Co(III)-catalyzed alkenylation of 2-pyridones by using terminal alkyne as a reaction partner with high regioselectivity has been demonstrated for the first time. The reaction conditions are mild and compatible with a wide range of substrate combinations. It also shows good functional group tolerance. It proceeds through cyclometalation followed by alkyne insertion and protodemetalation steps. The formation of fiveand seven-membered cobaltacycle intermediates was also detected through highresolution mass spectrometry.
Herein, nickel-catalyzed synthesis
of polyarylcarbazole through
sequential C–H bond activations has been described. Regioselective
indole C2/C3 functionalization has been achieved in the presence of
indole C7-H, which is quite challenging. In addition, this approach
also gives easy access to building a heteropolycyclic motif through
C6/C7 C–H functionalization of indoline. This methodology is
not limited to aromatic internal alkynes as coupling partners; aliphatic
alkynes have also shown good tolerance. Notably, during the optimization
the catalytic enhancement with sodium iodide as an additive has been
observed. We have also studied the photophysical properties of these
highly conjugated molecules.
A Ni-catalyzed C6 followed by C5 cascade C−H activation/[2 + 2 + 2] annulation of 2-pyridone with alkynes has been achieved. A change in the reaction pathway was achieved by tuning the reaction conditions and incorporating a directing group. A wide variety of substrates and alkynes are amenable to this transformation. The key to success for this transformation is the use of sodium iodide as an additive. More importantly, we detected the five-membered metallacycle intermediate through HRMS wherein iodide is ligated to the metal.
An earth-abundant and inexpensive
Mn(I)-catalyzed alkylation of
2-pyridone with maleimide has been reported for the first time, in
contrast to previously reported Diels–Alder products. Notably,
an unexpected rearrangement has been discovered in the presence of
acetic acid, which also provides a unique class of compounds bearing
three different N-heterocycles with an all-carbon
quaternary center. Furthermore, single crystal X-ray and HRMS revealed
a five-membered manganacycle intermediate. This methodology tolerates
a wide variety of functional groups delivering the alkylated products
in moderate to excellent yields.
Herein,
the ruthenium-catalyzed regioselective sp
2(C–H) monoalkenylation of N-arylpyridones
has been demonstrated, where the pyridone was utilized as a weakly
coordinating directing group. Importantly, the current methodology
has been effectively applied to the synthesis of many drug analogues
such as pirfenidone, naproxen, ibuprofen, geraniol, umbelliferone,
pregnenolone, and estrone. This methodology tolerates a wide range
of functional groups and yields up to 93% yield. A six-membered ruthenium
complex was also detected by HRMS.
Bismuth(iii)-catalyzed regioselective alkylation of tetrahydroquinolines and indolines have been demonstrated for the synthesis of the bioactive cores of biaryl oxindoles and CYP19 inhibitors.
A rhodium-catalyzed oxidative C−H/N−H dehydrogenative [3 + 2] annulation strategy has been reported between anilines and N-allylbenzimidazole for the synthesis of 2methylindole scaffolds. An N-allylbenzimidazole has been used as a 2C synthon for the synthesis of indole, and more importantly, this transformation involves the cleavage of the thermodynamically stable C−N bond of allylamine. Detailed mechanistic studies have been performed and a key intermediate was detected in HRMS. This transformation proceeds through a cascade of C(sp 2 )−H allylation followed by intramolecular cyclization.
An earth-abundant and inexpensive Mn(I)-catalyzed alkylation of 2-pyridone with maleimide has been reported for the first time, in contrast to previously reported Diels-alder product. The directing group was easily removed after functionalization. Notably, unexpected migration of pyridine ring has been discovered in presence of zinc, and acetic acid conditions, which also provides a new route to quaternary carbon centers which contain two heterocycles. Furthermore, single crystal X-ray and HRMS revealed a five-membered manganacycle intermediate. This methodology tolerates a wide variety of functional groups delivering the alkylated products in moderate to excellent yields.
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