Novel selective heterocyclization of the Michael adducts of ene-hydrazines with dimethyl acetylenedicarboxylate
Abstract
Cyclization of the Michael adducts 1 and 6 formed from ene-hydrazines and dimethyl acetylenedicarboxylate (DMAD) in the presence of polyphosphoric acid (PPA) produced the fused 1,2-diazepine rings 2 and 7. However, the adducts when heated in 1,2,3,4-tetrahydronaphthalene (tetralin) preferentially provided the fused pyridone rings 4 and 10 and the fused pyrrole rings 5 and 11.
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