5-ACYL-2H-PYRAN-2-ONES IN THE SCHMIDT REACTION:MIGRATION OF THE PYRAN-2-ONE RING

摘要

The Schmidt reaction of the 5-acyl-2H-pyran-2-ones(1a-f)using NaN_3/H_2SO_4 was investigated.The reaction proceeded with complete regioselectivity in the 5-acetyl series to give the corresponding 5-acetylamino derivatives(2a-c)via pyran-2-one ring migration.In contrast,the reaction applied to the 5-benzoyl-2H-pyran-2-ones(1d-f)led to the formation of both regioisomers,(2d-f)and(3d-f).The latter resulted from the phenyl shift in this reaction and were obtained as minor products.The 3,5-diacylamino-2H-pyran-2-ones(2a)and(2d)were selectively debenzoylated at position 3.