N-Formylmorpholine → 4,4-dimethyl-3,4-dihydro-2H-thiochromene-6-carbaldehyde

Participants

Reaction Conditions

Reaction Steps

The 6-bromo-4,4-dimethyl-3,4-dihydro-2H-1-benzothiopyran (2.62 g, 10 mmol) prepared in the previous step (b) and in solution in 5 ml of anhydrous THF, is added at 66° C. to magnesium (0.30 g, 12 mmol) in 1 ml of anhydrous THF. The mixture is agitated at reflux of the THF until quasi-complete consumption of the magnesium (30 minutes). The reaction medium is then cooled to −10° C. and at this temperature, the N-formylmorpholine (1.2 ml, 12 mmol) in 2 ml of THF is added. At the end of the addition, the reaction medium is brought to ambient temperature for 1 hour. After hydrolysis by 10 ml of an aqueous saturated NH4Cl solution at 0° C. and extraction with ethyl ether (5×30 ml), the organic phase is dried over MgSO4, filtered and evaporated. The raw product is purified by flash chromatography on silica (eluent petroleum ether:ethyl ether:100:5). 2.00 g of 6-formyl-4,4-dimethyl-3,4-dihydro-2H-1-benzothiopyran is obtained (yield=61%).

Provenance & Evidence