The skraup syntheses and NMR spectra of some methylnaphthyridines

Abstract

Some mono‐ and dimethylnaphthyridines were prepared by the application of the Skraup reaction to various 2‐ and 4‐aminopyridines. The proton magnetic resonance spectral data assignments are reported. The chemical shifts of the methyl protons are calculated.

A Benefit of Using the IDSCRF- over UFF-Radii Cavities and Why Joint Correlations of NMR Chemical Shifts Can Be Advantageous: Condensed Pyridines as an IEF-PCM/GIAO/DFT Case Study

“…An analogous situation was reported for the structurally similar 3,5,7-trimethyl-1 H indole system . In fact, weak (∼1 Hz) long-range coupling constants n J HH were observed for some of our products, but their origin was also not fully clear (interactions through 4 or 5 bonds). , …”

“…38 In fact, weak (∼1 Hz) longrange coupling constants n J HH were observed for some of our products, but their origin was also not fully clear (interactions through 4 or 5 bonds). 39,40 The above problem was a more general issue, and its overcoming with the aid of GIAO predicted that σ K 's seemed to be valuable. Therefore, we decided to perform (i) unambiguous 1 H/ 13 C NMR signal assignments of products 2−10.…”

Electrochemical and spectral investigations of ruthenium(II) complexes of 1,8-naphthyridine and its 2-methyl and 2,7-dimethyl derivatives

“…The tetrakis 2-mnapy compound exhibits a more complex spectrum as a result of the unsymmetrical ligand. 23 A striking double resonance is observed for the 2-methyl protons with the ratio of areas being 1 ( 2.72):3 ( 2.47). This finding may indicate that the 2-mnapy complex is seven coordinate with one molecule functioning as a monodentate ligand as a result of the steric constraints of fitting four 2-mnapy molecules around a Ru(II) center.…”

“…The importance of -back-bonding or synergic bonding in phen and bipy com plexes has been studied extensively10 while such information for napy complexes is derived from a limited number of studies of carbonyl complexes.1 u 2 The electronic solution spectra of Fe(2,7-dmnapy)32+ and Fe(2-mnapy)42+ 7•8 are devoid of an absorption attributable to a metal to ligand charge transfer (MLCT) transition, the existence of which is usually taken as strong evidence for metal-ligand involvement.10•13•14 Although the Fe(napy)42+ species exhibits a medium intensity band, there is doubt as to the correctness of its assignment as a MLCT transition. 23 The net import of this information is that to date no strong evidence or claim can be made for the participation of the naphthyridine ligands in -back-bonding.…”

“…Contribution from the Department of Chemistry, Texas A&M University, College Station, Texas 77843. Received February 23,1977 Abstract: A derivative of Ru3(CO)i2, in which two cis axial CO ligands are replaced by the bidentate ligand 1,2-diazene (pyridazine), has been prepared and characterized structurally and stereodynamically by x-ray crystallography and 13C NMR. The arrangement of the equatorial (in-plane) CO groups is changed from all terminal as in Ru3(CO)i2 and now consists of three terminal ones and three slightly unsymmetrical bridging ones.…”