A Simple and Efficient Enantioselective Synthesis of 2-Alkylidene-3-alkyl-1,4-benzodioxanes by Palladium-Catalyzed Annulation of Benzene-1,2-diol and Propargylic Carbonates

[reaction: see text] Benzene-1,2-diol reacts with various propargylic carbonates in the presence of a palladium catalyst and a chiral atropoisomeric diphosphine to give 2-alkylidene-3-alkyl-1,4-benzodioxanes in good yields and 56-97% enantiomeric excess.