Mauricio Maldonado

NUCLEOPHILIC SUBSTITUTION AT THE AMINALIC CARBON OF SOME MACROCYCLIC POLYAMINALS

I N T R O D U C T I O N Benzotriazole (1) is a synthetic aid which has become very useful in obtaining several organic compounds due to the properties it confers on its derivatives. Benzotriazole derivatives can be obtained by displacing a halogen in alkyl or acyl halides, a hydroxyl group in alcohols and an alkoxyl group in acetals or ketals. Other important routes involve adding benzotriazole to aldehydes (and their conjugate analogues), to imines, to iminium salts, and to enamines. Katrytzky et al (1,2) reported that benzotriazol derivatives 4a and 5a were obtained by ethane1,2-diamine and propane-1,3-diamine reaction, respectively, with benzotriazole and formaldehyde in water at 20°C. Katritzky et al (3,4) has also reported synthesising l,3-bis(benzotriazol-yl-methyl)-2,3-dihydrobenzilimidazol 6a by reacting benzotriazole with formaldehyde and o-phenylenediamine. However, it is well known (5,6) that diamines, such as ethane-1,2diamine, propane-1,3-diamine and o-phenylenediamine, react easily with formaldehyde in aqueous medium to produce macrocyclic polyaminals l ,3,6,8-tetraazatricyclo[4.4.1.1 ]dodecane 1; 1:3,7:9,13:15,19:21-tetramethyleneperhydropyrimidine 2, and 6 H , I 3 H 5:12,7:14-dimethanedibenzo[d,i] [ l ,3,6,8]tetrazecine 3, respectively.

Efficient tetrahydrosalen synthesis from mannich-type bases

Abstract Synthesizing a variety of tetrahydrosalens from hydrolyzing 1,3‐bis(2′‐hydroxy‐5′‐substituted‐benzyl)imidazolidines with hydrochloric acid is described. Further reaction of such tetrahydrosalens with aldehydes yielded 2‐substituted‐1,3‐bis(2′‐hydroxy‐5′‐substituted‐benzyl)imidazolidines.

Synthesis and characterization of two sulfonated resorcinarenes: a new example of a linear array of sodium centers and macrocycles.

Two sulfonated resorcinarenes were synthesized by reacting C-tetra(butyl)resorcinarene or C-tetra(2-(methylthio)ethyl)resorcinarene with formaldehyde in the presence of sodium sulfite. Their structures were determined via FT-IR, 1H-NMR, 13C-NMR and mass spectrometry. Thermal gravimetric analyses of the derivatives were also carried out and revealed the presence of water molecules in the solid state. The sulfonated product of C-tetra(butyl)resorcinarene was characterized by an X-ray crystal structure determination. The asymmetric unit contains eight molecules of water and two of acetone, and analysis indicated that sulfonated resorcinarene prefers a cone configuration (rccc conformation) in the solid state. In the crystal array, classical hydrogen bond interactions O-H···O and intermolecular contacts were observed. In the crystal packing, a linear array of capsules of sulfonated resorcinarenes was generated for a chain of sodium atoms and sulfonate groups.

1,3-Bis[(1H-benzotriazol-1-yl)meth-yl]-2,3-dihydro-1H-benzimidazole.

In the title compound, C21H18N8, the two (benzotriazol-1-yl)methyl groups are located in an anti position with respect to the benzimidazoline moiety. The dihedral angles between the benzotriazole ring systems and the central benzimidazoline moiety are 57.03 (4) and 81.01 (3)°. The crystal packing is stabilized by two C—H⋯π interactions.

FT-IR and DFT studies of the proton affinity of small aminal cages.

The proton affinity scale of small aminal cages was investigated using experimental and theoretical methodologies. The formation constant (K(f)) was determined for 1:1 hydrogen-bonded complexes between p-fluorophenol (PFP) and some aminal cage type (B) in CCl(4) at 298 K using FT-IR spectrometry. Then, the total interaction energy (E(PFF***B)), the energy of protonation (E(HB+)), the HOMO-LUMO GAP values and the Fukui index were calculated using the DFT/B3LYP/6-31 G(d,p) level of theory as theoretical descriptors. The values of the formation constant and energy changes vary with the tetrahedral character of the nitrogen lone pair. Good correlation between experimental and theoretical scales was observed, evidence for the existence of a relationship between the total energy of interaction calculated by structural parameters and the proton affinity in this series.

