Beyond the Balz-Schiemann reaction: the utility of tetrafluoroborates and boron trifluoride as nucleophilic fluoride sources.

摘要: The Balz-Schiemann synthesis of aryl fluorides via the thermal decomposition diazonium tetrafluoroborate salts represents both earliest and most proverbial example BF4 ion as a nucleophilic fluoride source. Mechanistic studies reaction have accrued strong experimental support for an SN1 mechanism intermediacy cation, which is quenched by transfer directly from ion. A notable advance in this area has been development Ohmori co-workers fluorinative variant Mitsunobu reaction, involving electrooxidative generation subsequent alkoxytriphenylphosphonium tetrafluoroborates, allowing conversion alcohols to corresponding alkyl with inversion configuration. Although stereoselectivity during C-F bond formation reactions proceeding (putative) carbocation intermediates can be highly variable, ring-opening strained rings or ?iranium fluoroborate ions typically proceeds high stereoselectivity.