Reaction Between 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione and <Emphasis Type="Italic">tert</Emphasis>-Butyl Isocyanide in the Presence of Primary or Secondary Amines

Summary. 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione (the condensation product of Meldrums acid and acetone) reacts smoothly with tert-butyl isocyanide in the presence of primary or secondary amines to produce N-tert-butyl-2,2-dimethylbutyramide derivatives and/or 1-tert-butyl-4,4-dimethyl-2,5-dioxopyrrolidine-3-carboxamides in good yields.     

Kinetics of the Electrocatalytic Oxidation of 2,2-Dimethylolpropionaldehyde

A new method of synthesis 2,2-dimethylolpropionic acid from 2,2-dimethylolpropionaldehyde was put forward. The electrochemical oxidation behavior of 2,2-dimethylolpropionaldehyde has been investigated on a Ti/SnO₂ + Sb₂O₄/PbO₂ electrode by cyclic voltammetry (CV) and stable polarization curves in sulfuric acid. The results showed that it was an irreversible reaction controlled by diffusion. The formation mechanism of 2,2-dimethylolpropionic acid in the sulfuric acid was then proposed and the transfer coefficients of the reaction were calculated. It was concluded that RCHO+ỌH_ads→RCHOỌH_ads was the rate-determining step in the electrolysis process. The rate of this step obtained from the assumed process agrees well with experiment.     

Synthesis,characterization and crystal structure of a chiral polymeric Cu(II) complex bridged by tartrate

A chiral metal-organic coordination polymer, [Cu(Tar)(2,2′-bipy) · 5H₂O] (1) (Tar = L-tartrate dianion, 2,2′-bipy = 2,2′-bipyridine), has been synthesized by hydrothermal reaction of Cu(OAc)₂, Na₂T (H₂T = 2,3-O-isopropylidene-L-tartaric acid) and 2,2′-bipyridine, and characterized by IR, UV–vis spectra, elemental analyses, TG-DTA, and single crystal X-ray diffraction. In the hydrothermal reaction, the protection group isopropylidene for tartaric acid was hydrolyzed. The crystal structure of the coordination polymer 1 shows that each tartrate chelates two Cu(II) ions at opposite ends using one carboxylate oxygen and one hydroxyl oxygen and each Cu(II) ion is chelated by two halves of tartrate dianions, forming coordination polymer chains. Distorted octahedral geometry around copper is completed by a chelating 2,2′-bipyridine molecule. The 2,2′-bipyridine groups in two of parallel 1-D chains are interwoven, constituting ladder-shaped double chains. Strong offset π–π stacking interactions with a face-to-face distance of 3.33 Å for pyridine rings are observed. All the lattice water molecules hydrogen-bond to each other or to the carbonyl oxygen of tartrate, forming a 3-D supramolecular structure.     

Aspects of tautomerism. 8. Solvolysis of some pseudo and normal acid chlorides

Pseudo acid chlorides derived from levulinic acid ando-benzoyl-benzoic acid, solvolyse in aqueous acetone, aqueous dioxane and aqueous dimethylformamide by aS _Nl process. Their reaction pattern is distinct from that of typical normal acid chlorides, viz.,p-benzoylbenzoyl chloride and fluorene-9-one-1-carboxylic acid chloride, which solvolyse by aS _N2 pathway. No evidence for tautomerism could be obtained either between the normal and pseudo forms of the acid chlorides or the derived ion pairs.     

Formation and Structural Characterization of Metal Complexes derived from Thiosalicylic Acid

The formation and structural aspects of some metal complexes of thiosalicylic acid (TSA) were studied. The μ‐bridging tetra‐coordinated Ru complex, [Ru(C₆H₄(CO₂)(μ‐S)(H₂O)]₂ ( 1 ) was formed by hydrothermal reaction of TSA with RuCl₃. The complexes [M(dtdb)(phen)(H₂O)]_n ( 2 – 4 ) (M = Zn^II, Co^II, Ni^II, dtdb = 2,2′‐dithiodibenzoate anion, phen = 1,10‐phenanthroline) were obtained by the slow diffusion technique and the in situ S–S bond formation was confirmed by elemental, spectral and X‐ray analysis. Reaction of TSA with CuCl₂ and 2,2′‐bipyridine (bipy) under the slow diffusion technique yielded the dimer [Cu(tdb)(bipy)] ( 5 ) (tdb = thiodibenzoic acid), where the in situ generation of 2,2′‐thiodibenzoic acid was observed.     

