From: Olga Tšubrik (olga7$##$ut.ee)
Date: Mon Dec 06 1999 - 13:48:06 EST
Dear colleagues,
I have some problems in the synthesis of Ph-NH-NH-P(+)Ph3 Br(-)
(2-phenylhydrazino)triphenylphosphonium bromide. I do it by condensing
phenylhydrazine with triphenylphosphine dibromide in the presence
of triethylamine under argon (Horner, Oediger, Liebigs Ann. Chem., 1959,
627, 142).
When I use commercially available reagent triphenylphosphine
dibromide Ph3PBr2 (from Aldrich) I have got 89% yield of the produkt.
But I have also prepared Ph3PBr2 from triphenylphosphine and bromine
(under argon, all glassware was oven-dried, I prepared it just before
use by addition of bromine to Ph3P in dry bensene or methylene chloride
with cooling). Then I react Ph3PBr2 immediately with phenylhydrazine. In
this case I have only ca 50% yield of the product. Why only 50%?
Can someone give me some ideas and suggestions.
Thank in advance.
Olga Tshubrik
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