The
new hybrid-type squaramide-fused amino alcohol containing both
a Brønsted basic site and hydrogen-bonding sites in the molecule
showed a high catalytic activity as an organocatalyst in the enantioselective
domino Michael addition/cyclization reaction of oxoindolines with
cyclic 1,3-diketones to afford the chiral spiro-conjugated oxindoles
featuring 2-aminopyrans fusing with carbo-heterocyclic ring systems
with excellent chemical yields (up to 98%) and enantioselectivities
(up to 95% ee). The obtained chiral spiro-conjugated 2-aminopyrans
bearing quaternary stereogenic carbon center could be used as synthetic
precursors for several natural products that have a broad spectrum
of fascinating biological activities.
Asymmetric Michael addition of β-keto esters with trans-β-nitroolefins using chiral amino amide organocatalyst was tried and afforded synthetically useful chiral Michael adducts in both excellent chemical yields (up to 99%) and stereoselectivities (up to dr. 99:1, up to 98% ee).
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