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

Abstract

(E)-3-Arylidene-4-diazopyrrolidine-2,5-diones previously shown to yield two products in reactions with tetrahydrofuran mediated by rhodium carbenes—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.

Entry to new spiroheterocycles via tandem Rh(II)-catalyzed O–H insertion/base-promoted cyclization involving diazoarylidene succinimides

“…A rich synthetic platform for the design of various types of spiroheterocycles is provided by cyclic diazo compounds [ 10 ]. Recently, we and others have demonstrated the efficient use of diazoarylidene succinimides (DAS, 1 ) in the synthesis of spiro-annulated pyrrolidine-2,5-diones by catalyzed spirocyclizations involving aldehydes [ 11 ], tetrahydrofuran [ 12 – 13 ], and in the O–H insertion/Claisen rearrangement/intramolecular oxa-Michael addition cascade [ 14 ] ( Scheme 1 ).…”

Entry to new spiro heterocycles via tandem Rh(II)-catalyzed O–H insertion – base-promoted cyclization involving diazo arylidene succinimides

“…[6][7][8][9] A rich synthetic platform for the design of various types of spiro heterocycles is provided by cyclic diazo compounds. [10] Recently, we and others have demonstrated the efficient use of diazo arylidene succinimides (DAS, 1) in the synthesis of spiro-annulated pyrrolidine-2,5-diones by catalyzed spirocyclizations involving aldehydes, [11] tetrahydrofuran, [12,13] and in the O-H insertion/Claisen rearrangement/intramolecular oxa-Michael addition cascade [14] (Scheme 1).…”