(19), 131 (16), 119 (32), 105 (21), 91 (23). HRMS (EI+): calcd for
C20H26O2, 282.1984; found, 282.1979.
156 (4), 155 (26), 154 (100). HRMS (FAB+): calcd for C11H15O
(M + 1)+, 163.1123; found, 163.1125.
rac-2,6,6-Trimethyl-1-(trimethylsilylethynyl)cyclohex-2-en-
1-ol (13)
(Z)-3-(2-Iodoethen-1-yl)-2,4,4-trimethylcyclohex-2-en-
1-one (16)
A cooled (0 °C) solution of trimethylsilylacetylene (1.38 mL,
9.77 mmol) in THF (10 mL) was treated with nBuLi (7.02 mL,
1.34 M in hexane, 9.41 mmol) and stirred for 30 min. The
mixture was cooled down to −78 °C and a solution of 2,6,6-
trimethylcyclohex-2-en-1-one 7 (1.0 g, 7.23 mmol) in THF
(20 mL) was added. The resulting mixture was allowed to warm
up to 0 °C and H2O (5 mL) was added. An aqueous solution of
10% AcOH was added until pH = 7. The reaction was extracted
with TBME (3×). The aqueous layer was saturated with brine
and then extracted with TBME (3×). The combined organic
layers were dried over Na2SO4 and the solvent was evaporated.
The residue was purified by column chromatography (silica gel,
95:5 hexane:EtOAc) to afford 1.19 g (70%) of 13 as a white
solid (mp 37–39 °C, TBME). 1H-NMR (400.13 MHz, CDCl3): d
5.5–5.4 (m, 1H, H3), 2.1–2.0 (m, 2H, 2H4), 1.85 (s, 3H, C2–CH3),
1.6–1.5 (m, 1H, H5), 1.4–1.5 (m, 1H, H5), 1.03 (s, 6H, C6–2CH3),
0.14 (s, 9H, Si–(CH3)3) ppm. 13C-NMR (100.61 MHz, CDCl3):
d 134.3 (s), 124.1 (d), 107.1 (s), 89.7 (s), 74.5 (s), 37.0 (s), 31.4
(t), 24.0 (q), 22.9 (q), 22.6 (t), 19.4 (q), −0.2 (q, Si–(CH3)3) ppm.
FTIR (NaCl): m 3600–3300 (br, OH), 2964 (s, C–H), 2923 (s,
C–H), 2164 (m, CC), 1250 (s) cm−1. MS (FAB+): m/z (%) 236
(M+, 8), 235 (23), 226 (12), 221 (16), 220 (24), 219 (100), 217 (13),
167 (19), 165 (20). HRMS (FAB+): calcd for C14H25OSi (M + 1)+,
237.1675; found, 237.1670.
nBuLi (0.2 mL, 0.67 M in hexane, 0.13 mmol) was added
dropwise to a suspension of CuCN (5.5 mg, 0.062 mmol) in
THF (0.5 mL), at −78 °C. After stirring for 10 min, Bu3SnH
(0.034 mL, 0.13 mmol) and a solution of 3-ethynyl-2,4,4-
trimethylcyclohex-2-en-1-one 15 (10 mg, 0.062 mmol) in THF
(1 mL) were added and the mixture was stirred for 3 h at −78 °C
and for 1 h at −30 °C. After addition of NH4Cl:NH3 1:5 (1 mL),
it was extracted with TBME (3×). The organic layers were
dried (Na2SO4) and the solvent was evaporated. The residue
was disolved in CH2Cl2 (3 mL) and a solution of I2 (61.2 mg,
0.24 mmol) in CH2Cl2 (5 mL) was added over 25 min. An
aqueous Na2S2O3 solution (2 mL) was added, and the organic
layer was washed with an aqueous Na2S2O3 solution (3×), dried
and the solvent was evaporated. The residue was purified by
column chromatography (silica gel, 95:5 hexane:EtOAc) to
afford 9.1 mg (51%) of 16 a colorless oil. 1H-NMR (400.13 MHz,
(CD3) 2CO): d 7.27 (d, J = 8. 6 Hz, 1H, H1), 6.86 (d, J = 8.6 Hz,
1H, H2), 2.46 (t, J = 6.8 Hz, 2H, 2H6), 1.88 (t, J = 6.8 Hz, 2H,
2H5), 1.71 (s, 3H, CH3), 1.17 (s, 6H, C4–2CH3 ppm. MS (EI+):
m/z (%) 290 (M+,100), 153 (49), 234 (36), 233 (33), 199 (26), 163
(95), 155 (63), 135 (22), 121 (97), 120 (40), 119 (46), 105 (66), 103
(52), 91 (97), 79 (52), 77 (86), 75 (30), 69 (27), 67 (22), 65 (48).
