An efficient and convenient copper-catalyzed method has been developed to achieve direct ortho-C-H/N-H annulation to synthesize phenanthridinones with arynes. This method highlights an emerging strategy to transform inert C-H bonds into versatile functional groups in organic synthesis and provides a new way to synthesize phenanthridinone alkaloids efficiently.
An efficient and convenient method enabling direct amination of unactivated methylene C(sp 3 )−H bonds to form C−N bonds with azodiformates as amino source is described. This method highlights the emerging strategy of unactivated methylene as versatile functional groups in organic synthesis and provides a strategy to construct functionalized C−N bonds for the synthesis of complex molecules.
A dearomative remote activation strategy for the asymmetric functionalization of benzylic C-H bonds of heteroaryl aldehydes under bifunctional Brønsted base catalysis has been developed. The in situ generated o-QDMs-type dienolate intermediates were efficiently and stereoselectively trapped by nitroolefins through an asymmetric Michael/nitro-aldol cascade reaction. Using this strategy, a wide variety of synthetically significant tetrahydrodibenzothiophene and tetrahydrodibenzofuran derivatives were synthesized in good yields with high enantioselectivities.
Vinylogous reactivity of olefinic azlactones was realized through the development of a chiral amine-catalyzed highly stereoselective allylic-allylic alkylation with Morita-Baylis-Hillman carbonates. The Lewis base activation of electrophile and Brønsted base activation of nucleophile were efficiently combined, giving access to multifunctional acyclic α-amino acid derivatives in a highly stereocontrolled manner. The synthetic utility of these versatile synthons was further demonstrated by the facile synthesis of protected cyclic quaternary α-amino acids.
A catalytic asymmetric hetero-Diels-Alder (HDA) reaction has been achieved through hydrogen-bond directed γ-addition of olefinic azlactones to isatins. This methodology provides an efficient access to spirooxindole dihydropyranones in moderate to good yields and with excellent enantioselectivities.
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