Synthesis of Highly Polysubstituted Cyclopentadienes through Oxypalladation Initiated Domino Heck Reactions of Internal Alkynes

Abstract

We describe a facile approach to prepare a variety of densely polysubstituted cyclopentadiene derivatives in good yields (52%-75%) through palladium(II)-catalyzed oxypalladation initiated domino Heck reactions of internal alkynes with diverse carboxylic acids and phthalimide in the presence of glycine as ligand. Control experiments revealed that the free NH2 and COOH groups of glycine played an important role on accelerating the reaction. The reaction showed broad substrate scope for carboxylic acids and was easily performed at gram scales. The present method features high regioselectivity of internal alkyne, the formation of four C-O/C-C bonds in a one-pot reaction, and the first example to access cyclopentadiene scaffolds by oxypalladation reaction.