Transition-metal-free borylation of allylic and propargylic alcohols

Abstract

The base-catalyzed allylic borylation of tertiary allylic alcohols allows the synthesis of 1,1-disubstituted allyl boronates, in moderate to high yield. The unexpected tandem performance of the Lewis acid-base adduct, [Hbase]+[MeO-B2pin2]- favored the formation of 1,2,3-triborylated species from the tertiary allylic alcohols and 1-propargylic cyclohexanol at 90 °C. A transition-metal-free allylic borylation of tertiary allylic alcohols provides access to new allylic boronates. The reactions were carried out in the presence of 15 mol % of Cs2CO3 and MeOH to promote the Lewis acid-base adduct formation [Hbase]+[MeO-B2pin2]-, which may be responsible for generating unprecedented 1,2,3-polyborated products.