Silver-catalyzed decarboxylative acylation of quinoxalin-2(1H)-ones with α-oxo-carboxylic acids

Abstract

A novel silver-catalyzed decarboxylative acylation of α-oxo-carboxylic acids was developed, by which various 3-acyl quinoxalin-2(1H)-ones were synthesized by direct C-H bond acylation of quinoxalin-2(1H)-ones. In this method, α-oxo-carboxylic acids served as efficient acylating reagents to in situ generate the required active acyl radical. Its excellent chemoselectivity allowed the molecular diversity of 3-acyl quinoxalin-2(1H)-ones to be achieved by convenient functionalizations of both N1- and C3-positions.

Metal‐Free C3 Hydroxylation of Quinoxalin‐2(1H)‐ones in Water

“…[2] Traditionally, Nfunctionalized quinoxaline-2,3-diones are prepared through base-promoted condensation reaction between mono N-substituted 1,2-diaminobenzenes and oxalyl chloride (or ethyl chloroglyoxalate) (Scheme 1a). Given the readily available quinoxalin-2(1H)-ones, significant progress has been achieved on the CÀ H bond functionalization of quinoxalin-2(1H)-ones, including the regioselective alkylation, [3] alkoxylation, [4] arylation, [5] acylation, [6] amination, [7] trifluoromethylation [8] and phosphonation reaction [9] . Given the readily available quinoxalin-2(1H)-ones, significant progress has been achieved on the CÀ H bond functionalization of quinoxalin-2(1H)-ones, including the regioselective alkylation, [3] alkoxylation, [4] arylation, [5] acylation, [6] amination, [7] trifluoromethylation [8] and phosphonation reaction [9] .…”

“…[2a,b] However, from a practical and eco-friendly point of view, those procedures still suffer from some drawbacks, such as the difficulties of preparation and isolation of mono N-substituted substrates, the usage of toxic oxalyl chloride and volatile organic solvent, and harsh reaction conditions. Given the readily available quinoxalin-2(1H)-ones, significant progress has been achieved on the CÀ H bond functionalization of quinoxalin-2(1H)-ones, including the regioselective alkylation, [3] alkoxylation, [4] arylation, [5] acylation, [6] amination, [7] trifluoromethylation [8] and phosphonation reaction [9] . During the past decade, water has received much attention as the expected reaction medium for organic reactions due to safety, cost and environmental concerns.…”

Photoredox Catalyst Free, Visible Light‐Promoted C3−H Acylation of Quinoxalin‐2(1H)‐ones in Water

“…In 2017, Wang, Hu and co-workers reported an Ag (I)-mediated decarboxylative acylation of α-oxo-carboxylic acids with quinoxalin-2(1H)-ones, leading to various 3-acyl quinoxalin-2(1H)-ones in good average yields (Scheme 1a). [12] Shortly after this discovery, the group of Yuan and Qu disclosed a TBHP-mediated direct 3-acylation of quinoxalin-2(1H)-ones by using arylaldehydes as the acyl radical precursors (Scheme 1b). [13] In a very recent contribution, the utilization of acyl hydrazine as acylating reagents to realize the direct 3-acylation of quinoxalin-2(1H)-ones was also realized by He et al (Scheme 1c).…”

Visible‐Light‐Induced Trifluoromethylation of Quinoxalin‐2(1H)‐Ones under Photocatalyst‐Free Conditions

“…[1] Common synthetic route based on the acylation of benzene-1,2-diamines with arylglyoxylic acid, followed by subsequent cyclization, [2] suffered from several drawbacks such as prefunctionalization and multi-step procedure. Over the past years, direct CÀ H bond functionalization of quinoxalin-2(1H)-ones has emerged as an attractive approach to 3substituted quinoxalin-2(1H)-ones in modern organic synthesis, such as CÀ H arylation, [3] alkylation, [4] acylation, [5] amidation, [6] amination, [7] benzylation [8] and phosphonation [9] (Scheme 1, a).…”