Abstract
The synthesis and physicochemical properties of benzosiloxaboroles, the silicon analogues of an important class of heterocyclic compounds-benzoxaboroles is presented. They were prepared by halogen lithium exchange reactions of (2-bromophenyl)boronates with n-BuLi followed by the silylation or boronation of (2-lithiophenyl)dimethylsilanes. The cyclization of the resulting 2-(dimethylsilyl)phenylboronates apparently occurs through intramolecular dehydrogenative cyclization reaction in the presence of water. Unlike the case for benzosiloxaborole, the formation of its analogue containing a thiophene ring is thermodynamically unfavorable, which was confirmed by theoretical calculations. The presence of a B-O-Si linkage results in increased Lewis acidity with respect to the analogous benzoxaboroles. The acidity is strongly enhanced by fluorination or introduction of phenyl groups at the silicon atom. Selected compounds show good antifungal activity, and thus they are potential small-molecule therapeutic agents. They can also serve as effective receptors for biologically relevant diols under neutral pH conditions.