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

Rh(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.

Keywords: N–H-insertion; Wolff rearrangement; diazo compounds; oxidation cleavage; transition-metal-catalyzed reactions.

Scheme 1

Catalytic reactions of diazocarbonyl compounds with unsaturated δ-amino esters.

Figure 1

The structures of the starting compounds 1–3 and catalysts used in this study.

Scheme 2

The assumed pathway for the occurance of amides 6a–c by way of the catalytic Wolff rearrangement.

Scheme 3

The assumed mechanism for the formation of the amides 4 and 7 during oxidative cleavage of the N–H-insertion products F.