1. Demystifying Microwave Assistance in Homogeneous Catalysis
Andrew W. Holland, Department of Chemistry, Idaho State University, Pocatello, ID,
Microwave heating has been found to accelerate many chemical reactions, but the origin of this effect is often unclear. This coupling reaction is one such example.
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We have monitored the progress of the reaction over time under both conditions in an attempt to locate the key difference – does one reaction start faster? Continue longer? Proceed with a consistently higher rate?
rapid early reactions,
then much lower rate
Under both conditions, the final outcome of this reaction is dominated by rapid conversion occurring at very early reaction times – this suggests catalyst deactivation may be a critical factor.
More detailed data for very early reaction times, and kinetic profiles for related microwave-accelerated transformations are currently being collected.
PdOAc and PdCl2 comparable, dba worse
DPEphos, BINAP, DPPF all comparable, DPPE worse, some conversion with PPh3
Need a bit over 1 equiv for best results
Definitely air sensetive, but sparging solution gave results almost as good
microwave reaction complete, oil bath nearly stopped within 20 min