Light-Induced Reactions of Diazotetrahydrofuranone without Elimination of Nitrogen: Experimental and Mechanistic Study.

The energies and lifetimes of the excited states (S1, S2, S5, T1) of a diazotetrahydrofuranone were determined using experimental and computational methods. It was shown that direction of the diazoketone photochemical transformations without elimination of nitrogen is determined by multiplicity and energy of the excited state, generated by UV irradiation of diazo compound: isomerization to α-ketodiazirine proceeds from the singlet S1 state, whereas the alternative process of C-H insertion with hydrazone formation occurs through the triplet T1 state. The most probable excited state that leads to elimination of nitrogen and Wolff rearrangement is one of the highest singlet excited states of diazotetrahydrofuranone.

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

Rh(II)-сatalyzed reactions of aroyldiazomethanes, diazoketoesters and diazodiketones with α,ß-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.