¨
C. Tanyeli, C¸ . Iyigun / Tetrahedron 59 (2003) 7135–7139
7138
added. The mixture was allowed to reflux until the dark
brown colour disappeared (also monitored by TLC). The
reaction mixture was diluted with an equal amount of ethyl
acetate and the organic phase was washed with 1N HCl
(3£50 mL), followed by saturated NaHCO3 (3£50 mL) and
brine (2£50 mL). The organic phase was dried over MgSO4
and evaporated in vacuo. The crude product was separated
by flash column chromatography using ethyl acetate/hexane
as eluent.
1:4) 0.26; nmax (neat) 3717, 3155, 2926, 1709, 1462, 1363,
1095 cm21; dH (400 MHz, CDCl3) 7.32–7.11 (2£5H and
1H, m, CPhPh and vCHb), 6.21 (1H, d, J¼10 Hz, vCHa),
3.66 (1H, d, J¼14 Hz, CHaHb), 2.75 (1H, d, J¼14 Hz,
CHaHb), 1.88 (3H, s, MeCO2), 0.97 (3H, s, MeCOAc); dC
(100.6 MHz, CDCl3) 195.6, 170.2, 154.4, 147.3, 129.1,
128.9, 128.3, 127.9, 127.5, 127.2, 127.0, 80.2, 50.3, 45.3,
24.2, 21.7; HRMS (EI): Mþ, found 320.1412, C21H20O3
requires 320.1413.
3.2.1. 6-Acetoxy-3,6-dimethyl-2-cyclohexen-1-one 2a.
(0.81 g, 64%) as a colourless oil; Rf (EtOAc/hexane 1:2)
0.22; nmax (neat) 3342, 2924, 1740, 1678, 1436, 1372, 1251,
1153, 1093, 1025 cm21; dH (400 MHz, CDCl3) 5.83 (1H, s,
CHv), 2.77–2.85 (1H, m, vCMeCHaHb), 2.26–2.41 (2H,
m, CMeOAcCH2), 1.99 (3H, s, MeCO2), 1.89 (3H, s,
vCMe), 1.81–1.86 (1H, m, vCMeCHaHb), 1.36 (3H, s,
COAcMe); dC (100.6 MHz, CDCl3) 195.9, 170.0, 160.9,
125.5, 80.4, 32.4, 30.2, 24.6, 22.2, 21.9; HRMS (EI): Mþ,
found 182.0940, C10H14O3 requires 182.0943.
3.2.6. 6-Acetoxy-6-methyl-4-isopropyl-2-cyclohexen-1-
one 2f. (1.21 g, 82%) as a colourless oil, Rf (EtOAc/hexane
1:4) 0.17; nmax (neat) 3405, 2960, 2867, 2251, 1709, 1674,
1460 cm21; dH (400 MHz, CDCl3) (8:2 diastereomeric
mixture) (major isomer) 6.69 (1H, dd, J¼10, 4 Hz,
vCHb), 5.96 (1H, d, J¼10 Hz, vCHa), 2.49–2.53 (1H,
m, vCHCH), 2.42–2.44 (1H, m, CHMe2), 1.99–2.07 (2H,
m, CH2), 1.93 (3H, s, MeCO2), 1.47 (3H, s, MeCOAc), 0.87
(2£3H, d, J¼7 Hz, CHMe2); (minor isomer) 6.69 (1H, dd,
J¼10, 4 Hz, vCHb), 5.96 (1H, d, J¼10 Hz, vCHa), 2.44–
2.48 (1H, m, vCHCH), 2.42–2.44 (1H, m, CHMe2), 1.99–
2.07 (2H, m, CH2), 1.95 (3H, s, MeCO2), 1.49 (3H, s,
MeCOAc), 0.89 (2£3H, d, J¼7 Hz, CHMe2); dC
(100.6 MHz, CDCl3) (major isomer) 195.4, 170.2, 152.1,
128.3, 80.8, 40.2, 37.1, 31.6, 21.7, 21.0, 19.6, 19.3; (minor
isomer) 191.4, 169.2, 150.3, 125.6, 80.9, 41.2, 37.5, 30.6,
21.8, 21.4, 19.7, 19.1; HRMS (EI): Mþ, found 210.1256,
C12H18O3 requires 210.1256.
3.2.2. 6-Acetoxy-3,5,5,6-tetramethyl-2-cyclohexen-1-one
2b. (1.12 g, 76%) as a white solid, mp 82–858C; Rf (EtOAc/
hexane 1:3) 0.25; nmax (neat) 3432, 3017, 2975, 2253, 1737,
1686, 1639, 1436, 1372, 1248, 1217 cm21; dH (400 MHz,
CDCl3) 5.70 (1H, s, CHv), 2.45 (1H, d, J¼18 Hz,
CMe2CHaHb), 1.90 (3H, s, MeCO2), 1.79 (1H, d, J¼
18 Hz, CMe2CHaHb), 1.77 (3H, s, vCMe), 1.36 (3H, s,
COAcMe), 1.02 (3H, s, CMeaMeb), 0.80 (3H, s, CMeaMeb);
dC (100.6 MHz, CDCl3) 199.1, 172.0, 158.4, 125.5, 87.7,
46.5, 42.8, 26.2, 26.1, 24.8, 23.7, 16.0; HRMS (EI): Mþ,
found 210.1255, C12H18O3 requires 210.1256.
