A Solution to the 2-Pyridyl Organometallic Cross-Coupling Problem: Regioselective Catalytic Direct Arylation of Pyridine N-Oxides
摘要:
Direct arylation reactions of pyridine N-oxides occur in excellent yield with complete selectivity for the 2-position with a wide range of aryl bromides. This reactivity permits the use of inexpensive, commercially available, and bench-stable pyridine N-oxides as replacements for problematic 2-metallapyridines in palladium-catalyzed cross-coupling reactions.
Metal-catalyzed coupling process comprising reacting a compound of general formula 1 with a compound A-X, to obtain a compound of general formula 2, which may further be converted to a compound of general formula 3
An efficient ligand-free Pd(OAc)2-catalyzed selectivearylation of pyridine N-oxides using potassium (hetero)aryltrifluoroborates as coupling partners via C–H bond activation was achieved in the presence of TBAI. This approach has a broad substrate scope and shows moderate to high yields.
Decarboxylative cross‐coupling reactions of substituted 2‐carboxyazine N‐oxides, with a variety of (hetero)arylhalides, by bimetallic Pd0/CuI and Pd0/AgI catalysis are reported. Two possible pathways, a conventional bimetallic‐catalyzed decarboxylative arylation, as well as a protodecarboxylative/direct CH arylation sequence have been considered. These methods provide the first general decarboxylative
据报道,通过双金属Pd 0 / Cu I和Pd 0 / Ag I催化,取代的2-羧嗪N-氧化物与各种(杂)芳基卤化物发生脱羧交叉偶联反应。两种可能的途径,传统的双金属催化的芳基化脱羧,以及一个protodecarboxylative /直接ç ħ芳基化序列已被考虑。这些方法为2-羧嗪系列提供了第一个通用的脱羧芳基化方法。
Activation of Unstrained Ketone C(O)–C Bond: 1,2-Nucleophilic Addition Followed by β-Carbon Elimination Strategy
moiety followed by β-C elimination strategy was less studied. Here a palladium-catalyzed C–C bond activation of an unstrained ketone enabled by a removable directing group through β-C elimination to synthesize 2-arylpyridine is described. The protocol features wide substrate scope with yields up to 95%, good functional group tolerance, and functionality of natural products. The 2-arylpyridine N-oxide