An organocatalytic domino Michael-alkylation reaction: highly enantioselective construction of spiro-cyclopentanoneoxindoles and tetronic acid scaffolds

A new organocatalytic asymmetric domino Michael-alkylation reaction of methyleneindolinones and gamma-halogenated-beta-ketoesters is described. A variety of spiro-cyclopentanoneoxindoles were obtained in high yields (up to 96%), good diastereoselectivities (up to 12: 1 dr) and excellent enantioselectivities (up to > 99% ee) via alpha-alkylation. Interestingly, O-alkylated products with tetronic acid motifs could be obtained by tuning the N-protecting groups on methyleneindolinones with excellent enantioselectivities (up to 499% ee).