Regioselective and Stereodivergent Synthesis of Enantiomerically Pure Vic-Diamines from Chiral β-Amino Alcohols with 2-Pyridyl and 6-(2,2′-Bipyridyl) Moieties

In this report, we describe the synthetic elaboration of the easily available enantiomerically pure β-amino alcohols. Attempted direct substitution of the hydroxyl group by azido-functionality in the Mitsunobu reaction with hydrazoic acid was inefficient or led to a diastereomeric mixture. These outcomes resulted from the participation of aziridines. Intentionally performed internal Mitsunobu reaction of β-amino alcohols gave eight chiral aziridines in 45–82% yield. The structural and configuration identity of products was confirmed by NMR data compared to the DFT calculated GIAO values. For 1,2,3-trisubstituted aziridines slow configurational inversion at the endocyclic nitrogen atom was observed by NMR at room temperature. Moreover, when aziridine was titrated with Zn(OAc)2 under NMR control, only one of two N-epimers directly participated in complexation. The aziridines underwent ring opening with HN3 to form the corresponding azido amines as single regio- and diastereomers in 90–97% yield. Different results were obtained for 1,2-disubstituted and 1,2,3-trisubstituted aziridines. For the later aziridines ring closure and ring opening occurred at different carbon stereocenters, thus yielding products with two inverted configurations, compared to the starting amino alcohol. The 1,2-disubstituted aziridines produced azido amines of the same configuration as the starting β-amino alcohols. To obtain a complete series of diastereomeric vic-diamines, we converted the amino alcohols into cyclic sulfamidates, which reacted with sodium azide in SN2 reaction (25–58% overall yield). The azides obtained either way underwent the Staudinger reduction, giving a series of six new chiral vic-diamines of defined stereochemistries.

Palladium(II) and platinum(II) mixed ligand complexes of metronidazole and saccharinate or benzisothiazolinonate ligands, synthesis and spectroscopic investigation

Six palladium (II) and platinum (II) mixed ligand complexes of metronidazole (mnz) and saccharinate (sac) or benzothiazolinolate (bit) complexes of the type [ML2(mnz)2], M = Pd or Pt, L = sac or bit, have been prepared in moderate to high yield. The newly prepared complexes have been characterized by elemental (C,H,N,S) analysis, conductivity measurements, infrared and 1H-NMR spectra. Characterization data showed that the mnz ligand in all of the prepared complexes is coordinated to metal center through the imidazole nitrogen atom. The (sac) anion ligand is coordinated through the endocyclic nitrogen atom, while the (bit) anion ligand is coordinated through the nitrogen atom in the palladium complex and through the oxygen atom of the carbonyl group in the platinum complexes. The geometry of the Pd (II) and Pt (II) complexes is square planar complexes. http://dx.doi.org/10.25130/tjps.24.2019.105

Hydrogen bonding, π–π stacking and van der Waals forces-dominated layered regions in the crystal structure of 4-aminopyridinium hydrogen (9-phosphonononyl)phosphonate

The asymmetric unit of the title molecular salt, [C5H7N2+][(HO)2OP(CH2)9PO2(OH)−], consists of one 4-aminopyridinium cation and one hydrogen (9-phosphonononyl)phosphonate anion, both in general positions. As expected, the 4-aminopyridinium moieties are protonated exclusively at their endocyclic nitrogen atom due to a mesomeric stabilization by the imine form which would not be given in the corresponding double-protonated dicationic species. In the crystal, the phosphonyl (–PO3H2) and hydrogen phosphonate (–PO3H) groups of the anions form two-dimensional O—H...O hydrogen-bonded networks in theabplane built from 24-membered hydrogen-bonded ring motifs with the graph-set descriptorR66(24). These networks are pairwise linked by the anions' alkylene chains. The 4-aminopyridinium cations are stacked in parallel displaced face-to-face arrangements and connect neighboring anionic substructuresviamedium–strong charge-supported N—H...O hydrogen bonds along thecaxis. The resulting three-dimensional hydrogen-bonded network shows clearly separated hydrophilic and hydrophobic structural domains.

Preparation and structure of silver complexes with 4-nitroimidazole

The reaction of 4-nitroimidazole (NO2ImH) with AgNO3 and AgBF4 in neutral or weakly acidic aqueous media yielded the insoluble [Ag(NO2Im)] compound, whose infrared and 13C NMR spectra are consistent with a polymeric chain of deprotonated ligands bridging silver atoms via the endocyclic nitrogen atoms. In strongly acidic solution, [Ag(NO2ImH)2]X salts (X = NO3, BF4) were obtained and their crystal structures were determined. [Ag(NO2ImH)2]NO3: monoclinic, P2/n, a = 14.214(1), b = 12.571(2), c = 14.222(1) Å, β = 111.38(7)°, Z = 8, R = 0.021, 3443 observed reflections; [Ag(NO2ImH)2]BF4; monoclinic, P21/c, a = 9.543(4), b = 6.478(2), c = 20.869(9) Å, β = 90.84(3)°, Z = 4, R = 0.027, 1646 observed reflections. In both compounds, the two-coordinated metal forms roughly collinear bonds to two neutral ligands via the endocyclic nitrogen atom adjacent to the nitro group. One oxygen of each nitro group makes a secondary Ag—O bond near the equatorial plane. The anions are hydrogen bonded to the ligand N—H groups and do not directly interact with the metal. Solution 1H and 13C NMR spectra show that the cationic complexes dissociate in DMSO. The infrared and CP-MAS 13C NMR spectra are discussed in connection with the coordination patterns observed. Keywords: silver, imidazole, crystal structure, infrared spectroscopy, nuclear magnetic resonance.

Mass Spectra of C-Amino- and C-Azido-l,2,4-triazoles

A study of low resolution mass spectra of 1,2,4-triazoles shows that fragmentations of C-amino-l,2,4-triazole nuclei are analogous to the three fragmentation modes reported for pyrrole. The extent to which these fragmentations account for the peaks in the mass spectra depends on the substituents of the 1,2,4-triazoIes. Mass spectra of C-azido-l,2,4-triazoles cannot be interpreted by the three modes found for pyrrole. Without exception, their mass spectra contain a base peak which is shown, with the aid of deuterium labeling, to represent an ion formed by the loss of four nitrogen atoms plus the substituent on the endocyclic nitrogen atom.