Nitrogen → tert-Butyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-3,4-dihydropyridine-1(2H)-carboxylate

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Reaction Conditions

Reaction Steps

A flask with 4,4,4′,4′,5,5,5′-heptamethyl-2,2′-bi(1,3,2-dioxaborolane) (10.48 g, 43.7 mmol), (dppf)PdCl2 (0.930 g, 1.139 mmol), and potassium acetate (11.18 g, 114 mmol) was flushed with N2 (3×), then 1,4-dioxane (100 mL) was added followed by a solution of tert-butyl 5-(trifluoromethylsulfonyloxy)-3,4-dihydropyridine-1(2H)-carboxylate and tert-butyl 3-(trifluoromethylsulfonyloxy)-5,6-dihydropyridine-1(2H)-carboxylate (1:1 ratio, 12.58 g, 38.0 mmol) in 1,4-dioxane (100 mL). The solution was heated in an 80° C. oil bath for 20 hours. The reaction was quenched with water (100 mL) and the aqueous layer extracted with EtOAc (3×100 mL). The combined organic layers were washed with saturated aqueous NaCl (100 mL), dried with magnesium sulfate (MgSO4), and concentrated. The residue was purified by silica gel chromatography using ISCO™ (330 g SiO2, O-20% EtOAc/hexane) to give tert-butyl 3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,6-dihydropyridine-1(2H)-carboxylate and tert-butyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-3,4-dihydropyridine-1(2H)-carboxylate (7.29 g, 23.58 mmol, 62.1% yield) (inseparable 2:1 mixture of olefin regioisomers) as a white solid.

Provenance & Evidence