4-(3-Bromophenoxy)butanoic acid → 8-Bromo-3,4-dihydrobenzo[b]oxepin-5(2H)-one

Participants

Reaction Conditions

Reaction Steps

To a stirred suspension of polyphosphoric acid (PPA, ca. 60 g) and celite (ca. 40 g) in 100 mL toluene was added crude 4-(3-bromophenoxy)butanoic acid 7 (ca. 58 mmol) in one portion, 10 mL toluene rinse. The resultant suspension was heated at 110° C. for 5 hr. The toluene was decanted through a plug of celite and the remaining slurry was washed repeatedly with toluene and ethylacetate. The eluent was concentrated and purified by flash column chromatography (4:1 hex:EtOAc) to give 8-bromo-3,4-dihydrobenzo[b]oxepin-5(2H)-one (7 g, ca. 50% y) 8. 1H NMR (DMSO-d6, 500 MHz) 7.55 (d, J=8.5 Hz, 1H), 7.37 (d, J=1.5 Hz, 1H), 7.35 (dd, J=8.5, 1.5 Hz, 1H), 4.24 (t, J=6.5 Hz, 2H), 2.79 (t, J=7.0 Hz, 2H), 2.14 (m, 2H).

Provenance & Evidence