To 6-chloro-3,3-dimethyl-2,3-dihydro-indole-1,5-dicarboxylic acid 1-tert-butyl ester (0.067 g, 0.21 mmol) in DMF (1.03 mL) was added N,N-diisopropylethylamine (0.126 μL, 0.72 mmol) and O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (0.08 g, 0.21 mmol) at room temperature. After stirring for 10 minutes, N-hydroxyacetamidine (0.015 g, 0.41 mmol) was added and the reaction stirred for 18 h. DMF (3.44 mL) was added and the reaction heated to 120° C. for 3 h. Water was added and the mixture extracted with diethyl ether (3×). The combined organic extracts were dried over sodium sulfate, filtered and concentrated. Chromatography (silica gel, gradient elution, 0-60%, EtOAc in petrol 40-60) gave the title compound (36 mg). MS: [M+H]+=364.
