5,6-Dihydro-4H-1,2-oxazines in Organic Synthesis: Catalytic Hydrogenation of [(5,6-Dihydro-4H-1,2-oxazin-3-yl)methyl]malonates to Methyl 7-Oxo-1-oxa-6-azaspiro[4.4]nonane-8-carboxylates

摘要

[(5,6-Dihydro-4H-1,2-oxazin-3-yl)methyl]malonates undergo a cascade transformation into substituted methyl 7-oxo-1-oxa-6-azaspiro[4.4]nonane-8-carboxylates under catalytic hydrogenation conditions over Raney nickel. A mechanistic scheme involving initial N-O bond cleavage with the formation of imines as key intermediates is suggested.