Carbon Dioxide → ethyl 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole-2-carboxylate
Reaction equation
O=[C:2]1O[N:5]=[N+:4]2[CH2:7][CH2:8][CH2:9][CH:3]12.C(OCCOCC)C.[C:18]([O:22][CH2:23][CH3:24])(=[O:21])[C:19]#C.C(=O)=O>>[N:5]1[N:4]2[CH2:7][CH2:8][CH2:9][C:3]2=[CH:2][C:19]=1[C:18]([O:22][CH2:23][CH3:24])=[O:21]Participants
Conditions
- Temperature
- 122.5 °C
Procedure
The 3a,4,5,6-Tetrahydro-3-oxo-3H-pyrrolo[1,2-c][1,2,3]oxadiazol-7-ium ylide (971 g, 7.70 mol, made as in example 2) and 1,2-diethoxyethane (DEE, 2913 mL) are charged to a multinecked 12 L round bottom flask, is equipped with a water cooled condenser, and purged with nitrogen. The stirred solution is heated to 120-125° C. under a nitrogen atmosphere and ethyl propiolate (971 g, 9.90 mol) is added dropwise over a period of 3 hours (carbon dioxide evolution). The reaction is held at 120-125° C. for about 5 hours until the conversion is >99% (<1% of residual 3a,4,5,6-tetrahydro-3-oxo-3H-pyrrolo[1,2-c][1,2,3]oxadiazol-7-ium ylide, by GC-MS analysis). The mixture is then concentrated under oil pump vacuum using a rotary evaporator with a bath temperature up to 70° C. to a residue. About 1.5 kg of toluene is then added to the residue and the mixture is concentrated once more. A dark oil is obtained [1218 g, 46.9% strength, (HPLC) in 41% (real yield of ethyl 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole-2-carboxylate, from crude 3a,4,5,6-tetrahydro-3-oxo-3H-pyrrolo[1,2-c][1,2,3]oxadiazol-7-ium ylide].
Workup
- customis equipped with a water cooled condenser
- custompurged with nitrogen
- concentrationThe mixture is then concentrated under oil pump vacuum
- customa rotary evaporator with a bath temperature up to 70° C. to a residue
- additionAbout 1.5 kg of toluene is then added to the residue
- concentrationthe mixture is concentrated once more
Sources & evidence
- ORD record
- ord-d091a5da7cd343828f966c76d7cb7083
- Source dataset
- uspto-grants-2007_10
- Patent number
- US07276611B2
Reaction notes
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