$$\hbox {Re}_{2}\hbox {O}_{7}$$ Re 2 O 7 -catalyzed formal [3 + 2] cycloaddition for diverse naphtho[1,2-b]furan-3-carboxamides and their biological evaluation

Abstract

Diverse naphtho[1,2-b]furan-3-carboxamide derivatives 12a-12q were synthesized in high yield via the novel Re2O7-catalyzed formal [3 + 2] cycloaddition of 1,4-naphthoquinones with β-ketoamides as the key step. This methodology offers several advantages, such as environmentally benign character, the use of a mild catalyst, high yields, and ease of handling. The synthesized compounds were screened for their tyrosinase inhibitory, antioxidant, and antibacterial activities. The results showed that compound 12c exhibited excellent tyrosinase inhibitory activity with an IC50 of 13.48 μg/mL, which is comparable to that of kojic acid (IC50 = 19.45 μg/mL). Compounds 12a, 12b, and 12i displayed moderate antioxidant activities in a DPPH assay. Compound 12m showed good activity against S. aureus (MIC = 16 μg/mL), and compound 12p was found to be active against E. coli (MIC = 16 μg/mL).

Synthesis of functionalized 3-aryl-3H-benzofuranone derivatives from aryl acetate via [3 + 2] annulation of 1,4-dihydroxy-2-naphthoic acid ester

“…Kimpe's group has developed a method to construct naphtho[1,2- b ]furan-2(3 H )-one via Michael addition/cyclization of 2-methoxycarbonyl-1,4-naphthoquinone and β-ketoesters activated by AcOH. 19 In 2016, Lee's group reported a [3 + 2] cycloaddition of 1,4-naphthoquinones with β-ketoamides to synthesize naphtho[1,2- b ]furan-3-carboxamide derivatives using 1,4-dihydroxy-2-naphthoic acid as a starting material, which was preferentially oxidized to 1,4-naphthoquinones 20 (Scheme 1c). Despite these impressive achievements, a more efficient and concise method would be developed with phenol instead of quinone to realize a similar cycloaddition reaction.…”