Synthesis of isoquinoline derivatives by Diels-Alder reactions of 2(1H)-pyridones having an electron-withdrawing group with methoxy-1,3-butadienes.

Diels-Alder (DA) reactions of 2(1H)-pyridones having an electron-withdrawing group at the 4-position with 2,3-dimethoxy- and 2-methoxy-1,3-butadienes gave isoquinoline derivatives. Furthermore, an isoquinoline alkaloid (6,7-dimethoxy-2-methyl-1(2H)-isoquinolone) was synthesized by elimination of hydrogen cyanide and dehydrogenation of the DA-adduct having a cyano group at the 4a-position.