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From: "guest" <guest@webshack-cafe.com>
Newsgroups: alt.drugs.chemistry
Subject: Isomerization of Allylbenzene
Date: 8 Nov 97 18:44:35 GMT
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Isomerization of Allylbenzene
=======================
Isomerization of Allylbenzene via Hydroxide Ion Extraction. [M Halpern, Y
Sasson & M Rabinovitz, J. Org. Chem. 1983, 48, 1022-1025] This is a method
of isomerising allyl-benzenes to propyl-benzenes in aqueous conditions at
only 70 C.

Allylbenzene was isomerized to trans- and cis-(-methyl-styrene.  The
reaction was run under varying conditions of mechanical stirring speed,
quat structure, initial catalyst concentration, temperature, catalyst
counterion, and aqueous NaOH concentration. Standard reaction conditions
consisted of 1.42 M allylbenzene in toluene, 5 mol % tetrabutylammonium
bromide (TBAB), 40 to 50% aqueous NaOH, 75 ° C and stirring speed of 850
rpm [at least 550 rpm is needed].  Other phase transfer catalysts can be
used. But ethyl-tri-octyl-ammonium undergoes extensive decomposition within
1.5 h due to the available ethyl group being convenient for Hoffman
elimination. Quats below a minimum organophilicity (eg.
tetra-propyl-ammonium) are ineffective. Catalyst decomposition may
effectively stop the reaction at 70%-98% conversion, depending on reaction
conditions.  [Quats containing methyl groups won't work here. They are
quickly degraded by the strong alkali. So quats from household products
can't be used. But, you never know - try it and find out!]


Oxidation of Isosafrole using performic acid.
=================================
Oxidations of alkenes have also been done using peracetic acid, perbenzoic
acid etc. I've seen mention of a method using per-boric acid.




