α-(3,7-Dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy)-diazines. Part 2: Functionalisation via directed ortho-metallation and cross-coupling reactions

The functionalisation of the title compounds via regioselective Directed ortho-Metallation (DoM) and cross-coupling reactions is studied. The compatibility of the 3,7-DiOxa-r-1-AzaBicyclo[3.3.0]Oct-c-5-ylmethoxy system (DOABO-CH₂O) to typical reaction conditions is established. Its role as Directed ortho-Metallation Group (DoMG) is examined, including competition with classical DoMGs, chlorine and methoxy. The chelating ability of some functionalised terms such as DOABO-CH₂O substituting chiral diarylmethanols and polyaza analogues of 2,6-terpyridine is discussed as intramolecular steric relationships determining configuration and aptitude to bind selectively transition metals, respectively.     

Direct cyclization of ortho-(1H-pyrrol-1-yl)aryl and heteroaryl carboxylic acids into fused pyrrolizinones

A series of fused heterocyclic compounds based on a pyrrolizinone structure have been prepared from ortho-(1H-pyrrol-1-yl)aryl and heteroaryl carboxylic acids by intramolecular Friedel-Crafts acylation promoted by bis(trichloromethyl) carbonate, in generally good yield without using Lewis acid catalysts.     

Active manganese dioxide promoted cyclization of ortho-(1H-pyrrol-1-yl)aryl and heteroaryl carboxylic acids to 5H-pyrrolo[1,2-a][3,1]benzoxazin-5-one derivatives

The hitherto unknown lactone 5H-pyrrolo[1,2-a][3,1]benzoxazin-5-one and six of its substituted derivatives have been prepared by active manganese dioxide promoted oxidative cyclization of the corresponding 2-(1H-pyrrol-1-yl)benzoic acids, under mild conditions, in moderate yields. The method was successfully extended to the cyclization of some ortho-(1H-pyrrol-1-yl)heteroaryl carboxylic acids and 2-(1H-indol-1-yl)benzoic acids.     

Competition Between Intra- and Intermolecular Hydrogen Bonding: o-Anisic Acid⋅⋅⋅Formic Acid Heterodimer

Four conformers of the heterodimer o-anisic acid–formic acid, formed in a supersonic expansion, have been probed by Fourier transform microwave spectroscopy. Two of these forms have the typical double intermolecular hydrogen-bond cyclic structure. The other two show the o-anisic acid moiety bearing a trans-COOH arrangement supported by an intramolecular O−H⋅⋅⋅O bond to the neighbor methoxy group. In these conformers, formic acid interacts with o-anisic acid mainly through an intermolecular O−H⋅⋅⋅O hydrogen bond either to the O−H or to the C=O moieties, reinforced by other weak interactions. Surprisingly, the most abundant conformer in the supersonic expansion is the complex in which the o-anisic acid is in trans arrangement with the formic acid interacting with the O−H group. Such a trans-COOH arrangement in which the intramolecular hydrogen bond dominates over the usually observed double intermolecular hydrogen bond interaction has never been observed previously in an acid–acid dimer.     

Self-assembly via intermolecular hydrogen-bonding between o-/m-/p-NH2 and BF2 groups on dipyrromethenes

Boron difluoride dipyrromethenes bearing configurationally different amine groups on a meso-phenyl ring were prepared and crystallized. The ortho- and para-amino groups allow the phenyl group to inductively release greater electron density into the dipyrromethenes resulting in relatively strong intermolecular hydrogen-bonding with the terminal BF₂ groups, whereas the meta-analog formed weaker hydrogen-bonds. The intensities of the ¹H NMR peaks in concentrated solutions all increased with F-decoupling.     

Mass spectral fragmentation patterns of 3,3-dimethyl-2,3,4,5,10,11-hexahydro-11-(o- and p-R-phenyl)-1H-dibenzo- [b,e][1,4]diazepin-1-ones. II

A study has been made of the fragmentation upon electron impact of 3,3-dimethyl-2,3,4,5,10,11-hexahydro-11-phenyl-1H-dibenzo[b,e][1,4]diazepin-1-one and fifteen of its derivatives containing chloro, bromo, methyl, methoxy, hydroxy, nitro, amino, carboxyl and carboxymethyl substituents on ortho and para positions of the 11-phenyl ring. All the spectra analyzed contain molecular ions and the principal fragmentation routes takes place either from the molecular or from (M⁺-1) ion. There are, however, some deviations from the general fragmentation pattern in the case of 1,4-dibenzodiazepin-1-ones with o-nitro, o-hydroxy and o-carboxyl substituents caused by direct interactions of these groups with the benzodiazepine ring.     

