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General procedure: To a stirred H2O (25 mL) suspension of the appropriateboronic acid-containing aldehyde (2.22 mmol) and 1 dropof formic acid was added an aqueous solution (5 mL) ofcarbohydrazide (100 mg, 1.11 mmol). Compound 7 wassynthesized using MeOH as the solvent. The reactionmixture was heated at reflux for 2 h, at which pointthe reaction was allowed to cool to room temperature(RT). The resulting precipitate was collected by suctionfiltration and washed with Et2O (2 × 10 mL) to afford thepentacyclic oxadiazadiborinanes as white or off-whitesolids.