastrointestinal damage, and greatly increases their tolerability in situations in which there is preexisting gastrointestinal inflammation. There is also evidence that these compounds are much better tolerated by the kidney. On the other hand, the analgesic and anti-thrombotic properties of NO-releasing NSAIDs significantly exceed those of the parent drugs. These compounds appear to represent a significant advance in the treatment of inflammation and pain and for prophylaxis of thrombotic conditions. Drug Dev. Res. 42:144–149, 1997. © 1997 Wiley-Liss, Inc.

1,2-Dialkyl-substituted 1,2-di(2-thienyl)ethylenes have been synthesized and investigated by cyclic voltammetry. The bulk of the alkyl substituents was modulated in order to progressively increase the torsional angle between the thiophene rings and the plane of the olefinic bond, from a fully planar structure to highly twisted systems. Distortion markedly affects the UV spectra and the oxidation peak potentials of the monomers. The electro-chemical polymerization experiments gave the following results: (i) (E)- and (Z)-dithienyl-ethylene systems produced polymers with identical properties; (ii) progressive deviation from planarity increased the oxidation peak potential of the monomer, as far as the polymerization was inhibited; (iii) long and rigid monomeric units reduced chain flexibility, leading to materials with low conductivity and unsatisfactory mechanical properties.

The main feature of β,β’‐bridge–α,α’‐bithienyls is that their conformation is controlled by the bridge length. This class of molecules could be useful for the understanding of the intra and intermolecular processes which determine the conductivity of the corresponding polymers. In this work we have recorded and studied (i) the electronic spectra of the monomers, (ii) the vibrational spectra (IR, Raman λexc=514 nm, FT–Raman λexc=1064 nm) of the monomers and polymers in the pristine state, (iii) the IR spectra of the doped polymers, and (iv) the IR spectra (probe) of the polymers photoinduced by visible light (pump). The interpretation of the spectra is made in terms of the ‘‘effective conjugation coordinate’’ theory. Poly(cyclopentabithiophene) P(T+1) has the largest π‐electron delocalization with a wide distribution of conjugation lengths. In poly(cycloheptabithiophene) P(T+3) π electrons are highly localized, while an intermediate situation is observed in poly(dihydrobenzobithiophene) P(T+2). The various...

The rearrangements of a few cyclic phenylhydrazones structurally related to 1-phenyl-Δ2-pyrazoline, 1-phenyl-1,4,5,6-tetra hydropyridazine, and 1-phenyl-4,5,6,7-tetrahydro-1,2-diazepine in hot polyphosphoric acid (PPA) are described. The five-membered-ring substrates (the pyrazolines) did not undergo the [3,3] sigmatropic rearrangement typical of the Fischer indolization, the main reaction course being homolytic N–N bond cleavage, leading to benzidine and its 4-(2-benzoylethyl)-4′-(3-phenyl-Δ2-pyrazolin-1-yl) derivative. The six-membered heterocycles underwent two different reactions, both evolving the tautomeric enehydrazine form: the first one is the [3,3] sigmatropic rearrangement, expected for open-chain hydrazones, affording 4-acyl-1,2,3,4-tetrahydroquinoline derivatives; the second one is a retro-Diels–Alder reaction producing methyleneaniline and α,β-unsaturated carbonyl, compounds. The seven -membered -ring substrate gave a 5-acyltetrahydrobenz[b]azepine, resulting from the [3,3] rearrangement, together with both a pyrrolidine and a pyrazine by-product; their formation involves homolytic N–N bond cleavage of the ring, a δ hydrogen abstraction, followed by intramolecular or intermolecular ring closure. Chemical proofs are given for the new structures.

The main feature of β,β’‐bridge–α,α’‐bithienyls is that their conformation is controlled by the bridge length. This class of molecules could be useful for the understanding of the intra and intermolecular processes which determine the conductivity of the corresponding polymers. In this work we have recorded and studied (i) the electronic spectra of the monomers, (ii) the vibrational spectra (IR, Raman λexc=514 nm, FT–Raman λexc=1064 nm) of the monomers and polymers in the pristine state, (iii) the IR spectra of the doped polymers, and (iv) the IR spectra (probe) of the polymers photoinduced by visible light (pump). The interpretation of the spectra is made in terms of the ‘‘effective conjugation coordinate’’ theory. Poly(cyclopentabithiophene) P(T+1) has the largest π‐electron delocalization with a wide distribution of conjugation lengths. In poly(cycloheptabithiophene) P(T+3) π electrons are highly localized, while an intermediate situation is observed in poly(dihydrobenzobithiophene) P(T+2). The various...

