1-(2-(Trimethylsilyl)ethyl) 1′-tert-butyl 5-bromospiro[indoline-3,3′-pyrrolidine]-1,1′-dicarboxylate (300 mg, 0.603 mmol) was dissolved in xylene (10 mL). Thereafter, sodium thiomethoxide (85 mg, 1.21 mmol), tris(dibenzylideneacetone)dipalladium(0) (100 mg, 0.11 mmol), and xantphos (87.0 mg, 0.15 mmol) were added to the above obtained solution at room temperature, and the thus obtained mixture was then stirred at 150° C. for 1 hour. Thereafter, the reaction solution was purified by silica gel column chromatography (hexane:ethyl acetate=3:1) to obtain 1-(2-(trimethylsilyl)ethyl) 1′-tert-butyl 5-(methylthio)spiro[indoline-3,3′-pyrrolidine]-1,1′-dicarboxylate (192 mg, 69%) in the form of a white amorphous product.
