Separation of trans-limonene and carvomenthene oxides
877
19.8; MS (m/z) :152(2), 137(8), 119(9), 108(76), by NMR for the complete disappearance of proton
94(89), 79(51), 67(93), 43(100)
attached to epoxide ring at position 2 in 1a and 2a,
respectively, at 3.06 and 3.01 ppm. After the reaction
was complete (4 h), methanol was evaporated and the
products were extracted into CH2Cl2 (30 ml × 3) by
aqueous work-up. The combined organic extracts was
dried over Na2SO4 and concentrated to afford the crude
product. It was then purified by fractional distillation
under reduced pressure to afford pure products. Physi-
cal and spectral data of isolated compounds is presented
here.
2.1b trans-Carvomenthene-oxide (2b): Yield 2.45 g,
(96.4%); b.p. 73–75◦C/0.66 kPa, [α]2D0 = +48◦ (c = 1,
1
MeOH); H NMR (500 MHz, CDCl3): δ = 2.96 (d,
1H, J = 5.3 Hz, -CH), 1.91–2.00 (m, 2H, -CH2), 1.61
(ddd, 1H, J1 = 14.51 Hz,J2 = 12.21 Hz, J3 = 4.8 Hz)
1.51 (dd, 1H, J1 = 15.0, J2 =11.62, -CH2), 1.37 (sept,
1H, J = 6.73 Hz, -CH), 1.29 (s, 3H, -CH3), 1.10 (dq,
2H, J1 = 12.46 Hz, J2 =4.16 Hz, -CH2), 1.01 (ds, 1H,
J1 = 6.15 Hz, J2 =2.05 Hz, -CH ), 0.82 (d, 6H, J =
6.92 Hz, -CH3); 13C NMR (125 MHz, CDCl3): δ =
59.2, 57.4, 38.9, 31.9, 30.6, 27.5, 22.7, 22.1, 19.3, 18.9;
MS(m/z): 154(2), 139(20), 125(13), 111(46), 97(9),
83(20), 69(24), 55(32), 43(100).
2.2a (1S,2S,4R)−2-hydroxy-1-methoxy-p-menthan-
◦
8(9)-ene (1c): Yield 2.16 g, (85%); b.p. 115–117
C/0.66 kPa; [α]D20 = +39◦ ; H NMR (500 MHz,
1
CDCl3): δ = 4.72 (br s, 2H, CH2), 3.68 (s, 1H, CH),
3.19 (s, 3H, OCH3), 2.24 (tt, 1H, J1 = 11.70 Hz,
J2 = 3.52 Hz, CH), 1.91 (ddd, 1H, J1 = 13.64 Hz,J2
= 12.29 Hz, J3 = 2.69 Hz, CH2), 1.80 (br, 1H, OH),
1.72 (s, 3H, CH3), 1.70 (dt, 1H,J1 = 3.72 Hz,J2 =
1.35 Hz, CH2 ), 1.62 (m, 1H, CH2), 1.56 (dt, 1H, J1 =
13.64 Hz,J2 = 1.77 Hz, CH2), 1.37-1.51 (m, 2H, CH2),
1.18 (s, 3H, CH3); 13C NMR (125 MHz, CDCl3):
δ = 149.4, 108.4, 74.8, 72.0, 48.0, 37.1, 33.5, 28.5,
25.7, 20.6, 19.9; MS (m/z): 184(2), 169(4), 152(10),
108(15), 85(100), 72(21), 55(19), 43(16).
