Substrate-Controlled Regioselective Alkylation of 4-Hydroxycoumarin with Diazo Compounds through TfOH Catalysis.

Control of the regioselectivity of nucleophiles toward alkylating agents is a fundamental problem in heterocyclic chemistry. Substrate-controlled TfOH-catalyzed alkylation of 4-hydroxycoumarin with diazo compounds has been developed to provide rapid access to the C3- or O-alkylated 4-hydroxycoumarins with high efficiency. The regioselectivity can be determined by varying the electronic nature of the diazo substrates, especially those bearing a methylthio group. [ABSTRACT FROM AUTHOR]