The first catalytic asymmetric [2 + 2] cycloaddition of oxabicyclic alkenes and terminal alkynes has been developed. This iridium-catalyzed enantioselective [2 + 2] cycloaddition allows the formation of four stereocenters in a single step with excellent enantioselectivity (94-->99% ee).
The first catalytic asymmetric conjugate addition of 1,3-dicarbonyl compounds to nitroenynes catalyzed by cinchona alkaloid-based thiourea organocatalysts has been developed. The 1,4-addition adducts were obtained solely, in moderate to good yields (up to 93%) with good enantioselectivities (up to 99% ee). This protocol affords a conceptually different entry to the precursors of pharmaceutically important chiral β-alkynyl acid derivatives and synthetically useful chiral nitroalkynes. Notably, the protocol worked well with both aryl- and alkyl-substituted alkynyl substrates.
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