Water → 5,7-Dimethylchroman-2-one

Participants

Reaction Steps

A mixture of 1-hydroxy-2-acetonaphthone (10.1 g), (1A), adamantanone (9 g) and pyrrolidine (10 cm3) in toluene (300 cm3) was boiled (10 hours) and water separated. The yellow reaction mixture turned first crimson and then dark brown. Toluene was removed under reduced pressure and the residual enamine crystallised from acetone as discoloured crystals (8 g). The enamine (2) (10 g) was treated with conc. hydrochloric acid (1 cm3) in methanol (200 cm3). The crimson solution was evaporated and the residual dark oil crystallised from acetone, yielding the chromanone (3) (8.4 g) as yellow needles. The chromanone (0.5 g) was reduced by sodium borohydride (0.5 g) in methanol to yield the chromanol (4) (0.32 g) which was heated with anhydrous copper sulphate to give HC7 (formula (5) R=H) (0.28 g) as a discoloured solid which was decolourised with activated charcoal and recrystallised from acetone.

Provenance & Evidence