Unusual Regioselectivity in Palladium‐Catalyzed Tandem C−H Arylation and C−H Amidation of cis‐Cinnamyl Hydroxamates: Facile Synthesis of 3‐Aryl‐2‐quinolones

Abstract

Tandem CÀ H-arylation and CÀ H-amidation of cis-cinnamyl hydroxamatesusing a single metal catalyst (and air as oxidant) leads to the formation of 3-aryl-2-quinolone ring system in a regioselective manner. The corresponding trans-isomer under identical conditions gives rise to 4-aryl-2-quinolone derivative.The complementary regioselectivity observed during tandem CÀ H-arylation CÀ H-amidation of isomeric substrates is unusual and of potential application.

Recent Progress in Pd-Catalyzed Tandem Processes

“…The proposed reaction mechanism involved an acid-directed ortho-C-H arylation/intramolecular decarboxylative annulation sequence mediated by Pd(II)/Pd(IV) transformations. The novel procedure of arylation-cyclization was developed for the synthesis of 3-aryl-2-quinolone (Figure 36) and 4-aryl-2-quinolone derivatives from simple E/Z geometric isomer precursors using oxygen as a co-oxidant [89]. Ghosh and Chattopadhyay [74] identified the following Pd-catalyzed tandem procedures, which can be applied for the synthesis of 4-aryl-2-quinolones:…”

“…In the developed approach, the unusual complementary regioselectivity was found in the tandem C-H-arylation C-H-amidation of isomeric substrates. The origin of selectivity was proposed at the C-H-arylation step [89]. Doma ńskiet al [90] described the tandem Pd-catalyzed three-component reaction that allowed for regio-and stereoselective perfluoroalkylative borylation of a variety of terminal and internal alkynes in the presence of perfluoroalkyl iodide and (Bpin) 2 .…”

Comprehensive Theoretical Study of Cp*IrIII-Catalyzed Intermolecular Enantioselective Allylic C–H Amidation: Reaction Mechanism, Electronic Processes, and Regioselectivity

“…Among these wellconstructed routes, transition metal-catalyzed C−H amidation is an efficient, direct, and classic method to access C−N bonds. 6−12 Many transition metals, such as Mn, 13,14 Fe, 15,16 Co, 17−19 Ni, 20,21 Cu, 22,23 Ru, 24−26 Rh, 27−29 Pd, 30,31 and Ir, 8,32−51 have been employed in the C−H amidation.…”

“…The carbon–nitrogen bonds are present in many of the most privileged structures found in both natural products and synthetic bioactive molecules, which play a pivotal role in medicinal chemistry, pharmaceutical science, and functional materials. − Hence, the approaches to create the C–N bonds have been studied in the past decades. Among these well-constructed routes, transition metal-catalyzed C–H amidation is an efficient, direct, and classic method to access C–N bonds. − Many transition metals, such as Mn, , Fe, , Co, − Ni, , Cu, , Ru, − Rh, − Pd, , and Ir, ,− have been employed in the C–H amidation.…”