Ewa Wolińska

Deoxygenative vs. Vicarious Nucleophilic Substitution of Hydrogen in Reactions of 1,2,4-Triazine 4-Oxides with α-Halocarbanions

The 3,6-diaryl-1,2,4-triazine 4-oxides 1a−e undergo a nucleophilic substitution of hydrogen with the α-halomethyl aryl sulfones 2, 3 and 7 by two alternative pathways: vicarious nucleophilic substitution (VNS) and/or an intramolecular deoxygenative process. The former pathway is found to dominate in the reaction of 1 with bromomethyl tolyl sulfone (7) yielding the 5-tosylmethyl-1,2,4-triazine 4-oxides 6, while the reaction with the chloromethyl aryl sulfones 2 and 3 leads to the 5-arylsulfonylchloromethyl-1,2,4-triazines 4 and 5, respectively, as the products of deoxygenative substitution. The reaction of 6-phenyl-1,2,4-triazine 4-oxide (1f) with the chloromethyl aryl sulfones 2 and 3 proceeds differently. At low temperature (−75 C) the products of the VNS reaction at position 5 (6f and 12f) are formed. At room temperature the 7-chloro-1-hydroxy-3-phenyl-7-(arylsulfonyl)-1,4,5-triazahepta-1,3,6-trienes 10f and 11f are obtained by addition of the carbanions 2 and 3 in the 3-position, followed by the ring opening of the resulting σ adduct. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Facile synthetic entry into rotationally restricted 9-arylacridines

Abstract The treatment of 2-(trifluoromethyl)aniline with 2,6-dimethylphenylmagnesium bromide yields 1-methyl-9-(2,6-dimethylphenyl)acridine by the formal reaction of one equivalent of the aniline and two equivalents of the Grignard reagent. Interestingly, one of the methyl groups is eliminated during the reaction, and the product contains three methyl groups only. In a similar way, the reaction of 2-(trifluoromethyl)aniline with 2-ethylphenylmagnesium bromide furnishes 9-(2-ethylphenyl)acridine devoid of one ethyl group. The mechanism is discussed.

Sequential amination of heteroaromatic halides with aminopyridine 1 - oxides and their N-protected derivatives based on novel aza-Smiles rearrangement

Abstract The SNAr and Pd-catalyzed amination of chloro derivatives of azines, diazines, and triazines with 2-aminopyridine 1-oxides and their N-protected derivatives was described.

N-{2-[(4S)-4-tert-Butyl-4,5-dihydro-1,3-oxazol-2-yl]phen-yl}-5,6-diphenyl-1,2,4-triazin-3-amine.

The title compound, C28H27N5O, was synthesized using palladium cross-coupling amination of 3-bromo-5,6-diphenyl-1,2,4-triazine with 2-[(4S)-4-tert-butyl-4,5-dihydro-1,3-oxazol-2-yl]aniline. The oxazoline ring is almost planar, with a maximum atomic deviation of 0.023 (5) Å. The phenyl rings make dihedral angles of 29.0 (1) and 54.6 (1)° with the triazine ring while the benzene ring makes a dihedral angle of 0.6 (1)° with the oxazoline ring. The conformation of the molecule is influenced by strong intramolecular N—H⋯N and weak C—H⋯N hydrogen bonds. In the crystal, screw-axis related molecules are linked into supramolecular chains by intermolecular C—H⋯O hydrogen bonds. π–π stacking is observed between the oxazoline and triazine rings of adjacent molecules, with a centroid–centroid distance of 3.749 (2) Å.

1,2,4-Triazine in Organic Synthesis. 16. Reactivity of 3-Substituted 6-Phenyl-1,2,4-triazines towards Phenylacetonitrile Anion in Polar Aprotic Solvents

The reactions of 3-X-6-phenyl-1,2,4-triazines (X = SMe, SPh, SO2Ph) with phenylacetonitrile anion in DMF were studied. In these reactions the ring transformation product 3-amino-4,6-diphenylpyridazine, the covalent addition product 3-X-5-(α-cyanobenzyl)-6-phenyl-2,5-dihydro-1,2,4-triazine, and the ipso-substitution product 3-(1-cyano-1-phenylmethyl)-6-phenyl-1,2,4-triazine were obtained. Analogous reactions carried out in DMA gave only the addition products in excellent yields as diastereomeric mixtures of the corresponding 2,5-dihydro-1,2,4-triazines.

