Organocatalytic regio-, diastereo- and enantioselective γ-additions of isoxazol-5(4H)-ones to β,γ-alkynyl-α-imino esters for the synthesis of axially chiral tetrasubstituted α-amino allenoates

The chiral phosphoric acid catalyzed regio-, diastereo- and enantioselective reaction of isoxazol-5(4H)-ones with β,γ-alkynyl-α-imino esters has been developed. With the established methodology, γ-addition of β,γ-alkynyl-α-imino esters and C-allenylation of isoxazol-5(4H)-ones were achieved with high regio- and stereoselectivities, affording diverse α-imino allenoates featuring an adjacent quaternary carbon stereocenter and an axially chiral tetrasubstituted allene motif in high yields.