HRMS (EI+): calcd for C11H15IO, 290.0168; found, 290.0179.
3-(1-Iodoethen-1-yl)-2,4,4-trimethylcyclohex-2-en-1-one (18)
2,4,4-Trimethyl-3-(trimethylsilylethynyl)cyclohex-2-en-
1-one (14)
Bu3SnH (0.029 mL, 0.11 mmol) was added to a solution
of 3-ethynyl-2,4,4-trimethylcyclohex-2-en-1-one 15 (17 mg,
0.105 mmol) and PdCl2(PPh3)2 (1.5 mg, 0.0021 mmol) in THF
(1.5 mL). After stirring for 10 min, CH2Cl2 (1 mL) and a solution
of I2 (40 mg, 0.157 mmol) in CH2Cl2 (4 mL) were added. The
reaction mixture was stirred for 1 h and an aqueous Na2S2O3
solution (2 mL) was added. The organic layer was washed with
an aqueous Na2S2O3 solution (3×), dried and the solvent was
evaporated. The residue was purified by column chromato-
graphy (silica gel, 95:5 hexane:EtOAc) to afford 22.3 mg (73%)
of a yellow solid (mp 72–75 °C, TBME). 1H-NMR (400.13 MHz,
CD2Cl2): d 6.09 (d, J = 1.6 Hz, 1H, H2), 5.91 (d, J = 1.6 Hz, 1H,
H2), 2.6–2.4 (m, 2H, 2H6), 1.9–1.8 (m, 2H, 2H5), 1.70 (s, 3H,
CH3), 1.47 (s, 3H, CH3), 1.20 (s, 3H, CH3) ppm. 13C-NMR
(100.62 MHz, (CD3)2CO): d 198.9 (s), 162.7 (s), 131.3 (s), 128.7
(t), 100.2 (s), 38.7 (t), 36.2 (s), 34.6 (t), 29.2 (q), 26.6 (q), 13.2
(q) ppm. FTIR (NaCl): m 2962 (m, C–H), 2927 (m, C–H), 1667
(s, CO) cm−1. MS (EI+): m/z (%) 290 (M+, 10), 164 (12), 163
(100), 148 (12), 135 (25), 121 (11), 107 (13), 105 (11), 93 (11), 91
(19), 79 (10), 65 (13). HRMS (EI+): calcd for C11H15IO, 290.0168;
found, 290.0176.
A solution of 2,6,6-trimethyl-1-(trimethylsilylethynyl)cyclo
hex-2-en-1-ol 13 (111.5 mg, 0.472 mmol) in CH2Cl2 (1 mL)
was added to a suspension of PCC (0.218 g, 0.99 mmol) and
silica gel (0.218 g, 3.63 mmol) in CH2Cl2 (2 mL). The resulting
suspension was stirred for 4 h. The mixture was filtered through
Celite® and the solvents were removed. The residue was purified
by column chromatography (silica gel, 95:5 hexane:EtOAc)
to afford 74.6 mg (67%) of 14 as a white solid (mp 38–42 °C,
TBME). 1H-NMR (400.13 MHz, CDCl3): d 2.48 (t, J = 6.7 Hz,
2H, 2H6), 1.95 (s, 3H, C2–CH3), 1.85 (t, J = 6.7 Hz, 2H, 2H5),
1.24 (s, 6H, C4–2CH3), 0.25 (s, 9H, Si–(CH3) 3) ppm. 13C-NMR
(100.62 MHz, CDCl3): d 198.3 (s), 150.0 (s), 138.2 (s), 111.2 (s),
101.8 (s), 36.3 (t), 35.2 (s), 34.2 (t), 27.7 (q, 2×), 14.5 (q), −0.3
(q, Si–(CH3)3) ppm. FTIR (NaCl): m 2962 (m, C–H), 2135 (w,
CC), 1673 (s, CO) cm−1. MS (FAB+): m/z (%) 235 (M + 1+,
100), 234 (M+, 15), 223 (19), 222 (17), 221 (71), 219 (22), 208 (18),
207 (81), 193 (29), 191 (23), 155 (17), 154 (47). HRMS (FAB+):
calcd for C14H23OSi (M + 1)+, 235.1518; found, 235.1513.
