3,4-dihydro-2H-pyran → HCID 59582216, compound

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Reaction Steps

To a flask (1 L) under N2 at room temperature, were added 3,6-dibromocarbazole (50 g), dichloromethane (500 mL), 3,4-dihydro-2H-pyran (40 g), p-toluenesulfonic acid monohydrate (1 g). The reaction was stirred overnight. NaHCO3 (3 g) was added, and the reaction was stirred for 1 h. After filtration, the solvent in the filtrate was removed by evaporation. MeOH (1 L) was added for reflux under N2 for 2 h. Filtration when it was warm gave 37.5 g product. The MeOH (800 mL) was removed by evaporation, and solid came out. Filtration gave 12.5 g product. Both products are white, single spot on TLC, and GS-MS and 1H NMR showed they are pure product. The overall yield is 80%. Second and Third Reactions following the reaction scheme above produce compound (2) and (3), respectively, according to the scheme below:

Provenance & Evidence