Transition-metal-catalyzed carbon–carbon and carbon–heteroatom bond formations are among the most heavily used types of reactions in both academic and industrial settings. As important as these are to the synthetic community, such cross-couplings come with a heavy price to our environment, and sustainability. E Factors are one measure of waste created, and organic solvents, by far, are the main contributors to the high values associated, in particular, with the pharmaceutical and fine-chemical companies which utilize these reactions. An alternative to organic solvents in which cross-couplings are run can be found in the form of micellar catalysis, wherein nanoparticles composed of newly introduced designer surfactants enable the same cross-couplings, albeit in water, with most taking place at room temperature. In the absence of an organic solvent as the reaction medium, organic waste and hence, E Factors, drop dramatically.
Interactions between palladium nanoparticles and nanomicelles containing in situ-generated hydrogen and an alkyne lead to high yields of product Z-alkenes. These reactions are general, take place in water at ambient temperatures, and offer recycling of the aqueous reaction mixture along with low overall E Factors.
Nickel nanoparticles, formed in situ and used in combination with
micellar catalysis, catalyze Suzuki Miyaura cross-couplings in water under very
mild conditions.
Allylic and benzylic alcohols can be selectively oxidized to their corresponding aldehydes or ketones in water containing nanoreactors composed of the designer surfactant TPGS-750-M. The oxidation relies on catalytic amounts of CuBr, bpy, and TEMPO, with N-methyl-imidazole; air is the stoichiometric oxidant.
Cyclopropenylmethyl acetates have been shown to undergo rapid and stereoselective gold catalyzed rearrangement to Z-acetoxydienes in high yield. DFT calculations have shown that while several reaction pathways can be envisaged only a single, ring-opening one operates.
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