Methylboronic Acid → 5-Methylene-3-(2,2,3,3-tetrafluoro-2,3-dihydrobenzo[b][1,4]dioxin-6-yl)thiazolidin-2-imine

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Reaction Steps

An alternative procedure for the preparation of the titled compound follows. The acetyl-imine (Example 22B, 725 mg, 2.0 mmol) was dissolved into acetic acid (5 mL) and treated with a solution of methylboronic acid (180 mg, 3.0 mmol) in acetic acid (2 mL). After the solution was stirred for 5 minutes, it was further treated with solid sodium perborate (491 mg, 6.0 mmol). The mixture was stirred at room temperature overnight, and then more sodium perborate (163 mg, 2.0 mmol) was added. After 2 hours, the solution was concentrated thrice from EtOAc (3×15 mL), partitioned between 2:1 EtOAc/hexanes (15 mL) and water (5 mL) with enough concentrated NH4OH to bring the aqueous pH to 8. The aqueous phase was separated and extracted with more 2:1 solution, and the combined organic phases were twice washed with a mixture of water (2 mL) and concentrated NH4OH (0.5 mL), washed with brine, dried (Na2SO4), concentrated, and chromatographed on silica (50% CH2Cl2/hexanes, then 0 to 4% EtOAc/CH2Cl2) to give the titled compound.

Provenance & Evidence