Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

Abstract

SummaryRh(II)-сatalyzed reactions of aroyldiazomethanes, diazoketoesters and diazodiketones with α,β-unsaturated δ-aminoesters, in contrast to reactions of diazomalonates and other diazoesters, give rise to the Wolff rearrangement and/or oxidative cleavage of the initially formed N–H-insertion products. These oxidation processes are mediated by Rh(II) catalysts possessing perfluorinated ligands. The formation of pyrrolidine structures, characteristic for catalytic reactions of diazoesters, was not observed in these processes at all.

Rhodium-Catalyzed Aerobic Decomposition of 1,3-Diaryl-2-diazo-1,3-diketones: Mechanistic Investigation and Application to the Synthesis of Benzils

“…Further, a closer inspection of the results, as listed in Table , implied to us that 3b was also possibly derived from the ketene intermediate that led to 4b , and the competition of the ketene between O 2 and H 2 O might account for the ratios of the two products (as in entries 2 and 6 in Table ). Moreover, extensive investigations have demonstrated that molecular oxygen can be activated by Rh­(I)- or Rh­(II)-complexes through the interaction with a transition-metal center. Accordingly, we assume that the dirhodium­(II) catalyst (simplified as RhL n ) employed in our studies is partially oxidized to a rhodium peroxide or peroxy radical complex ,, upon exposure to oxygen, which are tentatively assigned as cat-O 2 (Rh 2 6+ or Rh 4+ ) and cat-O 2 • (Rh 2 5+ or Rh 3+ ), as shown in Scheme .…”