A new phosphine-free Co(ii) complex-catalyzed synthesis of various quinoxalines via dehydrogenative coupling of vicinal diols with both o-phenylenediamines and 2-nitroanilines is reported. This complex was also effective for the synthesis of quinolines. The practical aspect of this catalytic system was revealed by the one-pot synthesis of 2-alkylaminoquinolines.
A simple air- and moisture-stable, highly efficient ruthenium NNN pincer complex is reported for the first time to catalyze the tandem transformation of various aromatic and aliphatic nitro compounds into the corresponding N-methylated amines in up to 98 % yield by using methanol as a green methylating agent. Gram-scale reactions of challenging nitro substrates demonstrated the practical application aspects of this catalytic system. Importantly, the N-methylamine moiety could be smoothly introduced to various complex molecular structures without using any expensive palladium/phosphine/amine-based cross-coupling reactions.
The
inexpensive and simple NiBr2/1,10-phenanthroline
system-catalyzed synthesis of a series of quinoxalines from both 2-nitroanilines
and 1,2-diamines is demonstrated. The reusability test for this system
was performed up to the seventh cycle, which afforded good yields
of the desired product without losing its reactivity significantly.
Notably, during the catalytic reaction, the formation of the heterogeneous
Ni-particle was observed, which was characterized by PXRD, XPS, and
TEM techniques.
Direct and selective
synthesis of N,N-dimethylated amines from
nitriles using methanol as C1 building blocks is reported using an
air- and moisture-stable ruthenium complex. Following this process,
various aromatic as well as aliphatic nitriles were converted to the
corresponding N-methylated amines. Interestingly, tandem C-methylation
as well as N-methylation was achieved by introducing multiple methyl
groups. The practical aspect of this process was revealed by preparative-scale
reactions with different nitriles and the synthesis of anti-allergic
drug “avil”. Several kinetic experiments and detailed
DFT calculations were carried out to understand the mechanism of this
process.
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