Ligand-Effect in Gold(I)-Catalyzed Rautenstrauch Rearrangement: Regio- and Stereoselective Synthesis of Bicyclo[3.2.1]octa-3,6-dienes through Cyclodimerization of 1-Ethynyl-2-propenyl Esters

Gold(I) complexes bearing sterically demanding phosphine ligands such as (t)BuXphos catalyze the cascade Rautenstrauch rearrangement/[4 + 3] cycloaddition of 1-ethynyl-2-propenyl esters. The reaction provides an efficient and straightforward route to bicyclo[3.2.1]octa-3,6-dienes with high regio- and stereoselectivity. The formation of the [4 + 3] cycloadducts likely proceeds through the cycloaddition, of a gold(I) carbenoid/gold-stabilized allyl cation intermediate with cyclopentadiene arising from Rautenstrauch rearrangement.