The reaction of the N-benzylamides of N-heterocyclic carboxylic acids 3 and 6–9 with phosphorus pentachloride affords heterocondensed imidazoles 4 and 10–14 by a scheme reminiscent of Wallach's imidazole synthesis starting from N.N′-dialkyloxamides. Kinetic and labelling experiments are described which support a mechanism involving nitrite ylide species and allow a better understanding of the Wallach reaction. The limiting parameter for the formation of heteroanellated imidazoles is the electron availability of the heterocyclic ring.

The synthesis and application of three examples of a new class of chiral (C2) atropisomeric diphosphines characterized by two interconnected five-membered heteroaromatic rings, with hindered rotation around the interanular bond, are described. Optically pure (+)- and (−)-2,2‘-bis(diphenylphosphino)-4,4‘,6,6‘-tetramethyl-3,3‘-bibenzo[b]thiophene (tetraMe-bitianp) (1a) and the parent unsubstituted system (+)- and (−)-bitianp (1b) were synthesized. They were found to be optically stable at 100 °C and were successfully employed as ligands in the Ru(II)-catalyzed hydrogenation of α- and β-oxo esters to the corresponding α- and β-hydroxy esters and in the hydrogenation of olefinic substrates. The optical and chemical yields were comparable with those reported for the same Ru(II)-binap-catalyzed reactions carried out under the same experimental conditions. The 2,2‘-bis(diphenylphosphino)-3,3‘-bibenzo[b]furan (1c), the oxygenated analogue of bitianp, was found to be configurationally unstable at room temperature....

Two new chiral atropisomeric biheteroaromatic diphosphines are described: 2,2′-bis(diphenylphosphino)-1,1′-bibenzimidazole (3a) and 3,3′-dimethyl-1,1′-bis(diphenylphosphino)-2,2′-biindole (4a). Structural characterization is given and configurational stability at room temperature demonstrated. The oxidation potential was recognized as a good tool to evaluate the electronic availability of the phosphorus atom in the series of biheteroaromatic diphosphines. Its value increases parallel to the electronic demand of the heterocyclic system and also depends on the position of the diphenylphosphino group.

[reaction: see text] The 2,5-dimethyl-3,4-bis[(2R,5R)-2,5-dimethylphospholano]thiophene (UlluPHOS), a new thiophene-based analogue of (R,R)-1,2-bis(phospholano)benzene (Me-DuPHOS), was synthesized, geometrically and electronically characterized, and employed as ligand of Rh and Ru in some standard hydrogenation reactions of prostereogenic functionalized carbon-carbon and carbon-oxygen double bonds. The synthesis of UlluPHOS is much easier than that provided for Me-DuPHOS. UlluPHOS and Me-DuPHOS display very similar geometries, while the electronic availability of the former is higher than that exhibited by the latter. The Rh and Ru complexes of UlluPHOS produced excellent enantiomeric excesses (98.9-99.5%) in the hydrogenation of N-acetyl-alpha-enamino acids and reaction rates higher than those found when employing the analogous complexes of Me-DuPHOS.

Some C2v symmetric cyclopenta[2,1-b;3,4-b′]bithiophenes differently substituted at the 4 position with a calix[4]arene group were synthesized and electrochemically polymerized by anodic coupling. The polymers were characterized by cyclic voltammetry, UV-vis and FTIR spectroscopy. Quartz crystal microbalance analysis showed strong affinity and selectivity of the polymers for toluene and acetone from the gas phase. The absorption process associated with the calix unit was satisfactorily described through a Langmuir isotherm, while a very small linear contribution was given by the polythiophene backbone. The absorption capacity of these materials was found to be higher by a magnitude of three orders than those displayed by cyclopentabithiophene-based polymers devoid of the calix unit, thus supplying strong, though indirect, proof of the role played by the calix units in the absorption process.

A reliable methodology, applicable on a process-scale level, for producing enantiomerically pure chiral γ-lactones by enantioselective hydrogenation of γ-ketoesters, followed by cyclisation of the resulting γ-hydroxyesters, has been developed. The multi-step procedure was transformed into a one-pot reaction. A very efficient chiral Ru-complex, based on the biheteroaromatic diphosphine ligand tetraMe-BITIOP, was developed as a catalyst, capable of coupling fast kinetics with high stereoselection levels. Its structure was fully elucidated through 31P NMR, EPR and X-ray single-crystal analyses. The optimal experimental conditions are as follows: hydrogen pressure = 30 psi, S/C ratio = 2000, 30% in weight substrate concentration. Yields are quantitative and enantiomeric excesses in the range 98–99.9%. Sensorial tests on the antipodes of two γ-lactones demonstrated the very different properties of the enantiomers.

