Rh(III)-Catalyzed Decarboxylative Coupling of Acrylic Acids with Unsaturated Oxime Esters: Carboxylic Acids Serve as Traceless Activators

Abstract

α,β-Unsaturated carboxylic acids undergo Rh(III)-catalyzed decarboxylative coupling with α,β-unsaturated O-pivaloyl oximes to provide substituted pyridines in good yield. The carboxylic acid, which is removed by decarboxylation, serves as a traceless activating group, giving 5-substituted pyridines with very high levels of regioselectivity. Mechanistic studies rule out a picolinic acid intermediate, and an isolable rhodium complex sheds further light on the reaction mechanism.

Correlating Reactivity and Selectivity to Cyclopentadienyl Ligand Properties in Rh(III)-Catalyzed C–H Activation Reactions: An Experimental and Computational Study

“…Among this set of ligands, several had been described previously by us ( Rh2–3 , 19 Rh7 , 8h Rh10–11 , 9,19 and Rh20–22 15,18,46b ) and others ( Rh13 10 and Rh19 , 17 Figure 1). Nevertheless, we became restricted by the narrow number of Cp X Rh(III) derivatives available in the literature.…”

Visible‐Light‐Promoted Iminyl‐Radical Formation from Acyl Oximes: A Unified Approach to Pyridines, Quinolines, and Phenanthridines

“…[1] During the past few years, transition-metal catalysis has been demonstrated as a powerful tool for breaking the N À O bond of acyl oximes through oxidative addition of the metal to the NÀO bond and the subsequent formation of various multisubstituted heterocycles, such as pyridines, indoles, isoquinolines, and imidazoles (Scheme 1 a). [2] Another pathway for cleavage of the N À O bond is homolysis under microwave (> 160 8C) or UV irradiation. This method has been employed to produce several heterocycles by radical cyclization of iminyl-radical intermediates (Scheme 1 b).…”

Visible‐Light‐Promoted Iminyl‐Radical Formation from Acyl Oximes: A Unified Approach to Pyridines, Quinolines, and Phenanthridines

“…[1] During the past few years,t ransition-metal catalysis has been demonstrated as ap owerful tool for breaking the N À O bond of acyl oximes through oxidative addition of the metal to the NÀOb ond and the subsequent formation of various multisubstituted heterocycles,s uch as pyridines,i ndoles, isoquinolines,a nd imidazoles (Scheme 1a). [2] Another pathway for cleavage of the N À Ob ond is homolysis under microwave (> 160 8 8C) or UV irradiation. This method has been employed to produce several heterocycles by radical cyclization of iminyl-radical intermediates (Scheme 1b).…”