Asymmetric [4+2]-Cycloaddition of Anthracene Derivatives via Hydrazone Activation

Enantio- and diastereoselective dearomative [4+2]-cycloaddition reaction between N,N-dimethylhydrazone derived from 9-anthracenecarboxaldehyde and α,β-unsaturated aldehydes is reported. The developed strategy utilizes HOMO-rising activation of diene (via hydrazone formation) and aminocatalytic LUMO-lowering activation of dienophile (via iminium ion formation). High chemical and stereochemical efficiency have been obtained owing to the application of Jørgensen catalyst. Target cycloadducts were subjected to selected transformations aiming at unmasking the hydrazone moiety that proceeded with preservation of optical purity introduced in the organocatalytic step.