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Synthesis of MDP2P From 1,3-Benzodioxole
by Friedel-Crafts Alkylation with 2-Nitropropene

Written by Scooby Doo

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To a 3-necked 500 ml flask under a nitrogen atmosphere was added 300 mL of dry DCM, 0.1 mole of 2-Nitropropene (8.7g) and 0.5 moles of 1,3-Benzodioxole (61 g). The flask was then secured within a dewar flask sitting on top of a magnetic stirplate. Dry ice was added to the dewar flask which was filled with acetone until a temperature of approx -78C was acquired. Once the internal flask temperature of -70C was reached, 0.1 mole (19 g) of TiCl4 was dripped slowly into the stirred solution. The temp started to rise so the addition was controlled to keep the internal flask temp around -60C to -70C. The flask was then stirred for 30 mins at -70C, by which time the precipitate which formed from the addition had dissipated. The dewar flask was removed and the stirring solution was allowed to warm up to room temperature, during which time the black solution will change viscosity and colour.

To hydrolyze the formed nitro-titanium complex, 100 mls of water was added to the solution which was then refluxed for 2 hours. During the reflux a brown gas (probably NO2) is evolved. The flask was cooled and vacuum filtered (cleans it up a lot) the water layer seperated and discarded. The organic layer was then washed with 3x200 mL of 10% NaOH and 1x200 mL of a brine solution. It was then dried with magnesium sulfate, the DCM evaporated and resulting orange-yellow oil vacuum distilled. The 1,3-Benzodioxole came over at 40-45C at 10 mbar then a yellow-green fluorescent oil (MDP2P) began distilling at 135C at 3 mbar.

8 grams of MDP2P was collected, corresponding to 45% yield from 2-Nitropropene or 23.5% from 1,3-Benzodioxole (calculated on the amount of 1,3-Benzodioxole not recovered during workup).

Reference: Tetrahedron Letters, Vol 29, No 24, pp. 2977-2978 (1988)