Pinacol → Ethanol heptane

Participants

Reaction Steps

Pd(Ph3P)4 (469 mg, 0.406 mmol) was added to a pressure tube containing a mixture of bromide (28) (4.008 g, 10.22 mmol), bis(pinacolato)diboron (5.422 g, 21.35 mmol), potassium acetate (2.573 g, 26.21 mmol) and 1,4-dioxane (80 mL). The reaction flask was purged with nitrogen, capped and heated with an oil bath at 80° C. for 16.5 hours. The reaction mixture was filtered and the filtrate was concentrated in vacuo. The crude material was partitioned carefully between CH2Cl2 (150 mL) and an aqueous medium (50 mL water+10 mL saturated NaHCO3 solution). The aqueous layer was extracted with CH2Cl2, and the combined organic phase was dried (MgSO4), filtered, and concentrated in vacuo. The resulting material was purified with flash chromatography (sample was loaded with eluting solvent; 20-35% ethyl acetate/CH2Cl2) to provide boronate (17), contaminated with pinacol, as an off-white dense solid; the relative mole ratio of (17) to pinacol was about 10:1 (1H NMR). The sample weighed 3.925 g after ˜2.5 days exposure to high vacuum. 1H NMR (DMSO-d6, δ=2.5 ppm, 400 MHz): 12.22/11.94/11.87 (m, 1H), 7.79-7.50/7.34-7.27 (m, 5H), 4.86-4.70 (m, 1H), 3.52 (app br s, 1H), 3.36 (m, 1H), 2.27-1.77 (m, 4H), 1.45-1.10 (m, 21H). LC/MS: Anal. Calcd. for [M+H]+ C24H35BN3O4: 440.27. found 440.23.

Provenance & Evidence