ortho-, meta- and para-nitrophenylgold(I) complexes

Treatment of [BzPh₃P][AuCl₂] with [Hg(x-C₆H₄NO₂)₂] (x = o, m, or p) gives anionic gold(I) complexes of the type [BzPh₃P][Au(R)Cl](R = o-, m- or p-C₆H₄NO₂, Bz = C₆H₅CH₂). The chloro ligand in [Au(o-C₆H₄NO₂)Cl]^? can be replaced by bromo or iodo ligands by use of NaBr or NaI. The anions [Au(R)Cl]^? react with neutral monodentate ligands, L, to give neutral mononuclear complexes [Au(R)L] (R = o-C₆H₄NO₂, L = PPh₃, AsPh₃; R = m-C₆H₄NO₂, L = PPh₃) and with 1,2-bis(diphenylphosphino)ethane (dpe) to give [Au₂(R)₂(dpe)] (R = o-C₆H₄NO₂). The corresponding [Au(p-C₆H₄NO₂)Cl]^? reacts with PPh₃ or AsPh₃ to give mixtures containing [AuClL]. The anionic ortho-nitrophenylgold(I) complex is much more stable than its meta- or para-nitrophenyl isomers. These are thought to be the first reports of nitrophenylgold(I) complexes.     

An electron density study on cis-1-(2-hydroxymethyl-cyclopentenyl)uracils

A topological charge electron density analysis using the Atoms in Molecules (AIM) theory on B3LYP/6-31++G**//B3LYP/6-31G* charge densities was performed for the series of the five cis-1-(2-hydroxymethyl-Δⁿ-cyclopentenyl))uraciles (n=1-5). These compounds are carbocyclic analogues of nucleosides that belong to an important class of antiviral or antitumoral compounds where the hydroxymethyl group and the heterocyclic base are bonded to adjacent carbons of a cyclopentene ring. The change of position of the double bond within the cyclopentene ring does not significantly affect the electron distribution of the base (that always carries a substantial negative charge), but alters the orientation of the base and the hydroxymethyl group (3-, and 4-cyclopentenyl derivarives being the exception as they present very similar conformations).     

Cyclophosphazenes tethered together via N-ring centres with ortho-, meta- and para-xylylene linkers

Hexakis (organoamino) cyclotriphosphazenes (RNH)₆P₃N₃ {R = i-Bu (1), R = i-Pr (2)} react with ortho-, meta- and para-derivatives of α,α′-dibromo xylene in 2:1 ratio to form salts of compositions [{(RNH)₆P₃N₃}₂xyl]Br₂, {R = i-Bu, o-xyl (3); R = i-Pr, m-xyl (4); R = i-Pr, p-xyl (5)}. These contain dications consisting of two phosphazene rings, which are tethered together via ring N centres by a xylylene unit. X-ray structure analyses show that the substitution pattern at the xylylene bridge controls the orientation and distance between the two tethered phosphazene rings. The solid state structures exhibit dense networks of hydrogen bonds linking dications and anions. Direct N-H?N bonds between dications are observed in the crystal structure of 3.     

Polarography of o- and p-nitrophenyl acetic acids

Polarography of o- and p-nitrophenyl acetic acids has been carried out in aqueous buffers (pH 2.0 to 12.0) of constant ionic strength (1.0 M) at 30 ± 0.5 °C. The nitro group underwent a diffusion-controlled reduction (6e) over the whole pH range. The number of electrons involved in the reduction was found by incorporating the values of diffusion coefficients, obtained by using a McBain-Dawson cell, into the Ilkovic equation. Koutecky's method has been used to compute the kinetic parameters (αn_aand ?log k^o_f,h) for the reduction of the nitro group and a reduction mechanism is proposed.     

Synthesis of 1,2,3,4-tetrahydroisoquinolines and 2,3,4,5-tetrahydro-1H-2-benzazepines combining sequential palladium-catalysed ortho alkylation/vinylation with aza-Michael addition reactions

1-Substituted 1,2,3,4-tetrahydroisoquinolines and 2,3,4,5-tetrahydro-1H-2-benzazepines were synthesised from o-iodoalkylbenzene, N-Cbz-bromoalkylamine and an electron-poor olefin through a one-pot palladium-catalysed sequence involving ortho alkylation, alkenylation and intramolecular aza-Michael reaction.     

The influence of selected metals and halogens on the electronic system of benzoic acid

The influence of halogens and metals on the electronic system of the aromatic ring in lithium, sodium and potassium complexes with p-halogenobenzoic acids has been investigated by means of ¹³C and ¹H NMR, IR and Raman spectroscopy and semi-empirical calculations. It has been shown that ionic potentials and electronegativities of halogens and metals are the main factors responsible for perturbations of the electronic charge distribution in the ring.     

The influence of selected metals and halogens on the electronic system of benzoic acid

The influence of halogens and metals on the electronic system of the aromatic ring in lithium, sodium and potassium complexes with p-halogenobenzoic acids has been investigated by means of ¹³C and ¹H NMR, IR and Raman spectroscopy and semi-empirical calculations. It has been shown that ionic potentials and electronegativities of halogens and metals are the main factors responsible for perturbations of the electronic charge distribution in the ring.     

