The turnovers of a gold(III) chloride catalyst were increased by 3,300% with the addition of several equivalents of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and catalytic amounts of copper(II) chloride. A three-component coupling reaction between piperidine, phenylacetylene, and benzaldehyde yielded a propargylic amine in quantitative conversions and isolated yields when gold(III) chloride was added in catalytic amounts, but the gold catalyst decomposed and had little to no reactivity when a second set of piperidine, phenylacetylene, and benzaldehyde was added after the reaction was complete. Thus, only one cycle was possible with gold(III) chloride. The addition of TEMPO and copper(II) chloride to reactions with gold(III) chloride maintained the catalytic activity of gold for up to 33 cycles. This result demonstrates a new way to greatly increase the turnovers of a gold(III) chloride catalyst with the addition of inexpensive, commercially available reagents.

The development of a method for site-isolation of Grubbs second-generation catalyst from MCPBA is described. In these reactions, Grubbs catalyst was dissolved in a solvent consisting of a mixture (1:1 v/v) of 1-butyl-3-methylimidazolium hexafluorophosphate and methylene chloride and completely encapsulated within a thimble fabricated from polydimethylsiloxane (PDMS). A series of molecules that react by cross metathesis or ring-closing metathesis were added to the interior of the thimble and allowed to react. In the last step, m-chloroperoxybenzoic acid (MCPBA) dissolved in MeOH/H₂O (1:1 v/v) was added to the exterior of the PDMS thimble. Small organic molecules diffused through the PDMS to react with MCPBA to form epoxides, but the Grubbs catalyst remained encapsulated. This result is important because Grubbs catalyst catalytically decomposes MCPBA at ratios of MCPBA to Grubbs of 3000 to 1. The yields for this two-step cascade sequence ranged from 67 to 83 %. The concept behind this sequence is that small organic molecules have high flux through PDMS but large molecules—such as Grubbs catalyst—and ionic reagents—such as MCPBA—have much lower flux through PDMS. Small molecules can thus react both outside and inside PDMS thimbles, whereas incompatible catalysts and reagents remain site-isolated from each other. This method does not require alteration of structures of the catalysts or reagents, so it may be applied to a wide range of homogeneous catalysts and reagents. To demonstrate further that the catalyst was encapsulated, the Grubbs catalyst was successfully recycled within the cascade sequence.