Hydrochloric Acid → 6-Bromo-3'-methylspiro[chroman-2,1'-cyclopentan]-4-one

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Reaction Steps

A mixture of 1-(5-bromo-2-hydroxy-phenyl)-ethanone (2.193 g, 10.2 mmol), 3-methylcyclopentanone (2 g, 20.4 mmol) and pyrrolidine (1.67 mL, 19.43 mmol) in MeOH (42 mL) was stirred at room temperature overnight, followed by reflux for 2 days. The mixture was concentrated in vacuo to give the residue, which was added water and HCl (36%) until pH=1. The mixture was extracted with EtOAc and then the organic layer was concentrated to give 6-bromo-3′-methylspiro[chroman-2,1′-cyclopentan]-4-one, which was purified by chromatography (PE:EA 300:1-200:1) (2.3 g, 76%). 1H NMR (CDCl3): 7.94 (d, 1H), 7.52-7.49 (m, 1H), 6.83-6.79 (m, 1H), 2.79 (m, 2H), 2.39-2.22 (m, 0.5H), 2.21-1.95 (m, 3H), 1.91-1.75 (m, 1H), 1.67-1.57 (m, 1H), 1.51-1.41 (m, 0.5H), 1.31-1.15 (m, 1H), 1.08-0.98 (m, 3H).

Provenance & Evidence