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

HRID 458366Notes

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-429175fa4f3f4315a15d7d05b99f0684
Source dataset: uspto-grants-2007_03
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US07189756B2

Reaction notes

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