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To a dry 3 liter 3-necked flask equipped with mechanical stirrer, thermometer and nitrogen inlet was added 1.5 liter of dry dichloromethane (a) and 95 g of dry pyridine (b). The stirred solution was cooled ot an internal temperature of 5° and 60 g of chromium trioxide (c) was added in one portion. The mixture was stirred an additional 5 minutes and then allowed to warm to 20° over 60 minutes, giving a solution of Collins reagent. A solution of 16.2 g of trans-5-phenyl-4-penten-1-ol (d) in 100 ml of dry dichloromethane (e) was then added rapidly. The mixture was stirred an additional 15 minutes and then decanted from the residue. The residue, a black tar, was washed with ether (3×500 ml) and the combined organic solution was worked up in the usual manner. Evaporation of the solvent gave the aldehyde (15 g) as a pale yellow liquid. TLC; silica gel HF254 ; ethyl acetate/benzene 1:9 Rf 0.50.

1. customdecanted from the residue
2. washThe residue, a black tar, was washed with ether (3×500 ml)
3. customEvaporation of the solvent