Catalytic Carbonylative Double Cyclization of 2-(3-Hydroxy-1-yn-1-yl)phenols in Ionic Liquids Leading to Furobenzofuranone Derivatives
A catalytic carbonylative double cyclization method for the synthesis of furo[3,4-b]benzofuran-1(3H)-ones is reported. It is based on the reaction between readily available 2-(3-hydroxy-1-yn-1-yl)phenols, CO, and oxygen carried out in the presence of catalytic amounts of PdI2 (1 mol %) in conjunction with KI (20 mol %) and 2 equiv of diisopropylethylamine at 80 degrees C for 24 h under 30 atm of a 1:4 mixture of CO-air. Interestingly, the process was not selective when carried out in classical organic non-nucleophilic solvents (such as MeCN or DME), leading to a mixture of the benzofurofuranone derivative and the benzofuran ensuing from simple cycloisomerization, whereas it turned out chemo…
Dimethyl 2,2′-[Carbonylbis(azanediyl)](2S,2′S)-bis[3-(4-hydroxyphenyl)propanoate]
The thus‐far unknown ureic derivative dimethyl 2,2′‐[carbonylbis(azanediyl)](2S,2′S)‐ bis[3‐(4‐hydroxyphenyl)propanoate] has been efficiently synthesized by enantiospecific oxidative carbonylation of readily available L‐tyrosine methyl ester, using a very simple catalytic system (PdI2 in conjunction with KI) under relatively mild conditions (100 °C for 5 h in DME as the solvent and under 20 atm of a 4:1 mixture CO‐air).