Catalytic Conversion of Alcohols into Carboxylic Acid Salts in Water: Scope, Recycling, and Mechanistic Insights.

The catalytic conversion of alcohols into carboxylic acid salts in water was performed in the presence of ruthenium complexes supported by aliphatic PNP pincer ligands preformed or formed in situ. High activity toward a wide substrate scope was achieved with turnover number values of up to 4000. The air-stable catalytic system can be recycled by using toluene as a catalyst-immobilizing phase; the activity is maintained after five consecutive runs. Finally, mechanistic studies allowed some fundamental aspects related to water activation to be unveiled and to the mechanism postulated.

Iodocyclization versus diiodination in the reaction of 3-alkynyl-4-methoxycoumarins with iodine: synthesis of 3-iodofuro[2,3-b]chromones.

The reaction of 3-alkynyl-4-methoxycoumarins with molecular iodine in chlorinated solvents allows access to 3-iodofurochromones in good to excellent yields as the result of a iodocyclization-demethylation process. Competitive diiodination of the coumarin acetylene moiety could be eliminated by simply performing the reactions in refluxing 1,2-dichloroethane, owing to the thermal instability of the resulting (E)-1,2-diiodoethenylcoumarins.

A Pd-catalyzed heteroannulation approach to 2,3-disubstituted furo[3,2-c]coumarins.

The Pd-catalyzed cyclofunctionalization of 3-alkynyl-4-methoxycoumarins with aryl halides resulted in the selective formation of 3-arylfuro[3,2-c]coumarins in lieu of the expected regioisomeric 3-arylfuro[2,3-b]chromones. A mechanism involving the linear to angular rearrangement of a Pd-containing furan intermediate was proposed.