Synthesis of 3-Substituted Chromones and Quinolones from Enaminones

Abstract

A facile and efficient synthetic route to 3-substituted chromones and quinolones was developed. Silver triflate was employed to activate the electrophile to react with various readily available enaminones.

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-Mediated Tandem Oxidative-Coupling/Annulation of o-Hydroxyaryl Enaminones with Cycloheptatriene

“…To evaluate the substrate scope of this approach, various enaminones 1 were prepared and subjected to the optimized reaction conditions ( Table 2). Regardless of the electron-donating or electron-withdrawing substituents on the benzene ring, the reaction proceeded smoothly and afforded the corresponding products 3b-3p in good to excellent yields (entries [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Notably, the introduction of a nitro substituent para to the OH group gave the product 3n in 73% yield (entry 14).…”

“…8 As far as 3-alkylchromones are concerned, the first example was elaborated by reacting enaminones with 5.0 equiv of alkyl halide promoted by 1.0 equiv of AgOTf (Scheme 1a). 9 Similarly, the Li group reported the cyclobenzylation of enaminones with benzyl bromide mediated by 3.0 equiv of NaI at 80 °C (Scheme 1a). 10 In 2019, Baik, Patil, and coworkers developed the gold-carbene mediated cycloaddition of enaminones with diazo compounds (Scheme 1b).…”

C3‐Functionalized Chromones Synthesis by Tandem C−H Elaboration and Chromone Annulation of Enaminones

“…As shown in the postulated reaction mechanism, the Ag(I) salt first activated the alkyl halide to react with enaminones 1 to provide alkylated iminium 8 . The annulation of 8 as well as subsequent amine elimination on 9 yielded the products 7 (Scheme ) . Benzyl bromide could undertake similar alkylation reactions more efficiently in the presence of only NaI …”

Synthesis and Functionalization of 4‐Quinolones – A Progressing Story

“…Joussot et al introduced an efficient methodology to synthesize the 3‐substituted 4‐quinolones in a one‐pot technique which involved the cyclization of appropriate enaminones ( 128 ) with diverse electrophiles in the presence of Ag I catalyst (Scheme ) …”