Ethanol → 1,3-Dihydroisobenzofuran

Participants

Reaction Steps

To a one liter 3-neck flask under nitrogen was added 250 ml of dry tetrahydrofuran followed by 4.61 g of lithium aluminum hydride (95%). Phenolphthalein (20.0 g) dissolved in 250 ml of dry tetrahydrofuran was added dropwise to the well-stirred lithium aluminum hydride suspension at a rate to prevent a violent reaction. Addition was completed in 90 minutes. The reaction mixture was then refluxed for 30 minutes by applying external heat. Silica gel TLC in ether showed some unreacted phenolphthalein was present. Refluxing was continued for 21/2 hours. Silica gel TLC in ether showed no further changes. The heat source was removed, and 60 ml of ethyl acetate was added to the reaction mixture to destroy unreacted lithium aluminum hydride. Then 200 ml of saturated ammonium chloride was added and the pH adjusted to about 4 to 6 with 1N HCl. The organic portion was decanted and the solvent removed under reduced pressure leaving a yellow oil. The oil was dissolved in 350 ml of ether and the ether extracted with a total of 4 liters of 10% sodium carbonate to remove unreacted pheolphthalein. Then the ether was removed leaving a yellow oil which was dissolved in one liter of boiling 20% ethanol: 80% water mixture to give a clear, pink-red solution. Upon cooling, an off-white crystalline product formed, and the solution was allowed to stand in the refrigerator for three days. The solids were filtered, washed with room temperature 20% ethanol to remove a yellow-pink color and collected giving a very pale yellow, crystalline product. Recrystallization from 750 ml of 20% ethanol gave 11.8 g of the corresponding phthalan as a very pale yellow crystalline solid. Silica gel TLC in ether showed only one spot corresponding to the phthalan.

Provenance & Evidence