Sequentially Pd/Cu‐Catalyzed Alkynylation‐Oxidation Synthesis of 1,2‐Diketones and Consecutive One‐Pot Generation of Quinoxalines

Abstract

We report a simple and efficient one‐pot synthesis of 1,2‐diketones by concatenation of two Pd/Cu‐catalyzed processes: Pd0/CuI‐catalyzed Sonogashira coupling of terminal alkynes with aryl (pseudo)halides furnishes internal alkynes, which are directly transformed by PdII/CuII‐catalyzed Wacker‐type oxidation with DMSO and oxygen as dual oxidants to furnish 1,2‐diketones. With this efficient, catalyst economical process, various aryl iodides and triflates are efficiently transformed in high yields into symmetrically and unsymmetrically substituted 1,2‐diketones with various functional groups. This process can be readily extended to a consecutive one‐pot synthesis of quinoxalines in a diversity‐oriented fashion.

Recent Expedition inPd‐CatalyzedSonogashira Coupling and Related Processes†

“…Two years later, Müller disclosed a sequential Sonogashira/Wacker‐type oxidation reaction for the synthesis of 1,2‐diketones by aryl iodides or triflates and terminal alkynes (Scheme 4c). [ 39 ] The 1,2‐diketones then underwent a one‐pot consecutive cyclization with 1,2‐diaminobenzene derivatives to yield quinoxalines.…”

Multicomponent and One‐pot Syntheses of Quinoxalines

“…With this consecutive one‐pot methodology in hand, 14 examples of quinoxalines were synthesized with variable substituents ranging from electron‐withdrawing to electron‐donating, and also anellated diaminoarenes were successfully applied in the reaction sequence in moderate to very good yields (Scheme 11). [25] …”

“… Sequentially Pd/Cu‐catalyzed one‐pot alkynylation‐oxidation‐cyclocondensation synthesis of quinoxalines in a consecutive three‐component fashion [25] …”

Transition Metal‐Catalyzed Synthesis of 1,2‐Diketones: An Overview

“…Recently, Müller and co‐workers developed an one‐pot synthesis of 1,2‐diketones 102 by using a dual Pd/Cu metal system starting from terminal alkynes 100 and aryl iodides/triflates 101 in good to excellent yields (Scheme 38). [62] The reaction proceeds via Sonogashira coupling between terminal alkynes 100 and aryl (pseudo)halides 101 to generate the internal alkynes, which undergoes Wacker‐type oxidation with DMSO and oxygen as dual oxidants to afford the 1,2‐diketones 102 . Under the optimized conditions, a variety of substituted aryl iodides and triflates 101 were successfully transformed into the corresponding 1,2‐diketones 102 in high yields.…”