O-hydroxy Aromatic Aldehydes Research Articles

Synthesis of novel silica encapsulated spiropyran-based thermochromic materials.

A series of novel spiropyrans were synthesized through the condensation of substituted 3,3-dimethyl-2-methyleneindoline with different nitro-substituted o-hydroxy aromatic aldehydes. Indoles were initially substituted with a variety of alkanes and esters moieties. The substituted 3,3-dimethyl-2-methyleneindoline was then reacted with nitro-substituted o-hydroxy aromatic aldehydes to yield the respective spiropyrans. The synthesized novel spiropyrans were encapsulated in silica nano-shells to protect them from the effect of moisture and pH. The thermochromic behaviour of novel spiropyrans was studied by UV-visible spectroscopy. The thermally induced isomerization of spiropyran derivatives was carried out in a water/ethanol mixture. The thermal isomerization of spiro-heterocyclic (colourless form) to merocyanine (MC) (coloured form) was a discontinuous process and was observed in a temperature range of 5–60°C via UV-visible spectrometer. The absorption process occurs reversibly regardless of the heating/cooling sequence. The spiropyran derivatives, therefore, have a potential application for colorimetric temperature indication.

Evaluation of the protolytic equilibria and catalytic activity of sugar-based Schiff base ligands with VO2+ and MoO22+ cations in sulfoxidation and epoxidation reactions

Based on the two anomeric methyl 3-amino-2,3-dideoxy-d-arabino-hexopyranosides ten new sugar-modified Schiff base ligands have been synthesized after monocondensation reaction with five o-hydroxyaromatic aldehydes, i.e. salicylaldehyde and its five para-substituted derivatives. The acidity constants and acid-base equilibria processes in polar solution were calculated from data obtained after spectrophotometric titrations at room temperature. The first acidity constant is found to be associated with the deprotonation of an enamine nitrogen and the second constant correspond to the deprotonation of the phenolate oxygen. The contribution of the enol-imine and keto-enamine tautomeric forms and prototropic 1,5-rearrangement has been discussed with the help of the spectroscopic IR, UV–Vis and NMR techniques. Finally, in situ generated catalysts were carried out by mixing separately all synthesized sugar-based Schiff bases with VO(acac)2 or MoO2(acac)2, and have been tested in asymmetric sulfoxidation of thioanisole and the epoxidation of styrene, cyclohexene and S(−)-limonene using tert-butyl hydroperoxide (TBHP) as the terminal oxidant.

Intracomplex Dioxomolybdenum(VI) Compounds with Alcoholimines of Aromatic o-Hydroxyaldehydes. Crystal Structure of 2-Hydroxynaphthylidene Monoethanolimine (H2L) and Solvated Complex [MoO2(L) · C5H5N

Intracomplex Dioxomolybdenum(VI) Compounds with Alcoholimines of Aromatic o-Hydroxyaldehydes. Crystal Structure of 2-Hydroxynaphthylidene Monoethanolimine (H2L) and Solvated Complex [MoO2(L) · C5H5N

Intramolecular Hydrogen Bonds in Normal and Sterically Compressed o-Hydroxy Aromatic Aldehydes. Isotope Effects on Chemical Shifts and Hydrogen Bond Strength.

A number of o-hydroxy aromatic aldehydes have been synthesized to illustrate the effect of steric compression and O···O distances on the intramolecular hydrogen bond and the hydrogen bond energies. Hydrogen bond energies have been calculated using the ‘hb and out’ method using either the MP2 method or the B3LYP functional with the basis set 6-311++G(d,p). However, several compounds cannot be treated this way. Hydrogen bond energies are also determined using electron densities at bond critical points and these results are in good agreement with the results of the ‘hb and out’ model. Two-bond deuterium isotope effects on 13C chemical shifts are suggested as an experimental way to obtain information on hydrogen bond energies as they easily can be measured. Isotope effects on aldehyde proton chemical shifts have also been measured. The former show very good correlation with the hydrogen bond energies and the latter are related to short O···O distances. Short O···O distances can be obtained as the result of short C=C bond lengths, conjugative effects, and steric compression of the aldehyde group. Short O···O distances are in general related to high hydrogen bond energies in these intramolecularly hydrogen-bonded systems of resonance assisted hydrogen bond (RAHB) type.

