Synthesis of Isoquinoline-Derived Diene Esters and Quinolin-2(1 H )-ylidene-Substituted 1,5-Diones from Enynones and (Iso) Quinoline N -Oxides.

An efficient synthetic method was developed to access isoquinoline-derived diene esters from enynones and isoquinoline- N -oxides in an atom-economic manner. The isoquinoline-substituted diene esters were obtained in moderate to excellent yields via [3 + 2]-cycloaddition and isoxazole ring opening followed by a [1,5]-sigmatropic rearrangement reaction, which resulted in one C-C and two C-O bond formations. Further, quinolin-2(1 H )-ylidene-substituted 1,5-diones were achieved by reaction of enynones with quinoline- N -oxides in very good to high yields.