Synthesis of 2-Quinolinones via a Hypervalent Iodine(III)-Mediated Intramolecular Decarboxylative Heck-Type Reaction at Room Temperature

Abstract

A hypervalent iodine­(III)-mediated intramolecular decarboxylative Heck-type reaction of 2-vinyl-phenyl oxamic acids has been developed. The unique ring-strain-enabled radical decarboxylation mechanism is preliminarily revealed. This protocol features metal-free reaction conditions and operational simplicity, allowing the lactamization of 2-vinylanilines using a readily accessible carbonyl source and the synthesis of various 2-quinolinones with excellent chemoselectivity at room temperature.

Silver-Catalyzed Decarboxylative Radical Addition/Cyclization of Oxamic Acids with Alkenes towards Quinolin-2-ones

“…Based on the present results and related reports in the literature, 6,[10][11][12] a plausible reaction mechanism is proposed as shown in Figure 2. First, Ag(I) is oxidized by persulfate anion to form Ag(II), which then triggers a single-electrontransfer process of the N-aryloxamic acid 1 to regenerate the Ag(I) and form the N-arylcarbamoyl radical A with release of CO 2 .…”

“…10 Recently, Wang's group reported a decarboxylative lactamization of 2-vinylphenyloxamic acids mediated by hypervalent iodine(III), involving a ring-strain-permitted radical decarboxylation process. 11 Liu and co-workers recently reported an approach to the construction of CF 2 -containing 3,4-dihydroquinolin-2-ones through the decarboxylative radical addition/cyclization of oxamic acids with gem-difluoroolefins (Scheme 1b). 12 Despite the advances made in this area, the scope of the alkene substrates is very limited and considerable challenges remain in the reactions of electron-rich olefins with N-arylcarbamoyl radicals and in the synthesis of 3,4-unsubstituted quinolinones by a radical pathway.…”

PdCl2‐Catalyzed Oxidative Cyclization of N‐(2’‐Alkynylaryl)‐1,3‐ketoamides: Synthesis of 3,4‐Diacyl‐2‐Quinolones

“…Previous synthesis of 2-quinolones based on different bond disconnections. [2][3][4][5][6][7][8] Scheme 2. The proposed oxidative annulation of 1,3-ketoamides 1 to 2quinolones 2.…”

“…Substrates with variation on R 3 (1 ii-nn) and R 4 (1 oo-qq) were next assessed (Table 4). Reactions of 1 ii (R 3 = 3-OMeÀ Ph) and 1 jj (R 3 = 4-OMeÀ Ph) were rather uneventful that products 2 ii and 2 jj were produced in comparable 77% and 72% yields, respectively.…”

“…As summarized in Scheme 1, different disconnections on the 6-membered N-heterocycle of the 2-quinolone scaffold could be classified, revealing a myriad of possible assembling pathways that were previously reported. [2][3][4][5][6][7][8] Among these disconnections, the synthesis of 3,4-diacyl-2-quinolones (2) via oxidative annulation of alkynyl substrates of type A were reported (Disconnection 4) using either 10 mol% of CuCl 2 and 2.0 equiv of DBU in DMF under oxygen at 100°C [5b] (1-24 h) or 3.0 equiv of Mn(OAc) 3 in DCE under oxygen at 70°C (3-24 h). [5c] Our recent report of Pd(PPh 3 ) 2 Cl 2 -catalyzed ceric ammonium nitrate (CAN)-promoted synthesis of 2,4-diacylfuran derivatives from 2-propargylated 1,3-ketoesters [9] broadened the horizon of synthetic utilities of the cooperative activities between cerium (IV) and palladium(II) complexes in promoting efficient organic transformations.…”