171 Page 4 of 9
J. Chem. Sci.
(2018) 130:171
J = 2.0 Hz, 2H), 1.75 (s, 3H), 1.65–1.55 (m, 6H), 1.48–1.45 IR (neat, cm−1): 3345, 3278, 3210, 2947, 2876, 2091, 1475,
(m, 2H) ppm; 13C NMR (100 MHz, CDCl3): δ 211.1, 210.7, 1320, 1280, 1259, 1229, 1182, 1131, 1119, 1065, 1001, 972,
132.5, 129.0, 120.2, 114.3, 63.2, 54.5, 54.4, 51.9, 51.8, 51.4, 868, 802; 1H NMR (400 MHz, CDCl3): δ 4.43 (s, 2H), 3.46 (s,
51.3, 50.6, 49.7, 32.4, 28.1, 25.6, 25.5, 22.4 ppm; HRMS 2H), 2.54(s, 2H), 2.38(d, J = 14.5Hz, 2H), 1.98(s, 2H), 1.80
(ESI, Q-ToF): m/z calcd for C18H16O2 [M + H]+ 293.1536; (s, 2H), 1.75 (s, 6H), 1.61–1.56 (m, 6H), 1.48 (t, J = 6.7 Hz,
found: 293.1545.
2H), 1.15 (t, J = 7.1 Hz, 2H) ppm; 13C NMR (125 MHz,
CDCl3): δ 126.4, 75.5, 49.8, 46.7, 46.0, 43.4, 36.7, 32.2, 29.8,
25.8, 25.6, 20.4 ppm; HRMS (ESI, Q-ToF): m/z calcd for
C21H28NaO2 [M + Na]+ 335.1982; found: 335.1980.
General procedure for the synthesis of cage diones 35, 36,
37 and 38 via reduction
To a stirred solution of cage diones 22, 23, 24, and 25 (0.17–
1.07 mmol) in dry ethyl acetate (5 mL) was added catalytic
amount of 10% Pd/C. Later, the cage diones were hydro-
genated using hydrogen gas (H2 balloon) under atmospheric
pressure at room temperature for 5 h. After completion of the
reaction (TLC monitoring), the reaction mixture was filtered
off with the aid of Celite pad and filtrate was concentrated
under reduced pressure. The obtained crude residue was puri-
fied by column chromatography on silica gel using 8–10%
ethyl acetate in petroleum ether as eluent to give the saturated
diones 35, 36, 37 and 38 as colourless solids.
General procedure for the synthesis of cage propellanedi-
ols 31, 32, 33 and 34
A solution of cage diones 22, 23, 24, and 25 (0.13–0.37 mmol)
in dry methanol (10 mL), NaBH4 (0.52–1.48 mmol) was
added at 0◦C in small portions over a period of 10 min. After-
wards, the reaction mixture was stirred for another 20 min
at the room temperature. After completion of the reaction
(monitored by TLC), methanol was removed under vacuo
and the crude residue was quenched by addition of water and
was extracted with ethyl acetate. The combined organic lay-
ers were washed with brine solution, dried over anhydrous
Na2SO4 and concentrated under reduced pressure. The crude
products were obtained after evaporation of solvent followed
by purification by column chromatography on silica gel using
10–15% EtOAc in petroleum ether as eluent to yield the cage
diols 31, 32, 33 and 34 as colourless solids.
◦
Cage dione 35: colourless solid; M.p. 107–109 ◦C; pre-
pared from cage dione 22 (50 mg, 0.18 mmol); Yield: 45 mg
(89%); IR (neat, cm−1): 2942, 1745, 1722, 1449, 1264,
Cage diol 31: colourless solid; M.p. 134–136 C; prepared
fromcagedione22(100mg, 0.37mmol);Yield:95mg(95%);
IR (neat, cm−1): 3477, 3372, 3213, 2959, 1705, 1476, 1114;
1H NMR (400 MHz, CDCl3): δ 5.65 (t, J = 2.9 Hz, 1H), 5.21
(s, 2H), 3.45 (d, J = 6.0 Hz, 2H), 2.62 (s, 2H), 2.39–2.26
(m, 2H), 2.15–2.08 (m, 2H), 1.79 (s, 3H), 1.76 (dd, J = 15.6,
7.1 Hz, 1H) 1.66–1.56 (m, 3H), 0.52–0.49 (m, 2H), 0.28–0.25
(m, 2H) ppm; 13C NMR (100 MHz, CDCl3): δ 136.1, 120.8,
75.6, 75.4, 47.7, 47.6, 47.5, 46.8, 46.7, 43.9, 43.8, 35.2, 31.3,
29.9, 24.7, 5.2, 4.4 ppm; HRMS (ESI, Q-ToF): m/z calcd for
C18H22O2 [M + Na]+ 293.1512; found: 293.1516.
