A catalytic asymmetric decarboxylative [4+2] cycloaddition of vinyl benzoxazinanones with methyleneindolinones has been established, which provided a series of chiral tetrahydroquinoline-based 3,3'-spirooxindoles in high yields (up to 96%) and with excellent diastereo- and enantioselectivities (all >95 : 5 d.r., up to 99% ee). This reaction not only represents the first example of catalytic enantioselective [4+2] cycloaddition between methyleneindolinones and Pd-containing 1,4-dipoles, but also demonstrates the great practicability of catalytic asymmetric decarboxylative cycloadditions in the synthesis of enantio-enriched polycyclic compounds.
An efficient domino 1,6-addition/intramolecular cyclization reaction between para-quinone methides (p-QMs) and azlactones under Brønsted acid catalysis was established. A series of highly functionalized dihydrocoumarins were constructed in good to excellent yields (up to 96%) with excellent diastereoselectivities (all >20:1 d.r.). In this process, the Brønsted acid plays a crucial role not only in activating the two substrates, but also in controlling the diastereoselectivity of the reaction via hydrogen-bonding interactions. In addition, this protocol demonstrates the great practicability of utilizing p-QMs in domino reactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.