Palladium-Catalyzed Cyclization of 1-Iodo-Substituted 1,4-, 1,5-, and 1,6-Dienes as Well as of 5-Iodo-1,5-dienes in the Presence of Carbon Monoxide

Abstract

A series of ω-alkene-containing alkenyl iodides were prepared via (a) various allyl-, homoallyl-, and higher ω-alkenylmetalation reactions of alkynes involving Zn, Al−Zr, Zn−Zr, and Cu, (b) trans-hydroalumination and Cu-catalyzed trans-carbomagnesiation of propargyl alcohols, and (c) Zr-promoted alkyne−alkene coupling. Various factors affecting three cyclic acylpalladation (Types I−III Ac-Pd) and three cyclic carbopalladation (Types I−III C-Pd) processes of the ω-alkene-containing alkenyl iodides under the influence of CO and Pd−phosphine catalysts have been delineated. In the presence of methanol or other alcohols at relatively high pressures (30−100 atm) of CO (Conditions IV), Type II Ac-Pd products containing five-membered ketones, such as 22, 26−28, 30, and 32, can be obtained generally in high yields. The order of rates of various carbonylative cyclization reactions producing five-membered rings is as follows: lactonization > Type II Ac-Pd reaction > C-enolate trapping with malonate anion. The prepa...