Chlorotrimethylsilane → Tert-butyl 4-(5-chloropyridin-2-yl)piperidine-1-carboxylate

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

Zn dust (225 mg, 3.5 mmol) was stirred in THF (1 mL) under Ar and 1,2-dibromoethane (50 μL) was added at room temperature. The mixture was heated to 65° C. for 3 min and allowed to cool to room temperature before trimethylsilyl chloride (70 μL) was added and the mixture was stirred at room temperature for 30 min. A solution of 4-iodo-N-Boc-piperidine (840 mg, 2.7 mmol) in THF (1.5 mL) was slowly added and the reaction mixture was stirred at 40° C. for 2 h. Pd2(dba)3 (22 mg, 0.024 mmol) and P(2-furyl)3 (23 mg, 0.10 mmol) were mixed in THF (0.5 mL), the mixture stirred at room temperature for 10 min and then added to the organozink reagent solution, followed by 2-bromo-5-chloro-pyridine (624 mg, 3.24 mmol) in THF (1 mL) and DMA (4 mL). The reaction mixture was heated at 80° C. for 3 h, allowed to cool to room temperature and then filtered through Celite and diluted with EtOAc. The filtrate was washed with saturated aqueous NaHCO3 and brine, dried Na2SO4 and concentrated. Purification on SiO2 eluting with heptane/EtOAc 95:5 to 2:1 gave tert-butyl 4-(5-chloropyridin-2-yl)piperidine-1-carboxylate as an yellow oil (128 mg, 16%). The oil was dissolved in THF (1.5 mL) and conc HCl (1.5 mL) and stirred at RT for 30 min. Concentration several times with toluene and EtOH gave the title compound (89 mg, 89%)

Herkunft & Nachweise