VERBENONE IN THE SYNTHESIS OF o-MENTH-1-EN-3-ONE
1155
reaction progress was monitored and the composi-
tion of products synthesized was checked by GLC on
a chromatograph Chrom-5 equipped with a glass column
(2000´2 mm) packed with a Chromaton-N-AW-DMCS
carrier (0.160.20), liquid phaseApiezon L.
ized with ammonia solution, extracted with hexane to
remove the impurity of dienone IV, then with ether. On
evaporating the ether the fine crystalline product obtained
was recrystallized from ethanol. Yield 72%, mp 108
1
109°C. IR spectrum, n, cm : 3310, 3215, 3080 (NH),
3030 v.w (=CH), 2975, 2915, 2870, 2830 (CHaliph),
1660 v.s (C=Oamide + C=Oconjug.ketone), 1620 (C=Cconjug.),
1550 (NHamide). 1H NMR spectrum, d, ppm: 1.34 s and
The initial verbenone (commercial product) was
distilled at the atmospheric pressure, bp 224225°C (750
mm Hg), nD18 1.4976.
2
1.47 s (3H each, 8-CH3), 1.72 m(1H, H5a, J 13.6,
Verbenone E- and Z-oximes (II) + (III) were
obtained by a common procedure [2]. The stereoisomers
ratio (2:5) was estimated from NMR spectra by the ratio
of the integral intensity of olefin protons signals:
d 6.44 ppm at the syn-orientation of the oximine hydroxy
group (Z-isomer) and 5.79 ppm at its anti-orientation
(E-isomer) [7]. The separation of the stereoisomeric
oximes II and III was performed by recrystallization.
Therewith the precipitate from hexane was enriched with
the minor component, E-isomer II.After two subsequent
crystallization the sample obtained contained no less than
90% of compound II, mp 102104°C. The mixture
obtained by evaporation of the mother liquor was
recrystallized from acetonitrile. After three-fold re-
crystallization the Z-isomer of the oxime was of 94%
purity (according to NMR data), mp 119120°C [6].
23Ja,a' 12.0 and 10.5 Hz, 23Ja,e' 3.6 and 5.4 Hz), 1.92 s
(6H, COCH3 and =CCH3), 2.06 d.d.d (1H, H4a, 2J 14.8,
3Ja,a' 10.5, 3Ja,e' 5.4 Hz), 2.33 m(2H, H4e + H5e) 3.07 d.d
(1H, H6a, Ja,a' 12.0, Ja,e' 3.6 Hz), 5.78 q (1H, =CH,
WJ 1.2 Hz), 6.20 (1H, NH). Mass spectrum, m/z (Irel, %):
209 [M]+ (2), 194 [M CH3]+ (<1), 181 (<1), 166 M
COCH3]+ (1), 152 [MNCOCH3]+ (8), 150 [M
NH2COCH3]+ (27), 135 [MNH2COCH3CH3]+ (15),
124 (3), 110 (40), 95, 82, 70, 58 (100), 43.
3
3
5,7,7-Trimethyl-3-azabicyclo[4.1.1]oct-4-en-2-
one (XVIII) was obtained by rearrangement of E-isomer
of oxime II in a 72% yield, mp 111112°C. IR spectrum,
1
n, cm : 3300 (NH), 3060 (=CH), 2955, 2925, 2855
(CHaliph), 1640 (C=Oconjug.lactam), 1610 (C=Cconjug.).
1H NMR spectrum (CDCl3), d, ppm: 0.86 s (3H, 7-CH3-
syn), 1.40 s (3H, 7-CH3-anti), 1.65 d.t (1H, H7a', 2J 10.2,
Ritter reaction with compounds IIII was carried out
by a conventional procedure [1, 2].
3
4
3J1,7 and J6,7 1.8 Hz), 1.89 d (3H, 5-CH3, J 1.4 Hz),
2.25 d.t (1H, H6, J6,8e' and J6,1 5.6, J6,8a' 1.8 Hz),
3
4
3
o-Mentha-1,6-dien-3-one (IV). A light oily sub-
stance obtained from verbenone (I) by the Ritter reaction
in the presence of 4 equiv of sulfuric acid and isolated
after evaporating ether contained prevailingly compound
IV with a small impurity of amidoketone V (~45%). To
remove the latter the reaction product was dissolved in
a 5-fold volume of hexane. The minor component was
practically insoluble in hexane and precipitated after
cooling the solution in a refrigerator. On evaporating the
hexane solution pure diene-3-on IV was obtained. Yield
2.64 d.t (1H, H1, J1,8e' and J1,6 5.6, J1,8a' 1.8 Hz),
3
4
3
2.75 d.t (1H, H8e', 2J10.2, 3J8e',1 and 3J8e',6 5.6 Hz), 6.46 q
4
(1H, H4, JCH 1.4 Hz). Mass spectrum, m/z (Irel, %):
3
166 [M]+ (38), 151 [M CH3] (17), 138 (6), 110 (100),
95, 84, 77, 63, 43.
5,7,7-Trimethyl-2-azabicyclo[4.1.1]oct-4-en-3-
one (XIX) was obtained by rearrangement of Z-isomer
of oxime III in a 76% yield, mp 144145°C (publ.:
1
mp 143144°C [6]). IR spectrum, n, cm : 3280 (NH),
3060 (=CH), 2955, 2925, 2865 (CHaliph), 1645
(C=Oconjug.lactam), 1600 (C=Cconjug.). 1H NMR spectrum,
d, ppm: 0.85 s (3H, 7-CH3-syn), 1.44 s (3H, 7-CH3-anti),
1
75%, nD18 1.5230. IR spectrum, n, cm : 3030 v.w (=CH),
2970, 2915, 2855 (CHaliph.), 1660 (C=Oconjug.), 1610
(C=Cconjug.). 1H NMR spectrum (CDCl3), d, ppm: 1.86 s
and 1.93 s (3H each, both 8-CH3), 2.10 d (3H, 1-CH3,
4J 1.2 Hz), 2.29 t (2H, C5H2, 3J 6.2 Hz), 2.67 t (2H,
2
3
3
1.68 d.t (1H, H7a , J 10.2, J7a',1 and J7a',6 1.8 Hz),
'
4
3
1.85 d (3H, 5-CH3, J 1.5 Hz), 2.22 d.t (1H, H6, J6,8e'
and 4J6,1 5.6, 3J6,8a' 1.8 Hz), 3.61 d.t (1H, H1, 3J1,8e and
3
C4H2, J 6.2 Hz), 5.89 d (1H, H2, 4J 1.2 Hz). Mass
4J1,6 5.6, 3J1,8a' 1.8 Hz), 2.76 d.t (1H, H8e , 2J 10.2, 3J1,8e
'
spectrum, m/z (Irel, %): 150 [M]+ (36), 135 [M CH3]+
and 3J6,8e 5.6 Hz), 5.78 q (1H, H4, 4JCH3 1.5 Hz). In the
1H NMR spectrum published in [6] were assigned only
the methyl groups signals and the signal of the olefin proton
at C4 atom. Mass spectrum, m/z (Irel, %): 166 [M]+ (42),
151 [M CH3] (19), 138 (7), 110 (100), 95, 84, 63, 43.
(24), 122 (4), 110 (100), 95, 82, 70, 55, 43.
8-Acetamido-o-menth-1-en-3-one (V) was obtain-
ed by carrying out the Ritter reaction in the presence of
8 equiv of sulfuric acid. The reaction mixture was neutral-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 42 No. 8 2006