5,5',6,6'-Tetra-methyl-3,3'-bi-1,2,4-tri-azine.

In the title compound, C10H12N6, the two 5,6-dimethyl-1,2,4-triazine halves of the molecule are related by a centre of symmetry. The two triazine rings are coplanar to within a maximum deviation of 0.013 (2) Å from the mean plane of the ring atoms. In the crystal, molecules form layers parallel to the (100) crystallographic plane. Adjacent layers are held together via a C—H⋯π interaction involving molecules related by an a-glide plane.

Structural characterization of copper complexes with chiral 1,2,4-triazine-oxazoline ligands

Abstract The crystal structure determination of oxazoline-1,2,4-triazine ligand 1f and pyridine-oxazoline ligand 2g was used to analyze their conformational preferences when forming complexes with metals. Proton nuclear magnetic resonance (1H NMR), electrospray ionization mass spectrometry and UV-vis spectroscopy as well as theoretical calculation using molecular mechanics (MM) were adopted to study the composition and geometry of oxazoline-1,2,4-triazine ligands 1 complexes with copper(II) acetate monohydrate. The study revealed that during the complexation, (i) Cu(II) ion is reduced to Cu(I) upon the ligand-to-metal charge transfer transition and (ii) the ligands form with copper(I) 2:1 (L:Cu) complexes of tetrahedral geometry. On the basis of the findings, the catalytic cycle and the active transition state for the enantioselective nitroaldol reaction (the Henry reaction) catalyzed by 1–Cu are proposed.

Chiral oxazoline ligands with two different six-membered azaheteroaromatic rings – synthesis and application in the Cu-catalyzed nitroaldol reaction

Abstract Synthesis and catalytic activity of chiral ligands 5,6-diphenyl-3-{3-[(4S/R)-4-R/Ar-4,5-dihydro-1,3-oxazol-2-yl]pyridin-2-yl}amino-1,2,4-triazines 2 and their analogs 3 possessing an N-oxide function in the pyridine ring are described. The pivotal step in the synthesis of ligands 2 is the Buchwald-Hartwig Pd-catalyzed cross-coupling reaction between 3-bromo-5,6-diphenyl-1,2,4-triazine (7a) and enantiopure 3-(4,5-dihydro-1,3-oxazol-2-yl)pyridin-2-amines 6a–d. Aromatic nucleophilic substitution of chlorine in 3-chloro-5,6-diphenyl-1,2,4-triazine (7b) with 3-(4,5-dihydro-1,3-oxazol-2-yl)pyridin-2-amine 1-oxides 12 was investigated as the key reaction in the synthesis of ligands 3. Two undesired derivatives 13 or 14, resulting from unexpected reactions of 3, were isolated depending on reaction conditions. Compounds 2 and 3 as well as the side products 13 and 14 were screened as chiral ligands in the copper catalyzed enatioselective nitroaldol reaction.

Synthesis of quinolines and acridines by the reaction of 2-(perfluoroalkyl)anilines with lithium and Grignard reagents

Abstract This review summarizes the synthesis of quinolines and acridines by the reactions of anionically activated 2-(perfluoroalkyl)anilines. Mechanistic studies including isolation of the intermediate aza-ortho-xylylene are discussed.

Acridine Synthesis by the Reaction of 2-(Perfluoroalkyl)aniline with ortho-Alkyl-Substituted Aromatic Grignard Reagent: Mechanistic Studies

The reaction of 2-(perfluoroethyl)aniline and its higher perfluoroalkyl analogues with an arylmagnesium bromide substituted with a methyl or ethyl group at the ortho position furnishes an acridine containing a shorter perfluoroalkyl group at the 9-position and devoid of the methyl or ethyl group of the Grignard reagent. Yields are in the range of 46–93 %. The intermediary of a substituted aza-ortho-xylylene has been postulated for related transformations in the literature previously, but this intermediate product has never been isolated. As part of this work, the labile product E-27 (half-life of 6 h at 23°C) was isolated for the first time and characterized by infrared spectroscopy, electron impact mass spectrometry, fast atom bombardment mass spectrometry, and 1H NMR. Experimental evidence was also obtained regarding the elimination of the ortho-alkyl group of the Grignard reagent during the course of the reaction as an alcohol.