3-Ethynyl-2,4,4-trimethylcyclohex-2-en-1-one 15
rac-3-Ethynyl-2,4,4-trimethylcyclohex-2-en-1-ol (19)
A cooled (0 °C) solution of 2,4,4-trimethyl-3-(trimethylsilyl-
ethynyl)cyclohex-2-en-1-one 14 (95.7 mg, 0.402 mmol) in
THF (1.5 mL) was treated with nBu4NF (0.5 mL, 1 M in THF,
0.5 mmol) and stirred for 15 min. The mixture was diluted with
TBME (4 mL) and washed with aqueous NaHCO3 (1 × 5 mL).
The aqueous layer was extracted with TBME (3×), the combined
organic layers were washed with brine (3×), dried over Na2SO4
and the solvent was evaporated. The residue was purified by
column chromatography (silica gel, 95:5 hexane:EtOAc) to
afford 46.5 mg (70%) of a white solid (mp 77–79 °C, TBME).
1H-NMR (400.13 MHz, CDCl3): d 3.73 (s, 1H, H2), 2.48 (t,
J = 7.1 Hz, 2H, 2H6), 1.94 (s, 3H, C2–CH3), 1.85 (t, J = 7.1 Hz,
2H, 2H5), 1.24 (s, 6H, C4–2CH3) ppm. 13C-NMR (100.62 MHz,
NaBH4 (7.6 mg, 0.201 mmol) was added carefully to a cooled
solution (0 °C) of 3-ethynyl-2,4,4-trimethylcyclohex-2-en-
1-one 15 (32.6 mg, 0.201 mmol) and CeCl3·7H2O (75 mg,
0.249 mmol) in absolute EtOH (2 mL). After stirring for 1 h,
an aqueous NH4Cl solution (2 mL) was added and the mixture
was extracted with TBME (3×). The combined organic layers
were dried over Na2SO4 and the solvent was evaporated. The
residue was purified by column chromatography (silica gel,
80:20 hexane:EtOAc) to afford 30.6 mg (93%) of a white solid
(mp 47–49 °C, TBME). 1H-NMR (400.13 MHz, CDCl3): d 4.02
(t, J = 4.8 Hz, 1H, H1), 3.13 (s, 1H, H2), 2.00 (s, 3H, C2–CH3),
1.7–1.5 (m, 2H, 2H6), 1.5–1.4 (m, 2H, 2H5), 1.15 (s, 3H, CH3),
1.08 (s, 3H, CH3) ppm. 13C-NMR (100.62 MHz, CDCl3): d 142.3
(s), 126.9 (s), 82.2 (d), 81.6 (s), 69.0 (d), 34.2 (s), 33.2 (t), 28.8
(q), 28.2 (t), 27.6 (q), 19.2 (q) ppm. FTIR (NaCl): m 3600–3100
(br, OH), 2961 (s, C–H), 2937 (s, C–H), 2866 (m, C–H), 2087
(CD3) CO): d 198.3 (s), 146.2 (s), 140.2 (s), 94.9 (d), 82.1 (s),
2
37.9 (t), 36.8 (s), 35.6 (t), 28.8 (q, 2×), 15.6 (q) ppm. FTIR
(NaCl): m 3200 (s, CH), 2969 (m, C–H), 2082 (m, CC), 1654
(s, CO) cm−1. MS (FAB+): m/z (%) 163 (M + 1+, 7), 161 (3),
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 3 3 6 8 – 3 3 7 3
3 3 7 1