Synthesis
The general procedure for the synthesis of 2-methylfuran-5-boronic acid pinacol ester from 2-methylfuran and pinacolborane is as follows: according to the reaction scheme for the boronation of Example 9-aromatic five-membered heterocyclic rings (Fig. 2a), to a scintillation vial fitted with a magnetic stirring bar were added a cobalt complex of 1-4,2-methylfuran (0.01 mmol), 2-methylfuran (1 mmol) and pinacolborane ( 1 mmol). The reaction process was monitored by analyzing an aliquot of the mixture by GC-FID. The reaction mixture was stirred at room temperature until the reaction was complete and subsequently quenched by exposure to air. The resulting solid was dissolved in CDCl3 and filtered through a Pasteur pipette fitted with a silicone plug, followed by 1H and 13C NMR spectroscopy without further purification. If the reaction conditions need to be adjusted, the above reaction can be carried out in 2 ml of tetrahydrofuran (THF). Figure 2(a) demonstrates the percentage conversion of cobalt complexes 1-4, and the values in parentheses are the isolated yields. In addition, Figure 2(b) describes in detail the other boronation products achieved using cobalt complexes 2 and 3 according to the aforementioned reaction parameters.
References
[1] Patent: WO2015/89119, 2015, A1. Location in patent: Page/Page column 34
[2] ACS Catalysis, 2018, vol. 8, # 6, p. 5017 - 5022
[3] Journal of the American Chemical Society, 2014, vol. 136, # 11, p. 4133 - 4136
[4] Chemistry - An Asian Journal, 2010, vol. 5, # 7, p. 1657 - 1666
[5] Science, 2015, vol. 349, # 6247, p. 513 - 516