2.1c (1S,2S,4R)-1-methyl-4-(prop-1-en-2-yl)cyclo-
hexane-1,2-diol (1d): b.p. 115–117◦C/0.46 kPa;
[α]D20 = +42◦ (c = 1, MeOH); Yield: 2.1 g (90 %); 1H
NMR (500 MHz, CDCl3): δ = 4.72 (s, 2H, -CH2), 3.61
(t, 1H, J = 3.12 Hz, -CH), 2.21–2.29 (m, 1H, -CH),
1.91 (ddd, 1H, J1 = 13.99 Hz,J2 = 11.47 Hz, J3 =
2.84 Hz, -CH2), 1.72–1.77 (m, 1H, -CH2), 1.71 (s, 3H),
1.61–1.66 (m, 1H, -CH2), 1.52–1.56 (m, 2H, -CH2),
1.47–1.52 (m, 1H, -CH2), 1.24 (s, 3H, -CH3); 13C
NMR (125 MHz, CDCl3): δ = 148.9, 108.6, 73.5, 71.1,
37.1, 33.6, 33.3, 26.1, 25.8, 20.7; MS (m/z): 170(2),
152(34), 137(21), 111(21), 108(46), 93(40),82(35),
71(80), 67(46), 55(32), 43(100).
2.2b (1S,2S,4R)−2-hydroxy-1-methoxy-p-menthane
(2d): Yield 2.17 g, (86.8%); b.p. 102–104◦C/0.33 kPa;
1
[α]D20 = 33◦ (c = 1, MeOH); H NMR (500 MHz,
CDCl3): δ = 3.62 (s, 1H, CH), 3.17 (s, 3H, CH3),
2.40 (br, 1H, OH), 1.63–1.72 (m, 2H, -C(3)H2 and
-C(6)H2), 1.52–1.59 (m, 1H, -CH2), 1.50 (dd, 1H,
J1 = 12.95 Hz,J2 = 3.59 Hz, -CH2), 1.43–1.47 (m,
1H, -CH), 1.40–1.43 (m, 1H, -CH2), 1.32–1.38 (m,
1H, -CH), 1.18–1.22 (m, 1H, -CH2), 1.15 (s, 3H,
-CH3), 0.87 (t, 6H, J = 6.67 Hz, -CH3); 13C NMR
(125 MHz, CDCl3): δ = 75.2, 72.2, 48.0, 36.2, 32.0,
31.5, 28.6, 23.7, 19.8, 19.7, 19.5; MS (m/z): 186(6),
171(4), 154(4), 143(4), 136(11), 125(2), 111(10),
97(2), 85(100), 83(4), 72(20), 55(17), 43(13).
2.1d (1S,2S,4R)-4-isopropyl-1-methylcyclohexane-1,
2-diol (2c): b.p. 123–125◦ C/0.46 kPa; [α]2D0 = +43◦
(c = 1, MeOH); Yield 2 g, (85%); 1H NMR (500 MHz,
CDCl3): δ = 3.59 (t, 1H, J = 3.45 Hz, -CH), 1.93 (br,
2H, -OH confirmed by D exchange), 1.64–1.74 (m, 2H,
-CH2), 1.56–1.61 (m, 1H, -CH2), 1.50–1.53 (m, 1H,
-CH2), 1.46–1.50 (m, 2H,-CH2), 1.33–1.38 (m, 2H,
-C(4)H and –C(5)H2), 1.24 (s, 3H, -CH3), 0.88 (t, 6H,
J = 7.54 Hz, -CH3); 13C NMR (125 MHz, CDCl3):
δ = 73.7, 36.4, 33.4, 32.3, 31.0, 29.3, 25.8, 23.9, 19.7,
19.6; MS (m/z): 172(8), 154(4), 139(11), 111(52),
97(13), 83(28), 71(100), 55(48), 43(91).
2.3 Catalyst reusability test
Retention of catalytic activity of InCl3 was checked
by carrying out reaction over 10 cycles. Under each
cycle, the reaction was carried out on 10 mmol scale,
after completion of the reaction, the usual work-up
2.2 General procedure for separation of
trans-limonene and carvomenthene oxides in methanol
In a two-necked RB flask, a solution of cis-/trans- afforded the mixture of trans-epoxide and 1d. The
epoxide (30 mmol) in methanol (50 ml) and InCl3 aqueous layer obtained at work-up stage, was separated
(3 mmol) was taken. The solution was stirred at room and utilized for succeeding reactions. The sequence
temperature. Progress of the reaction was checked of operation was followed in every subsequent cycle