The effect of substituents on the extraction behavior of hydroxamic acids

The extraction behavior of several alkyl-substituted hydroxamic acids in chloroform solution with several metal ions is described. Among the N-phenylacylhydroxamic acids used, those with o-alkyl substituents on either the phenyl or acyl ring generally do not extract metals, apparently because of steric problems at the O=CNO^? chelation site. An improved synthesis of substituted hydroxamic acids is reported.     

Characterization of the high molecular mass chlorinated matter in spent bleach liquors (SBL): 3—Mass spectrometric interpretation of aromatic degradation products in SBL

The aromatic content of the high molecular matter in pulp mill bleachery effluents has been characterized after chemical degradation in the laboratory followed by derivatization and gas chromatographic/mass spectrometric analysis. Aromatic molecules with carboxy, hydroxy, methoxy and chloro substituents were separated and identified by recording their computer-reconstructed ion current chromatograms. About 70 aromatic carboxylic acids were tentatively identified as degradation products. Aromatic compounds with hydroxy groups were derivatized to trideuteromethoxy groups in order to distinguish them by mass spectrometry from compounds with naturally occurring methoxy groups. Single and double hydrogen atom transfer between methyl ester and methoxy groups were observed in some molecules and given special attention when they occurred ortho to each other. A methoxy group substituted ortho to a methyl carboxylate resulted in an unusual fragmentation.     

A simple and one-pot synthesis of 2,3,4,5-tetrasubstituted 4,5-dihydro-3H-1,4-benzodiazepines

2,3,4,5-Tetrasubstituted 4,5-dihydro-3H-1,4-benzodiazepines were synthesized in one-pot by a new sequential Ugi 4CC/Staudinger/aza-Wittig reaction, starting from easily accessible o-azidobenzaldehyde, α-amino ketone hydrochloride, isocyanide and carboxylic acid.     

Infrared spectra of p-, m- and o-fluorobenzaldehyde in low temperature argon matrices

Three structural isomers of fluorobenzaldehyde (p-, m- and o-forms) have been investigated in detail with matrix-isolation infrared spectroscopy, in the 700-3000 cm⁻¹ region, combined with the UV photoexcitation and the density functional calculations. Two rotamers (syn and anti) were identified for m- and o-fluorobenzaldehyde upon the photoexcitation and most of the bands of each rotamer were assigned. It is shown that the formation of the intramolecular C-H?F hydrogen bond for the anti rotamer of o-FB results in the shortening of the aldehyde C-H bond length and that the C-F and/or CO bond lengths are shortened for the syn rotamer of o-FB presumably due to the repulsion between the aldehyde O and F atoms.     

Conformational preferences of 2-methoxypyridine from 1H and 13C NMR and from STO-3G molecular orbital calculations

Observable coupling over five formal bonds between the methoxy group protons and the ortho ring proton in 2-methoxypyridine, coupliugs between the methoxy group carbon and ring protons, and methoxy carbon spin-lattice relaxation times are all consistent with a preference for the planar cis conformer, in which conjugation is favoured and repulsions between the methyl group and the ortho hydrogen are reduced. Small-amplitude torsioas about the C-2–O bond may carry the methoxy group away from this orientation, but more distant conformations can probably be excluded. Methyl group rotation is less hindered in the cis than in the trans conformer. Molecular orbital calculations at the STO-3G level, with complete geometry optimization, support the conduskus drawn from experimental evidence.     

Photoacid generators (PAGs) based on N-acyl-N-phenylhydroxylamines for carboxylic and sulfonic acids

Simple and efficient photoacid generators (PAGs) for carboxylic and sulfonic acids based on N-acyl-N-phenylhydroxylamines have been demonstrated. Irradiation of o-carboxylates and thermally rearranged o-arenesulfonates of N-acyl-N-phenylhydroxylamines using UV light (≥254 nm) in aqueous methanolic solution resulted in efficient generation of carboxylic and sulfonic acids, respectively. The carboxylic acid generation ability of N-acyl-N-phenylhydroxylamines was found to be dependent on their N-acyl substituents. Further, polymer bearing o-arenesulfonates of N-acyl-N-phenylhydroxylamine was synthesized and demonstrated as PAG for sulfonic acids.     

The ortho effect in mass spectra. Insight into the tightening of activated complexes for the loss of ketene from phenyl acetates and ethylene from phenetoles from INDO molecular orbital calculations

INDO Molecular orbital calculations of the energetically most favourable conformation of the molecular ions of phenyl acetate and its o-fluoro- and o-chloro-analogs indicate bond formation between carbonyl oxygen and ortho halogen. For the molecular ions of phenetole and its o-fluoro and o-chloro-analogs, no ring formation is observed. These results are in accord with the frequency factor changes found for the ortho substitution in these systems by halogens.