Electro-organic reactions. Part 52: Diels–Alder reactions in aqueous solution via electrogenerated quinodimethanes

ortho-Quinodimethanes (o-QDMs) are conveniently generated cathodically in aqueous electrolyte in the presence of N-methylmaleimide, which acts as both redox mediator and dienophile. endo-Diels–Alder adducts are formed efficiently and rapidly and competition from electrohydrodimerisation of N-methylmaleimide is completely suppressed. Kinetic and coulometric evidence suggests that initial electron transfer is to a complex between the o-QDM precursor and N-methylmaleimide (hydrophobic packing).