5154-00-7Relevant articles and documents
Ferracyclic carbamoyl complexes related to the active site of [Fe]-hydrogenase
Turrell, Peter J.,Hill, Amanda D.,Ibrahim, Saad K.,Wright, Joseph. A.,Pickett, Christopher J.
, p. 8140 - 8146 (2013)
The active site of the [Fe]-hydrogenase features an iron(ii) centre bearing cis carbonyl groups and a chelating pyridine-acyl ligand. Reproducing these unusual features in synthetic models is an intriguing challenge, which will allow both better understanding of the enzymatic system and more fundamental insight into the coordination modes of iron. By using the carbamoyl group as a surrogate for acyl, we have been able to synthesize a range of ferracyclic complexes. Initial reaction of Fe(CO)4Br2 with 2-aminopyridine yields a complex bearing a labile solvent molecule, which can be replaced by stronger donors bearing phosphorus atoms to produce a number of derivatives. Introduction of a hydroxy group using this method is unsuccessful both with a free OH group and when this is silyl-protected. In contrast, the analogous reactions starting from 2,6-diaminopyridine does allow synthesis of complexes bearing a pendant basic group.
The Lactam-Lactim Tautomerization of Monoamino-Substituted 2-Pyridinols in Tetrahydrofuran
Fujimoto, Akira,Inuzuka, Kozo
, p. 2292 - 2299 (2007/10/02)
MINDO/3 calculations have been performed on 3-amino-, 4-amino-, 5-amino-, and 6-amino-2-pyridinols to estimate their molecular geometries.The lactam-lactim tautomerization from amino-2-pyridone to amino-2-pyridinol was expected for 5-amino- and 6-amino-2-pyridinols from the MINDO/3 calculations.In addition, their dimer formation energies were evaluated by the CNDO/2 method.Among the four amino-2-pyridones, 6-amino-2-pyridone has the largest dimer formation energy and 3-amino-2-pyridone the smallest.Furthermore, to certify the tautomerization of 3-amino-, 5-amino-, and 6-amino-2-pyridinols the UV absorption and fluorescence spectra were measured, and compared with those of their O-methyl and nuclear N-methyl derivatives.From the UV spectral data the equilibrium constants of the lactam-lactim tautomerization were determined for 5-amino and 6-amino derivatives in tetrahydrofuran (THF) at various temperatures.The lactam form is more stable than that of the lactim; the enthalpy changes between two forms of 5-amino and 6-amino derivatives were estimated to be 7.9 and 6.3 kJ mol-1, respectively.The lactam and lactim dimers of these two derivatives were found to be easily formed in THF and ether.From the fluorescence spectral data the lactim dimer of 6-amino derivative was found to be formed in the lowest excited ?,?* singlet state.On the other hand, the 3-amino derivative exists predominantly in the lactam monomer form in both the ground and the lowest excited ?,?* singlet states.
