References
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Wei X.
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<A NAME="RD08902ST-1B">1b</A>
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Blackburn L.
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Kanno H.
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<A NAME="RD08902ST-6">6</A>
Corey EJ.
Gilman NW.
Ganem BE.
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<A NAME="RD08902ST-8A">8a</A>
To
a mixture of cinnamyl alcohol (134 mg, 1 mmol), sodium cyanide (49
mg, 1 mmol) and activated manganese dioxide (Aldrich 21764-6, 1.31
g, 15 mmol) stirring in tetrahydrofuran (10 mL), was added methanol
(0.2 mL, 5 mmol). The reaction was heated to reflux and left to
stir for 5 hours. The resulting mixture was then filtered through Celite® and
the solvent removed under reduced pressure. Extraction with dichloromethane
(50 mL), was followed by washing with water (2 × 10 mL)
and then saturated sodium chloride solution (10 mL), before drying
over magnesium sulfate. Filtration and removal of solvent in vacuo
gave methyl trans-cinnamate (113 mg,
70%), as light yellow crystals, which was pure according
to 1H NMR spectroscopy, mp 35 °C; lit.
[14a]
mp 35-36 °C.
<A NAME="RD08902ST-8B">8b</A>
Ethyl acetate, methyl
acetate, acetonitrile and dimethyl formamide were also investigated
as co-solvents without leading to improved yields.
<A NAME="RD08902ST-9">9</A>
Alternatives to NaCN have also been
investigated (e.g. KCN, LiCN, NaCl2O, NaI, NaSCN, NaSCOMe,
KOCN (using 2 equiv in each case). Only KCN (64%), LiCN
(56%) and KOCN (6%) afforded methyl cinnamate.
<A NAME="RD08902ST-10">10</A>
Most of the esters and amides are
known compounds and were identified by comparison of their 1H
NMR spectra with published data. Novel compounds were fully characterised.
<A NAME="RD08902ST-11">11</A>
A mixture of benzyl alcohol (108 mg,
1 mmol), iso-butylamine (0.5 ml, 5 mmol),
sodium cyanide (49 mg, 1 mmol) and activated manganese dioxide (1.31
g, 15 mmol) was stirred in THF (15 mL) at r.t., After 30 min, a
second batch of activated manganese dioxide (1.31 g, 15 mmol) was added
and the reaction stirred for a further 23.5 h. The resulting mixture
was then filtered through Celite® with additional
dichloromethane being used to wash the Celite®. The
combined organics were washed with water (2 × 20 mL) and
then dried over magnesium sulfate. Filtration, removal of solvent
in vacuo and chromatography on silica (petroleum ether-ether,
2:3) gave N-iso-butylbenzamide (153 mg, 86%),
as a white solid, which was pure according to
1H
NMR spectroscopy; mp 55.8-56.1 °C (lit.
[14b]
mp
54-56 °C).
<A NAME="RD08902ST-12">12</A>
For an alternative manganese dioxide
route to a limited range of carboxamides, which does not use sodium
cyanide, see ref.
[5]
<A NAME="RD08902ST-13">13</A>
Preliminary studies indicate that
improved yields can be obtained with allylic alcohols if low temperatures
(0 °C) are employed; the use of hexane as solvent can also
improve yields in some cases. Further studies are being carried
out which will be included in a full paper.
<A NAME="RD08902ST-14A">14a</A>
Kendall J.
Booge JE.
J.
Am. Chem. Soc.
1916,
38:
1712
<A NAME="RD08902ST-14B">14b</A>
Gajda T.
Zwierzak A.
Synthesis
1981,
1005
