Unassisted formation of hemiaminal ether from 4-aminopyridine and o-vanillin - experimental and theoretical study

Abstract

The reactions between o-vanillin and three isomeric aminopyridines lead to imines of diverse spatial conformation and reactivity. The direct products of these simple reactions carried out in methanol are either imine compounds formed in the reactions of 2-amino-and 3-aminopyridine with o-vanillin or the α-aminoether formed in the reaction of o-vanillin with 4-aminopyridine. The Schiff-type derivative of 4-aminopyridine and o-vanillin, which is described in this paper for the first time, is very reactive and can only be obtained indirectly from the α-aminoether in anhydrous conditions. All compounds are characterized by X-ray diffraction and FT-IR and NMR spectroscopies. The DFT calculations at all-electron BLYP/Q4ZP level of theory are utilized to explain the differences between the reactivity of isomeric aminopyridines and their imine derivatives.

Synthesis, spectroscopic, thermal, crystal structure properties, and characterization of new Hofmann-Td-type complexes with 3-aminopyridine

“…However, when the structures of complexes 1 and 2 are examined, it is seen that the 3AP is bound only from the nitrogen atom in the pyridine ring to the cadmium transition metal atom [12,34]. Similar binding pattern has also been seen in studies with the 4AP ligand molecule [48,49]. Some noticeable small frequency shifts of the 3AP in the vibration spectra of complexes 1 and 2 are thought to be due to changes in environmental conditions compared to the case where the 3AP does not form compounds due to the formation of compounds.…”

Reactions of cobalt(ii) chloride and cobalt(ii) acetate with hemisalen-type ligands: ligand transformation, oxidation of cobalt and complex formation. Preliminary study on the cytotoxicity of Co(ii) and Co(iii) hemisalen complexes

“…Ligands HL1–HL5 were synthesized as described. 18,34,60 Moreover CoCl 2 ·6H 2 O was heated in vacuum to 140 °C for 2 days to obtain an anhydrous salt. Acetonitrile was dried over P 2 O 5 , methanol over magnesium swarf and subsequently both solvents were distilled under argon.…”

Synthesis, spectroscopic, thermal, crystal structure properties and characterization of new Hofmann-type-like clathrates with 4-aminopyridine and water

“…Various studies conducted by many researchers with the 4AP are encountered in the literature [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Especially Akyüz et al studied Hofmann type complexes composed through combination of 4AP with TM atoms [15,18].…”

“…In literature studies, the Hofmann type complexes and different kinds of complexes obtained by other researchers using 4AP were encountered. However, the vast majority of the complexes obtained by other researchers are in powder form, and those obtained in the form of a single crystal are very few [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”