Domino Reaction of Naphthoquinone and β‐Arylpyruvic Acids: Synthesis of 3‐(Naphthoquinonyl)naphthofuran‐2(3H)‐ones

Abstract

Unprecedented reactivity between naphthoquinone and β‐aryl‐α‐keto acids has been uncovered. The process combined the redox properties of the Michael‐type naphthoquinone acceptor with arylpyruvic acid, which is acting first as a C3‐donor pro‐nucleophile and later as an acylating agent. As a result, densely substituted naphthofuran‐2(3H)‐ones were generated in a mild and simple one‐pot reaction.

Metal‐Free Tandem Rearrangement/Lactonization: Access to 3,3‐Disubstituted Benzofuran‐2‐(3H)‐ones

“…Thef ormation of I was proven by the presence of 3q following basic work-up after 5, 10, 15 or 20 minutes (Table 1, entries 1-4). Although it was not possible to isolate the diarylboronic ether 5, 1 H, 11 B and 19 FNMR spectra support its formation. Moreover,t he NMR ratio between I and II after 5minutes (ca.…”

“…[7] Methods for the synthesis of the lactone framework have also been investigated, such as metalcatalyzed CÀHa ctivation/CÀOb ond formations, [8] tandem Friedel-Crafts/lactonization, [9] Reppe-type cyclocarbonylation, [10] and the condensation of phenol derivatives. [11] However,these methods often require pre-functionalized building blocks,a nd methods to synthesize 3,3-diaryl and 3-aryl-3benzylic structures remain limited ( Figure 1). …”

Metallfreie Tandem‐Umlagerung/Lactonisierung: Zugang zu 3,3‐disubstituierten Benzofuran‐2‐(3H)‐onen

“…B. metallkatalysierte C-H-Aktivierung/C-O-Bindungsbildungen, [8] Tandem-Friedel-Crafts/Lactonisierungen, [9] Cyclocarbonylierungen vom Reppe-Typ [10] oder die Kondensation von Phenolderivaten. [11] Da diese Methoden jedoch oft vorfunktionalisierte Bausteine erfordern, sind die Synthesewege zu 3,3-Diaryl-und 3-Aryl-3-benzylstrukturen begrenzt (Abbildung 1).…”

Improved Method for Preparation of 3-(1H-Indol-3-yl)benzofuran-2(3H)-ones

“…Since both indole and benzo–furanone structural fragments are omnipresent in nature and listed as privileged scaffolds for drug discovery, chimeric indigo-, or isoindigo-like molecules possessing both these moieties also attracted certain attention. There are several reports describing the preparation of these unique compounds and studies of their applications in medicinal chemistry and material sciences [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. A common theme described in these reports is the metal-catalyzed C-C bond-forming reactions to accomplish the coupling between the indole and benzofuranone building blocks [ 1 , 5 , 8 , 10 ].…”

“…A common theme described in these reports is the metal-catalyzed C-C bond-forming reactions to accomplish the coupling between the indole and benzofuranone building blocks [ 1 , 5 , 8 , 10 ]. Other approaches used a Lewis acid-mediated reaction of indole derivatives with properly functionalized aromatic precursors (typically phenols or quinones) to furnish a five-membered lactone cycle in benzofurane [ 2 , 6 , 7 ]. We have recently established a synthetic approach towards benzofuro[2,3-b]quinoline cores employing a cascade transformation beginning with the condensation of indole and 1-methoxy-2-(2-nitrovinyl)benzenes in polyphosphoric acid (PPA).…”