Pyrano(2,3-g)indole-2-carboxylic acid, 1,7,8,9-tetrahydro- → Pyrano(2,3-g)indole, 1,7,8,9-tetrahydro-

Participants

Reaction Steps

7,8-Dihydro-9H-pyrano[2,3-g]indole, 6,7-dihydro-5H-pyrano[3,2-g]indole and 5,6-dihydro-7H-pyrano[2,3-e]indole were prepared according to the procedure described in Example 3, using a mixture [(2,3-g):(3,2-f):(2,3-e)—11:1:4] of 7,8-dihydro-9H-pyrano[2,3-g]indole-2-carboxylic acid, 6,7-dihydro-5H-pyrano[3,2-f]indole-2-carboxylic acid and 5,6-dihydro-7H-pyrano[2,3-e]indole-2-carboxylic acid (3.12 g, 14.4 mmol) to produce, after flash column chromatography (and without further separation on a second column) a mixture [(2,3-g):(2,3-e)—72:28] of products (2.01 g, 80%) as a white, crystalline solid [Rf 0.46 (SiO2; dichloromethane)] which was used without further purification. Also collected was 6,7-dihydro-5H-pyrano[3,2-f] indole (250 mg, 10%) as an off-white solid [Rf 0.33 (SiO2; dichloromethane)].

Provenance & Evidence