Regiocontrolled palladium-catalyzed direct C2-arylations of Methoxalen using benzenesulfonyl chlorides and C2,C3-diarylations using aryl bromides as the aryl sources

Abstract

Conditions for the regioselective palladium-catalyzed direct C2-arylation and C2,C3-diarylation of Methoxalen are described. The use of benzenesulfonyl chlorides as the coupling partner allowed control of the regioselectivity of the arylation in favor of the C2 carbon of Methoxalen. This method tolerates a variety of substituents on the benzenesulfonyl chloride derivative. Notably, 2-, 3-, and 4-bromobenzenesulfonyl chlorides and 4-iodobenzenesulfonyl chloride were coupled with Methoxalen without cleavage of the C-Br or C-I bonds. Conversely, the use of an excess amount of aryl bromides as the aryl source provides access to C2,C3-diarlyated Methoxalenes.