SyntheticPage 435
Published Jul 05, 2010
A solution of PPh3 (1.05 eq, 21 mmol, 5.50 g) in anhydrous THF (100 mL) was cooled to -78oC using an actone/CO2 low temperature bath. To this cooled solution was added DIAD (1.04 eq, 20.8 mmol, 4.20 g, 4.04 mL) to give a yellow solution. The reaction was stirred for 1 hr at -78oC and under N2, after which time a white precipitate was observed. To this suspension was added the 4-pentyn-1-ol (1.25 eq, 25.4 mmol, 2.13 g, 2.32 mL) and the reaction was stirred for a further 20 min at -78oC. After this time 3,4,5,6-tetrahydrophthalimide (1.0 eq, 20.0 mmol, 3.00 g) was added in one portion, the reaction was stirred at -78oC for 1 hr before allowing to warm to RT. On warming to RT the precipitate was observed to disappear. Stirring at RT was continued for 16 hrs. The THF was removed in vacuo and the crude oil then redissoved in minimal Et2O (approx. 10 mL). This solution was cooled in the freezer for 2 hrs before filtering under vacuum to remove precipitated triphenylphosphine oxide (Nb. if precipitation does not occur, scratching the vessels glass will encourage the process). The filtrate was concentrated in vacuo and purified by column chromatography (SiO2, 10% EtOAc/Petrol) to give a colourless oil (4.28 g, 99%).