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While under a nitrogen atmosphere, a solution of tert-butyl 4-(4-chlorophenoxy)-2-(diphenylmethyleneamino)butanoate (450 mg, 1.0 mmol) in tetrahydrofuran (7 mL) was cooled to −78° C. and treated with sodium bis(trimethylsilyl)amide (2.0 mL, 1.0 M in tetrahydrofuran, 2.0 mmol) in a dropwise manner. After the addition was complete, stirring was continued for 30 minutes and 2-(4-iodobutyl)-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane (931 mg, 3.0 mmol) was slowly added to the reaction mixture. Stirring was continued for 2 more hours, and then slowly warmed to room temperature overnight. The resulting solution was poured into water, and extracted with ethyl acetate (3×). The combined organic phase was washed with saturated aqueous sodium chloride, dried over anhydrous magnesium sulfate, filtered and concentrated. Purification by flash column chromatography (silica gel, 0-15% ethyl acetate in heptane) gave tert-butyl 2-(2-(4-chlorophenoxy)ethyl)-2-(diphenylmethyleneamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)hexanoate as a colorless oil (486 mg. 77%); 1H NMR (CDCl3, 300 MHz) δH 7.54 (d, J=7 Hz, 2H), 7.36 (m, 4H), 7.18-7.32 (m, 6H), 6.82 (d, J=9 Hz, 2H), 4.19 (m, 1H), 4.04 (m, 1H), 2.39 (ddd, J=14 Hz, J2=9.5 Hz, J3=5.0 Hz, 1H), 2.22 (ddd, J1=13.5 Hz, J2=9.5 Hz, J3=5.0 Hz, 1H), 1.73 (m, 2H), 1.14-1.46 (m, 4H), 1.34 (s, 9H), 1.18 (s, 12H) and 0.76 (t, J=7 Hz, 2H); MS (+CI): m/z for C37H47BClNO5: expected 631.3. found 632.3 (M+H)+, 576.3 (M+H-isobutene)+.

1. additionAfter the addition
2. stirringStirring
3. extractionextracted with ethyl acetate (3×)
4. washThe combined organic phase was washed with saturated aqueous sodium chloride
5. dry with materialdried over anhydrous magnesium sulfate
6. filtrationfiltered
7. concentrationconcentrated
8. customPurification by flash column chromatography (silica gel, 0-15% ethyl acetate in heptane)