Highly Regioselective, Sequential, and Multiple Palladium-Catalyzed Arylations of Vinyl Ethers Carrying a Coordinating Auxiliary:  An Example of a Heck Triarylation Process

This article describes the development of new auxiliary-accelerated Heck multiarylations by intramolecular presentation of the oxidative addition complex. The introduction of a specific, palladium-coordinating dimethylamino group allows for the desired chelation-accelerated and chelation-controlled tri- and diarylation reactions. We report (a) the first example of a Heck triarylation process, (b) highly selective palladium-catalyzed diarylations of alkyl vinyl ethers, and (c) a very rapid two-phase protocol for the microwave-assisted hydrolysis of amino-substituted, arylated vinyl ethers constituting an entry to diarylated ethanals and substituted desoxybenzoins. X-ray structures and product patterns support the suggested substrate-controlled Heck reaction pathway. The catalyst-directing alkyl dimethylamino functionality was rapidly (1-2 min) and efficiently released by microwave hydrolysis after Heck multiarylation reactions. The liberated aromatic carbonyl compounds were thereafter isolated and fully characterized.