Synthesis and keto-enol tautomerism of ethyl 4-oxo-3,4-dihydro-1H-pyrano[3,4-b]quinoline-3-carboxylate

An efficient method has been developed for the synthesis of a novel β-keto ester-containing pyranoquinoline compound, i.e., ethyl 4-oxo-3,4-dihydro-1H-pyrano[3,4-b]quinoline-3-carboxylate. The method entails a two-step synthesis. The first step involves the Williamson-type reaction of ethyl 2-bromomethyl-3-quinoline-3-carboxylate with ethyl hydroxyacetate in anhydrous benzene to afford the intermediate ethyl 2-[(2-ethoxy-2-oxoethoxy)methyl]quinoline-3-carboxylate. The second step includes the Dieckmann condensation reaction of the resulting intermediate in the presence of sodium ethoxide in anhydrous toluene to afford the desired pyranoquinoline containing β-keto ester moiety. Keto-enol tautomerism of the compound thus obtained was investigated by spectroscopic methods.

Synthesis and Spectroscopic Characterisation of Some Neutral Tetracoordinated Germanium (IV) Alkoxyalkanolates

Compounds of the type, [Ge(OPri)4-n(OCH2CH2OR)n], (where R = Me, Et, n-Bu and n = 1-4) have been synthesised in high yields by the interactions of germanium tetraisopropoxide with alkoxyalkanols (HOCH2CH2OR) in different stoichiometries in refluxing anhydrous benzene, and are monomeric in refluxing benzene. All these compounds can be purified by distillation under reduced pressure. IR and NMR (1H and 13C) spectral studies indicate a tetrahedral geometry around the germanium atom.

An interesting azirine induced reaction of the cyclopentadienyliron dicarbonyl dimer

Reaction of cyclopentadienyliron dicarbonyl dimer with a series of 2-arylazirines in anhydrous benzene (room temperature or 40 °C, 41–96 h) affords cycloaddition products (pyrazines, isoxazoles) and the dimer of cyclopentadienone (1,8-diketo-4,7-methano-3a,4,7,7a-tetrahydroindene). The formation of the latter product is proposed to occur via a complex in which each cyclopentadienyl ring is π-complexed to one iron atom and σ-bound to another.

The Dimerization Constant of Nitrobenzene in Benzene: A Critique of Partition as a Thermodynamic Method

The dimerization constant (K) of nitrobenzene in benzene was determined at 5.5 and 25 °C by means of partition (solvent extraction). A hydration study was performed at these temperatures to determine the extent of hydration of nitrobenzene in the benzene phase. Published freezing point depression data for the anhydrous benzene–nitrobenzene system were used to obtain a value of K at 5.5 °C. The heats of solution of nitrobenzene in benzene (anhydrous) were determined at 25 °C. The heat of solution and freezing point depression data were combined to obtain a value of K for the anhydrous system at 25 °C. At each of 5.5 and 25 °C the value of K determined by partition was significantly smaller than the corresponding value of K for the anhydrous system, and the discrepancy was larger at 25 than at 5.5 °C. It was found that by fitting a simple electrostatic model to the difference in the values of K found at 5.5 °C, the difference at 25 °C could be predicted.

L'oxydation chromique et les esters chromiques

Rates of decomposition of chromic acid esters derived from secondary alicyclic alcohols and rates of oxidation of these cyclanols by chromic esters derived from tertiary alcohols have been measured in anhydrous benzene. The results obtained are compared to those of other workers for reactions held in polar solvents. A mechanism is suggested to explain the observed results.

Ions and Aggregates of Tetra-n-Butylammonium Picrate in Nonaqueous Solvents: A Thermodynamic Study

Values of ΔG0, ΔH0, and ΔS0 at 25 °C were obtained by distribution studies and by calorimetry, for the dimerization and trimerization of tetra-n-butylammonium picrate (1) in anhydrous benzene, chlorobenzene, and o-dichlorobenzene. The standard enthalpy of sublimation of 1 was calculated. The values of ΔG0 for the ionization, dimerization, and trimerization of 1 were linear functions of the reciprocal of the dielectric constant of the solvent. The intercepts and slopes of these graphs are interpreted; partial desolvation of the ions, and of the monomers on association is invoked. A simple potential function is used with the data, in order to deduce suitable models of the dimer and the trimer of 1.

Synthesis of Diphytanyl Ether Analogues of Phosphatidic Acid and Cytidine Diphosphate Diglyceride

The chemical synthesis of 2,3-di-O-phytanyl-sn-1-glycerophosphate was carried out in two ways: (a) by phosphorylation of 2,3-diphytanyl-sn-glycerol with diphenylphosphoryl chloride in pyridine, followed by catalytic hydrogenolysis of the phenyl groups; and (b) by condensation of 1-iodo-2,3-di-O-phytanyl-sn-glycerol with silver di-p-nitrobenzyl phosphate in anhydrous benzene, followed by catalytic hydrogenolysis of the p-nitrobenzyl groups. The free diether phosphatidic acid obtained was converted to the dipotassium and disodium salts. The diether phosphatidic acid was also converted to the diether analogue of cytidine diphosphate diglyceride by condensation with cytidine monophosphate morpholidate in pyridine. The physical properties of these diether analogues are described, as well as their stabilities towards acid hydrolysis.

Studies in Niobium (V) - Schiff Base Complexes

A number of new niobium (V) - Schiff base complexes of the type Nb (SB) x (OPri) 5 - 2x and Nb(SB)2(SBH) (where SB2⊖ and SBH⊖ are anions of the Schiff bases and x =1 or 2) have been synthesised by the interaction of niobium pentaisopropoxide with the Schiff bases in different stoichiometric ratios. The molecular weight determinations and IR studies of a few derivatives have also been carried out.Scanty references are available in the literature regarding the Schiff base complexes of niobium (V) and tantalum (V) 1, 2 and such derivatives have been prepared from the corresponding metal chlorides and the Schiff bases. In a series of papers published earlier 3, 4, a more convenient method, for the synthesis of such derivatives, by the interaction of metal alkoxides with the Schiff bases in anhydrous benzene medium, has been reported. The present paper describes the synthesis of several new niobium (V) derivatives with the Schiff bases derived from the condensation of salicylaldehyde or o-hydroxyacetophenone with n-hydroxyalkylamines.