Molecules 2011, 16
6573
Discover Labmate® microwave reactor at 0 °C and 290 W, with rapid stirring for 1.5 h. Subsequently,
the catalyst was removed by filtration and the liquid obtained was evaporated to dryness and purified
on a chromatographic column to give selectively the desired cyanohydrin 3 (yield 94.1%).
(
(7-Isocyanooctahydrospiro[2,4,1-(epiethane[1,1,2]triyl)cyclobuta[cd]pentalene5,2'[1,3]dioxolan]-7-
yl)oxy)trimethylsilane (3). Yellow solid (yield 94.1%). m.p. 94–95 °C; GC-MS for C H NO Si;
1
7
23
3
+
+
+
−1
(
317 g/mol): [M+1] = 318, [M+29] = 346, [M−CN] = 291; FTIR-ATR (cm ): 2955, 2240, 1307,
1
1
251, 1102, 880, 838, 782; FAB-MS m/z (rel. int.%): obs. 317.1422 (55.2) cal. 317.1447; H-NMR
(CDCl
3
, 500 MHz): δ (ppm) 3.94–3.91 (m, 2H), 3.83–3.79 (m, 1H), 3.74 (ddd, J = 7.6, 6.7, 6.4 Hz,
1
2
H), 3.02–2.99 (m, 1H), 2.83 (tq, J = 4.7, 1.6 Hz, 1H), 2.71–2.65 (m, 4H), 2.50–2.46 (m, 1H),
13
.23–2.20 (m, 1H), 1.70 (d, J = 11.1 Hz, 1H), 1.25 (dt, J = 11.0, 1.7 Hz, 1H), 0.24 (s, 9H); C-NMR
): δ (ppm) 123.10, 114.40, 75.15, 65.96, 62.42, 51.56, 47.42, 44.96, 44.75, 43.91,
9.79, 39.59, 38.60, 34.46, 0.86.
(125 MHz; CDl
3
3
2
,6 3,1
5,9
3
.4. Deprotection Procedure for the Pentacyclic [5.4.0.0 .0 0.0 ]undecane-8,11-dione Mono-
ethylene Acetal Cyanosilylated 3
Conventional heating method. In a closed system the cyanohydron of the pentacyclic
[5.4.0.02,6.03,10.05,9] undecane-8,11-dione monoethylene acetal (1.0 mmol) and acetonitrile (1.0 mL)
were placed with sulphated zirconia (25 mg). The reaction mixture was stirred for 6 h at 60 °C.
Subsequently, the catalyst was filtered selectively obtaining the desired new product 4 (yield 90.1%).
Microwave-assisted. In a closed system, there were placed the product cyanohydrin of the pentacyclic
[
5.4.0.02,6.03,10.05,9]undecane-8,11-dione monoethylene acetal 3 (1.0 mmol) and acetonitrile (1.0
mL) in the presence of sulphated zirconia (25 mg). The reaction mixture was stirred in a CEM
Discover Labmate® microwave reactor at 60 °C and 100 W for 20 min, with rapid stirring. Subsequently
the catalyst was filtered selectively obtaining the desired new product 4 (yield 91.7%).
7
-Isocyanooctahydrospiro[2,4,1-(epiethane[1,1,2]triyl)cyclobuta[cd]pentalene-5,2'-[1,3]dioxolan]-7-
+
+
3
ol (4). Yellow oil. GC-MS for C14H15NO (m.w.: 245 g/mol): [M+1] = 246, [M+29] = 274,
+
−1
[M+41] = 286; FTIR-ATR (cm ): 3433, 2974, 2871, 2247, 1342, 1275, 1212, 1143, 1036, 904, 868,
1
644; FAB-MS m/z (rel. int.%): Obs. 245.0989 (66.3) calc. 245.1052; H-NMR (500 MHz, CDCl
3
):
δ (ppm), 3.82–3.80 (m, 2H), 3.78–3.75 (m, 2H), 3.26–3.22 (m, 1H), 3.21–3.17 (m, 1H), 2.87–2.79 (m,
H), 2.75–2.72 (m, 1H), 2.64–2.61 (m, 1H), 2.13–2.11 (m, 1H), 1.99 (dt, J = 10.9, 1.5 Hz, 1H), 1.64
4
1
3
(
dt, J = 11.0, 1.6 Hz, 1H); C-NMR (125 MHz, CDCl ): δ (ppm) 122.63, 117.96, 78.44, 68.15, 61.94,
3
6
0.63, 53.70, 50.83, 45.38, 43.58, 43.38, 42,76, 42.23, 41.25.
4
. Conclusions
We have demonstrated that the use of sulphated zirconia and hydrotalcites Mg/Al, provides efficient
results in the organic transformations as protection, cyanosililation and deprotection of the pentacyclo
2
,6 3,10 5,9
[
5.4.0.0 .0 .0 ]undecane-8,11-dione, under soft treatment and in the absence of solvents.
Microwave-assisted method improves the performances that are obtained under thermal classic
conditions and diminishing the reaction times.