Fluorous Organocatalysis

Over the past decade, much interest has been devoted to the development of highly efficient organocatalysts for a variety of reactions, and the pace of growth in this field of chemistry has been breathtaking.  Fluorous organocatalysts are of high interest because they are expected to be soluble under typical solution phase reaction conditions, yet they can still be easily separated from the reaction mixture for subsequent reuse.

Part I. Separation achieved by fluorous solid-phase extraction (F-SPE)

A chiral fluorous imidazolidinone catalyst provides consistently high enantioselectivities in Diels-Alder reactions of dienes and α,β-unsaturated aldehydes. The catalyst can readily be separated from the reaction products by fluorous solid-phase extraction, and it is recovered in excellent purity, ready for reuse.

Applications of chiral fluorous imidazolidinone catalyst

Fluorous imidazolidinone catalyzed Diels-Alder Reaction

Organic product and fluorous imidazolidinone catalyst were separated by F-SPE

 Cartridge can be reused after wash with acetone or THF

Part II. Separation achieved by liquid-liquid extraction (LLE)

     A fluorous prolinol precatalyst bearing only 34 fluorine atoms has been immobilized in the hydrofluoroether solvent HFE-7500.  The CBS reduction of acetophenone proceeded rapidly, in high yield and in high ee in the absence of any organic solvent.  The organic product was stripped from the HFE-7500 phase with a polar solvent, and the HFE-7500 phase was reused “as is” with satisfactory results through eight runs.  This process is an attractive prototype for the large scale use, recovery and reuse of fluorous organocatalysts.

Fluorous oxazaborolide catalyzed CBS reduction

Organic product and fluorous prolinol precatalyst were separated by LLE