Trifluoroacetic acid → 2-(4-Allylchroman-6-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

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Reaction Steps

A stirred solution of 4-allyl-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)chroman-4-ol (1.80 g, 5.69 mmol) and triethylsilane (7.27 ml, 45.5 mmol) in DCE (30 ml) was treated with TFA (14.03 ml, 182 mmol) by rapid addition at ambient temperature. The reaction was stirred for 10 min, then carefully quenched with sat'd. aq. NaHCO3 (200 mL). The organic layer was concentrated and the residue was purified by biotage (80 g SiO2, 0% (3 CV), 0-60% (15 CV), 60% (2 CV), EtOAc in hexanes) to afford the desired product (0.942 g, 3.14 mmol, 55.1% yield) as a viscous clear oil. 1H NMR (400 MHz, CDCl3) δ 7.64 (s, 1H), 7.56 (dd, J=8.2, 1.4 Hz, 1H), 6.80 (d, J=8.0 Hz, 1H), 5.90-5.76 (m, 1H), 5.15-5.04 (m, 2H), 4.23-4.14 (m, 2H), 2.89 (dq, J=10.0, 5.0 Hz, 1H), 2.75-2.62 (m, 1H), 2.35-2.22 (m, 1H), 2.09-1.96 (m, 1H), 1.92-1.81 (m, 1H), 1.34 (s, 12H). LCMS (M+H)=301.3.

Provenance & Evidence