Watts, photons, volts, and flow: Using microwave heating, photocatalysis, electrochemistry, and continuous-flow processing as tools for greener chemistry

POLITANO, FABRIZIO; NANDI, JYOTI; LEÓN SANDOVAL, ARTURO; LEADBEATER, NICHOLAS E.

Seattle

Conferencia; 24th Annual Green Chemistry & Engineering Conference; 2020

American Chemical Society - Green Chemistry Institute

New technologies are having a significant impact on preparative organic chemistry,potentially making processes cleaner, faster, and easier. They in essence offer a bridgebetween organic synthesis and sustainability. Sealed-vessel microwave reactors allowchemists to perform reactions in a few minutes, at high temperature, reducing chemicalhazard exposures and reducing by-product formation. When scalability is desired,continuous flow processing can be employed; reactions optimized using microwaveheating being scaled up in flow. Photocatalysis and electrochemical synthesis arerecognized as environmentally friendly methodologies. In oxidation and reductionreactions hazardous redox reagents can be replaced by photons or electric current.Our research group employs all these technologies in the laboratory and we will presentan overview of our work here. In each case, in addition to highlighting the applicability ofthe technology, the green chemistry features will be highlighted. Attention will befocused on:(1) A fast, easy route to benzimidazole-N-oxides in batch using microwave heatingtogether with water as a solvent,(2) Scale-up of the benzimidazole-N-oxide methodology using continuous-flowprocessing, highlighting how the transition from batch to flow is made,(3) Oxidative functionalization reactions performed using visible-light photoredoxcatalysis in conjunction with oxoammonium cations, particular attention being focusedon the conversion of alcohols, amines, and aldehydes to nitriles and amides,(4) Electrochemical conversion of aldehydes to amides performed in conjunction with anitroxide catalysts.