STUDY OF THE REACTION OF SPECIFICALLY SUBSTITUTED 2H-1,4 OXAZIN-2-ONES WITH ACETYLENIC-COMPOUNDS AS A POTENTIAL ROUTE FOR SPECIFIC 3-PYRIDINECARBOXYLATES OR 4-PYRIDINECARBOXYLATES

Cycloaddition-elimination reactions between 3,5-dichloro-2H-1,4-oxazin -2-one and ethyl 4-hydroxyalkynoates have been studied. 4,6-Dichlorofu ro[3,4-c]pyridinie-3(1N)ones have been generated, dechlorinated or tra nsformed into the corresponding 3-pyridinecarboxylates. As the regiois omeric lactones and the corresponding 4-pyridinecarboxylates cannot be realised in this way, the synthesis of a 3-tributylstannyloxazinone a nd 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.