Unprecedented stereochemical control in the intramolecular ene-reactions of δ,ε-unsaturated aldehydes using exceptionally bulky organoaluminum reagents: Elucidation of the transition state

Article abstract of DOI:10.1016/S0040-4020(01)89682-4

Unprecendented stereochemical control has been achieved in the type II intramolecular ene reactions of δ,ε-unsaturated aldehydes leading to trans-cyclohexanols with excellent selectivity under very mild conditions, using exceptionally bulky methylaluminum bis(4-bromo-2,6-di-tert-butylphenoxide) (MABR). Success of the stereocontrolled cyclization can be ascribable to the ability of this modified organoaluminum reagents, MABR, to change the conformation of the transition state. Examining the ene reactions of substrates 7, 11, 14 with MABR, the stereochemical outcome of the present organoaluminum-promoted intramolecular ene reactions is further elucidated.