Trimethyl borate → [4-(Cyclopropylmethyl)phenyl]boronic acid
Reaction equation
Br[C:2]1[CH:7]=[CH:6][C:5]([CH2:8][CH:9]2[CH2:11][CH2:10]2)=[CH:4][CH:3]=1.C([Li])CCC.[B:17](OC)([O:20]C)[O:18]C>O1CCCC1.CCCCCC>[CH:9]1([CH2:8][C:5]2[CH:6]=[CH:7][C:2]([B:17]([OH:20])[OH:18])=[CH:3][CH:4]=2)[CH2:11][CH2:10]1Participants
Conditions
- Temperature
- -70 °C
Procedure
1-Bromo-4-(cyclopropylmethyl)benzene (2.11 g) was dissolved in anhydrous tetrahydrofuran (20 ml) and cooled to -70° C. under an argon atmosphere. A 1.25M solution of n-butyl lithium in hexane (8.8 ml) was added at such a rate that the temperature did not exceed -65° C. with stirring, which was maintained for a further 30 minutes. Trimethyl borate was added slowly keeping the temperature below -60° C. and the reaction mixture was stirred for a further 1.5 hours at -70° C. After warming to -5° C., the reaction was quenched by the addition of a saturated aqueous solution of ammonium chloride (50 ml) and the organic phase was separated. The aqueous layer was extacted with ethyl acetate (2×30 ml) and combined organic phases were dried (MgSO4) and evaporated to give 4-(cyclopropylmethyl)phenylboronic acid (1.52 g); 1H NMR (d6 -DMSO): 0.2 (d, 2 H), 0.5 (d, 2 H), 0.9-1.07 (m, 1 H), 2.5 (partly obscured by DMSO), 7.2 (d, 2 H), 7.7 (d, 2 H); mass spectrum (-ve ESP) 175 (M-H)-.
Workup
- customdid not exceed -65° C.
- temperaturewhich was maintained for a further 30 minutes
- customthe temperature below -60° C.
- stirringthe reaction mixture was stirred for a further 1.5 hours at -70° C
- temperatureAfter warming to -5° C.
- customthe reaction was quenched by the addition of a saturated aqueous solution of ammonium chloride (50 ml)
- customthe organic phase was separated
- dry with materialwere dried (MgSO4)
- customevaporated
Sources & evidence
- ORD record
- ord-b65b3327bc8342fea9afbd94d6be7767
- Source dataset
- uspto-grants-1999_02
- Patent number
- US05866568
Reaction notes
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