Intermolecular reactions, cross-coupling with alkenes

An interesting sequential reaction, consisting of an intermolecular alkene carbometallation and subsequent intermolecular alkyne cross-coupling, has been reported (Scheme 8.87) [601]. Starting from an immobihzed tropane framework 459, stoichiometric carbopalladation yields a stable organopalladium intermediate, which in the presence of copper(I) iodide undergoes coupling with an added terminal acetylene. 

A sequential RCM/sHicon-assisted cross-coupling reaction has been developed and was applied to the formation of natural products. - First, an RCM reaction using Schrock s catalyst, similar to eq 18, is performed to give 40, and this is followed by an intermolecular palladium cross-coupling reaction with various aryl iodides. TBAF is added followed by the Pd(dba)2 catalyst to generate the coupled aryl alkenes 41 (eq 19). ... 

Intermolecular coupling of a vinyl ether with styrene at a carbon anode in methanol is successful, giving a mixture of the cross coupled product and the two homocoupled products [49], Intramolecular coupling between an enol ether and an alkene centre, as in 24 and 25, proceeds to give the cyclized product in good yield [50], Five and six membered rings can be constructed in this way. An easily oxidised vinyl ether group is necessary to initiate the reaction and the second alkene... 

In addition to the iminium-salt-based chemistry and to cross-coupling processes, aqueous formaldehyde can also be used as the carbonylated substrate in the Prins reaction, an intermolecular ene-type acid-catalyzed reaction with alkenes providing 1,3-dioxanes (Adams and Bhatnagar, 1977). 

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