Applications of Stevens [1,2]-shifts of cyclic ammonium ylides. A route to morpholin-2-ones

Article abstract of DOI:10.1021/jo00099a041

2-(N,N-Dialkylamino)ethyl diazoacetoacetates 2 were prepared in two steps from readily available ethanolamines 1 . When heated in the presence of catalytic Cu, the substrates cleanly formed morpholinones 3, presumably via the intermediacy of copper cathenoids and cyclic ammonium ylides. In most cases involving benzylic or allylic migrating groups, ylide [1,2]-shift occurred in good yield (55-80%). In the case of benzhydryl containing substrate 2g, only dimer 4 was isolated. Simple alkyl groups failed to undergo the rearrangement, with the exception of tert-butyl case 2i, which furnished morpholinone 3i in low yield. Substituted allylic case 21 gave only [1,2]-shift product 3l, with no evidence for competing [2,3]-shift to give 3l'. Diazoacetates 2n-p also underwent conversion to morpholinones 3n-p in 19-64% yield with Cu(acac)₂ catalysis.