APPLICATION OF IMIDAZOLINES BASED ON TALL OIL FATTY ACIDS AND THEIR QUATERNARY SALTS FOR THE SEPARATION OF THE BINARY NON-AQUEOUS AZEOTROPE SYSTEMS

Методом экстрактивной (в том числе солевой) ректификации с использованием имидазолинов и четвертичных солей на их основе разделены на компоненты неводные двойные азеотропные системы. В качестве разделяющих агентов выбраны: промышленный продукт 1-гидроксиэтил-2-алкенил-2-имидазолин на основе жирных кислот таллового масла, а также его четвертичные соли - хлорид и тетрафторборат 1-гидроксиэтил-2-алкенил-3-бензил-2-имидазолиния. Для разделения были использованы неводные азеотропные системы: ацетон-метанол, метилацетат-метанол, этилацетат-этанол и хлороформ-метанол. Равновесие жидкость-пар в соответствующих тройных системах исследовано в модифицированном приборе Отмера при 101,3 кПа, состав жидкой и паровой фаз определен газохроматографическим методом анализа. Минимальные концентрации (в мольных долях) имидазолина и имидазолиниевых солей для разрушения азеотропов составили 0,156-0,264. Для корреляции экспериментальных данных о парожидкостном равновесии в системах, содержащих имидазолиниевые соли использована электролитная модель NRTL. Средние абсолютные отклонения расчетных данных от экспериментальных значений мольного содержания растворителей в паровой фазе и температуры в системах составили 0,007-0,008 и 0,25-0,35 К, соответственно. The non-aqueous binary azeotrope systems have been separated into components by the method of extractive rectification (and salt rectification) using imidazolines and their quaternary salts. The following were selected as separating agents: industrial product 1-hydroxyethyl-2-alkenyl-2-imidazoline based on tall oil fatty acids, as well as its quaternary salts - chloride and tetrafluoroborate 1-hydroxyethyl-2-alkenyl-3-benzyl-2-imidazolinium. Non-aqueous azeotrope acetone - methanol, methyl acetate - methanol, ethyl acetate - ethanol, and chloroform - methanol systems were used for separation. The vapor-liquid equilibrium in the corresponding ternary systems was investigated in a modified Othmer still at 101.3 kPa, the composition of the liquid and vapor phases was determined by gas chromatographic analysis. The minimum concentrations (in molar fractions) of imidazoline and imidazolinium salts for the azeotrope breaking were 0.156-0.264. The mean absolute deviations between experimental and calculated data for the solvent mole fraction in the vapor phase and temperature in the imidazolinium salt containing systems were 0,007-0,008 and 0,25-0,35 К respectively.

The pKa values of N-aryl imidazolinium salts, their higher homologues, and formamidinium salts in dimethyl sulfoxide

The effects of substitution, ring size and cyclisation on the pKa values of imidazolinium salts, higher homologues and formamidinium salts in DMSO are quantified, considering structural and electronic motifs along with crystallographic analyses.

Kekulé diradicaloids derived from a classical N-heterocyclic carbene

Two-electron reduction of bis(1,3-imidazolinium) salts 2 and 3 with KC8 gives rise to stable diradicaloids 4 and 5, respectively. Calculations reveal a very low singlet–triplet energy gap ΔES–T for 5 (10.7 kcal mol−1), while ΔES–T for 4 (29.1 kcal mol−1) is rather large.

One-pot synthesis of imidazolinium salts via the ring opening of tetrahydrofuran

One-pot synthesis of C2-hydroxypropyl-substituted imidazolinium salts, active catalysts for the aza-Diels–Alder reaction, via the ring opening of THF is reported.

Effect of imidazolinium salts bearing hydroxy substituents on palladium-catalysed Suzuki–Miyaura and Heck coupling reactions

Palladium anionic complexes with imidazolinium cations containing hydroxyl substituents were used as catalyst precursors in the Suzuki–Miyaura and the Heck cross-coupling. High activity of anionic complexes was noted in the Suzuki–Miyaura reaction of 2-bromotoluene with phenylboronic acid at 40 oC in 2-propanol and a 2-propanol/water mixture using conventional heating or microwaves. Similarly, bromonaphtalene and iodonaphtalene reacted efficiently with naphtylboronic acid and 4-methylnaphtylboronic acid. A remarkably lower activity was noted when anionic palladium complexes were employed in the Heck coupling of 2,3-dihydrofuran with iodobenzene. An increase in conversion in the Heck reaction was achieved when Pd(OAc)2 was used as a catalyst precursor together with imidazolinium salts as co-catalysts.

Application of imidazolinium salts and N-heterocyclic olefins for the synthesis of anionic and neutral tungsten imido alkylidene complexes

The convenient synthesis, structural characterization and catalytic properties in olefin metathesis of three anionic tungsten imido alkylidenes and one neutral, NHO-bearing tungsten imido alkylidene complex are presented.

Efficient synthetic protocols for the preparation of common N-heterocyclic carbene precursors

The one-pot condensation of glyoxal, two equivalents of cyclohexylamine, and paraformaldehyde in the presence of aqueous HBF4 provided a straightforward access to 1,3-dicyclohexylimidazolium tetrafluoroborate (ICy·HBF4). 1,3-Dibenzylimidazolium tetrafluoroborate (IBn·HBF4) was obtained along the same lines. To synthesize 1,3-diarylmidazolium salts, it was necessary to isolate the intermediate N,N'-diarylethylenediimines prior to their cyclization. Although this additional step required more time and reagents, it led to a much more efficient overall process. It also proved very convenient to carry out the synthesis of imidazolinium salts in parallel to their imidazolium counterparts via the reduction of the diimines into diammonium salts. The critical assembly of the C2 precarbenic unit was best achieved with paraformaldehyde and chlorotrimethylsilane in the case of imidazolium derivatives, whereas the use of triethyl orthoformate under microwave irradiation was most appropriate for the fast and efficient synthesis of imidazolinium salts. This strategy was applied to the synthesis of six common N-heterocyclic carbene precursors, namely, 1,3-dimesitylimidazolium chloride (IMes·HCl), 1,3-dimesitylimidazolium tetrafluoroborate (IMes·HBF4), 1,3-dimesitylimidazolinium chloride (SIMes·HCl), 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride (IDip·HCl or IPr·HCl), 1,3-bis(2,6-diisopropylphenyl)imidazolinium chloride (SIDip·HCl or SIPr·HCl), and 1,3-bis(2,6-bis(diphenylmethyl)-4-methylphenyl)imidazolium chloride (IDip*·HCl or IPr*·HCl).