New in the synthesis of practically important five-membered boracarbocycles by transmetallation of aluminacarbocycles with boron halides

The data obtained by the authors in the field of chemistry of substituted borolanes and 2,3-dihydro-1H-boroles are summarized. The authors developed a selective method for the synthesis of five-membered boracarbocycles via transmetalation of aluminacarbocycles, obtained by catalytic cycloalumination of unsaturated compounds (terminal olefins or acetylenes) with AlEt₃ in the presence of Cp₂ZrCl₂ as a catalyst, by boron halides (BF₃·Et₂O, BCl₃, BBr₃). Some examples of the use of this approach to modify steroid compounds (in particular, to introduce a borolan fragment into them) are described in this review.