One-Pot Multistep Synthesis of 4-Acetoxy-2-amino-3-arylbenzofurans from 1-Aryl-2-nitroethylenes and Cyclohexane-1,3-diones

Abstract

[reaction: see text] A novel method for synthesizing 4-acetoxy-2-amino-3-arylbenzofurans (4) from 1-aryl-2-nitroethylenes (1) and cyclohexane-1,3-diones (2) is described. The method features one-pot operation of a solution of 1 and 2 in THF with catalytic Et3N (rt, 12 h) followed with Ac2O, Et3N, and DMAP (rt, 5 h), although the process consists of 13 elementary reactions.

Crystal structures of butyl 2-amino-5-hydroxy-4-(4-nitrophenyl)benzofuran-3-carboxylate and 2-methoxyethyl 2-amino-5-hydroxy-4-(4-nitrophenyl)benzofuran-3-carboxylate

“…A search of the Cambridge Structural Database (CSD, Version 5.40, November 2018 with February 2019 updates; Groom et al, 2016) found 25 structures that match the fragment made of benzofuran substituted at the 2-position with -NX 2 (X = C, H). The hits found are crystal structures determined at temperatures in the range 103-298 K. Among these, 11 structures match the 2-amino-benzofurane fragment present in BF1 and BF2: DOZYIB (Caruso et al, 2009), FERXEG (Otsuka et al, 2004), FUFBEO (Murai et al, 2004), GOWHEF (Tandel et al, 1998), GUYXEE (Yi et al, 2010), QINXUI (Roviello et al, 2013), RAMZAH and RAMZEL (Ishikawa et al, 2005), RISSAP and RISSET (Li et al, 2014) and SECDUZ (Becker et al, 1989). Of these, two are similar to the title compounds: 2-amino-3-(p-tolyl)benzofuran-4-yl acetate and 2-amino-3-(4-methoxyphenyl)benzofuran-4-yl acetate (RAMZEL and RAMZAH) in which the aryl ring is inclined to the benzofuran ring system by 61.9 (5) and 52.1 (6) , respectively [69.26 (16) Table 3 Interaction energies for BF1-molA (kJ mol À1 ).…”

Synthesis of New Bicyclic Hydroxamic Acids with Cytotoxic Activity

“…The chemical identification of products 3a-f was carried out using FTIR, 1 H NMR, 13 C NMR and mass spectral data. Finally, the hydrogenation reaction for compound 3a in the presence of Raney Nickel in ethanol produced compound 4, and subsequent dehydrogenation with Pd/C led to the pyrrole 5 (Scheme 3), confirming the structure of 1-hydroxy-6,6-dimethyl-3-phenyl-3,5,6,7tetrahydro-1H-indole-2,4-dione (3a) and probably the heterocyclic framework of the other products, instead of 2-hydroxyiminofuran derivatives [19].Additionally, to corroborate the structure of pyrrole 5, it was prepared through a different synthetic route [20].…”

Five‐Membered Heterocycles: Benzofuran and Related Systems

“…Saito has described a novel method for the generation of 4-acetoxy-2-amino-3-arylbenzofurans from 1-aryl-2-nitroethylenes and cyclohexane-1,3-diones [70]. This one-pot operation shows high efficiency (Scheme 7.39).…”