Trimethyl borate → Benzenepropanoic acid, 4-borono-α,α-dimethyl-

Temperature

-70 °C

1-bromo-4-(2-carboxy-2-methylpropyl)benzene (1.93 g) was dissolved in anhydrous tetrahydrofuran (20 ml) and cooled to −70° C. A 1.25M solution of n-butyl lithium in hexane (18 ml) was added dropwise with stirring under an argon atmosphere, such that the temperature did not exceed −65° C. After a further 20 minutes, trimethyl borate was slowly added at −65° C. and the reaction mixture was allowed to attain −15° C. The reaction was quenched by the addition of a saturated aqueous solution of ammonium chloride (50 ml) and the mixture acidified by the addition of 2M hydrochloric acid. The organic phase was separated and the aqueous layer was extracted with ethyl acetate (2×50 ml). The combined organic phase was washed with brine (15 ml) and evaporated and the residue was triturated with hexane to give 4-(2-carboxy-2-methylpropyl)benzeneboronic acid (1.2 g); 1H NMR (DMSO-d6): 1.06 (s, 6H), 2.78 (s, 2H), 7.11 (d, 2H), 7.67 (d, 2H), 7.9 (br s, 2H), 12.2 (br s, 1H); mass spectrum (−ve ESP) 221 (M−H)−.

1. customdid not exceed −65° C
2. customto attain −15° C
3. customThe reaction was quenched by the addition of a saturated aqueous solution of ammonium chloride (50 ml)
4. additionthe mixture acidified by the addition of 2M hydrochloric acid
5. customThe organic phase was separated
6. extractionthe aqueous layer was extracted with ethyl acetate (2×50 ml)
7. washThe combined organic phase was washed with brine (15 ml)
8. customevaporated
9. customthe residue was triturated with hexane

ORD record

ord-e90a8191d2164c38ad65e9a61a9c8ac3

Source dataset

uspto-grants-2001_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06258817B1