Nicola Della Ca’ et al.
FULL PAPERS
(B, 10 mol%) and 15 mL of CH3CN. The autoclave was
sealed, purged at room temperature several times with CO2
with stirring (10 bar), and eventually was pressurized with
40 bar of gaseous CO2 at room temperature. After stirring
of the mixture at 1008C for 24 h, the autoclave was cooled,
degassed and opened. The products were recovered using
15 mL of CH2Cl2 and then purified by column chromatogra-
phy on silica gel, using hexane-acetone from 9:1 to 7:3 as
eluent.
Experimental Section
General Remarks
Solvents and chemicals were of reagent grade and were
used without further purification. MeCN was dried over 3 ꢂ
molecular sieves and stored under nitrogen. All reactions
were analyzed by TLC and by GC using a 30 m SE-30 capil-
lary column. Column chromatography was performed on
silica gel 60 (70–230 mesh). Melting points were measured
with an Electrothermal apparatus and are uncorrected.
Electron impact mass spectra [m/z, relative intensity (%)]
were determined with a GC-MS apparatus at 70 eV ioniza-
tion energy. Infrared (IR) spectra were recorded on an FT-
IR 5700 spectrophotometer. Elemental analyses were per-
4-Methylene-1,3-dioxaspiro
G
(1c):
Yield: 470 mg (56%) (Table 3, entry 4); colourless liquid. IR
(film): n=2940 (s), 2864 (m), 1841 (s), 1814 (s), 1685 (s),
1450 (m), 1311 (m), 1271 (m), 1201 (m), 1129 (m), 1060 (s),
1023 (s), 852 (m), 769 (m) cmÀ1 1H NMR (300 MHz,
;
CDCl3): d =1.56–1.79 (m, 6H, 3CH2), 1.97–2.02 (m, 4H,
2CH2), 4.27 (d, J=3.8 Hz, 1H, =CHH), 4.75 (d, J=3.8 Hz,
1H, CHH); 13C NMR (75 MHz, CDCl3): d=159.0, 147.0,
90.7, 79.3, 38.1, 28.4, 19.9; GC-MS: m/z=168 (M+, 1), 99
(100), 81 (64), 79 (10), 69 (3), 55 (5), 43 (5); anal. calcd. for
C9H12O3: C 64.27, H 7.19; found: C 64.18, H 7.17.
formed at our analytical laboratory. H NMR and 13C NMR
1
spectra were recorded in CDCl3 at 300 and 75 MHz, respec-
tively, using the solvent as internal standard (7.26 ppm for
1H NMR and 77.0 ppm for 13C NMR). Chemical shifts (d)
and coupling constants (J) are given in ppm and in Hz, re-
spectively. The reported configurations (E or Z) were as-
signed on the basis of decoupling, COSY, and NOESY cor-
relation experiments.
4-Phenyl-4-methyl-5-methylene-1,3-dioxolan-2-one (1d):
Yield: 646 mg (68%) (Table 3, entry 6); white solid, mp
29.7–30.98C. IR (KBr): n=2985 (m), 1820 (s), 1686 (s), 1449
(w), 1297 (w), 1225 (m), 1122 (m), 1063 (m), 1022 (s), 698
(m) cmÀ1 1H NMR (300 MHz, CDCl3): d=1..96 (s, 3H,
;
General Procedure for the Catalytic Synthesis of
Carbonates in scCO2 (Table 1 and Table 2)
CH3), 4.45 (d, J=4.0 Hz, 1H, =CHH), 4.94 (d, J=4.0 Hz,
1H, =CHH), 7.25–7.50 (m, 5H, ArH); 13C NMR (75 MHz,
CDCl3): d=155.5, 148.0, 144.1, 129.5, 125.4, 90.6, 87.4, 26.9;
GC-MS: m/z=190 (M+, 1), 146 (15), 131 (17), 118 (100),
117 (86), 103 (45), 91 (17), 77 (40), 63 (8), 51 (26), 43 (8);
anal. calcd. for C11H10O3: C 69.46, H 5.30; found: C 69.60, H
5.35.
The propargyl alcohol (5.0 mmol) was transferred to a 125-
mL stainless steel autoclave together with the catalyst (B,
10 mol%). The autoclave was sealed, purged at room tem-
perature several times with CO2 with stirring (10 bar), and
eventually charged with 44 g of liquid CO2 at room tempera-
ture (by weighing it before and after the pressurization).
