Transition Metal-induced Activation Of Alkynes Leading To Cyclization Reactions

Recently, much attention has been paid to the activation of alkynes with transition metal compounds as powerful and useful methods to construct structurally complex molecules. In this context, we summarized the most significant recent reported transformations of propargylic esters, including rhodium, ruthenium, nickel, gold and platinum metal catalyst.A simple and tandem synthetic approach, which offers an efficient, direct route to highly substituted indenes, has been developed by palladium or nickel-catalyzed cyclization of propargylic compounds and nitrogen nucleophiles. The reaction takes place under mild conditions, and a possible mechansim is proposed. The structure was definitively secured by an X-ray crystal structure analysis.The diverse and rich reactivity of the readily available propargylic esters has continued to attract the interest of different research groups. We report herein a gold (â…¢)-catalyzed [3+3]-cycloaddition of propargyl esters and azomethine imines. This report represents the first example of a formal cycloaddition between alkenyl metal carbenoids and 1,3-dipoles. In contrast to the previously reported cycloadditions, this reaction highlights the difference in the reactivity of alkenyl Fischer carbenes and the alkenyl Au-carbenoids generated from the rearrangement of propargyl esters.