Catalyst Loading Controls Chemoselectivity: Unusual Effect in Rhodium(II) Carbene Insertion Reactions with Tetrahydrofuran

(E)-3-Arylidene-4-diazopyrrolidine-2,5-diones previously shown to yield two products in reactions with tetrahydrofuran mediated by rhodium carbenes & mdash;tetrahydrofur-2-yl-substituted product of C-H insertion and spirocyclic product of formal C-O insertion. Accidentally, it was noted that the ratio of the two products depends on the catalyst loading, and the phenomenon was investigated in detail. It was found to be of preparative significance: by solely changing the catalyst loading from 0.01 mol% to 10 mol%, one can obtain sound yields of either of the two products. Mechanistic and kinetic interpretation of this new phenomenon has been proposed.

Automated summary

The ratio of the products obtained from the reaction between E-3-Arylidene-4-diazopyrrolidine-2,5-diones and tetrahydrofuran mediated by rhodium carbenes was found to be dependent on the catalyst loading. By adjusting the catalyst loading, either of the two products can be obtained in good yields. Mechanistic and kinetic interpretation of this phenomenon has been proposed.