Topic
Annulation
About: Annulation is a research topic. Over the lifetime, 10152 publications have been published within this topic receiving 189701 citations.
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TL;DR: Rh(III)-catalyzed transannulation of arenes with 7-azabenzonorbornadienes for enantioselective synthesis of cis -dihydrocarbazoles and a chiral rhodacycle has been isolated as an active intermediate.
Abstract: C-H bond activation is mostly limited to ortho selectivity. Activation of both ortho and meta C-H bonds constitutes a particularly important strategy for annulation, but has rarely been studied in enantioselective systems. Reported herein is rhodium(III)-catalyzed asymmetric [3+2] transannulation of arenes with 7-azabenzonorbornadienes. Two distinct classes of arenes have been identified as substrates, and the coupling proceeded with high enantioselectivity and excellent diastereoselectivity through sequential activation of ortho and meta C-H bonds.
68 citations
TL;DR: A novel selective copper-catalyzed radical annulation of benzene-linked 1,n-enynes with azido-benziodoxolone to access fused pyrroline compounds has been developed, which proceeds via the addition of the azide radical to the alkene, annualtion, and azidation cascade.
68 citations
TL;DR: This protocol provides four divergent reaction types, including two unexpected annulations with an oxygen transposition process, which lead to diverse types of phenalenyl-fused pyrylium cations comprising a four-, five-, or six-ring-fuse π-conjugated core.
Abstract: Described herein is the synthesis of stable oxonium-doped polycyclic aromatic hydrocarbons (PAHs) by the rhodium-catalyzed C-H activation/annulations of naphthalene-type aldehydes with internal alkynes. This protocol provides four divergent reaction types, including two unexpected annulations with an oxygen transposition process, which lead to diverse types of phenalenyl-fused pyrylium cations comprising a four-, five-, or six-ring-fused π-conjugated core. The annulations exhibit an exquisite regioselectivity and a high tolerance of sensitive functional groups. These PAHs feature intriguing photophysical properties such as full-color tunable fluorescence emission, high quantum yield, and positively charged core, and can be reduced easily to the phenalenyl radicals.
67 citations
TL;DR: In this paper, a mild and efficient route for the synthesis of quinolines and polycyclic quinoline using FeCl 3 or Mg(ClO 4 ) 2 as a novel catalyst via Friedlander annulation was described.
Abstract: A mild and efficient route for the synthesis of quinolines and polycyclic quinolines utilising FeCl 3 or Mg(ClO 4 ) 2 as a novel catalyst via Friedlander annulation was described.
67 citations
TL;DR: This work represents the first example of asymmetric catalysis of ammonium ylides bearing α-substitutions, and the catalytic [4 + 1] annulation pathway of ammonia ylide catalysis is also unprecedented.
Abstract: Ammonium ylides have a long history in organic synthesis, but their application in asymmetric catalysis is still underdeveloped in regard to both substrate scope and reaction pathways compared with phosphorus and sulfur ylides. Here a previously unreported asymmetric [4 + 1] annulation reaction of 3-bromooxindoles and electron-deficient 1-azadienes has been developed through ammonium ylide catalysis of a newly designed 2′-methyl α-isocupreine (α-MeIC), efficiently delivering spirocyclic oxindole compounds incorporating a dihydropyrrole motif in excellent enantioselectivity (up to 99% ee). To the best of our knowledge, this work represents the first example of asymmetric catalysis of ammonium ylides bearing α-substitutions, and the catalytic [4 + 1] annulation pathway of ammonium ylides is also unprecedented. Moreover, 1H NMR, mass spectroscopy, and computational calculation studies were conducted, and the catalytic cycle and a tentative explanation of the enantioselective mechanism have been successfully ...
67 citations