Efficient synthesis of chiral C2-symmetric diamines via allylboration of bis-N,N′-metallodiimines

An enantioselective synthesis of C2-symmetric bis-homoallylic aromatic and heteroaromatic diamines in 54–89% yields, in 73–94% de and ⩾98% ee has been achieved via the allylboration of the corresponding N,N′-bis(trimethylsilyl)dialdimines and N,N′-bis(diisobutylalumino)dialdimines with B-allyldiisopinocampheylborane in the presence of methanol, followed by alkaline hydrogen peroxide workup. One-pot synthesis of stable N,N′-bis(benzaldimine–triethylborane) complexes and subsequent allylboration to afford benzene diamines is also described.