Stereoselective Allyl Enol Carbonates for the Synthesis of Chiral Aldehydes Bearing All Carbon Quaternary Stereocenters via the Decarboxylative Asymmetric Allylic Alkylation (DAAA)

A stereoselective synthesis of carbonates derived from 3-hydroxy-2-aryl acrylates was devised that can form the Z - or E -stereoisomer in very high Z / E ratios (50:1 and 1:99, respectively). The stereochemical outcome depends on the choice of base, addition of TMEDA and reaction temperature. The Z - and E -stereoisomers have different reactivities towards the DAAA reaction, with the E -stereoisomer displaying both greater reactivity and enantiodifferentiation with chiral ligands. The DAAA of E -stereoisomer analogues takes place in excellent yields ranging from 96–99% and enantioselectivities ranging from 42–78% ee.