Chemistry Reference
In-Depth Information
(20.5 mL) containing triethylamine (1.25 mL, 8.97 mmol) at room temperature, a
solution of triphosgene (1.78 g, 5.98 mmol) in THF (4.5 mL) was added dropwise
via a cannula over a period of 10 min. The resulting heterogeneous reaction mix-
ture was refluxed for 5 h and then concentrated in vacuo. The residue was tritu-
rated with diethyl ether and filtered through a plug of glass wool. The combined
filtrate and washings were concentrated in vacuo to give a yellow oil, which was
distilled under reduced pressure to afford 872 mg (69%) of (S)-(
)-5-ethyl-5-
methyl-1,3-dioxolane-2,4-dione 1148 as a colorless liquid.
Starting from triphosgene and 1,1
0
-ferrocenediols, 1,3-dioxa-[3]ferroceno-
phan-2-ones ''ferrocenylenecarbonates'' Fe(C
5
H
4
O)
2
CO, and the corresponding
thio derivative 1,3-dithia-[3]ferrocenophan-2-one,
''ferrocenylenedithiocarbonate''
Fe(C
5
H
4
S)
2
CO 1150, were obtained [811].
(CCl
3
O)
2
CO
S
SLi
Fe
Fe
O
THF, -78 °C
S
SLi
* 2THF
1149
1150
Typical procedure. 1,3-Dithia-[3] ferrocenophan-2-one Fe(C
5
H
4
S)
2
CO 1150 [811]:
To a
78
C,
a solution of triphosgene (0.33 mmol, 98 mg) in THF (5 mL) was added dropwise.
After warming to ambient temperature, the solution was decanted off from the
precipitated LiCl, filtered through Celite, and concentrated in vacuo. Recrystalliza-
tion of the residue from CH
2
Cl
2
afforded colored crystals, which decomposed at
194
C; yield 224 mg (82%).
The regioselective preparation of five-membered cyclic carbonates by treat-
ment of 1,2,3-, 1,2,4-, or 1,2,5-triols with triphosgene, dimethyl carbonate,or1,1
solution of Fe(C
6
H
4
SLi)
2
2THF 1149 (406 mg, 1 mmol) in THF (20 mL) at
O
-
carbonyldiimidazole has been reported [812].
The substituted 1,2,3-triol 1151 reacts with triphosgene in the presence of pyr-
idine (Method A) to afford five-membered 1,2-cyclic carbonate 1152 as the sole
product. However, reaction of 1,2,3-triol 1151 with dimethyl carbonate (Method B)
affords the more stable internal cyclic carbonate 1153.
Typical procedure. (2S,3S)-4-Benzyloxy-1,2,3-butanetriol 1,2-cyclic carbonate 1152
(Method A) [812]: To a stirred solution of triphosgene (104 mg, 0.35 mmol) in di-
chloromethane (1 mL) at
70
C were added pyridine (0.29 mL, 3.59 mmol) and a
solution of triol 1151 (125 mg, 0.59 mmol) in dichloromethane (1 mL). Once the
addition was complete, the reaction mixture was allowed to warm to room tem-
perature. The resultant homogeneous solution was quenched with saturated aq.
ammonium chloride solution, washed with 1 n aq. HCl, saturated aq. NaHCO
3
,
and brine, and dried over anhydrous MgSO
4
. The organic layer was filtered and
concentrated in vacuo. The crude product was purified by column chromatography
on silica gel using EtOAc/hexanes (1:1) as eluent to afford (2S,3S)-4-benzyloxy-
1,2,3-butanetriol 1,2-cyclic carbonate 1152 (108 mg, 77%).
