ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 11, pp. 1723−1724. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © L.V. Timokhina, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 11, p. 1729.
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Alcoholysis of 3-Alkoxy-2-cyclohexene-1-thiones
L. V. Timokhina
aFaworsky Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
Irkutsk, 664033 Russia
e-mail: tim@irioch.irk.ru
Received October 29, 2008
DOI: 10.1134/S1070428009110268
3-Alkoxy-2-cyclohexene-1-thiones Ia and IIa that we
formerly synthesized are exclusively reactive compounds
[1]. They especially readily react with nucleophilic
reagents at the C–Oalk bond (aminolysis, thiolysis) due
to the conjugation of the alkoxy group with the
thiocarbonyl fragment [1, 2]. The oxygen analogs of
thiones do not enter into such reactions or react in far
more stringent conditions [3].
thione (Ia). A solution of 0.7 g (3.8 mmol) of
ethoxythioketone IIa and 0.02 g of TsOH in 3 ml of
methanol was kept for 17 h at 10°C, then the reaction
mixture was poured in 30 g of ice-water mixture, the
precipitate was filtered off. We obtained 0.64 g (99%)
of methoxythioketone Ia identical to an authentic sample
[1].
Reaction of 5,5-dimethyl-3-methoxy-2-
cyclohexene-1-thione (Ia) with ethanol. Under the
conditions described above in the reaction of
methoxythioketone Ia with ethanol a mixture was isolated
of ethoxythioketone IIa and methoxy derivative Ia in a
ratio 1:1 (by 1H NMR data). 1H NMR spectrum, δ, ppm,
compound Ia: 0.88 s (6H, 5-Me2), 2.23 d (2H, H4), 2.73
s (2H, H6), 3.77 s (CH3O), 6.47 t (1H, HC=); compound
IIa: 1.03 s (6H, 5-Me2), 1.36 t [CH3CH2O,
3J(CH3CH2O) 7.0 Hz], 2.22 d (2H, H4), 2.72 s (2H, H6),
3.98 q (CH3CH2O), 6.42 t (1H, HC=).
One more proof of the high lability of the
heterosubstituent in compounds Ia and IIa is their
alcoholysis. It turned out that in alcoholic medium in the
presence of traces of p-toluenesulfonic acid at 10–20°C
easily occurred transalkylation of alkoxythioketones Ia
and IIa. For instance, 5,5-dimethyl-3-ethoxy-2-
cyclohexene-1-thione (IIa) in methanol completely
converted into 5,5-dimethyl-3-methoxy-2-cyclohexene-1-
thione (Ia). The similar conversion of 5,5-dimethyl-3-
ethoxy-2-cyclohexene-1-one (IIb) occurred only at boiling
of the reaction mixture.
5,5-Dimethyl-3-methoxy-2-cyclohexene-1-one
(Ib). A solution of 0.3 g (1.8 mmol) of ethoxyketone IIb
and 0.01 g of TsOH in 7 ml of methanol was boiled for 2
h. The residue after evaporation of methanol was
dissolved in benzene and washed with water. The benzene
extract was dried with Na2SO4 and evaporated in a
vacuum. We obtained 0.26 g (96%) of methoxyketone
Ib identical to an authentic sample [4].
1H NMR spectra were rgistered on a spectrometer
Bruker DPX-400 (operating frequency 400.1 ΜHz) from
solutions in CDCl3, internal reference HMDS. The
reaction progress was monitored by TLC on Silufol UV-
254 plates, eluent chlorofor–ethyl acetate, 2:1.
In its turn methoxythioketone Ia reacted with ethanol
giving an equilibrium mixture of compounds Ia and IIa.
5,5-Dimethyl-3-methoxy-2-cyclohexene-1-
Scheme.
Me
Me
Me
Me
EtOH/H+
MeOH/H+
EtO
X
MeO
X
IIà, IIb
Ià, Ib
X = S (a), O (b).
1723
Timokhina
