HFIP Promoted C3 Alkylation of Lawsone and 4-Hydroxycoumarin with Alcohols by Dehydrative Cross-Coupling.

An environmentally benign system for the direct alkylation of lawsones and 4-hydroxycoumarins with alcohols in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) is reported. The reaction proceeded smoothly via a dehydrative cross-coupling process by utilizing the unique properties of HFIP. A variety of alkylated products and subsequent one-pot cyclized products (pyranonaphthoquinones and pyranocoumarins) could be obtained in 40-93% yields.