                Epoxidation of Alpha-Methylstyrene and Its Lewis
                    Acid Rearrangement to 2-Phenylpropanal

                            David L. Garin, et. Al.
                     J Chem Ed, Volume 73 (6), 555  (1996)

Epoxidation of Alpha-Methylstyrene 

A mixture of 1.2 g (10 mmol) of alpha-methylstyrene, 25 mL of methylene
chloride, and 4 g of anhydrous sodium carbonate is placed in a 100mL flask
fitted with a magnetic stirring bar and in a water bath. Stir the suspension and
add 3.0 mL of 32% peracetic acid solution (14 mmol; Aldrich Chemical Co.; d=1.13
g/mL) over a period of 5-10 min. maintaining the temperature at or slightly
below room temperature. Frothing will occur. Allow the mixture to stir for 2 h
at or below 25 °C. Filter the reaction mixture and wash the filter cake with 4
mL of methylene chloride. To remove the excess peracid, prepare a small column
of alumina using a disposable glass Pasteur pipet. Wedge a small piece of filter
paper into the bowl of the pipet using a wooden applicator stick and fill with
two inches of alumina (80-200 mesh). Using another pipet, transfer the reaction
solution through the alumina column. Test this filtrate for peracid with starch
iodide test paper. If necessary, refilter through another alumina column. Remove
the solvent at ambient temperature. Analyze the product mixture via proton NMR
and determine the ratio of product to starting material by integrating the
proton signals on carbon-bearing oxygen (2.8 and 3.0 ppm) and the olefinic
protons (5.2 and 5.4 ppm) and/or the corresponding methyl proton signals (1.8,
2.2 ppm, respectively) all of which are distinctly separate even on 60 MHz
instruments.

Rearrangement of Epoxide with Boron Trifluoride Etherate

One half of the epoxide product mixture is dissolved in 10 mL of methylene
chloride in a small sample vial fitted with a magnetic stirring bar. Add 4 drops
of boron trifluoride solution (1:2 in CH2Cl2) to the vial while stirring. Cap
the vial and let the reaction proceed for 15 min. Carefully transfer the
reaction mixture through a small alumina column, prepared as before, to remove
the BF3. Remove the solvent and analyze the product via IR or NMR (the aldehyde
proton gives a doublet at 9.8 ppm, CDCl3. Unreacted styrene will be polymerized
by the BF3 and can be removed as described below. The purchased
alpha-methylstyrene reagent contains some polymeric material.

