ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 1, pp. 162!163. + Pleiades Publishing, Ltd., 2006.
Original Russian Text + A.V. Arkhipova, K.V. Malkova, T.N. Sokolova, V.R. Kartashov, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80,
No. 1, pp. 162!163.
Synthesis of a New Thiocarbamate by the Reaction of Benzyl
Thiocyanate with Camphene, Catalyzed by Heteropoly Acids
A. V. Arkhipova, K. V. Malkova, T. N. Sokolova, and V. R. Kartashov
Nizhni Novgorod State Technical University, Nizhni Novgorod, Russia
Received May 30, 2006
Abstract-The reaction of benzyl thiocyanate with camphene in the presence of heteropoly acids, 12-phos-
photungstic and 12-silicotungstic, at 65oC was studied. S-Benzyl (1,7,7-trimethylnorbornyl)thiocarbamate was
prepared in 66% yield.
Previously  we reported on the reactions of a se-
ries of thiocyanates with a natural terpene, camphene,
in the presence of concentrated sulfuric acid, yielding
the coresponding N-substituted thiocarbamates. We
examined the possibility of using heteropoly acids
(HPAs) for catalyzing this reaction. It is of funda-
mental importance for catalysis that HPAs have high
Brønsted acidity, considerably exceeding that of com-
mon mineral acids and traditional acid catalysts .
By the reaction of benzyl thiocyanate with cam-
phene in the presence of the most typical tungstic
prepared a new camphene derivatives, S-benzyl (1,7,7-
It should be noted that benzyl thiocyanate does not
react with camphene in the presence of sulfuric acid
as catalyst .
The reaction was performed in acetic acid, taking
into account published data on related syntheses of
N-substituted thiocarbamates . Heteropoly acids of
the Keggin structure in acetic acid are relatively weak
electrolytes dissociating by the first step only , but
in the acidity they exceed by 235pK units the tradi-
tional acid catalyst, sulfuric acid .
The initial camphene : thiocyanate molar ratio was
1 : 1.48. The reaction was performed with water addi-
tions, because without water the HPA precipitates. It
should also be noted that small amounts of water al-
low the reaction to be performed at a relatively low
It is known  that camphene can isomerize in
acid-catalyzed reactions; as a result, several com-
pounds are usually formed. Comparison of the
NMR spectrum of the purified product with those of
various camphene derivatives  allowed identifica-
tion of the compound obtained.
Analysis of the mother liquor revealed formation
of small amounts of isobornyl acetate and isoborneol
along with the major product, benzyl (1,7,7-trimethyl-
norbornyl)thiocabamate. These by-products were iden-
tified by GLC using authentic samples.
We optimized the concentrations of the acids used,
reaction temperature, and reactant weight ratio. We
found that the reaction mixture, when heated above
65oC, undergoes tarring (as judged from its color and
amount of the bottoms), which considerably decreases
the yield of the target product.
The heteropoly acid H
catalyzes the reaction in question. On the whole, how-
ever, it does not surpass in performance H
This fact is consistent with close strength of these
acids. It is known that the strength of heteropolytung-
stic acids depends on the nature of the central atom