Hydrochloric Acid → racemic-3,4-dihydro-7-(phenylmethoxy)-2H-1-benzopyran-2-carboxaldehyde

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Reaction Steps

The ether ester product from example 82 (6.9 g, 22 mmoles) was dissolved in 70 ml of toluene and the solution was cooled to -78° C. (dry-ice-acetone bath). With stirring, 15.6 ml of a 25% solution of diisobutylaluminum hydride in toluene was added dropwise. The reaction mixture was stirred at -78° C. for 2 hours whereupon 2.5 ml of methanol was cautiously added followed by 2N HCl and ice. The mixture was extracted with ethyl acetate and the organic extracts were combined, washed with saturated brine, dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure. The residue (7.6 g) was chromatographed on silica gel. Elution with 9:1 toluene-ethyl acetate gave 5.6 g (70%) of racemic-3,4-dihydro-7-(phenylmethoxy)-2H-1-benzopyran-2-carboxaldehyde as a pale yellow oil.

Provenance & Evidence