One-pot catalytic asymmetric borylation of unsaturated aldehyde-derived imines; functionalisation to homoallylic boronate carboxylate ester derivatives.

The β-borylation reaction of α,β-unsaturated aldehyde-derived imines, formed in situ, has been studied using a one-pot methodology, as a route to β-boryl aldehydes. The instability of the β-boryl aldehydes meant that derivatisation was required and routes to both acetal derivatives and homoallylic boronates were examined. β-Boryl acetals were also found to be unstable, however, the formation of homoallylic boronate derivatives using an in situ imine hydrolysis-Wittig olefination protocol was found to be suitable, resulting in an efficient synthesis with high enantiomeric excesses.