Trifluoroacetic acid → 5,6-Dihydrophenanthridine

Participants

Reaction Steps

The intermediate dihydrophenanthridine was prepared from 8-fluoro-6-methylphenanthridine, (Example 32, Method A, Step b, 2.00 g, 9.45 mmol), by treatment with sodium borohydride (1.79 g, 47.4 mmol) and trifluoroacetic acid (2.9 mL, 37.9 mmol) in tetrahydrofuran (38 mL). In a separate, second step, the dihydrophenanthridine was treated with triethylamine (2.7 mL, 19 mmol) and 3-fluoro-4-methoxybenzenesulfonyl chloride (0.78 g, 3.5 mmol, 1.1 equivalents) in dichloromethane (5 mL) according to the procedure and in the same manner as described in Example 32, Method A, Step d. The crude product was purified by re-crystallization from a mixture of ethyl acetate-hexane to yield 8-fluoro-5-[(3-fluoro-4-methoxyphenyl)sulfonyl]-6-methyl-5,6-dihydrophenanthridine as a homogeneous solid (1.08 g, 84% from the dihydrophenanthridine), m.p. 146-147° C.;

Provenance & Evidence