Synthesis
General procedure for the synthesis of benzofuran-2-boronic acid pinacol esters from 2,3-benzofuran and pinacolborane: According to the reaction scheme for the boronation of Example 9-aromatic five-membered heterocyclic rings (Fig. 2a), cobalt complex (0.01 mmol, selected from 1-4), 2-methylfuran (1 mmol), and pinacolborane (1 mmol) were added to a scintillation vial fitted with magnetic stirring bar. 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 stopper, followed by 1H and 13C NMR spectroscopy without further purification. Depending on the experimental requirements, the above reaction can also be carried out in 2 ml of tetrahydrofuran (THF). Figure 2a illustrates the percentage conversion of cobalt complexes 1-4, with the values in parentheses being the isolated yields. In addition, Figure 2b describes in detail the results of other boronation products achieved using cobalt complexes 2 and 3 under the same reaction conditions.
References
[1] Chemical Communications, 2003, # 23, p. 2924 - 2925
[2] Journal of the American Chemical Society, 2014, vol. 136, # 11, p. 4133 - 4136
[3] Patent: WO2015/89119, 2015, A1. Location in patent: Page/Page column 34
[4] Chemical Communications, 2003, # 23, p. 2924 - 2925
[5] ACS Catalysis, 2018, vol. 8, # 6, p. 5017 - 5022
