Gold-catalyzed cyclization and subsequent arylidene group transfer of O-propioloyl oximes
Gold-catalyzed cyclizations of O-propioloyl oximes via C-N bond formation followed by arylidene group transfer were successfully carried out to afford the corresponding 4-arylideneisoxazol-5(4H)-ones in good to excellent yields. As an example, (E)-benzaldehyde O-3-phenylpropioloyl oxime (1a) was reacted in acetonitrile at 25 °C in the presence of Au(PPh3)NTf2 (5 mol %) to give 4-benzylidene-3-phenylisoxazol-5(4H)-one (2a) in 90% yield. On the basis of crossover experiments, the arylidene "migration" was shown to proceed in an intermolecular manner.
Nakamura, Itaru,Okamoto, Masashi,Terada, Masahiro
supporting information; experimental part
p. 2453 - 2455
(2010/07/05)
Cycloaddition Reactions of 3-Methyloxazolium-5-olates to 4-Arylidene-5(4H)-isoxazolones
The unstable cycloadducts formed from benzylideneisoxazolones 2 and oxazolium-5-olates 1 undergo CO2 elimination to afford the stereoisomeric substituted 3,7-diazaspirononane derivatives 3, which were isolated in one case (3a,b).On further reaction, compounds 3 are transformed into pyrrole-3-carboxylic acids 4.Reaction paths and regiochemical behaviour are discussed. - Keywords: 5(4H)-Isoxazolones, 4-arylidene-/ Muenchnones/ Pyrrole-3-carboxylic acids