Boron trifluoride etherate → (2S,4R)-4-tert-butoxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid benzyl ester

HRID 1006835Notes

Reaction equation

[CH2:1]([O:8][C:9]([C@@H:11]1[CH2:15][C@@H:14]([OH:16])[CH2:13][N:12]1[S:17]([C:20]1[CH:29]=[CH:28][C:27]2[C:22](=[CH:23][CH:24]=[CH:25][CH:26]=2)[CH:21]=1)(=[O:19])=[O:18])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.B(F)(F)F.CCOCC.[CH3:39][C:40](=[CH2:42])[CH3:41].C(=O)(O)[O-].[Na+]>ClCCl>[CH2:1]([O:8][C:9]([C@@H:11]1[CH2:15][C@@H:14]([O:16][C:40]([CH3:42])([CH3:41])[CH3:39])[CH2:13][N:12]1[S:17]([C:20]1[CH:29]=[CH:28][C:27]2[C:22](=[CH:23][CH:24]=[CH:25][CH:26]=2)[CH:21]=1)(=[O:19])=[O:18])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1

Participants

Conditions

Temperature: -20 °C

Procedure

Tert-Butyletherification: To a solution of (2S,4R)-4-hydroxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid benzyl ester (14.8 g) in dichloromethane (140 ml) were added boron trifluoride ethyl etherate (3 ml) and isobutylene (cooled and liquefied at −30° C., 170 ml) at −30° C. The turbid reaction mixture was stirred at −20° C. for 2 h, poured onto a saturated sodium bicarbonate solution, and extracted with dichloromethane. The organic phases were washed with water, dried over magnesium sulphate and concentrated. The residue was chromatographed on silica gel using EtOAc/hexane 1:4 and 1:2 as eluents to obtain (2S,4R)-4-tert-butoxy-1-(naphthalene-2-sulfonyl)-pyrrolidine-2-carboxylic acid benzyl ester (16.4 g) as a glassy syrup, MS: 467 (M).

Workup

customThe turbid reaction mixture
extractionextracted with dichloromethane
washThe organic phases were washed with water
dry with materialdried over magnesium sulphate
concentrationconcentrated
customThe residue was chromatographed on silica gel

Sources & evidence

ORD record: ord-ec731da895bb443e99c66ab6b5e97401
Source dataset: uspto-grants-2004_09
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US06790860B2

Reaction notes

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