38439-33-7Relevant articles and documents
2,6-Diamination of substituted pyridines via heterogeneous Chichibabin reaction
Mastalir, Matthias,Pittenauer, Ernst,Allmaier, Günter,Kirchner, Karl
, p. 333 - 336 (2016)
A series of ring substituted pyridines were selected for the sodium amide initiated heterogeneous Chichibabin amination to obtain 2,6-diaminopyridine derivatives which are important synthons for the preparation of PNP pincer ligands. The substrates were treated with an excess of sodium amide in neat mineral oil as solvent under an argon atmosphere. The reaction required temperatures of up to 215°C under vigorous stirring with an overall reaction time of 3-5 h. In the case of methyl, tert-butyl, phenyl, pyridinyl, and hydroxyl substituted pyridines the desired products were obtained in good to excellent yields (63-96%). Thus, the Chichibabin reaction provides an inexpensive and economic alternative to methodologies starting from halopyridines or pyridine N-oxides provided that the substituents are inert under the harsh reaction conditions.
A Highly Active and Easily Accessible Cobalt Catalyst for Selective Hydrogenation of C=O Bonds
R?sler, Sina,Obenauf, Johannes,Kempe, Rhett
supporting information, p. 7998 - 8001 (2015/07/08)
The substitution of high-price noble metals such as Ir, Ru, Rh, Pd, and Pt by earth-abundant, inexpensive metals like Co is an attractive goal in (homogeneous) catalysis. Only two examples of Co catalysts, showing efficient C=O bond hydrogenation rates, are described. Here, we report on a novel, easy-to-synthesize Co catalyst family. Catalyst activation takes place via addition of 2 equiv of a metal base to the cobalt dichlorido precatalysts. Aldehydes and ketones of different types (dialkyl, aryl-alkyl, diaryl) are hydrogenated quantitatively under mild conditions partially with catalyst loadings as low as 0.25 mol%. A comparison of the most active Co catalyst with an Ir catalyst stabilized by the same ligand indicates the superiority of Co. Unique selectivity toward C=O bonds in the presence of C=C bonds has been observed. This selectivity is opposite to that of existing Co catalysts and surprising because of the directing influence of a hydroxyl group in C=C bond hydrogenation.
Design and synthesis of porphyrins bearing rigid hydrogen bonding motifs: Highly versatile building blocks for self-assembly of polymers and discrete arrays
Shi,Barkigia,Fajer,Drain
, p. 6513 - 6522 (2007/10/03)
Two aldehydes, 2,6-diacetamido-4-formylpyridine (7) and 1-butyl-6-formyluracil (11), are used to synthesize five pyridyl and four uracyl meso-subsituted porphyrins. With these complementary porphyrin building blocks, it is possible to build various types of multi-porphyrin supramolecules with different spatial relationships in predefined geometries. The formation and properties of self-complementary dimers and a dosed tetrameric square are presented as a basis of comparison to the latter system in the solid state. An X-ray structure of 5,10-bis(4-tert-butylphenyl)-15,20-bis-(3,5-diacetamido-4-pyridyl)porphyrin confirms its molecular structure and reveals a hydrogen-bonded supramolecular organization mediated by water molecules.
