Synthesis of trisubstituted 1,3-oxazin-6-ones via base-catalyzed ring-opening annulation of cyclopropenones with N-(pivaloyloxy)amides

The base-catalyzed [3+3]-type annulation between cyclopropenones and N-(pivaloyloxy)amides is reported. The formal insertion of a 1,3-N,O-dipole into a cyclopropenone C-C bond yields a six-membered azalactone structure. In the presence of catalytic K2CO3 at 60 degrees C in THF, the disubstituted cyclopropenone couples with benzamides, acrylamides, and a phenylacetamide to produce 2,4,5-trisubstituted 1,3-oxazin-6-ones in 23-99% yield. (C) 2018 Elsevier Ltd. All rights reserved.