Boron trifluoride → 2,2,3-Trimethyl-4-(3-oxo-1-cyclopenten-1-yloxy)-6-cyano-3-chromanol

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Reaction Steps

2.1 g of 1,3-cyclopentanedione are dissolved in 200 ml of THF under N2, 650 mg of NaH (80% in mineral oil) are added, the mixture is stirred for 1 hour, a solution of 4.6 g of 2,2,3-trimethyl-3,4-epoxy-6-cyanochroman ("IIa") in 20 ml of THF, then 2.4 ml of BF3 etherate are added successively and the mixture is stirred overnight at 20°. The mixture is evaporated and the 2,2,3-trimethyl-4-(3-oxo-1-cyclopenten-1-yloxy)-6-cyano-3-chromanol ("A") obtained is purified by chromatography on silica gel (ethyl acetate/methanol 100:1); m.p. 204°-206° (from isopropanol).

Provenance & Evidence