N-bromobutanimide → Methyl 2-bromomethyl-6-(tert-butyldimethylsilyloxy)benzoate

Beteiligte Stoffe

Reaktionsschritte

N-Bromosuccinimide (7.6 g) was added to a solution of methyl 2-(tert-butyldimethylsilyloxy)-6-methylbenzoate (Intermediate 13, 11.9 g) in carbon tetrachloride (150 mL) and the mixture was stirred and heated to reflux. Azo-bis-isobutyronitrile (0.1 g) was added and the mixture was illuminated with a 500 W tungsten filament lamp for 2 hours. The mixture was cooled and left to stand overnight then filtered through a 25 g silica cartridge eluting with a mixture of ethyl acetate and pentane (20%). The eluent was evaporated to dryness and the residue was redissolved in carbon tetrachloride (150 mL) and N-bromosuccinimide (6.96 g) was added. The mixture was heated to reflux and azo-bis-isobutyronitrile (0.1 g) was added. The resultant mixture was illuminated with a 500 W tungsten filament lamp overnight. After cooling, the mixture was filtered and the solid was washed with pentane. The combined organic solutions were evaporated to dryness and the residue was purified by chromatography on silica, eluting with a mixture of TBME and pentane with a gradient of 0-10% to give methyl 2-bromomethyl-6-(tert-butyldimethylsilyloxy)benzoate (4.99 g) as a yellow oil.

Herkunft & Nachweise