[CH3:1]/[C:2](=[CH:5]\[F:6])/[CH2:3]O.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.N(C(OCC)=O)=NC(OCC)=O.[C:38]1(=[O:48])[NH:42][C:41](=[O:43])[C:40]2=[CH:44][CH:45]=[CH:46][CH:47]=[C:39]12>C1COCC1>[C:38]1(=[O:48])[N:42]([CH2:1]/[C:2](/[CH3:3])=[CH:5]/[F:6])[C:41](=[O:43])[C:40]2=[CH:44][CH:45]=[CH:46][CH:47]=[C:39]12A solution of (E)-2-methyl-3-fluoroallyl alcohol (prepared in Step D) (17.11 g), triphenylphosphine (49.80 g), diethyl azodicarboxylate (33.06 g) and phthalimide (27.93 g) in THF (500 ml) is stirred at room temperature overnight. The THF is evaporated and the oily residue is extracted three times with hexane giving a powdery solid which is subsequently extracted three times with ether. The combined extracts are evaporated and the residue (63 g) is purified by chromatography on silica gel (950 g) using a mixture of 20% diethyl ether/light petroleum. The major fraction is a colorless crystalline mass (28.6 g, 69% yield) which is essentially pure product. A small portion can be crystallized from hexane to give (E)-1-phthalimido-2-methyl-3-fluoro-2-propene as colorless plates: m.p. 57°-58° C.
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