The synthesis of the previously unreported 5,6‐dimethoxycyclopentano[h]isoquinoline (1) by way of a Pomeranz Fritsch ring closure of the diethyl acetal of 4,5‐dimethoxy‐7‐indanylidene aminoacetaldehyde (3) is reported. Acetylation of the N‐oxide of 1 yielded the corresponding N‐acetyl‐1‐isoquinolone, which readily converted to the 1‐isoquinolone on exposure to atmospheric moisture. Several diesters of the dihydroxy analog of 1 are reported.