The synthesis of pyrano[3,2-e]indoles and pryano[2,3-f]indoles as rotationally restricted phenolic analogs of the neurotransmitter serotonin

The synthesis of two rotationally restricted phenolic analogs (1a and 1b) of the neurotransmitter serotonin have been accomplished. The syntheses of 8.9-dihydropyrano[3,2-e]indole (13a) and 7,8-dihydropyrano[2,3-f]indole (13b), which formed the template for these targets, are outlined. These novel fused-indoles represent rotationally restricted phenolic analogs of 5-hydroxyindole. The reaction sequence of Claisen rearrangement, olefin hydroxylation, and intramolecular Mitsunobu reaction was used to form the fused-dihydropyran rings.