3.2.7. 6-Acetoxy-6-ethyl-3,5,5-trimethyl-2-cyclohexen-1-
one 2g. (0.83 g, 53%) as a colourless oil, Rf (EtOAc/hexane
1:4) 0.22; nmax (neat) 3421, 2967, 1735, 1660, 1440,
1376 cm21; dH (400 MHz, CDCl3) 5.11 (1H, s, vCH), 2.47
(1H, d, J¼18 Hz, CHaHb), 2.31 (1H, d, J¼18 Hz, CHaHb),
2.13–2.19 (2H, m, MeCH2), 2.07 (3H, s, MeCO2), 1.88 (3H,
s, vCMe), 1.07 (6H, s, Me2C), 0.87 (3H, t, J¼7 Hz,
MeCH2); dC (100.6 MHz, CDCl3) 208.0, 171.1, 158.1,
124.9, 81.3, 59.4, 47.3, 37.4, 30.0, 27.8, 21.1, 19.2, 13.7;
HRMS (EI): Mþ, found 224.1416, C13H20O3 requires
224.1413.
3.2.3. 6-Acetoxy-3,5,6-trimethyl-2-cyclohexen-1-one 2c.
(1.11 g, 81%) as a colourless oil; Rf (EtOAc/hexane 1:5)
0.22; nmax (neat) 3397, 2253, 1735, 1676, 1380, 1257 cm21
;
dH (400 MHz, CDCl3) (1:1 diastereomeric mixture) 5.83
(1H, s, vCH), 5.76 (1H, s, vCH), 3.09–3.18 (2£1H, m,
MeCH), 2.21–2.62 (2£2H, m, CMeCH2), 2.01 (3H, s,
MeCO2), 1.97 (3H, s, MeCO2), 1.88 (3H, s, vCMe), 1.84
(3H, s, vCMe), 1.49 (3H, s, COAcMe), 1.19 (3H, s,
COAcMe), 0.99 (3H, d, J¼7 Hz, MeCH), 0.93 (3H, d, J¼
7 Hz, MeCH); dC (100.6 MHz, CDCl3) 196.4, 196.0, 169.8,
169.5, 160.3, 158.1, 125.1, 123.6, 83.4, 82.6, 38.3, 37.1,
33.6, 29.7, 24.1, 23.8, 21.3, 18.8, 16.4, 14.7, 14.0; m/z (EI)
198 (13), 197 (100), 152 (13), 139 (19), 137 (42); HRMS
(EI): Mþ, found 196.1105, C11H16O3 requires 196.1100.
3.2.8. 6-Acetoxy-6-benzyl-3,5-dimethyl-2-cyclohexen-1-
one 2h. (1.47 g, 77%) as a colourless oil, Rf (EtOAc/hexane
1:5) 0.31; nmax (neat) 3012, 2961, 1730, 1652, 1493 cm21
;
dH (400 MHz, CDCl3) (only one isomer was isolated) 7.19–
7.26 (3H, m, Ph), 7.09 (2H, d, J¼6 Hz, Ph), 5.93 (1H, s,
vCH), 3.58 (1H, d, J¼14 Hz, PhCHaHb), 3.19 (1H, d, J¼
14 Hz, PhCHaHb), 2.80–2.83 (1H, m, MeCH), 2.44–2.50
(1H, dd, J¼18, 5 Hz, CHaHb), 2.28–2.34 (1H, dd, J¼18,
5 Hz, CHaHb), 2.05 (3H, s, MeCO2), 1.93 (3H, s, vCMe),
0.95 (3H, d, J¼7 Hz, MeCH); dC (100.6 MHz, CDCl3)
194.5, 170.2, 159.1, 135.3, 130.4, 128.2, 126.9, 125.1, 85.8,
40.3, 37.6, 35.0, 24.2, 21.5, 15.0; m/z (EI) 274 (17), 273
(100), 214 (8), 213 (47); HRMS (EI) Mþ, found 272.1401,
C17H20O3 requires 272.1413.
3.2.4. 6-Acetoxy-4,4,6-trimethyl-2-cyclohexen-1-one 2d.
(1.07 g, 78%) as a colourless oil; Rf (EtOAc/hexane 1:3)
0.27; nmax (neat) 3535, 3155, 2853, 1736, 1689, 1464,
1377 cm21; dH (400 MHz, CDCl3) 6.52 (1H, d, J¼10 Hz,
vCHb), 5.81 (1H, d, J¼10 Hz, vCHa), 2.62 (1H, d, J¼
14 Hz, CHaHb), 1.90 (3H, s, MeCO2), 1.79 (1H, d, J¼14 Hz,
CHaHb), 1.46 (3H, s, MeCOAc), 1.16 (3H, s, CMeaMeb),
1.14 (3H, s, CMeaMeb); dC (100.6 MHz, CDCl3) 195.3,
170.5, 157.6, 126.4, 84.3, 45.6, 34.6, 29.6, 25.2, 15.3, 14.5;
m/z (EI) 198 (14), 197 (100), 195 (19), 139 (13), 137 (37);
HRMS (EI): Mþ, found 196.1103, C11H16O3 requires
196.1100.
3.2.9. 5-Acetoxy-3,5-dimethyl-2-cyclopenten-1-one 2i.
(0.85 g, 72 %) as a colourless oil, Rf (EtOAc/hexane 1:4)
0.17; nmax (neat) 3018, 2400, 1735, 1672, 1521 cm21; dH
(400 MHz, CDCl3) 5.75 (1H, s, vCH), 2.80 (1H, d, J¼
18 Hz, CHaHb), 2.32 (1H, d, J¼18 Hz, CHaHb), 1.88 (3H, s,
MeCO2), 1.82 (3H, s, vCMe), 1.16 (3H, s, MeCOAc); dC
(100.6 MHz, CDCl3) 205.4, 173.1, 170.2, 127.8, 81.4, 46.3,
3.2.5. 6-Acetoxy-6-methyl-4,4-diphenyl-2-cyclohexen-1-
one 2e. (1.05 g, 47%) as a colourless oil, Rf (EtOAc/hexane