Palladium mediated stereospecific synthesis of 3-enynyl substituted thioflavones/flavones

The stereocontrolled synthesis of enynes has been accomplished via a sequential Heck-Sonogashira reaction in a simple synthetic operation. A variety of terminal alkynes were reacted with 3-iodo(thio)flavone in the presence of a palladium catalyst and a copper salt affording a mild and one-pot method for the first synthesis of the corresponding 3-enynyl and/or alkynyl derivatives. The mechanism and scope of the reaction are discussed.