- Site-isolation and recycling of PdCl2 using PDMS thimbles
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(Chemical Equation Presented) Macroscopic thimbles composed of polydimethylsiloxane (PDMS) were used to site-isolate PdCl2 from the products of Wacker-Tsuji oxidations and Pd-mediated homocouplings. The reactions were completed on the interior of hollow thimbles, and the organic products were isolated by their selective flux to the exterior of the thimbles. Although organic molecules had high flux through the walls of the thimbles, PdCl 2 remained encapsulated as a result of its polar structure that rendered it insoluble in PDMS. In two examples, less than 0.002% of the PdCl2 added to the interior of the thimble partitioned to the exterior; thus, over 99.998% remained encapsulated on the interior of the thimble. Because it was encapsulated, this catalyst was readily recycled five times for the Wacker-Tsuji oxidation of styrene. A sequential reaction was also completed where p-methylstyrene was oxidized to 4′-methyl-acetophenone by PdCl2 on the interior of a thimble and then fluxed to the exterior to react with phenylmagnesium bromide to yield 1-phenyl-1-p-tolyl-ethanol. This method site-isolated PdCl2 catalysts without requiring them to be rendered heterogeneous, the addition of exogenous ligands, or any modifications to the catalyst. The catalyst was site-isolated by affecting its environment rather than by altering its ligand structure.
- Miller II, A. Lee,Bowden, Ned B.
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- PRO-FRAGRANCE COMPOUNDS
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A compound of Formula (I) wherein R1 represents a C3 to C20 hydrocarbon group derived from a fragrant alcohol of formula R1OH or from a fragrant aryl aldehyde or ketone of Formula (II), wherein: R2 is, independently, hydrogen atom, hydroxyl group, acetoxy group, -O(C=O)CH(CH3), optionally substituted C1-C6 alkyl group or C1-C6 alkoxy group, wherein any two of R2 may form an optionally substituted 5 or 6 membered ring, and R1 represents a radical derived from a fragrant alcohol of formula R1OH or from a fragrant aldehyde or from a fragrant aryl aldehyde or ketone of formula (II). The compounds are useful for example as a precursor for the prolonged delivery or release of fragrant compounds such as fragrant alcohols or aldehydes.
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(2014/12/09)
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