Diethyl Oxalate → 4,5-Dihydro-5,8-dimethyl-4-oxopyrano[3,2-b]indole-2-carboxylic acid

Participants

Reaction Steps

In a manner analogous to that of Example 14, 8.2 g (0.040 mole) of 1,5-dimethyl-3-hydroxy-1H-indol-2-yl methyl ketone (Example 12) was reacted with sodium metal (3.7 g, 0.16 mole) and diethyl oxalate (21.5 g, 0.20 mole) in 200 ml absolute ethanol. The red disodium salt intermediate was then converted to the title compound as described in Example 17. Two recrystallizations of the final product from DMF-water yielded yellow needles of mpt. 290°.

Provenance & Evidence