A Mild Rhodium Catalyzed Direct Synthesis of Quinolones from Pyridones: Application in the Detection of Nitroaromatics

Abstract

A rhodium catalyzed direct regioselective oxidative annulation by double C-H activation is described to synthesize highly substituted quinolones from pyridones. The reaction proceeds at mild conditions with broad scope and wide functional group tolerance. These novel quinolones were explored to recognize nitroaromatic compounds.

Solvent‐Controlled Rhodium‐Catalyzed C6‐Selective C−H Alkenylation and Alkylation of 2‐Pyridones with Acrylates

“…The possible reaction course can include the metallacycles 16 and 17 , which are formed from the rhodacycle 11 via second C−H cleavage at the C5 position. Formation of similar intermediates was proposed in the related rhodium‐catalyzed C−H coupling of 1 a with alkynes . Subsequent regioselective β‐hydride elimination and reductive elimination from 18 afford the observed doubly substituted product 15 .…”

Rhodium(III)‐Catalyzed C−H Bond Functionalization of 2‐Pyridones with Alkynes: Switchable Alkenylation, Alkenylation/Directing Group Migration and Rollover Annulation

“…In pioneering studies, Hirano and Miura introduced an easily attachable and detachable pyridine‐based directing group (DG) on the nitrogen atom of the 2‐pyridone skeleton to facilitate C6‐selective heteroarylation of 2‐pyridones [7c] . Subsequently, transition‐metal catalyzed directed alkynylation, [6d] alkylation, [7e,h,l,u] annulation, [7f,o] borylation, [7g] arylation, [7h,k,m] thiolation, [7i] allylation, [7j] amidation [7p,q] and alkenylation [7s,t] of 1‐(2‐pyridyl)‐2‐pyridones at the C6 positions have been successfully developed. In general, the pyridyl directing group in these C−H functionalizations remains intact and can be removed from the final products.…”

Manganese(I)‐Catalyzed Site‐Selective C6‐Alkenylation of 2‐Pyridones Using Alkynes via C−H Activation

“…While traditional cross‐coupling reactions of halogenated 2‐pyridones are still widely employed to access functionalized 2‐pyridone derivatives, [10] direct functionalization of 2‐pyridone C−H bonds using transition‐metal catalysts has recently evolved as an efficient and versatile synthetic tool for producing such products in a highly step‐ and atom‐economical manner with promising results being achieved in regioselective functionalization of 2‐pyridones at the positions of C3, C4, C5 and C6 [11] . In particular, since the seminal work by Hirano and Miura on the introduction of a pyridine group on the nitrogen atom of the 2‐pyridone skeleton to promote C6‐selective heteroarylation of 2‐pyridones, [12a] chelation‐assisted direct alkylation, [12b,i,j,m,o,s,t] arylation, [12f,h,k] borylation, [12e] thiolation, [12g] annulation, [12c,d,l,n] and amidation [12p–r] of 2‐pyridones at the C6 positions using transition‐metal catalysts have been successfully realized, mainly involving rhodium and ruthenium complexes. Nevertheless, there are surprisingly few examples of direct C−H alkenylation of 2‐pyridones at the C6 position despite the potential utility of such products [5d,13] .…”