Synthesis of paramagnetic spiropyran derivatives

Paramagnetic derivatives of spiropyran have been obtained by condensation of paramagnetic N-iminium salts with o-hydroxyaromatic aldehydes. The structures of three of the six synthesized radicals were proven by X-ray structural analysis.

Green chemical multicomponent approach for the synthesis of C3-pyranopyrazole-substituted coumarins

An efficient and rapid method was developed for the synthesis of C3-pyranopyrazole-substituted coumarins from one-pot five-component reaction of β-keto ester, hydrazine, O-hydroxy aromatic aldehydes, 6-methyl, 4-hydroxy pyranone and aromatic aldehyde in the presence of tri-ethylamine in solvent-free conditions. The microwave-assisted method reported herein offers advantageous shorter reaction times, higher yields and cleaner reaction compared with conventional heating methods.

Synthesis, characterization and electrochemical properties of copper(II) complexes derived from succinoyldihydrazine Schiff base ligands

Four new copper(II) complexes of the composition [Cu(H2L)(H2O)] have been synthesized by template method from reaction of copper(II) acetate, succinoyldihydrazine and some o-hydroxy aromatic aldehydes and ketones in aqueous methanol media. The composition of the complexes has been established on the basis of data obtained from analytical and mass spectral studies. The structure of the complexes has been discussed in the light of molar conductance, magnetic moment, Uv-vis, EPR and IR spectral studies. All of the complexes are non-electrolyte in DMSO. The μeff values for the complexes fall in the region 1.76–1.85BM which rules out the possibility of any M–M interaction in the structural unit of the complexes. The ligands coordinate to the metal centre in enol form through phenolate/naphtholate oxygen atoms and azomethine nitrogen atoms. The NMR spectra show that ligands are present in anti-cis configuration in uncoordinated state. In all of the complexes the copper centre adopts square pyramidal stereochemistry. The unpaired electron is present in dx2-y2 orbital in the ground state for copper centre in the complexes. The electron transfer reactions for the complexes have been studied by cyclic voltammetry.

An efficient route to coumarin derivatives under dual catalysis, an organo- and a Lewis acid catalyst

An efficient reaction of dialkyl acetylenedicarboxylate with various o-hydroxy aromatic aldehydes under dual catalysis with piperidine and FeCl3 in refluxing toluene afforded alkyl 2-oxo-2-(2-oxo-2H-chromen-3-yl) acetates in good to excellent yield. The advantages of this reaction include the use of easily available starting materials, one-pot reaction, mild reaction conditions and operational simplicity.

ChemInform Abstract: New Condensed Indoline Bis‐Spiropyrans.

AbstractBis‐spiro compounds (I)—(III) are obtained via a general three‐stage synthesis.

New condensed indoline bis-spiropyrans

For some time, bis-spiropyrans prove to have been at the center of attention of organic chemists. The reason for this is the significant increase in the chain of conjugation for possible opening simultaneously of two pyran fragments, as a result of which a strong bathochromic shift of the absorption band of the photoinduced form [1] must be observed. The introduction of indole fragments into bis-spiropyrans must also assist an increase in the conjugation chain on simultaneously opening two pyran rings. The synthesis of bis-spiropyrans was carried out by the interaction of aromatic o-hydroxy aldehydes with ketones [1], and spiropyrans are obtained by condensation of methylene bases with o-hydroxy aromatic aldehydes [1]. With the aim of obtaining new systems of bis-spiropyrans containing indole fragments, and developing a general method of obtaining isomeric indole bis-spiropyrans, we have studied the condensation of bisanalogs of methylene bases with salicylic aldehydes. Previously in letters [2, 3], we reported the synthesis of new bisanalogs of dimethylidenehexahydroindolo[4,5-e]indole and dimethylidenehexahydrodipyrrolo[1,2,3-d,e;3,2,1-i,j]benzo[g]quinoxa- line Fischer's bases and bis-spiropyran compounds based on them. In the present work, we describe a method for obtaining a new indole bis-spiro compound from the bismethylene base of dimethylidenehexahydro-indolo[7,6-g]indole and propose general three stages synthesis of new condensed indoline bis-spiropyrans based on hexamethyldihydrodipyrrolonaphthalenes 1-3 [4-6].

