Potassium tert-Butoxide-Catalyzed Dehydrogenative Cross-Coupling of Heteroarenes with Hydrosilanes

Abstract

A. 1-Methyl-2-(triethylsilyl)-1H-indole (2). An oven-dried 100-mL round-bottom Schlenk flask is equipped with a Teflon-coated magnetic stir bar (25 x 8 mm) and capped with a rubber septum (Note 1). The side arm of the flask is connected to Schlenk line and the flask is cooled to room temperature under vacuum and back-filled with nitrogen. Potassium tert-butoxide (1.34 g, 12.0 mmol, 0.2 equiv) is added to the flask under positive nitrogen flow (Notes 2 and 3), and then the flask is evacuated and back-filled with nitrogen three times. N-Methylindole (7.48 mL, 7.86 g, 60.0 mmol, 1.0 equiv) and triethylsilane (28.6 mL, 20.82 g, 179.5 mmol, 3.0 equiv) are added sequentially via syringe through the septum, resulting in a yellow heterogeneous mixture (Figure 1). After the septum is replaced with a glass stopper (Note 4), the reaction mixture is degassed (Note 5) and stirred at 45 oC for 76 h (Note 6), resulting in a dark purple solution. The heating bath is removed and the reaction mixture is allowed to cool to ambient temperature (~25 oC), then anhydrous diethyl ether (30 mL) is added slowly while stirring (Note 7).