Construction of Cyclic Sulfamidates Bearing Two gem-Diaryl Stereocenters through a Rhodium-Catalyzed Stepwise Asymmetric Arylation Protocol
摘要:
A rhodium-catalyzed stepwise asymmetric 1,4- and 1,2-addition of arylboronic acids to alpha,beta-unsaturated cyclic N-sulfonyl ketimines has been developed, providing a wide range of gem-diaryl-substituted chiral benzosulfamidateS with high optical purities. C-1-Symmetric chiral diene and branched chiral sulfur-olefin ligands were sequentially utilized in this double-arylation process for high stereocontrol. Further synthetic utility offers new opportunities for the facile construction of otherwise difficult to access polycyclic heterocycles.
A stereoselectiveinverse-electron-demandaza-Diels–Alder cycloaddition process of cyclic 1-aza-1,3-butadienes and α,β-unsaturatedaldehydes has been developed via dienamine catalysis. This reaction exhibits excellent β,γ-regioselectivity for enal substrates with substantial structural diversity and broad functionalities, readily producing highly enantioenriched fused piperidine derivatives and enabling
chemoselective dienophiles in normal-electron-demand Diels–Alderreactions with HOMO-raised trienamines, rather than typical 4π-participation in inverse-electron-demand versions. The enantioenriched cycloadducts could be efficiently converted to spiro or fused frameworks with high structural and stereogenic complexity by a sequential aza-benzoin reaction or other transformations.
A metal-free DBU catalyzed [3+2] cycloaddition of 3-homoacyl coumarins with cyclic 1-azadienes has been developed for the synthesis of cyclopentane-fused coumarins with excellent diastereoselectivity and complete chemoselectivity.