A novel one pot route to flavones under dual catalysis, an organo- and a Lewis acid catalyst

Substituted phenylacetylenes react with various o-hydroxy aromatic aldehydes under dual catalysis of piperidine and FeCl 3 in refluxing toluene to yield flavones in good to excellent yield. Atmospheric oxygen acts as stoichiometric oxidant in the process. Some of these compounds had been recently reported to show fair insecticidal activity against Spodoptera frugiperda.

Homogeneous green catalysts for olefin oxidation by mono oxovanadium(V) complexes of hydrazone Schiff base ligands

Three mono oxovanadium(V) complexes of tridentate Schiff base ligands [VO(OMe)L 1] ( 1), [VO(OMe)L 2] ( 2) and [VO(OMe)L 3] ( 3) obtained by monocondensation of 3-hydroxy-2-naphthohydrazide and aromatic o-hydroxyaldehydes have been synthesized (H 2L 1 = ( E)-3-hydroxy- N′-(2-hydroxy-3-methoxybenzylidene)-2-naphthohydrazide, H 2L 2 = ( E)-3-hydroxy- N′-(2-hydroxybenzylidene)-2-naphthohydrazide and H 2L 3 = ( E)- N′-(5-bromo-2-hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide). The complexes were characterized by spectroscopic methods in the solid state (IR) and in solution (UV–Vis, 1H NMR). Single crystal X-ray analyses were performed with 1 and 2. The catalytic potential of these complexes has been tested for the oxidation of cyclooctene using H 2O 2 as the terminal oxidant. The effects of various parameters including the molar ratio of oxidant to substrate, the temperature, and the solvent have been studied. The catalyst 2 showed the most powerful catalytic activity in oxidation of various terminal, cyclic and phenyl substituted olefins. Excellent conversions have been obtained for the oxidation of cyclic and bicyclic olefins.

Chiral dioxovanadium(V) Schiff base complexes of 1,2-diphenyl-1,2-diaminoethane and aromatic o-hydroxyaldehydes: Synthesis, characterization, catalytic properties and structure

A series of dioxovanadium(V) complexes of tridentate ligands obtained by monocondensation of chiral 1,2-diphenyl-1,2-diaminoethane and aromatic o-hydroxyaldehydes was synthesized. The complexes were characterized by spectroscopic methods in the solid state (IR) and in solution (UV–Vis, CD, 1H and 51V NMR). Single crystal X-ray analysis was performed with (VO 2L · H 2O) 2, denoted as ( 4 · H 2O) 2, where L is ( S, S)-1-amino-2-{(2′-oxido-4′,6′-dimethoxyphenyl)methylene}amino-1,2-diphenylethane. Crystal structure analysis revealed that ( 4 · H 2O) 2 contains oxo-bridged dimers of 4 joined with water molecules by hydrogen bonding interactions, and that two five-membered chelate rings in the dimeric molecule adopt different envelope conformations, one on the asymmetric carbon atom linked to the azomethine nitrogen and the other on the asymmetric carbon atom linked to the primary amino nitrogen. The ( S, S)- and ( R, R)-complexes bearing the methoxy substituent in positions 3 or 5 of the salicylidene moiety catalyze the oxidation of phenyl methyl sulfide by cumene hydroperoxide yielding the corresponding sulfoxide almost quantitatively with 34–39% enantiomeric excess.

Dioxovanadium(V) Schiff base complexes of N-methyl-1,2-diaminoethane and 2-methyl-1,2-diaminopropane with aromatic o-hydroxyaldehydes and o-hydroxyketones: synthesis, characterisation, catalytic properties and structure

Nineteen new dioxovanadium(V) complexes with unsymmetrical tridentate Schiff base ligands, obtained by a single condensation of 2-methyl-1,2-diaminopropane or N-methyl-1,2-diaminoethane with salicylaldehyde and its derivatives, 2-hydroxy-1-naphthaldehyde, 2-hydroxyacetophenone, 1-hydroxy-2-acetonaphthone and 2-hydroxybenzophenone, were prepared. The complexes were characterized by their 1H and 51V NMR, IR, and UV–Vis spectra. Crystal structure of the 2-(4-amino-4-methyl-2-aza-1-penten-1-yl-κ 2N)-3,5-dimethoxyphenolato-κO-dioxovanadium(V), VO 2(C 13H 19N 2O 3), has been obtained by X-ray diffraction studies. The structure revealed a rarely encountered in VO 2(tridentate Schiff base) complexes a distorted trigonal-bipyramidal coordination geometry. The complexes comprising ligands derived either from N-methyl-1,2-diaminoethane or 2-methyl-1,2-diaminopropane and 5-methoxysalicylaldehyde catalyse the oxidation of thioanisole to the corresponding sulfoxide by cumene hydroperoxide.

