Methane, dichloromethoxy- → HCID 10397697, compound

Participants

Reaction Steps

A solution of 6-methoxy-3,4-dihydrobenzopyran (133.0 g, 811 mmol) in dry methylene chloride (1850 mL) was cooled to 5° under nitrogen and titanium tetrachloride (145 mL, 250.2 g, 1319 mmol) was added dropwise over 15 minutes. Upon completion of this addition dichloromethylmethylether (60 mL, 76.26 g, 663 mmol) was added dropwise over 45 minutes. A slight exotherm was observed during the addition (reaction temperature=16°). The cooling bath was removed and the mixture allowed to stir for three hours, then quenched by the dropwise addition of water (300 mL). The resulting mixture was poured into water (1000 mL), the layers separated, and the organic layer washed with water (1000 mL). The combined aqueous layers were back extracted with methylene chloride (500 mL), then the combined organic extracts were washed with brine (2×1000 mL), dried (Na2SO4) and concentrated to a dark oil (152.0 g). Purification by preparative HPLC (Waters Prep 500, 9:1 hexane:ethylacetate as eluant) afforded, in order of elution, 6-methoxy-3,4-dihydrobenzopyran-5-carboxaldehyde (32.52 g, 20.9%) m.p. 52°-54°, 6-methoxy-3,4-dihydrobenzopyran-8-carboxaldehyde (31.83 g, 20.4%) m.p. 69°-71°, and 6-methoxy-3,4-dihydrobenzopyran-7-carboxaldehyde (31.49 g, 20.2%) m.p. 57°-59°.

Provenance & Evidence