5867-45-8Relevant articles and documents
Synthesis of unsymmetrical urea from aryl- or pyridyl carboxamides and aminopyridines using PhI(OAc)2via in situformation of aryl- or pyridyl isocyanates
Hunjan, Mandeep Kaur,Laha, Joydev K.,Singh, Neha
, p. 18815 - 18823 (2021/10/26)
A tandem synthesis of unsymmetrical ureas (N-aryl-N′-pyridylurea andN,N′-bipyridylurea) from aryl- or pyridyl carboxamides and aminopyridinesviaHofmann rearrangement has been reported. In particular, benzamides, picolinamide, nicotinamide, and isonicotinamide generate reactive intermediate isocyanates,in situ, in the presence of PhI(OAc)2, which upon further reaction with aminopyridines form urea derivatives. As the formation of pyridylisocyanates from their corresponding carboxamidesviaHofmann rearrangement remained unexplored previously, attempts have been made to trap the isocyanates. While the three pyridylisocyanates were trapped as their corresponding carbamates, 3-pyridylisocyanate was isolated and characterized. Unlike closely related previous methods reported for urea synthesis, the current method avoids direct use of isocyanates or eliminates the use of toxic phosgene for thein situgeneration of isocyanates.
Photorelease of Pyridines Using a Metal-Free Photoremovable Protecting Group
Dong, Zaizai,Fang, Xiaohong,Kou, Xiaolong,Tan, Weihong,Tang, Xiao-Jun,Wu, Yayun,Zhang, Zhen,Zhao, Rong,Zhou, Wei
supporting information, p. 18386 - 18389 (2020/08/24)
The photorelease of bioactive molecules has emerged as a valuable tool in biochemistry. Nevertheless, many important bioactive molecules, such as pyridine derivatives, cannot benefit from currently available organic photoremovable protecting groups (PPGs). We found that the inefficient photorelease of pyridines is attributed to intramolecular photoinduced electron transfer (PET) from PPGs to pyridinium ions. To alleviate PET, we rationally designed a strategy to drive the excited state of PPG from S1 to T1 with a heavy atom, and synthesized a new PPG by substitution of the H atom at the 3-position of 7-dietheylamino-coumarin-4-methyl (DEACM) with Br or I. This resulted in an improved photolytic efficiency of the pyridinium ion by hundreds-fold in aqueous solution. The PPG can be applied to various pyridine derivatives. The successful photorelease of a microtubule inhibitor, indibulin, in living cells was demonstrated for the potential application of this strategy in biochemical research.
Donor Strength Determination of Pyridinylidene-amide Ligands using Their Palladium-NHC Complexes
Huynh, Han Vinh,Vossen, Jeroen Thomas
supporting information, p. 12486 - 12493 (2020/09/02)
Pyridinylidene-amides (PYAs) are a relatively new type of N-donor ligands that can exist in three isomeric forms and adopt various resonance structures. This makes them electronically flexible, and in order to evaluate their electronic profile using the Huynh electronic parameter (HEP), seven structurally diverse mixed N-heterocyclic carbenes (NHCs)/PYA palladium complexes of the type trans-[PdBr2(iPr2-bimy)(PYA)] were prepared and fully characterized by various spectroscopic and spectrometric methods. This study shows that PYAs are among the strongest, formally neutral N-donors, but they are still weaker than phosphines and organometallic ligands such as NHCs. Notably, the donating abilities of isomeric PYAs are distinct and can be further fine-tuned by the choice of two substituents making them structurally and electronically versatile. These characteristics and the ease of their preparation hold promise for a wide applicability in coordination chemistry.