Selective O-Alkylation of the Crown Conformer of Tetra(4-hydroxyphenyl)calix[4]resorcinarene to the Corresponding Tetraalkyl Ether

Reactions of glycidyl methacrylate with the crown and chair conformers of tetra(4-hydroxyphenyl)calix[4]resorcinarene were studied. The reactions were done over epoxide groups present in the ester, which can easily undergo an opening reaction with hydroxyl groups in the macrocyclic system. Initially, epoxidation reactions were carried out with pure conformers, and it was observed that the reaction between tetra(4-hydroxyphenyl)calix[4]resorcinarene fixed in the chair conformation does not occur, while for the molecule fixed in the crown conformation only one tetraalkylated derivative was obtained. The obtained product was characterized using IR, 1H-NMR, 13C-NMR, COSY, HMQC and HMBC techniques. An exhaustive NMR study showed that the reaction is selective at the hydroxyl groups in the lower rim, without affecting the hydroxyl groups in the upper rim. In addition, the RP–HPLC analysis of the epoxidation reaction mixture, using both crown and chair conformers, showed that only the crown conformer reacted under tested conditions. Finally, a comparative study of the reactivity of tetranonylcalix[4]resorcinarene with glycidyl methacrylate showed that the reaction does not take place. Instead, the formation of the tetranonylcalix[4]resorcinarene tetrasodium salt was observed, which confirms that the hydroxyl groups in the upper rim are unreactive under these conditions.

(1H-Benzimidazol-1-yl)methanol

In the title compound, C8H8N2O, the N—CH2 and CH2—O bond lengths can be correlated to the manifestation of an anomeric effect in the N—CH2—O moiety. In the crystal, intermolecular O—H⋯N hydrogen bonds link the molecules into zigzag chains, with graph-set motif C(6), parallel to [001]. These chains are further linked into sheets by weak nonclassical C—H⋯O hydrogen bonds.

2,9-Dimethyl-6H,13H-5:12,7:14-dimethano­dibenzo[d,i][1,3,6,8]tetraazecine

In the title structure, C18H20N4, the aromatic rings are almost orthogonal [81.6 (2)°]. The molecule has symmetry 2 since it is situated on a crystallographic twofold axis. There are only weak intermolecular interactions present in the structure, notably C—H⋯π-electron ring interactions. The 1H and 13C NMR spectra are in accordance with the X-ray structure analysis.

1H-NMR spectroscopic and thermogravimetric research regarding alcohol interaction with tyrosine-derived azacyclophanes

This article describes the spectroscopic (1H-NMR) and thermogravimetric analysis of tyrosine-derived azacyclophanes. The results showed that these macrocycles could retain alcohol molecules through interactions involving hydrogen bonds between an alcohol and macrocycle heteroatoms and that alcohol release temperature depended on the structure of the macrocycle.

Conformational Aspects of the O-acetylation of C-tetra(phenyl)calixpyrogallol[4]arene

Reaction between pyrogallol and benzaldehyde results in a conformational mixture of C-tetra(phenyl)pyrogallol[4]arene (crown and chair). The conformer mixture was separated using crystallization procedures and the structures were determined using FTIR, 1H-NMR, and 13C-NMR. O-acetylation of C-tetra(phenyl)pyrogallol[4]arene (chair) with acetic anhydride, in pyridine results in the formation of dodecaacetyl-tetra(phenyl)pyrogallol[4]arene. The structure was determined using 1H-NMR and 13C-NMR finding that the product maintains the conformation of the starting conformer. On the other hand, the O-acetylation reaction of C-tetra(phenyl)pirogallol[4]arene (crown) under same conditions proceeded efficiently, and its structure was determined using 1H-NMR and 13C-NMR. Dynamic 1H-NMR of acetylated pyrogallolarene was studied by means of variable temperature in DMSO-d6 solution, and it revealed that two conformers are formed in the solution. Boat conformations for acetylated pyrogallolarene showed a slow interconversion at room temperature.