Y. J. Chang et al./Chemical Papers 66 (1) 33–38 (2012)
37
Fig. 1. Formation of 1-cyclohexen-1-ylethanon in NCW.
ZnSO4, all of which generated a high concentration
of H+.
tional Natural Science Foundation of China (Nos. 21073064,
21003049).
Initially, alcohol, I attacked by a proton originating
from NCW results in the formation of a tertiary carbo-
nium ion which then expels a proton from an adjacent
carbon atom, giving 1-ethynylcyclohex-1-ene, II. Next,
electrophilic attack produces a secondary carbonium
ion, which is attacked by H2O and results in III. Sub-
sequently, III eventually forms α,β-unsaturated ke-
tone, IV via tautomerisation. Such enyne intermedi-
ates have been detected spectroscopically (Parham et
al., 1954) and they have even been isolated (Ansell et
al., 1956; Smissmann et al., 1956) on several occasions.
However, a mechanism not involving an enyne as
intermediate was also probable in NCW. A proton
from NCW attacks the triple bond of I to form a car-
bonium ion, then through the cation exchange it forms
a tertiary carbonium ion which then expels a proton
from an adjacent carbon atom, generating III, which
then forms IV through tautomerisation.
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Conclusions
We performed the Rupe rearrangement of 1-
ethynylcyclohexan-1-ol in NCW in order to obtain 1-
cyclohexen-1-ylethanon as the main product and ex-
amine the influence of reaction r/w mole ratio, tem-
perature, and time on the product yield. The yield was
low (50 %) at 260◦C with the reaction time set at 60
min. However, when NaHSO4, FeCl3, or ZnSO4 was
introduced, the yield increased markedly and reached
as high as 88 % in the NaHSO4 aqueous solution un-
der the same reaction conditions. The catalytic ability
of additives decreased in the order: NaHSO4, FeCl3,
ZnSO4. A probable mechanism of the Rupe rearrange-
ment reaction of 1-ethynylcyclohexan-1-ol was pro-
posed based on the reaction products and reaction
principles. Compared with the traditional method,
this simple experimental procedure, rapid reaction,
high yield, and easy product detection could be ex-
pected to contribute to the development of a clean and
environmentally benign strategy for the rearrange-
ment of 1-ethynylcyclohexan-1-ol.
Kruse, A., & Dinjus, E. (2007). Hot compressed water as re-
action medium and reactant. Properties and synthesis re-
Acknowledgements. This research was supported by the Na-