Racemic (±)-3,3‘-bis(diphenylphosphinyl)-1,1‘-dimethyl-2,2‘-biindole (1c) (N-Me-2-BINPO) and (±)-3,3‘-bis(diphenylphosphinyl)-1,1‘-bis(methoxymethyl)-2,2‘-biindole (1d) (N-MOM-2-BINPO) were synthesized in satisfactory yields following a three-step reaction sequence, starting from indole. Resolution of racemic 1c and 1d was achieved through fractional crystallization of their diastereomeric adducts with optically active dibenzoyl tartaric acids, followed by alkaline decomplexation of the diastereomerically pure salts. Their trichlorosilane reduction gave enantiopure phosphines (+)- and (−)-(1a) (N-Me-2-BINP) and (+)- and (−)-(1b) (N-MOM-2-BINP). The electrochemical oxidative potential of 1a and 1b was found to be 0.52 and 0.60 V, respectively. Both the enantiomers of (1a) were tested as ligands of Ru(II) in asymmetric hydrogenation reactions of α- and β-oxoesters. Reactions were found to be outstandingly fast and enantioselection quite good. Comparative kinetic experiments on the hydrogenation reaction of ...

A series of 4-alkylidene-, 4-alkyl-, and 4,4’-dialkyl-sustituted 4H-[5,1-b;1,5-b’]cyclopentabithiophenes (CPDT) was designed in which the substituents in position 4 occupy well-defined areas in the space around the bithiophene unit to evaluate the effects played by their steric properties on the electrical conductivity of the materials resulting from anodic polymerisation. The geometry of all the monomers was either inferred from X-ray diffractometric analysis or calculated through molecular modelling techniques. The polymers were prepared under identical experimental conditions and characterized by CV, IR, and UV-vis spectroscopy and in situ conductivity. Various types of molecular descriptors were utilized to create QSPR models, which demonstrated a good relationship between the molecular structure of the monomers and the conductivity of the corresponding polymers.

The four-step straightforward synthesis of enantiopure (+)- and (-)-2,2',5,5'-tetramethyl-4,4'-bis-(diphenylphoshino)-3,3'-bithiophene (tetraMe-BITIOP), a new C2-symmetry chelating ligand for transition metals, is described, starting from 2,5-dimethylthiophene. The complexes of this electron-rich diphosphine with Ru(II) and Rh(I) were used as catalysts in some homogeneous hydrogenation reactions of prostereogenic carbonyl functions of alpha- and beta-ketoesters, of prostereogenic carbon-carbon double bonds of substituted acrylic acids, and of N-acetylenamino acids. The enantiomeric excesses were found to be excellent in all the experiments and comparable with the best results reported in the literature for the same reactions, carried out under similar experimental conditions, with the metal complexes of the most popular chiral diphosphine ligands as catalysts.

The synthesis and application of three examples of a new class of chiral (C(2)) atropisomeric diphosphines characterized by two interconnected five-membered heteroaromatic rings, with hindered rotation around the interanular bond, are described. Optically pure (+)- and (-)-2,2'-bis(diphenylphosphino)-4,4',6,6'-tetramethyl-3,3'-bibenzo[b]thiophene (tetraMe-bitianp) (1a) and the parent unsubstituted system (+)- and (-)-bitianp (1b) were synthesized. They were found to be optically stable at 100 degrees C and were successfully employed as ligands in the Ru(II)-catalyzed hydrogenation of alpha- and beta-oxo esters to the corresponding alpha- and beta-hydroxy esters and in the hydrogenation of olefinic substrates. The optical and chemical yields were comparable with those reported for the same Ru(II)-binap-catalyzed reactions carried out under the same experimental conditions. The 2,2'-bis(diphenylphosphino)-3,3'-bibenzo[b]furan (1c), the oxygenated analogue of bitianp, was found to be configurationally unstable at room temperature. Complete structural X-ray elucidation of the Pd complexes of 1a-c is reported. The advantages of these biheteroaromatic ligands over the classical biaryl systems are discussed.

Stereoelectronic effects enable 3-cyclopropyl and 3-cyclobutylthiophene to produce electrochemical polymers. Poly(3-cyclopropylthiophene) is the only good electroconducting poly(3-alkylthiophene) with a branched carbon directly connected to the thiophene ring.

