Tetrahydrofurans carbopalladation

A related one-pot three component coupling reaction leading to allyli-dene tetrahydrofuran derivatives 80 and which combines a conjugate addition of a propargyl alcohol with an activated olefin and an in situ palladium-catalyzed carbopalladation-cyclization in the presence of a large excess of allyl chloride has been recently developed by Lu and Iiu (Scheme 31) [77]. The cyclization process is here initiated by addition of a catalytic amount of Pd(OAc)2 and in marked contrast with the above-discussed reactions, a catalytic cycle involving divalent palladium proceeds in the reaction. In this process, the ester enolate formed in the Michael addition undergoes... 

An analogous carbopalladation-cyclizaton process has been applied to the synthesis of various substituted tetrahydrofurans using three components. This one-pot procedure involves an intermolecnlar addition of allylic alkoxides to Michael acceptors. The resulting enolate nndergoes cyclization via nucleophilic attack on the alkene-Pd complex. So as to avoid nndesired side reactions snch as the premature trapping of the alkoxide by the organopalladinm species, the alkoxide shonld be added via a syringe pump. ... 

---