The reaction of isoquinoline and dimethyl acetylenedicarboxylate with 1,2- and 1,4-benzoquinones: a novel synthesis of spiro[1,3]oxazino[2,3-a]isoquinolines

The 1,4-dipolar intermediate generated by the addition of isoquinoline to dimethyl acetylenedicarboxylate is trapped by 1,2- and 1,4-benzoquinones to afford spiro[1,3]oxazino[2,3-a]isoquinoline derivatives in high yields.