Diastereoselective [3 + 2] Cycloaddition of Lewis Acidic Alkenylboranes and Aldehydes

The [3 + 2] cycloaddition of Lewis acidic alkenylboranes with aldehydes is described, providing a high-yielding and stereoselective approach for the synthesis of five-membered boron-containing heterocycles. Notably, alkenylboranes are used as three-atom B-C═C building blocks. The reaction proceeded smoothly under mild conditions and formed three contiguous stereogenic centers. Additionally, the reaction tolerated a wide variety of substituents on aldehydes and led to BOC₃ cyclic scaffolds in 71-98% isolated yields and up to 20:1 dr.