Preparation and some properties of 2H-imidazole 1,3-dioxides,derivatives of alicyclic 1,2-dioximes

The corresponding 2H-imidazole 1,3-dioxides were obtained by the reaction of cyclohexanedione and cycloheptadione 1,2-dioximes with acetone, cyclopentanone, and methyl ethyl ketone. The reactions of these compounds with hydroxylamine hydrochloride, NaBH₄, a Grignard reagent, and acetic anhydride in the presence of H₂SO₄ were studied in the case of 2,2-dimethyl-4,5,6,7-tetrahydro-2H-benzimidazole 1,3-dioxide. Bromination of the latter and 2,2-dimethylcyclohepta-2H-imidazole 1,3-dioxide with N-bromosuccinimide gave the corresponding dibromo derivatives, the bromine atoms in which are replaced by acetoxy and hydroxy groups. 4,7-Dihydroxy-2, 2-dimethyl-4,5,6,7-tetrahydro-2H-benzimidazole 1,3-dioxide, which was obtained by oxidation with MnO₂ was converted to a quinone, viz., 2,2-dimethyl-4,7-dioxo-4,7-dihydro-2H-benzimidazole 1,3-dioxide. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 808–813, June, 1980.     

Application of variable-temperature kinetic experiments to oxidative addition reactions of dimethylplatinum(II) complexes with alkyl halides

Rate constants and activation parameters of oxidative addition reactions of [PtMe₂(2,2′-bipyridine)] with EtI and [Pt(p-MeC₆H₄)₂ (2,2′-bipyridine)] with MeI in solvents acetone and benzene have been obtained very easily and with good accuracy from variable-temperature spectrophotometric kinetic data using a method based on nonisothermal analysis. The results are compared with those obtained by the traditional isothermal method. It is shown that there are significant advantages to measuring the reaction rates under variable-temperature kinetic conditions, as compared to the constant-temperature kinetic method.     

Ring-chain tautomerism of acetone N-methylated thiosemicarbazones

Ring-chain tautomerism of acetone N-methylated thiosemicarbazones was studied by nmr spectroscopy. Acetone thiosemicarbazone, acetone 2-methylthiosemicarbazone, and acetone 4-methylthiosemicarbazone exist as chain forms in DMSO-d₆ and ring forms in deuteriotrifluoroacetic acid. However, the compound obtained by reaction of acetone with 2,4-dimethylthiosemicarbazide exists only as the ring form 3,5,5-trimethyl-1,3,4-thiadiazolidine-2-methylimine both in DMSO-d₆ and in deuteriotrifluoroacetic acid, due to steric hindrance of the three methyl groups.     

Über Chalkogenolate. 200. Methylester der 2-Silapropan-2,2-bis(dithiocarbonsäure)

On Chalcogenolates. 200. Methyl Ester of 2-Silapropane-2,2-bis(dithiocarbonic acid) The hitherto not known title compound (H₃C)₂Si(? CS? SCH₃)₂ has been prepared in one-pot synthesis by reaction of dimethyl dichlorosilane with magnesium followed by CS₂ insertion and alkylation with methyl iodide. The compound has been characterized by means of diverse methods.     

DFT study of the structure of hydroxybenzoic acids and their reactions with OH and radicals

B3LYP/6-31++G(d) method was used for the structural study of 3,4,5-trihydroxybenzoic acid (3,4,5-THBA), 3,4-dihydroxybenzoic acid (3,4-DHBA), and 4-hydroxybenzoic acid (4-HBA). Calculated structures agree with available X-ray experimental data within 2%. The phenolic OH bond dissociation enthalpy (BDE) of all sites in each benzoic acid were determined and compared with those of phenol (for 4-HBA) and catechol (for 3,4-DHBA). The consistency between the calculated values and experimental ones are within 5.4% and 9.2%, respectively, for 4-HBA and 3,4-DHBA. The reactions of benzoic acids with and OH radicals were studied and it turns out that benzoic acids react differently with both radicals. We have shown that the reaction of hydroxybenzoic acids with the hydroxyl radical was governed by a phenolic hydrogen (H⁺ + e⁻) transfer from the acid to the radical, while for the superoxide radical, the reaction is governed by a proton (H⁺) transfer from the acid to the radical. The first reaction is evidenced by the delocalization of the radical on the entire quinone moiety, and the second reaction is evidenced by the negative NBO charge on the phenoxide moiety as well as the localization of the radical on the hydroperoxy (O₂H) moiety.     

