Replacing toxic organic solvents by water allows for a strong decrease of waste production and is an important contribution to Green Chemistry.[1] In the area of homogeneous gold catalysis, highly efficient and sustainable transformations have been achieved in nanomicelles derived from designer amphiphiles in bulk water.[2-5] Application of micellar catalysis to multicomponent reactions is challenging due to pronounced differences in the polarity of substrates, intermediates, and product. We now report the gold-catalyzed three-component spirocyclization of alkynols, hydrazines, and aldehydes to functionalized pyrazolidines under aqueous micellar conditions. This transformation has been performed previously in organic solvents without the possibility of recycling the gold catalyst.[6] Whereas only moderate yields were obtained using the vitamin E-derived surfactant TPGS-750-M, highly efficient spirocyclizations were achieved in micelles derived from poly(2-oxazolines).[5] In 3 M aqueous NaCl as bulk solvent and Ph3PAuNTf2 as catalyst, various combinations of the three substrates afforded the desired spirocyclic pyrazolidines with up to 85% yield. The catalyst solution can be recycled with minimal loss of activity.

Micellar gold catalysis: Three-component spirocyclization in bulk water

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.