Agnieszka Plutecka

Simple and practical direct asymmetric aldol reaction of hydroxyacetone catalyzed by 9-amino Cinchona alkaloid tartrates

A novel organocatalytic procedure for the direct aldol reaction of unprotected acetol and activated aromatic aldehydes catalyzed by 9-amino-9-epi-Cinchona ditartrates is presented. The protocol presented avoids the use of problematic solvents and toxic reagents as well as chromatographic purification of the products – instead a simple extraction has been applied for the isolation of pure aldols from the reaction mixture. This catalytic system provides exclusively linear aldols with quantitative yields and good syn-diastereoselectivity and enantioselectvitiy up to 90% ee. Further upgrading of the enantiomeric excess of syn-aldols up to 99% ee is easily accomplished by a single and reliable crystallization. The use of cinchonine or quinine-derived catalysts gives access to both enantiomers of syn-aldols for which the absolute configuration has been determined by X-ray diffraction. The operationally convenient and scalable organocatalytic procedure using cheap and renewable chemicals – both acetol and the catalysts, offers a sustainable and green way for the synthesis of a number of α-keto-syn-diols.

Hydrogen-bonding patterns in 2-amino-4,6-dimethylpyrimidinium hydrogen sulfate

In the title compound, C6H10N3+.HSO4-, the asymmetric unit consists of a hydrogen sulfate anion and a 2-amino-4,6-dimethylpyrimidinium cation. The hydrogen sulfate anions self-assemble through O-H...O hydrogen bonds, forming supramolecular chains along the b axis, while the organic cations form base pairs via N-H...N hydrogen bonds. The aminopyrimidinium cations join to the sulfate anions via a pair of hydrogen bonds donated from the pyrimidinium protonation site and from the exo amine group cis to the protonated site.

THE LIBRARY OF CINCHONA ALKALOIDS-1,2,3-TRIAZOLE DERIVATIVES: STRUCTURE AND FACILE ACCESS BY "CLICK CHEMISTRY"

New Cinchona alkaloids-1,2,3-triazole derivatives library was prepared readily and efficiently using Huisgen 1,3-dipolar cycloaddition of 9-azido substituted Cinchona alkaloids and various terminal and disubstituted alkynes (click chemistry). Spectroscopic, X-Ray, and molecular modelling data show that these derivatives maintain the conformation of the parent alkaloids.

Relationship between structure and photoinitiating abilities of selected bromide salts of 2-oxo-2,3-dihydro-1H-imidazo[1,2-a]pyridine (IMP): influence of the solvent and the substitution in benzaldehyde on the course of its reaction with IMP.

2-Oxo-2,3-dihydro-1H-imidazo[1,2-a]pyridinium bromide and its C3-substituted derivatives have been synthesized and structurally characterized by X-ray crystallography and quantum chemical calculations. Their potential as photoinitiators for free-radical polymerization has been investigated experimentally and compared with theoretical results. It has been established that the course of the reaction that introduces the substituted benzylidene group to the imidazole ring is different in the protic and dipolar aprotic solvents, and also depends on the character of the substituent, as the energy change in the reaction favours either R1R2C=CHR3 or R1R2CH-CH(OCH3)R3 formation.

Hydrogen-bonding and π–π inter­actions in 2-amino-4,6-dimethyl­pyrimidinium salicylate

In the crystal structure of the title compound, C6H10N3+.C7H5O3-, the asymmetric unit contains four crystallographically independent 2-amino-4,6-dimethylpyrimidinium and salicylate ions (Z = 8). In each of these, one of the pyrimidine N atoms is protonated, and the carboxylate group of the salicylate ion interacts with the pyrimidine group through a pair of N-H...O hydrogen bonds, forming an R2(2)(8) motif. The pyrimidine cations also form base pairs via a pair of N-H...N hydrogen bonds (involving the amino group and the unprotonated ring N atom), forming another R2(2)(8) motif. Three such R2(2)(8) motifs, fused together, constitute a closed cyclic aggregate, and the linking of these aggregates, arranged in consecutive layers, can be analysed in terms of off-face stacking interactions.

Hydrogen-bonding patterns in pyrimethaminium dinitrate

The title compound, 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidine-1,3-diium dinitrate, C12H15ClN42+.2NO3-, contains two crystallographically independent pyrimethamine (PMN) molecules, which differ in the relative orientations of the pyrimidine and benzene rings and of the ethyl substitutents. In both pyrimethamine molecules, all the pyrimidine N atoms are protonated, unlike most related compounds, in which only one pyrimidine N atom is protonated. The two pyrimethamine moieties are bridged by a variety of N-HO(nitrate) interactions, including some three-centre hydrogen bonds.

Probing the shapes of chiral bis-(o-naphthalimidobenzoyl) systems using X-ray and circular dichroism methods

CD (circular dichroism) and X-ray investigations have been carried out in order to identify the prevalent conformations and define the forces that determine the molecular and supramolecular organization of the alkyl-bridged bichromophoric [NAB, ortho-(1,8-naphthalimido)benzoyl] units, each consisting of the benzoyl substituted in the ortho position with the 1,8-naphthalimide group. The results reveal that NAB bichromophores incorporated into the same molecule exist in a variety of conformation/helicity combinations. The molecular structures are largely stabilized by local 1,3-CH/CO dipole-dipole interactions, while the crystal packing besides dispersive H...H interactions is mostly governed by multiple C-H...O(=C) and C-H...pi interactions. The relatively small contribution of pi...pi interactions comes from a pairwise off-face stacking between naphthalimide rings or from pairwise carbonyl...pi interactions. All these types of intermolecular interactions have been summarized quantitatively by means of a Hirshfeld surface analysis.