Step by step palladium mediated syntheses of new 2-(pyridin-2-yl)-6-R-nicotinic acids and esters

Taking advantage of palladium peculiar “rollover” C,N cyclometallation, it is possible to promote C(3) functionalization of 6-alkyl-substituted-2,2′-bipyridines. The carbonylation reaction of rollover species [Pd(Lⁿ)Cl]₂, (HL¹ = 6-isopropyl-2,2′-bipy, 1; HL² = 6-neopentyl-2,2′-bipy, 2; HL³ = 6-ethyl-2,2′-bipy, 3; HL⁴ = 6-methyl-2,2′-bipy, 4) allowed the synthesis of 2-(pyridin-2-yl)-6-alkyl-nicotinic acids or esters. These nicotinic derivatives are extremely rare and, as far as we know, quite unreported in the case of the 6-substituted molecules.     

Synthesis of two luminescent coordination polymers based on self‐assembly of Zn(II) with polycarboxylic acids ligands and heteroaromatic N‐donor

Using the principles of molecular self‐assembly, two novel zinc complexes {[Zn(phth)(bipy)(H₂O)][Zn(phth)(bipy)]·H₂O}_n (1) and [Zn(1,2,4‐btc)(bipy)(H₂O)·2H₂O]_n (2) were obtained by hydrothermal reaction of Zn(CH₃COO)₂·2H₂O with phthalic acid (phth), 1,2,4‐benzenetricarboxylic acid (1,2,4‐btc) and 2,2′‐bipyridine (bipy) respectively, and characterized by single‐crystal X‐ray diffraction. The crystal structures reveal that both complexes form one‐dimensional chain structures, and the zinc ions are five‐coordinated; there are two types of metal environment in the structure of the complex 1. The photophysical properties have been investigated with fluorescence excitation and emission spectra. Copyright © 2005 John Wiley & Sons, Ltd.     

Reaction of Zirconium Tetrachloride with 2,2-Dimethylbutanoic Acid

The reaction of ZrCl₄ with 2,2-dimethylbutanoic acid in excess of the acid and also in o-xylene at boiling point of the solvent was studied. Formed zirconium tetrakis(2,2-dimethylbutanoate) is volatile in vacuum that allows its using as a precursor for the preparation of inorganic materials by chemical vapor deposition. During the reaction Zr(C₆H₁₁O₂)₄ is condensed to form polynuclear complexes.     

Determination of fatty acid methyl esters derived from algae Scenedesmus dimorphus biomass by GC–MS with one‐step esterification of free fatty acids and transesterification of glycerolipids

Algae can synthesize, accumulate and store large amounts of lipids in its cells, which holds immense potential as a renewable source of biodiesel. In this work, we have developed and validated a GC–MS method for quantitation of fatty acids and glycerolipids in forms of fatty acid methyl esters derived from algae biomass. Algae Scenedesmus dimorphus dry mass was pulverized by mortar and pestle, then extracted by the modified Folch method and fractionated into free fatty acids and glycerolipids on aminopropyl solid‐phase extraction cartridges. Fatty acid methyl esters were produced by an optimized one‐step esterification of fatty acids and transesterification of glycerolipids with boron trichloride/methanol. The matrix effect, recoveries and stability of fatty acids and glycerolipids in algal matrix were first evaluated by spiking stable isotopes of pentadecanoic‐2,2‐d₂ acid and glyceryl tri(hexadecanoate‐2,2‐d₂) as surrogate analytes and tridecanoic‐2,2‐d₂ acid as internal standard into algal matrix prior to sample extraction. Later, the method was validated in terms of lower limits of quantitation, linear calibration ranges, intra‐ and inter‐assay precision and accuracy using tridecanoic‐2,2‐d₂ acid as internal standard. The method developed has been applied to the quantitation of fatty acid methyl esters from free fatty acid and glycerolipid fractions of algae Scenedesmus dimorphus .     

