Reaction #2139955

Reaction equation

3-benzyloxy-8-ethoxy-4,7-difluoro-6H-benzo[c]chromen-6-one

compound

4-bromo-1-ethoxy-2-fluorobenzene

ethylene glycol dimethyl ether

sodium borohydride

→

3-benzyloxy-8-ethoxy-4,7-difluoro-6H-benzo[c]chromene

Yield 78.0%

Solvents

THF

Conditions

Workup

1. 1
   workup.ADDITION2.37 ml (23.0 mmol) of boron trifluoride/THF complex were added with ice-
2. 2
   Temperaturecooling
3. 3
   OtherThe mixture was subjected to conventional purification

Procedure

2.00 g (5.24 mmol) of 3-benzyloxy-8-ethoxy-4,7-difluoro-6H-benzo[c]chromen-6-one, the compound of Example 841, were dissolved in 12 ml of THF, and 2.37 ml (23.0 mmol) of boron trifluoride/THF complex were added with ice-cooling. 24 ml of ethylene glycol dimethyl ether and then in portions 530 mg of sodium borohydride were subsequently added. The mixture was subsequently stirred at room temperature for 18 hours and then transferred onto ice. The mixture was subjected to conventional purification, giving 1.5 g (78% of theory) of 3-benzyloxy-8-ethoxy-4,7-difluoro-6H-benzo[c]chromene as colourless crystals. These were dissolved in THF, hydrogenated at a pressure of 1 bar in the presence of 0.6 g of Pd/C (5%), filtered and evaporated, giving 1.2 g (99% of theory) of 8-ethoxy-4,7-difluoro-3-hydroxy-6H-benzo[c]chromene as colourless crystals.

Source