Syntheses of New Carbonyl Derivatives from α‐Halohetaryl Ketones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Syntheses of New Carbonyl Derivatives from α-Halohetaryl Ketones

The Krohnke reaction of 2ω-bromoacetylphenoxathiin and 2-ω-bromophenoxathiin 10,10-dioxide, through N-ylide and S-ylide intermediates, leading to the corresponding glyoxals, was described. The condensation reaction of 2-ω-bromoacetylphenoxathiin with aromatic o-hydroxy aldehydes and further cyclization to new furan derivatives was also performed. The new compounds were characterized through elemental analysis and spectral data (IR, 1H NMR and 13C NMR).

Preparation and characterisation of new oxovanadium(IV) Schiff base complexes derived from amino acids and aromatic o-hydroxyaldehydes

A range of mostly new oxovanadium(IV) complexes is described. They contain coordinated Schiff bases, made from natural amino acids (glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, threonine, aspartic acid, and histidine) and salicylaldehyde or such derivatives as 3-, 4-, or 5-methoxy-salicylaldehyde. The coordination sphere is completed by simple ligands like water, 2,2′-bipyridyl or pyridine. The compounds are characterised and the nature of their coordination spheres shown by analysis, TLC, and by appropriate spectroscopy (EPR, IR, electronic and circular dichroism of solution and solids). In a few cases, magnetic properties are described to establish oxidation state. In several cases, the solubility of the compounds from racemic amino acids differs markedly from those containing the single enantiomer. The crystal and molecular structure of the related (and novel) compound with N-pyridoxylidene- d, l-isoleucinate, [VO(pyr- d, l-Ile)(bipy)]·H 2O is described. It contains two diastereomers. Denoting the chiral vanadium centres as A or C, these are and [ A(pyr- l-Ile)(bipy)] [ C(pyr- d-Ile)(bipy)].

Dioxaborinanes with an exocyclic phosphino group

The reaction of diphenylphosphine with o-hydroxy aromatic aldehydes and a diphenylboric acid ester in the presence of tertiary amines gave ammonium 5,6-benzo-and 5,6-naphtho-4-diphenylphosphoryl-2,2-diphenyl-1, 3-dioxa-2-boratacyclohexanes. The borylation of (α,2-dihydroxybenzyl)diphenylphosphine, generated in situ, with isobutyl phenylborate gave 5,6-benzo-4-diphenylphosphino-2-phenyl-1,3-dioxa-2-boracyclohexane, which, in contrast to 1,3,2,5-dioxa-boraphosphorinanes, has a high reactivity with respect to electrophilic and nucleophilic reagents and adds oxygen, sulfur, selenium, and pyridine to give the corresponding derivatives.

Molecular species of Schiff bases derived from o-hydroxyaromatic aldehydes. III. Schiff bases of pyridoxal and its analogs with unsaturated amino acids.

The analyses of the electronic absorption spectra and the band assignments to the molecular species were carried out on the methanol solutions of the Schiff bases of pyridoxal (PL), pyridoxal N-methochloride (PLM), and related aromatic aldehydes with α, β-, β, γ-, and γ, δ-unsaturated amino acids and their methyl esters. The Schiff bases of PL with propargylglycine, allylglycine, and vinylglycine had spectra similar to those with a saturated amino acid, showing the unsaturated bond is not conjugated with the azomethine bond. In neutral and alkaline solutions of the Schiff bases of PLM with esters of alanine, propargylglycine, and allylglycine, 2-4% of the Schiff bases was deprotonated at the α-carbon atom, forming a quinoid species absorbing at 500 nm. With ester of vinylglycine, a species absorbing at 534 nm was formed, indicating the quinoid structure with an extended conjugation. It is suggested from the spectral analysis of the Schiff bases of methyl dehydrovalinate that in species protonated at the phenolate or the azomethine the molecule is not planar and the planarity is achieved through the metal chelation.

Molecular species of Schiff bases derived from o-hydroxyaromatic aldehydes. I. Spectral assignments.

Molecular species of Schiff bases derived from o-hydroxyaromatic aldehydes. I. Spectral assignments.