Bulletin des societes chimiques belges vol:106 issue:9-10 pages:623-630
Cycloaddition-elimination reactions between 3,5-dichloro-2H-1,4-oxazin-2-one and ethyl 4-hydroxyalkynoates have been studied. 4,6-Dichlorofuro[3,4-c]pyridinie-3(1N)ones have been generated, dechlorinated or transformed into the corresponding 3-pyridinecarboxylates. As the regioisomeric lactones and the corresponding 4-pyridinecarboxylates cannot be realised in this way, the synthesis of a 3-tributylstannyloxazinone and the regiochemistry of the cycloaddition with methyl propiolate has been studied. This route is shown to be inefficient for the generation of biologically interesting 4-pyridinecarboxylates.