According to the “spacer” strategy we have previously proposed the monomers candidate for providing conductive polymers endowed with special properties should contain the polymerogenic rings (pyrrole or thiophene), as terminal units, linked to a central π-conjugatively active frame; we describe how it is possible in this way to control the redox potentials E of the polymers derived from such monomers. This control is beneficial because it is possible to increase the E° value of polypyrrole-type systems and decreases the E° value of polythiophene-type systems. Also, the “spacer”may be further functionalised and, being remote from the polymerisation site, cannot alter the conductivity characteristics typical of the polymer derived from the parent heterocycle (pyrrole or thiophene): such a functionalisation may provide the final, tailored, conductive polymer with special properties (e.g. solubility). If the central ring, acting as a spacer, is formed linking two positions of a di-heterocycle with a saturated chain, it is possible to partially control the twist angle between the heterocyclic units. Crystal and molecular structures have shown that dipyrrole units further linked through the nitrogen atoms are quite sensitive to the central ring size. With respect to the conductivity of unsubstituted polypyrrolc, the conductivity of the polymers derived from such monomers is dependent from the twist angle between the rings. This result is relevant to describe conditions of conjugation between the heterocyclic units of a monomer required to produce upon doping a conductive polymer.

In this review the ‘spacer’ strategy is described and evaluated in detail. According to this principle, the monomer contains, as terminal units, two polymerogenic rings (pyrrole or thiophene) linked to a central π-conjugatively-active frame; as spacers, we have investigated ethenylic, sulphide, and aromatic moieties. In this way the redox potentials, E 0 , of the polymers derived from such monomers can be calibrated by the substituent effect exerted by the spacer. This control is beneficial because it is possible to increase the E 0 value of polypyrrole-type systems and decrease the E 0 value of polythiophene-type systems. Also, the ‘spacer’ may be further functionalised and, being remote from the polymerisation site, cannot alter the conductivity characteristics typical of the polymer derived from the parent heterocycle (pyrrole or thiophene): such a functionalisation may provide the final, tailored, conductive polymer with special properties (e.g., solubility). If the central ring, acting as a ‘spacer’, is formed linking two positions of a di-heterocycle with a saturated chain, it is possible partially to control the twist angle between the heterocyclic units. Crystal and molecular structures have shown that dipyrrole units, further linked through the nitrogen atoms, are quite sensitive to the central ring size. With regard to the conductivity of unsubstituted polypyrrole, the conductivity of the polymers derived from such monomers is dependent upon the twist angle between the rings. This result is relevant to a description of conjugation conditions between the heterocyclic units of a monomer required to produce a conductive polymer on doping.

The intramolecular Heck reaction of the iodoaryl compound 1 with a (Z)-allyl silane moiety in the presence of the chiral ligand (+)-TMBTP 13 leads to the benzazepine 5b with 92% ee, whereas 3 with an (E)-allyl silane moiety in the presence of the chiral ligand (R)-BITIANP 14 gives 5a with 91% ee; in a similar way, 9 and 10 were transformed in the presence of 13 into the tetrahydroisoquinolines 11b and 12b with 86 and 84% ee, respectively.

The rearrangements of a few cyclic phenylhydrazones structurally related to 1-phenyl-Δ2-pyrazoline, 1-phenyl-1,4,5,6-tetra hydropyridazine, and 1-phenyl-4,5,6,7-tetrahydro-1,2-diazepine in hot polyphosphoric acid (PPA) are described. The five-membered-ring substrates (the pyrazolines) did not undergo the [3,3] sigmatropic rearrangement typical of the Fischer indolization, the main reaction course being homolytic N–N bond cleavage, leading to benzidine and its 4-(2-benzoylethyl)-4′-(3-phenyl-Δ2-pyrazolin-1-yl) derivative. The six-membered heterocycles underwent two different reactions, both evolving the tautomeric enehydrazine form: the first one is the [3,3] sigmatropic rearrangement, expected for open-chain hydrazones, affording 4-acyl-1,2,3,4-tetrahydroquinoline derivatives; the second one is a retro-Diels–Alder reaction producing methyleneaniline and α,β-unsaturated carbonyl, compounds. The seven -membered -ring substrate gave a 5-acyltetrahydrobenz[b]azepine, resulting from the [3,3] rearrangement, together with both a pyrrolidine and a pyrazine by-product; their formation involves homolytic N–N bond cleavage of the ring, a δ hydrogen abstraction, followed by intramolecular or intermolecular ring closure. Chemical proofs are given for the new structures.

