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Abstract

(Z)-1-Bromo-1-alkenylboronate esters were easily synthesized from the hydroboration of terminal alkynes with dibromoborane dimethyl complex under nitrogen atmosphere followed by treatment with propne-1,3-diol. These boronate esters are readily reacted with 1,3-dioxan-2-ylethyl)magnesium bromide in ether and tetrahydrofuran at -78 ºC for 1 h. The resulting "ate" complex upon addition of sodium methoxide in methanol undergo intramolecular nucleophilic substitution reactions to produce the corresponding (E)-alkenylboronate esters containing (1,3-dioxan-2-ylethyl) moiety in 70-82% isolated yields. The resulting intermediates are oxidized with sodium acetate and hydrogen peroxide to provide the corresponding β-keto cycloacetals in good yields (68-84%).

Keywords

Organoboranes Hydroboration Terminal alkynes β-keto cycloacetals

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G. Bhat, N., Dalu, Z., & Nieto, R. (2020). Novel Synthesis of β-Keto Cycloacetals via Organoboranes. Asian Journal of Organic & Medicinal Chemistry, 5(2), 171–173. https://doi.org/10.14233/ajomc.2020.AJOMC-P226
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