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7.4.6 One-Pot Ring Opening of Epoxides/Palladium-Catalyzed Dehydroborylation Reaction

DOI: 10.1055/sos-SD-230-00085

Pineschi, M.; Boldrini, C.Science of Synthesis: Advances in Organoboron Chemistry towards Organic Synthesis, (20191223.

The uncatalyzed ring-opening reaction of epoxides (e.g., 98) with lithiated bis[(pinacolato)boryl]methane leads to 1,3-hydroxydiboronates; a subsequent palladium-catalyzed formal dehydroboration yields 3-hydroxyalk-1-enylboronates 99. A strong base, such as 2,2,6,6-tetramethylpiperidide, is required for deprotonation of bis[(pinacolato)boryl]methane. Ring opening proceeds smoothly in tetrahydrofuran at room temperature. The subsequent dehydroboration is best catalyzed by allylpalladium(II) chloride dimer using allyl chloride as a stoichiometric oxidant, and requires heating up to 60 °C (Scheme 28).

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