        Preparation of MDP2P from safrole using a novel Wacker catalyst
           by Rhodium - as submitted to Total Synthesis II by Strike

Safrole can be oxidized to safrole epoxide with H2O2 in a two-phase system, 
using a quaternary phosphotungstic PTC. The formed safrole epoxide is then 
isomerized to MDP2P with LiI.

Preparation of the catalyst

A suspension of tungstic acid (2.50g, 10 mmol) in 7 ml of 30% aqueous  H2O2 was 
stirred and heated to 60°C until a colorless solution was  obtained. To this 
solution, filtered and cooled to room temperature, was  added 40% w/v H3PO4 
(0.62ml, ca 2.5 mmol), and the whole was diluted to  30 ml with water. To the 
resultant soluton, 2.09g of methyltrioctylammonium chloride (97% pure, equivalent 
to 2.027g, 5 mmol) in DCM (40 ml) was added dropwise with stirring over about 
2 min. Stirring was  continued for an additional 15 min. The organic phase was 
then separated,  dried over Na2SO4, filtered, and gently evaporated on a rotary 
evaporator under reduced pressure at 40-50°C (bath) to give 3.70 g (98.4%, based 
on the quaternary ammonium salt charged) of an almost colorless syrup. 

Ref:    C. Venturello, J. Org. Chem. 53, 1553-1557 (1988)


Oxidation of safrole to MDP2P

In a 100ml three-necked, round-bottomed flask equipped with mechanical stirrer, 
thermometer and a reflux condenser, a vigorously stirred mixture of the above 
catalyst (0.7g, 0.31 mmol), safrole (13.24g, 80mmol),  benzene (35 ml) and 40% 
w/v H2O2 (5.10ml, 60 mmol) was heated to 60°C and  kept at this temperature for 
60 min (External cooling is needed!). The mixture was cooled to room temp, the 
organic phase was separated and  diluted with 30 ml Et2O. In order to remove the 
catalyst, the organic  solution was first stirred with a solution of Na2CO3 
(0.75g) and Na2SO3  (0.75g) in water (10 ml) for a few minutes, then separated, 
dried over  Na2SO4 and passed through a short column (2.5 cm diam) of silica gel  
(50g), and ~300ml anhydrous Et2O was passed through the column to ensure  
complete elution of the products. The solvent was evaporated and the  residue 
dissolved in 18 ml of tetraglyme and treated with anhydrous LiI (0.130g, 0.97 
mmol) at 130°C for 5h. After cooling, the products were distilled under vacuum, 
recovering 5.17 grams safrole (saved for the next run) and collecting 6.25 grams 
of MDP2P.

Ref: 	C. Venturello, US Pat 4,731,482
     	C. Venturello, Synthesis, 1229-1231 (1992)
