Ethyl propiolate → ethyl 4H,6H,7H-pyrazolo(3,2-c)(1,4)oxazine-2-carboxylate

HRID 2216623Notes

Reaction equation

[N:1]1O[C:3]([O-])=[C:4]2[N+:9]=1[CH2:8][CH2:7][O:6][CH2:5]2.[C:11]([O:15][CH2:16][CH3:17])(=[O:14])[C:12]#C>CC1C=CC=CC=1C>[N:1]1[N:9]2[C:4]([CH2:5][O:6][CH2:7][CH2:8]2)=[CH:3][C:12]=1[C:11]([O:15][CH2:16][CH3:17])=[O:14]

Participants

Conditions

Temperature: 140 °C

Procedure

To a partial solution of 6,7-dihydro-4H-[1,2,3]oxadiazolo[4,3-c][1,4]oxazin-8-ium-3-olate (3.41 g, 24 mmol) in o-xylene (80 ml), was added ethyl propiolate (2.7 ml, 26 mmol). The mixture was stirred at 140° C. for 3 hr. An additional 2.0 ml (19 mmol) of ethyl propiolate was then added and the mixture was stirred at reflux for 18 hr. The final solution was evaporated under vacuum, and the residue was dissolved in a mixture of methylene chloride and hexanes (1:5). The solution was passed through a pad of silica gel and the filter pad was eluted with methylene chloride-hexanes, followed by ethyl acetate. The ethyl acetate eluent was evaporated and the residue washed with hexanes to give 4.10 g of a white solid; mp 63° C.; MS (ESI) m/z 197.1 (M+H).

Workup

stirringthe mixture was stirred
temperatureat reflux for 18 hr
customThe final solution was evaporated under vacuum
dissolutionthe residue was dissolved in a mixture of methylene chloride and hexanes (1:5)
washthe filter pad was eluted with methylene chloride-hexanes
customThe ethyl acetate eluent was evaporated
washthe residue washed with hexanes

Sources & evidence

ORD record: ord-bcc9dd7dab1b46ac8c9c2937242a1eb9
Source dataset: uspto-grants-2006_09
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US07112582B2

Reaction notes

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