The suppression of inter-ring torsions in quaterthiophenes changes the deactivation path of the excited state leading to the reduction of non-radiative decay and increase of the photoluminescence quantum yield. Tripler transient absorption spectra are strongly affected by central inter-ring bridging, showing features which are tentatively related to different conformers.

Ruthenium(II) dichloride complexes with (+)- and (–)-2,2′-bis(diphenylphosphino)-4,4′,6,6′-tetramethyl-3,3′-bibenzo[b]thiophene (1a), new chiral atropisomeric heterocyclic ligands, reduce α- and β-oxoesters to α- and β-hydroxyesters with an enantiomeric purity comparable, if not higher, to that reported for binap under the same experimental conditions.

Ring fusion of two terminal polymerogenic heterocycles (pyrrole or thiophene) onto a central [(hetero)aromatic] or carbocyclic ring strongly modifies, relative to pyrrole or thiophene, both the peak potentials of the monomer and the redox potential of the polymer. Conductivity, peak potentials and redox potentials of materials obtained by polymerization of pyrrolic and/or thiophene systems fused onto central benzene, cyclopentadiene, thiophene and pyrrole rings are reported. The approach can be exploited to beneficially design new polyheteroaromatics endowed with highly valued properties (good conductivities and environmental stability).

Using conformatcnally constrained bi- and ter-thiophenes, the effects of inter-ring torsional angles on spectroscopic properties of the corresponding polymers are demonstrated; effects on conductivity are complicated by inter-chain contributions.

The reaction of the N-benzylamides of N-heterocyclic carboxylic acids 3 and 6–9 with phosphorus pentachloride affords heterocondensed imidazoles 4 and 10–14 by a scheme reminiscent of Wallach's imidazole synthesis starting from N.N′-dialkyloxamides. Kinetic and labelling experiments are described which support a mechanism involving nitrite ylide species and allow a better understanding of the Wallach reaction. The limiting parameter for the formation of heteroanellated imidazoles is the electron availability of the heterocyclic ring.

The thermal cyclization of a few 2,6-dimethylphenylazo compounds to indazole derivatives is described.

The Wittig-Horner condensation of N-methylpyrrole-2-, and 2,5-dicarbaldehydes with diethyl heteroarylmethylphosphonates (heteroary =N-methylpyrrol-2-yl or 2-thienyl and the corresponding 2,5-diyl) leads to the (E)-1,2-diheteroarylethylenes (1) and (2), and the triheteroaryl derivatives respectively. A new entry into diethyl pyrrolylmethylphosphonates is described starting from the pyrrol-2-ylmethyltrimethylammonium iodide and the sodium salt of diethyl phosphite: the rate and the regiochemistry of the reaction is solvent dependent. The heteroarylethylenes (1)–(5) are electron-rich substrates affording charge transfer (c.t.) complexes with iodine and TCNQ (tetracyano-1,4-quinodimethane): the d.c. conductivities of the c.t. complexes are relatively low and fall in the range of semiconductors. I.r. frequencies of the CN stretching relative to the TCNQ moiety are used to evaluate the degree of charge transfer between the donor and the acceptor. It is believed that the radical cation of (5) arising by monoelectron transfer to TCNQ is the most stable charged species among the series considered.

Anodic coupling of the dihydrobenzodipyrrole isomers 1H,8H-pyrrolo[3,2-g]indole (1), 1H,7H-pyrrolo[3,2-f]indole (2), and 1H,5H-pyrrolo[2,3-f]indole (3) in 0,1 M tetraethylammonium perchlorate in acetonitrile produces polymeric films which are reversibly oxidized around 0,3 V vs. Ag/Ag+ with 0,5 electrons per monomeric unit. IR reflectance, UV-vis and cyclic voltammetry show that the oxidized polymers undergo easy overoxidation at the benzene ring without affecting the charge storage ability. Conductivities (0,2–5 Ω−1 · cm−1) are higher than those presented by chemically prepared samples (10−4 – 10−1 Ω−1 · cm−1) and are attributed to more ordered structures of the polymers.

The electroconductive polymer poly[(2,2′-dithienyl)-5,5′-diylvinylene] (1) was prepared by both electrochemical and chemical methods starting from trans-di(2-thienyl)ethylene (2). The electrochemically prepared material showed electrical conductivities of up to 40 Ω−1 · cm−1; the neutral, chemically prepared polymer was droped with iodine or arsenic pentafluoride but the conductivities were low. The experimental procedures are described and an interpretation of the results is given.