A solution of (5-bromo-pyrrolo[2,3-d]pyrimidin-7-yl)-acetic acid tert-butyl ester (220 mg, 0.71 mmol), tri-butyl(1-ethoxyvinyl)tin (285 μL, 0.85 mmol) and tetrakis(triphenylphosphine) palladium (16.28 mg, 14.1 μmol) in toluene (7 mL) was heated at 110° C. for 72 h under argon atmosphere. The mixture was allowed to cool to RT, poured into water and extracted with EtOAc (×2). The combined organic layers were dried (Na2SO4), filtered and concentrated. The crude residue was purified by flash column chromatography on silica gel (CH2Cl2 to CH2Cl2/MeOH 94:6). TLC, Rf (CH2Cl2/MeOH 9:1)=0.54; MS (UPLC/MS): 276.3 [M+H]+, 320.4 [M+HCOO]−; tR (HPLC conditions f): 1.40 min.
