Ring Transformation of 2-Phenacylidenoxazolidines: Investigations Concerning the Regiochemistry of the Addition of Hydroxylamine and the Ring Opening of Spiroannelated Intermediates

Article abstract of DOI:10.1002/ardp.19893221012

Acylketene O,N-acetals having the structure of 2-phenacyliden-oxazolidines 2 are formed by reaction of lithiated 2-alkyl-4,5-dihydrooxazoles 1 with benzoic acid esters.Under the conditions used, competitive 1,2- and 1,4-addition is observed.The ring opening of the resulting spiroannelated intermediates (3 and 4, resp.) occurs regiospecifically at the O-atom, leading to 5-(β-hydroxyethyl)-aminoisoxazoles 5 and 3-(β-hydroxyethyl)-aminoisoxazoles 7, respectively.Possible reaction mechanism are discussed, the structures of the regioisomeric compounds are substantianed by spectrometric methods, especially ms and 13C-NMR investigations.