1
1071; H NMR (500 MHz, CDCl3): δ 3.08–3.04 (m, 1H),
2.98–2.91 (m, 3H), 2.20–2.13 (m, 3H), 1.77–1.68 (m, 2H),
1.56–1.46 (m, 2H), 1.35–1.27 (m, 2H), 0.96 (d, J = 6.3 Hz,
3H), 0.72–0.62 (m, 4H) ppm; 13C NMR (125 MHz, CDCl3):
δ 213.8, 213.4, 55.55, 55.52, 51.8, 49.3, 45.9, 43.4, 37.9,
32.0, 28.7, 26.5, 23.0, 5.5, 4.1 ppm; HRMS (ESI, Q-ToF):
m/z calcd for C18H20NaO2 [M + Na]+ 291.1355; found:
291.1354.
◦
Cage diol 32: colourless solid; M.p. 207–209 C; prepared
Cage dione 36: colourless solid; M.p. 160–162 ◦C; prepared
from cage dione 23 (300 mg, 1.07 mmol); Yield: 274 mg
(90%); IR (neat, cm−1): 2955, 1742, 1727, 1461, 1266,
1178, 1088; 1H NMR (500 MHz, CDCl3): 2.97–2.95 (m,
4H), 2.17–2.15 (m, 2H), 1.90 (dd, J = 13.9, 8.1 Hz, 2H),
1.79–1.75 (m, 2H), 1.30 (dd, J = 13.8, 5.1 Hz, 2H), 0.77
(d, J = 6.7, 6H), 0.70–0.67 (m, 2H), 0.65–0.61 (m, 2H)
ppm; 13C NMR (125 MHz, CDCl3): δ 213.5, 55.5, 52.2, 49.3,
46.6, 37.8, 30.59, 30.53, 16.2, 5.5, 4.1 ppm; HRMS (ESI, Q-
ToF):m/zcalcdforC19H22NaO2 [M+Na]+ 305.1512;found:
305.1512.
fromcagedione23(100mg, 0.35mmol);Yield:85mg(85%);
IR (neat, cm−1): 3372, 1655, 1100; H NMR (400 MHz,
1
CDCl3): δ 3.48 (s, 2H), 3.21 (s, 4H), 2.64 (s, 2H), 2.39 (d,
J = 15.2 Hz, 2H), 2.09 (s, 2H), 1.76 (s, 6H), 1.64–1.57 (m,
2H), 0.53–0.49 (m, 2H), 0.28–0.26 (m, 2H) ppm; 13C NMR
(125 MHz, CDCl3): δ 126.5, 75.4, 47.7, 47.4, 46.7, 43.5, 36.6,
31.4, 20.4, 5.2, 4.4 ppm; HRMS (ESI, Q-ToF): m/z calcd for
C19H24NaO2 [M + Na]+ 307.1669; found: 307.1667.
◦
Cage diol 33: colourless solid; M.p. 128–130 C; prepared
from cage dione 24 (40 mg, 0.13 mmol); Yield: 31 mg
(76%); IR (neat, cm−1): 3386, 3220, 2955, 1112; H NMR
1
Cage dione 37: colourless solid; M.p. 132–134 ◦C; pre-
pared from cage dione 24 (50 mg, 0.17 mmol); Yield:
43 mg (85%); IR (neat, cm−1): 2959, 2945, 1744, 1440;
1H NMR (500 MHz, CDCl3): δ 2.99–2.84 (m, 4H), 2.40
(s, 2H), 2.19–2.14 (m, 1H), 1.72–1.66 (m, 6H), 1.60–1.46
(m, 6H), 1.33–1.25 (m, 2H), 0.95 (d, J = 6.3 Hz, 3H);
13C NMR (125 MHz, CDCl3): δ 213.7, 213.3, 65.4, 54.86,
54.82, 51.2, 51.0, 48.5, 45.8, 43.2, 32.3, 32.2, 32.0, 28.7,
28.5, 26.4, 25.7, 25.6, 23.0, 22.9 ppm; HRMS (ESI, Q-ToF):
(400 MHz, CDCl3): δ 5.63 (d, J = 5.3 Hz, 1H), 5.00 (s, 2H),
3.44 (s, 2H), 2.53 (s, 2H), 2.38–2.25 (m, 2H), 2.05–1.98 (m,
2H), 1.78 (s, 6H), 1.64–1.54 (m, 5H), 1.52–1.46 (m, 2H), 1.15
(t, J = 6.8, 1H) ppm; 13C NMR (125 MHz, CDCl3): δ 136.1,
120.8, 75.7, 75.5, 57.4, 49.8, 49.7, 46.8, 46.0, 45.9, 43.7, 43.6,
35.3, 32.2, 30.4, 29.8, 25.8, 25.6, 24.7 ppm; HRMS (ESI, Q-
ToF):m/zcalcdforC20H26NaO2 [M+Na]+ 321.1825;found:
321.1825.
◦
Cage diol 34: colourless solid; M.p. 212–214 C; prepared m/z calcd for C20H24NaO2 [M + Na]+ 319.1669; found:
from cage dione 25 (50 mg, 0.16 mmol); Yield: 45 mg (90%); 319.1668.