3,4-(Methylenedioxy)-beta-methylstyrene = isosafrole
"Three-component synthesis of (E)-,-unsaturated amides of the piperine family"
Rainer Schobert* , Sven Siegfried and Gary J. Gordon
J. Chem. Soc., Perkin Trans. 1, 2001, (19), 2393 - 2397
Results and discussion
... Olefination with ethylidenetriphenylphosphorane produced
cis-trans-isomeric mixtures of 3,4-(methylenedioxy)--methylstyrene ...
Experimental
3,4-(Methylenedioxy)--methylstyrene
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 0 °C.
The mixture was warmed to room temperature and stirred for 60 min.
A solution of piperonal 3a (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 distillation, bp 121 °C/15 Torr
(lit.[17] bp 123 °C/11.5 Torr), 3.0 g (18.5 mmol, 92%) as a colourless oil,
mixture of Z- and E-isomers (Z-E = 1:10)
[17] R. Hoering and G. Baum, Chem. Ber., 1909, 42, 3080
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