Primary-Secondary Diamine Catalysts for Malonate Additions to Enones

Significance

This work describes the highly enantioselective Michael addition of dibenzyl ­malonate 2 to enones 1 in the presence of a catalytic amount (20 mol%) of the TFA salt of the novel primary-secondary diamine 3. A broad range of benzylideneacetone derivatives, irrespective of their electronic nature, chalcone, an aliphatic enone, and cyclohexenone were suitable substrates yielding the corresponding products 4 in good to excellent yields (66-99%) and enantiomeric ratios of up to >99.5:0.5. Notably, in contrast to previous studies on the same reaction, the use of two equivalents of the malonate component was sufficient. The authors’ working hypo­thesis invokes a bifunctional iminium mechanism with the enone being activated as iminium ion (see Scheme, 5).