Pyrrole → 1-(2-Fluoro-4-iodophenyl)-2,5-dimethyl-1H-pyrrole

Participants

Reaction Steps

A 500 mL round bottom flask was charged with 2-fluoro-4-iodoaniline (53.3 g, 220 mmol), toluene (250 mL), TsOH·H2O (0.43 g, 2.3 mmol, 1 mol %), and acetonylacetone (30.8 g, 270 mmol, 1.2 eq). The solution was warmed to reflux under Dean-Stark conditions for 1 h, at which point GC/MS and TLC analysis indicate complete conversion to the pyrrole. The solution is cooled to room temperature, washed with aqueous NaHCO3, dried over MgSO4, filtered, and concentrated to provide a dark brown oil which crystallized upon standing (crude yield=72.8 g, 103% of theory). This material was homogeneous by HPLC and 1H nmr, and was suitable for use in the next reaction. An analytical sample was prepared by dissolving in 210 mL of hot hexanes, cooling, then concentrating to 50% of the original volume. Cooling in an ice bath with rapid stirring provided 35.5 g (49% recovery) of a brown, granular solid (m.p. 68-70° C.). 1H NMR (CDCl3): d 7.43 (t, J=27 Hz, 2H), 7.13 (t, J=20 Hz, 1H), 5.94 (s, 2H), 2.02 (s, 6H); 13C NMR (CDCl3) d 158.3 (d, J=254 Hz), 131.6, 128.9, 127.8 (d, J=3 Hz), 122.0, 120.3 (d, J=23 Hz), 106.4, 12.4; MS (El): m/z 268 (100).

Provenance & Evidence