A practical approach to the direct α-methylation of 1,8-naphthyridines under mild reaction conditions has been developed using simple and readily available DMSO as a convenient and environmentally friendly carbon source.
Reductive functionalization of N-heteroarenes remains to date a challenge due to the easy occurrence of direct reduction of such substances into non-coupling saturated cyclic amines. Herein, by developing an unprecedented manganese catalyst ligating with an unsymmetrical 2-aminotetrahydronaphthyridyl PNP-ligand, we have achieved a new reductive cross-coupling of indoles/pyrroles and N-heteroarenes
Room temperature C–H bond activation on a [PdI–PdI] platform
作者:Mithun Sarkar、Henri Doucet、Jitendra K. Bera
DOI:10.1039/c3cc44493g
日期:——
Heteroatom assisted C-H bond activation of 2-substituted naphthyridines with solvated Pd(I)2(CH3CN)6(BF4)2 provides bi- and trinuclear Pd(II) cyclometalated complexes, which provide valuable insight into potential intermediates in palladium catalyzed direct arylation reactions.
An iridium-catalyzed hydrogentransfer strategy, enabling straightforward access to tetrahydropyridine derivatives from aryl-1,8-naphthyridines and indolines was developed. This method has unprecedented advantages, including high step economy. In addition, it does not produce any byproducts or require an external high-pressure H2 gas source. The method offers an important platform for the transformation
开发了一种铱催化的氢转移策略,可以直接从 aryl-1,8-naphthyridines 和二氢吲哚获得四氢吡啶衍生物。这种方法具有前所未有的优势,包括高步骤经济性。此外,它不会产生任何副产品,也不需要外部高压 H 2气源。该方法为将 1,8-萘啶和二氢吲哚转化为功能化产品提供了重要平台。
Understanding C–H Bond Activation on a Diruthenium(I) Platform
作者:Arup Sinha、Moumita Majumdar、Mithun Sarkar、Tapas Ghatak、Jitendra K. Bera
DOI:10.1021/om301228h
日期:2013.1.14
Activation of the C-H bond at the axial site of a [Ru-I-Ru-I] platform has been achieved. Room-temperature treatment of 2-(R-phenyl)-1,8-naphthyridine (R = H, F, OMe) with [Ru-2(CO)(4)(CH3CN)(6)][BF4](2) in CH2Cl2 affords the corresponding diruthenium(I) complexes, which carry two ligands, one of which is orthometalated and the second ligand engages an axial site via a Ru center dot center dot center dot C-H interaction. Reaction with 2-(2-N-methylpyrrolyl)-1,8-naphthyridine under identical conditions affords another orthometalated/nonmetalated (om/nm) complex. At low temperature (4 degrees C), however, a nonmetalated complex is isolated that reveals axial Ru center dot center dot center dot C-H interactions involving both ligands at sites trans to the Ru-Ru bond. A nonmetalated (nm/nm) complex was characterized for 2-pyrrolyl-1,8-naphthyridine at room temperature. Orthometalation of both ligands on a single [Ru-Ru] platform could not be accomplished even at elevated temperature. X-ray metrical parameters clearly distinguish between the orthometalated and nonmetalated ligands. NMR investigation reveals the identity of each proton and sheds light on the nature of [Ru-Ru]center dot center dot center dot C-H interactions (preagostic/agostic). An electrophilic mechanism is proposed for C-H bond cleavage that involves a C(p(pi))-H -> sigma* [Ru-Ru] interaction, resulting in a Wheland-type intermediate. The heteroatom stabilization is credited to the isolation of nonmetalated complexes for pyrrolyl C-H, whereas lack of such stabilization for phenyl C-H causes rapid proton elimination, giving rise to orthometalation. NPA charge analysis suggests that the first orthometalation makes the [Ru-Ru] core sufficiently electron rich, which does not allow significant interaction with the other axial C-H bond, making the second metalation very difficult.