The application of diazo oxime ethers in the synthesis of heterocycles

Abstract

In this thesis, we have investigated the reactivities of diazo oxime ethers and their applications in the synthesis of various heterocycles.

As a result, 2-isoxazolines and 2H-azirines have been prepared from α-oximino diazo compounds with Rh2(Piv)4 under mild reaction conditions. Furthermore, 2H-azirines have been utilized in the one-pot reaction for pyrrole synthesis in the presence of 1,3-dicarbonyl compounds (Scheme 1).

Free carbenes could also be generated from photolysis. Irradiation of α-diazo oxime ethers in benzene solution afforded 2-alkyl/aryloxy-2H-azirines through facile N–O bond insertion in good to excellent yields. This protocol allowed for a tandem reaction of pyrrole synthesis via 2-alkoxy-2H-azirines formation and 1,3-dipolar cycloaddition (Scheme 2). In our continued work on N–O bond insertion, a number of 3-hydroxypyridines have been prepared from δ-oximino diazo compounds catalyzed by Rh2(tfacam)4 (Scheme 3).