Synthesis of fused oxazolocoumarins has been achieved from the one‐pot tandem reactions of o‐hydroxynitrocoumarins with benzyl alcohol in toluene under catalysis in a sealed tube at 150°C. The catalysis was performed by gold nanoparticles supported on TiO2 (0.4 mol% Au) or FeCl3 (5%) or silver nanoparticles supported on TiO2 (1.7 mol% Ag).

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Pyrano- and dipyranocoumarins are classes of naturally occurring organic compounds with very interesting biological activities. This review focuses on the synthetic strategies for the synthesis of pyranocoumarins and dipyranocoumarins and the biological properties of those compounds. The synthesis involves the formation of the pyran ring, at first, from a coumarin or the formation of pyranone moiety from an existing pyran. Pyranocoumarins and dipyranocoumarins present anti-HIV, anti-cancer, neuroprotective, antidiabetic, antibacterial, antifungal, anti-inflammatory activities. Especially khellactones and calanolides are usually potent and selective in anti-HIV activity. Decursin and decursinol derivatives are effective as anticancer, neuroprotective, antidiabetic, antibacterial, and antifungal agents.

Dipetalolactone and 4‐methyldipetalolactone are prepared in excellent yield by a one‐pot tandem propargylation/Claisen rearrangement/cyclization reaction of the corresponding 5,7‐dihydroxycoumarins with 3‐chloro‐3‐methylbut‐1‐yne in the presence of Cs2CO3 under microwave irradiation. The analogous reactions of propargyl chloride with esculetins or 5,7‐dihydroxycoumarins led to dipropargyloxy derivatives. The later by treatment with gold nanoparticles supported on TiO2 or BF3.Et2O in N,N‐dimethylformamide (DMF) under microwave irradiation resulted in very good to excellent yield to the corresponding fused dipyranocoumarins. The reactions of esculetins with 3‐chloro‐3‐methylbut‐1‐yne gave mainly exomethylene fused dioxino[g]coumarins.