Triisopropyl borate → HCID 131732188, compound

Participants

Reaction Conditions

Reaction Steps

5-(tert-Butyl-dimethyl-silanyloxymethyl)-indole-1-carboxylic acid tert-butyl ester (8b) (5.89 g, 16.3 mmol) was stirred in tetrahydrofuran (80 mL) and triisopropyl borate (4.18 g, 5.13 mL, 22.2 mmol) was added, and the reaction mixture was cooled to −5° C. To this was added the previously described lithiumdiisopropyl amide solution drop wise keeping the temperature between −5° C. and 0° C. After addition the reaction was stirred at −5° C. for 30 mins and then allowed to attain ambient temperature. The reaction mixture was concentrated in vacuo to yield crude indole-2-boronic acid-5-(tert-Butyl-dimethyl-silanyloxymethyl)-indole-1-carboxylic acid tert-butyl ester, which was dissolved in tetrahydrofuran (100 mL). Water (20 mL), potassium carbonate (6.17 g, 44.6 mmol), 3-iodo-5-nitro-1-(2-trimethylsilanyl-ethoxymethyl)-1H-pyridin-2-one, intermediate (6a) (5.87 g, 14.8 mmol) in tetrahydrofuran (20 mL) and [1,1′-Bis(diphenylphosphino)ferrocene)]dichloropalladium(II), complex with dichloromethane (0.605 g, 5 mol %) were added. The red suspension was degassed for 10 minutes and then heated at 60° C. for 2 hours. The reaction mixture was cooled and was partitioned between ethyl acetate (200 mL) and aqueous saturated sodium bicarbonate solution (200 mL). The organic layer was separated and the aqueous was extracted with a further portion of ethyl acetate. The combined ethyl acetate layers were washed with brine, dried (Na2SO4), filtered through a plug of celite and concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO2 eluting with hexane—15% ethyl acetate/hexane (gradient) to afford the desired title compound as a yellow solid, 8.44 g, 90%.

Provenance & Evidence