Propargyl amine synthesis catalysed by gold and copper thin films by using microwave-assisted continuous-flow organic synthesis (MACOS).

An effective multi-component reaction (MCR) protocol has been developed for the construction of propargyl amines from aldehydes, amines and terminal alkynes by using microwave-assisted continuous-flow organic synthesis (MACOS). The process is catalysed by thin films of either copper or gold that achieve temperatures in excess of 900 degrees C when irradiated with low levels of microwave power. The process works equally well for premixed solutions of the three starting materials, or as three separate streams, which improves the combinatorial efficiency of the method. The process tolerates a wide variety of functional groups and heterocycles, and conversion over these diverse substrates ranges from 70-90 %.

Gold film-catalysed benzannulation by microwave-assisted, continuous flow organic synthesis (MACOS).

Methodology has been developed for laying down a thin gold-on-silver film on the inner surface of glass capillaries for the purpose of catalysing benzannulation reactions. The cycloaddition precursors are flowed through these capillaries while the metal film is being heated to high temperatures using microwave irradiation. The transformation can be optimized rapidly, tolerates a wide number of functional groups, is highly regioselective, and proceeds in good to excellent conversion.

Gold-film-catalysed hydrosilylation of alkynes by microwave-assisted, continuous-flow organic synthesis (MACOS).

Thin gold films on the surface of glass capillaries have proven to be highly active catalysts for the rapid hydrosilylation of alkynes that are flowed through the reactor while being heated by microwave irradiation. The films are able to be reused at least five times with no loss of activity and with no detectable levels of gold showing up in the hydrosilylated products.

Diels-Alder cycloadditions by microwave-assisted, continuous flow organic synthesis (MACOS): the role of metal films in the flow tube.

Thin Pd films have been deposited on the inside of capillary-sized tubes through which compounds undergoing Diels-Alder reactions have been flowed while being heated with microwave irradiation; dramatic rate accelerations are observed in the presence of the film, which has been shown to play both a heating and catalytic role.

Pd PEPPSI-IPr-mediated reactions in metal-coated capillaries under MACOS: the synthesis of indoles by sequential aryl amination/Heck coupling.

A method has been devised for the microwave-assisted, continuous-flow preparation of indole alkaloids by a two-step aryl amination/cross-coupling sequence of bromoalkenes and 2-bromoanilines. This process requires both the presence of a metal-lined flow tube (a 1180 micron capillary) and the Pd PEPPSI-IPr catalyst; without either, the catalyst or the film, there is zero turnover of this catalytic process. A silver film has been shown to provide some conversion (48-62 %), but optimal results (quantitative) across a variety of bromoalkenes and bromoanilines were achieved by using a highly porous palladium film. Possible roles for the Pd film are considered, as is the interplay of the catalyst and the film.