One-pot Synthesis of 2-Substituted 4H-Chromeno[3,4-d]oxazol-4-ones from 4-Hydroxy-3-nitrocoumarin and Acids in the Presence of Triphenylphosphine and Phosphorus Pentoxide under Microwave Irradiation

Abstract

2-Substituted 4H-chromeno[3,4-d]oxazol-4-ones are prepared from 4-hydroxy-3-nitrocoumarin and acids by one-pot reaction in the presence of PPh3 and P2O5 under microwave irradiation or by one-pot two-step reactions in the presence of Pd/C and hydrogen and then P2O5 under microwave irradiation. The fused oxazolocoumarins were also synthesized from 3-amido-4-hydroxycoumarins and P2O5 under microwave irradiation. The 3-amido-4-hydroxycoumarins are obtained almost quantitatively from 4-hydroxy-3-nitrocoumarin, acids and PPh3 under microwave irradiation, or in the presence of Pd/C and H2 on heating. Preliminary biological tests indicate significant inhibition of soybean lipoxygenase and antilipid peroxidation for both oxazolocoumarins and o-hydroxyamidocoumarins.

One-pot synthesis of 5H-chromeno[3,4-b]pyrazin-5-one derivatives from 4-amino-3-nitrocoumarin and α-dicarbonyl compounds

“…4-Amino-3-nitro-2H-chromen-2one (1) and 3,4-diamino-2H-chromen-2-one (6) were prepared according to our recent publication. 29…”

“…[25][26][27] Recently, we performed the one-pot synthesis of fused oxazolocoumarins and imidazolocoumarins from o-hydroxynitrocoumarin or o-aminonitrocoumarin, respectively, using the PPh3 as reducing agent in the presence of carboxylic acids. 28,29 We envisioned that this reaction could also work for the one-pot synthesis of pyrazolocoumarins from 4-amino-3-nitrocoumarin and α-dicarbonyl compounds. Herein, we present our investigations towards this goal.…”

“…Herein, we present our investigations towards this goal. In parallel, we examined also the transformations of 3,4-diaminocoumarin (6) (prepared in 95% yield by the treatment of 1 with Pd/C in methanol under H2 atmosphere at room temperature for 45 min) 29 to the [3,4]-fused pyrazinocoumarins 4 and 5 by the treatment of 6 with the α-dicarbonyl compounds 2 in o-xylene under microwave irradiation (Method B) (Scheme 1). The reaction of 6 with glyoxal (2a) at 120 °C for 10 min resulted to 4a in 77% yield (Table 1, entry 13).…”

Synthetic Routes to Coumarin(Benzopyrone)-Fused Five-Membered Aromatic Heterocycles Built on the α-Pyrone Moiety. Part II: Five-Membered Aromatic Rings with Multi Heteroatoms

“…In 2018, Litinas and his coworkers summarized the previous scheme in a green chemistry methodology [ 57 ]. They described the reaction of 4-hydroxy-3-nitrocoumarin ( 81 ) with acids in a one-pot reaction in the presence of PPh 3 and P 2 O 5 under microwave irradiation.…”

“…They described the reaction of 4-hydroxy-3-nitrocoumarin ( 81 ) with acids in a one-pot reaction in the presence of PPh 3 and P 2 O 5 under microwave irradiation. Another one-pot two-step reaction was accomplished in the presence of Pd/C and hydrogen, followed by treatment with P 2 O 5 under microwave irradiation ( Scheme 26 ) [ 57 ].…”