Dependence of enantioselectivity on the distribution of a chiral hydrogenation catalyst between an aqueous and a micellar phase: investigations using pulsed field gradient spin echo NMR spectroscopy.

The enantioselectivity obtained from rhodium complex catalyzed hydrogenations conducted in water can often be increased considerably by the addition of amphiphiles. At present the reasons for this increase in selectivity are not fully understood. The application of pulsed field gradient spin echo NMR (PGSE-NMR) spectroscopy to determine the average diffusion coefficients of the catalysts in both known and novel examples of asymmetric hydrogenation shows definitively that the increase in enantioselectivity is coupled with an aggregation of the catalyst to the micelles.

A Novel Copper Chelate Catalyzed Ring Closure Reaction of 1,2-Bisketenes with Alcohols To Give 5-Alkoxy-2,3-dihydrofuran-2-ones.

Copper complexes with distorted tetrahedral structure in solution catalyze regioselectively the cyclization of 1,2-bisketenes with alcohols to give 5-alkoxy-2,3-dihydrofuran-2-ones in very high yields (shown on the right). It seems remarkable that these new compounds could remain undiscovered despite having structural similarities with a great number of well-investigated and biologically active butenolides.