Formaldehyde → 1,2,3,9-Tetrahydro-9-methyl-3-methylene-4H-carbazol-4-one

Participants

Reaction Steps

Kim et al. (Heterocycles 1997, 45, 2041) disclose a two-step synthesis of ondansetron. In the first step of the synthesis, 1,2,3,9-tetrahydro-9-methyl-4H-carbazol-4-one (compound of formula 1, Scheme 1) is reacted with a source of formaldehyde and morpholine in boiling glacial acetic acid to provide 1,2,3,9-tetrahydro-9-methyl-3-methylene-4H-carbazol-4-one (compound of formula 2, Scheme 1). In the second step of the synthesis, 1,2,3,9-tetrahydro-9-methyl-3-methylene-4H-carbazol-4-one is reacted with 2-methylimidazole in the presence of alumina (Al2O3) to provide ondansetron (See, Scheme 1).

Provenance & Evidence