Construction of Novel Kojic Acid Fused Furans by Domino Reactions of a Kojic Acid Derivative with (Z)‐Bromonitroalkenes

Abstract

A series of novel kojic acid fused furans have been synthesized by domino cyclization‐elimination reactions of a kojic acid derivative with (Z)‐bromonitroalkenes. In the presence of a bifunctional thiourea‐tertiary amine organocatalyst and sodium bicarbonate, the reactions provided the products in up to quantitative yields.

A Metal-Free Domino Process for Regioselective Synthesis of 1,2,4-Trisubstituted Pyrroles: Application toward the Formal Synthesis of Ningalin B

“…Among the synthesized β-bromo-β-nitrostyrene, 2a – 2c , 2f – 2i , and 2l are known, while 2d , 2e , 2j , 2k , and 2m are new, and their spectral data are as follows:…”

“…Following protocol A, using ( E )-1,5-di- tert -butyl-2-methoxy-3-(2-nitrovinyl)­benzene (0.73 g, 2.5 mmol), 2e was obtained as green solid (0.82 g, 88% yield); mp 120–124 °C. IR (neat): ν max 2989, 1714, 1607, 1479, 1275, 1260, 1017, 750 cm –1 ; 1 H NMR (400 MHz, CDCl 3 ) δ 8.83 (s, 1H), 7.83 (d, J = 2.2 Hz, 1H), 7.50 (d, J = 2.4 Hz, 1H), 3.77 (s, 3H), 1.40 (s, 9H), 1.33 (s, 9H); 13 C­{ 1 H} NMR (100 MHz, CDCl 3 ): δ 158.1, 145.7, 142.4, 134.6, 128.6, 128.0, 124.8, 123.9, 64.0, 35.3, 34.8, 31.4 (3C), 30.8 (3C).…”

“…Following protocol A, using ( E )-1-bromo-4,5-dimethoxy-2-(2-nitrovinyl)­benzene (0.72 g, 2.5 mmol), 2k was obtained as yellow solid (0.78 g, 85% yield); mp 133–135 °C. IR (neat): ν max 1713, 1668, 1488, 1428, 1367, 1258, 1198, 1151, 1017, 749 cm –1 ; 1 H NMR (400 MHz, CDCl 3 ): δ 8.90 (s, 1H), 7.66 (s, 1H), 7.15 (s, 1H), 3.95 (s, 3H), 3.93 (s, 3H); 13 C­{ 1 H} NMR (100 MHz, CDCl 3 ): δ 152.2, 148.0, 135.7, 122.4, 119.3, 115.8, 115.4, 112.2, 56.0, 56.2.…”

“…Following protocol A, using ( E )-2-methyl-5-(2-nitrovinyl)­furan (0.38 g, 2.5 mmol), 2m was obtained as pale yellow solid (0.52 g, 91% yield); mp 69–70 °C. IR (neat): ν max 3054, 2986, 1714, 1606, 1422, 1326, 1264, 1165, 1123, 895 cm –1 ; 1 H NMR (400 MHz, CDCl 3 ):δ 8.51 (s, 1H), 7.35 (d, J = 3.2 Hz, 1H), 6.00 (d, J = 3.2 Hz, 1H), 2.42 (s, 3H); 13 C­{ 1 H} NMR (100 MHz, CDCl 3 ): δ 159.3, 145.2, 125.0, 122.9, 122.4, 110.7, 14.2.…”