Boron tribromide → 2,4-Difluororesorcinol

Participants

Reaction Steps

A solution of Compound 3 (0.64 g, 3.7 mmol) in dichloromethane (0.3M, anhydrous) at room temperature under nitrogen is treated with boron tribromide solution (3.0 equivalents, 1.0M in dichloromethane, Aldrich or Fluka) via syringe over five minutes. The reaction is monitored by TLC, and takes 24-48 hours to reach completion; an additional 0.5 equivalents of boron tribromide solution is sometimes necessary to drive the reaction to completion. The reaction mixture is carefully quenched with water, and the resulting mixture is stirred until all precipitate dissolves. The resulting solution is extracted twice with ether. The ether extract is washed twice with brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure and purified by sublimation to yield 0.49 g (90%) of Compound 4 as a colorless crystalline solid: m.p. 100°-101° C.; 1H NMR (CDCl3) 8.99 (s, 1H), 8.62 (s, 1H), 6.32 (td, 1H), 6.05 (m, 1H); 19F (CDCl3) 145.4 (m, 1F), 156.0 (m, 1F). Anal. calc. for C6H4O2F2 ; C, 49.33; H, 2.76. Found: C, 48.96; H, 3.21; N, 0.028.

Provenance & Evidence