Rhodium
(Chief Bee)
12-02-02 19:00
No 385717
      Isosafrole via Wittig Olefination of Piperonal
(Rated as: excellent)
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3,4-(Methylenedioxy)--methylstyrene (Isosafrole)1

To a well stirred suspension of ethyltriphenylphosphonium bromide (7.5 g, 20.2 mmol) in dry THF (100 mL), a solution of n-butyllithium (12.6 mL of a 1.6 M solution in hexane, 20.2 mmol) was added dropwise over a period of 30 min at 0C. The mixture was warmed to room temperature and stirred for 60 min. A solution of piperonal (3.0 g, 20.0 mmol) in THF (25 mL) was then slowly added and the resulting mixture left stirring for a further 6 h. Water (100 mL) was added, the organic layer was separated, the aqueous phase extracted twice with diethyl ether and the combined organic phases were finally dried over MgSO4. After filtration and evaporation of the solvents the residue was eluted from silica gel with CH2Cl2 to remove phosphine oxide, and the residue was purified by vacuum distillation to give 3.0 g (18.5 mmol, 92%) of a mixture of cis- and trans-isosafrole (1:10) as a colourless oil, bp 121C/15 Torr (lit.2 bp 123C/11.5 Torr), 3.0 g (18.5 mmol, 92%) as a colourless oil, mixture of cis- and trans-isosafrole (1:10).

References:
1: J.Chem.Soc.Perkin Trans.1, 19, 2393-2397 (2001)
2: Chem. Ber. 42, 3008 (1909)
 
 
 
 
    GC_MS
(Hive Bee)
12-03-02 00:08
No 385771
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And not to mention that it will work for all our other beloved substituted benzaldehydes as well wink.

Ave Hive, synthetisandi te salutant!