Mass spectrometric synthesis. II. The reaction of catechol with acetone in a protic medium

The reaction of catechol with acetone, carried out in the chemical ionization chamber of a VG ZAB 2F mass spectrometer and in the presence of a protic medium (CH₅+), leads to 2,2-dimethyl-1,3-benzodioxole. This has been proved by exact measurements and collisionally activated dissociation mass analyzed ion kinetic energy spectra.     

Preparation and Characterization of Pure Thiosulfuric Acid

Pure thiosulfuric acid has not been prepared yet, although it is described in most textbooks of inorganic chemistry. Furthermore, no experimental evidence for the structure of thiosulfuric acid is known. Theoretical calculations predict the (SH)(OH) tautomer to be more stable than the (OH)(OH) tautomer. In this work we present the synthesis and spectroscopical characterization of pure thiosulfuric acid. X₂S₂O₃ (X = H, D) was obtained from the reaction of dry Na₂S₂O₃ with anhydrous HF at –60 °C. The experimental vibrational and NMR spectra together with quantum chemical calculations provide evidence for the predicted (SH)(OH) tautomeric structure.     

Triphenylamine-based novel PET sensors in selective recognition of dicarboxylic acids

The triphenylamine-based chemosensors 1 and 2 have been designed and synthesized, for the first time, for the selective recognition of dicarboxylic acids. Carboxylic acid binding takes place through charge neutral pyridyl amide receptor sites with concomitant quenching of fluorescence of the triphenylamine moiety. The bindings were examined using ¹H NMR, fluorescence and UV-vis spectroscopic methods. The receptor 1 was found to be selective for glutaric and adipic acids and the macrocycle 2 was specific for 2,2-dimethylmalonic acid.     

Formation of isoxazole derivatives via nitrile oxide using ammonium cerium nitrate (CAN): a novel one-pot synthesis of 3-acetyl- and 3-benzoylisoxazole derivatives

The reactions of alkenes and alkynes with ammonium cerium(IV) nitrate ((NH₄)₂Ce(NO₃)₆, CAN(IV)) in acetone under reflux gave the corresponding 3-acetyl-4,5-dihydroisoxazole and 3-acetylisoxazole derivatives. In the case of acetophenone, 3-benzoyl-4,5-dihydroisoxazole and 3-benzoylisoxazole derivatives were obtained. Reaction of acetone with CAN(IV) afforded the corresponding furoxan (3,4-diacetyl-1,2,5-oxadiazole 2-oxide) as the dimer of nitrile oxide. Moreover, it was found that yields of isoxazole derivatives were improved using ammonium cerium(III) nitrate tetrahydrate ((NH₄)₂Ce(NO₃)₅·4H₂O, CAN(III))-formic acid. The reaction mechanisms based on nitration and formation of nitrile oxide mediated by CAN(IV) or CAN(III) from acetone or acetophenone are also proposed.     

Synthesis and structural study of copolymers of l-lactic acid and bis(2-hydroxyethyl terephthalate)

Poly(ethylene terephthalate)-poly(lactic acid) (PET-PLLA) copolyesters were synthesized by the melt reaction of bis(2-hydroxyethyl terephthalate) (BHET) with l-lactic acid oligomers (OLLA) in the presence of SnCl₂, H₂O-p-toluene sulfonic acid, H₂O catalytic system. The ¹H and ¹³C NMR studies confirm the incorporation of lactate units in PET chains after reaction. Copolyesters containing nearly equimolar terephthalate/lactate ratio are not completely random and present some block-copolymer character, while the microstructure of PET-rich copolyesters is a random one. Due to a longer PET sequence length, the latter exhibit a melting point close to 210 °C while the other ones are amorphous. SEC/MALDI-TOF MS off-line coupling was used to obtain the absolute average molar masses of the copolyesters. The results indicate that the conventional polystyrene calibration method leads to a strong overestimation of PET-PLLA molar masses, while the determined by NMR is much closer to the SEC/MALDI value.     

Synthesis of a biphenyl-based axially chiral amino acid as a highly efficient catalyst for the direct asymmetric aldol reaction

A biphenyl-based axially chiral amino acid (S)-2 has been designed and synthesized. The new amino acid (S)-2 has been found to be a more efficient catalyst than (S)-1 in the direct asymmetric aldol reaction of acetone with aldehydes. For instance, the use of only 0.1 mol % of (S)-2 was sufficient to complete the reaction between acetone and 4-nitrobenzaldehyde, giving the corresponding aldol adduct in good yield with an excellent enantioselectivity.