[Synthesis]
The 1S,2S,5R-N,N,2-trimethyl-2-hydroxy-5-isopropenylcyclohexylamine oxide (1.430 g, 6.7 mmol) was heated in a Kugelrohr oven at 180 °C under 1 mmHg vacuum until the solid residue completely disappeared. The yellow distillate (1.317 g) was collected and purified by fast chromatography (ether:hexane=2:3) to afford the target product (1S,4R)-1-methyl-4-(1-methylethenyl)-2-cyclohexen-1-ol (0.752 g, 74% yield) as a colorless oil. the Rf value was 0.32 (ether:hexane=2:3); the specific optical rotation [α]D26: +60 (c=1.0, CHCl3), consistent with literature value [α]D23: +53.8 (CHCl3); IR spectrum (SeZn) showed absorption peaks: 3354 (medium, broad, O-H), 2967 (medium, C-H), 2935 (medium, CH), 2861 (medium, CH), 1644 (medium, C=C), 1105 (strong, CO), and 888 (strong, C=CH bent), 736 (strong, C=CH bent) cm-1; 1H NMR (500 MHz, CDCl3) chemical shift: δ 5.70 (1H, ddd, 3JH2-H3=10.0 Hz, 4JH2-H4=2.4 Hz, 4JH2-H6=1.4 Hz, H2), 5.65 (1H, ddd. 3JH3-H2=10.0 Hz, 3JH3-H4=2.4 Hz, 4JH3-H5=0.8 Hz, H3), 4.78 (1H, quin, 4JH9b-H10≈4JH9b-H4=1.6 Hz, H9b), 4.74 (1H, quin, 4JH9a-H10≈4JH9a-H4=0.88 Hz, H9a), 2.65 (1H, m, H4), 1.88-1.73 (2H, m, H5eq, H6eq), 1.73 (3H, s, H10), 1.66-1.51 (3H, m, H5ax, H6ax, OH), 1.29 (3H, s, H7) ppm; 13C NMR (125 MHz, CDCl3) chemical shift : 148.3 (C8), 134.1 (C2), 132.3 (C3), 110.7 (C9), 67.6 (C1), 43.6 (C4), 36.9 (C6), 29.6 (C7), 25.0 (C5), 21.0 (C10) ppm; low resolution mass spectra (GC-MS): m/z 152 (M+, 2%), 134 ( [M-H2O]+, 11%), 119 ([M-CH3-H2O]+, 32%), 91 (100%), 79 (37%), 77 (46%); Elemental analysis (C10H16O) Calculated values: C 78.90, H 10.59; Measured values: C 78.25, H 10.59, N < 0.05. |