Re: Keynote Paper 4:(fao METH-COHN Otto)
Nick Turner (N.J.Turner@exeter.ac.uk)
Wed, 21 Jun 95 10:28:18 +0100
Yours is a good question which until recently was troubling us.
However, it turns out that the reduction of aromatic nitro groups at high
pH (>10) using glucose is a well known reaction (see Vogel 4th Ed p. 724,
preparation IV,101) and has been used to prepare azoxybenzenes. The
reaction is fairly complicated and under certain conditions leads to the
formation of anilines. We have recently carried out some experiments, in
collaboration with Dr. Andy Wells at SmithKline Beecham, Tonbridge, in
which we compared the Vogel method with the "bakers yeast" method reported
by the Korean group (Tetrahedron Lett 1994, 3965). Essentially there was no
difference and thus we conclude that their so called "bakers yeast"
reduction is simply a variation on a well-known reaction. Presumably the
yeast acts a slow-release source of carbohydrates. At pH 10 and 70oC the
enzyme activity would clearly be very low.
Under our conditions (pH 6-7, room temp) we are seeing genuine
enzyme-catalysed reduction (Tetrahedron Lett 1994, 7867). The work has
recently progressed significantly beyond the results reported in the
ECTOC/Tet Lett papers and we shall soon be publishing further details
including a discussion of the Korean work along the lines outlined above.
Once again, well spotted! Regards NICK.
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