After stirring the mixture at 1008C for 24 h, the autoclave
was cooled, degassed, and opened. The products were recov-
ered using 15 mL of CH2Cl2 and then purified by column
chromatography on silica gel, using hexane-acetone from
9:1 to 7:3 as eluent.
General Procedure for the Catalytic Synthesis of
Carbonates and Carbamates in scCO2 in the Presence
of an External Nucleophile (Table 4 and Table 5)
The propargylic alcohol (5.0 mmol) was transferred to a
125-mL stainless steel autoclave together with the catalyst
(10 mol%) and an alcohol or an amine (5.0 mmol), acting as
external nucleophile. The autoclave was sealed, purged at
room temperature several times with CO2 with stirring
(10 bar), and eventually charged with 44 g of liquid CO2 at
room temperature (by weighing it before and after the pres-
surization). After stirring of the mixture at 1008C for 24 h,
the autoclave was cooled, degassed and opened. The prod-
ucts were recovered using 15 mL of CH2Cl2 and then puri-
fied by column chromatography on silica gel, using hexane-
acetone from 9:1 to 7:3 as eluent.
4,4-Dimethyl-5-methylene-1,3-dioxolan-2-one
(1a):
Yield: 262 mg (41%) (Table 1, entry 2); white solid, mp
27.5–28.38C. IR (KBr): n=2988 (m), 2939 (w), 1834 (s),
1689 (s), 1374 (m), 1316 (m), 1275 (s), 1175 (s), 1087 (s),
1
1036 (s), 856 (s), 770 (s) cmÀ1; H NMR (300 MHz, CDCl3):
d =1.59 (s, 6H, 2CH3), 4.28 (d, J=3.9 Hz, 1H, =CHH), 4.74
(d, J=3.9 Hz, 1H, =CHH); 13C NMR (75 MHz, CDCl3): d=
163.1, 149.2, 84.2, 74.0, 31.0; GC-MS: m/z=128 (M+, 2), 113
(2), 84 (8), 69 (9), 56 (72), 43 (36), 42 (47), 41 (100); anal.
calcd. for C6H8O3: C 56.24, H 6.29; found: C 56.38, H 6.33.
Di-(1,1-dimethyl-2-oxopropyl) carbonate (2a): Yield:
328 mg (57%) (Table 1, entry 1); yellow oil. IR (film): n=
2987 (m), 1740 (s), 1724 (s), 1674 (m), 1653 (w), 1457 (w),
Methyl 2-methyl-3-oxobutan-2-yl carbonate (6a): Yield:
536 mg (67%) (Table 4, entry 1); colourless liquid. IR (film):
n=2992 (s), 2960 (s), 2856 (m), 1809 (s), 1747 (s), 1725 (s),
1639 (w), 1443 (s), 1384 (s), 1368 (s), 1292 (s), 1157 (m),
1369 (w), 1305 (s), 1150 (m), 1112 (s), 920 (w) cmÀ1
;
1H NMR (300 MHz, CDCl3): d=1.53 (s, 12H, 4CH3), 2.18
(s, 6H, 2CH3); 13C NMR (75 MHz, CDCl3): d=206.0, 152.6,
85.8, 23.6, 23.2; GC-MS: m/z=230 (M+, 1), 187 (14), 147
(3), 86 (25), 85 (100), 71 (12), 57 (57), 43 (72); anal. calcd.
for C11H18O5: C 57.38, H 7.88; found: C 57.51, H 7.92.
1
1124 (m), 1028 (m), 947 (s), 860 (s), 795 (m) cmÀ1; H NMR
(300 MHz, CDCl3): d=1.37 (s, 6H, 2CH3), 2.03 (s, 3H,
CH3CO), 3.64 (s, 3H, OCH3); 13C NMR (75 MHz, CDCl3):
d=206.2, 154.2, 85.2, 54.6, 23.2, 22.9; GC-MS: m/z=160
(M+, 4), 117 (50), 85 (15), 73 (100), 59 (34), 57 (35), 43 (92),
41 (24); anal. calcd. for C7H12O4: C 52.49, H 7.55; found: C
52.32, H 7.46.
General Procedure for the Catalytic Synthesis of
Carbonates with Gaseous CO2 in CH3CN (Table 3)
The propargylic alcohol (5.0 mmol) was transferred to a
125-mL stainless steel autoclave together with the catalyst
3-n-Butyl-5,5-dimethyl-4-methyleneoxazolidin-2-one
(8a): Yield: 695 mg (76%) (Table 5, entry 1); colourless
144
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2011, 353, 133 – 146