Development and synthetic applications of the asymmetric anionic amino-Cope rearrangement

The thermal and anionic amino-Cope rearrangement of suitably functionalised 3-amino-1,5-hexadienes could potentially constitute a powerful tool for the stereoselective synthesis of highly functionalised acyclic or cyclic systems. [Illustration omitted.] Incorporation of β-aminoalcohol auxiliaries into the diene enabled high diastereoselectivity to be obtained during the 1,2-addition of the allyl Grignard reagent to α,β-unsaturated imines. Asymmetric anionic amino-Cope rearrangement of the diastereoisomerically pure 3-amino-1,5-diene substrates furnished the target aldehyde in good yield and with high levels of asymmetric induction (up to 94% e.e.). The aldehyde obtained was used as a non-racemic starting material to synthesise small heterocycles, with high levels of diastereoselectivity in some cases, providing a high yielding route to some important chiral building blocks. The successful formation of both tetrahydropyrans and lactones without any apparent loss of chirality was achieved and provided a background for investigation into the synthesis of piperidines, which could lead to a plausible route to biologically significant aza-sugars. [Illustration omitted.]