- 1,4,2-Dioxazol-5-ones as Isocyanate Equivalents: Chemoselective Non-Metal-Catalyzed Carboxamidation of Indoles
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1,4,2-Dioxazol-5-ones are known to undergo decarboxylation under thermal conditions followed by Lossen s rearrangement to give isocyanates. Described herein is the in situ trapping of the isocyanates by indoles to give indole-3-carboxamides in good to exc
- Vala, Anand,Parmar, Deepa,Rayani, Rahul,Kusurkar, Rakesh,Guduru, Ramakrishna,Kaneriya, Uttam,Gondaliya, Uday,Parmar, Nirali,Soni, Jigar Y.
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- Divergent Synthesis of Tunable Cyclopentadienyl Ligands and Their Application in Rh-Catalyzed Enantioselective Synthesis of Isoindolinone
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A series of rhodium complexes bearing sterically and electronically tunable cyclopentadienyl ligands, prepared by utilizing Co2(CO)8-mediated [2+2+1] cyclization as a key step, were synthesized. In the presence of 2.5 mol% of CpmRh4, unprecedented enantioselective [4+1] annulation reaction of benzamides and alkenes was achieved with a broad substrate scope under mild reaction conditions, providing a variety of isoindolinones with excellent regio-and enantioselectivity (up to 94% yield, 97:3 er). Preliminary mechanistic studies suggest that the reaction involves an oxidative Heck reaction and an intramolecular enantioselective alkene hydroamination reaction.
- Cui, Wen-Jun,Wu, Zhi-Jie,Gu, Qing,You, Shu-Li
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p. 7379 - 7385
(2020/08/19)
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- RhIII-Catalyzed C?H Activation of Aryl Hydroxamates for the Synthesis of Isoindolinones
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RhIII-catalyzed C?H functionalization reaction yielding isoindolinones from aryl hydroxamates and ortho-substituted styrenes is reported. The reaction proceeds smoothly under mild conditions at room temperature, and tolerates a range of functional groups. Experimental and computational investigations support that the high regioselectivity observed for these substrates results from the presence of an ortho-substituent embedded in the styrene. The resulting isoindolinones are valuable building blocks for the synthesis of bioactive compounds. They provide easy access to the natural-product-like compounds, isoindolobenzazepines, in a one-pot two-step reaction. Selected isoindolinones inhibited Hedgehog (Hh)-dependent differentiation of multipotent murine mesenchymal progenitor stem cells into osteoblasts.
- Shaaban, Saad,Davies, Caitlin,Merten, Christian,Flegel, Jana,Otte, Felix,Strohmann, Carsten,Waldmann, Herbert
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p. 10729 - 10734
(2020/07/25)
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- A Planar-Chiral Rhodium(III) Catalyst with a Sterically Demanding Cyclopentadienyl Ligand and Its Application in the Enantioselective Synthesis of Dihydroisoquinolones
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The rapid development of enantioselective C?H activation reactions has created a demand for new types of catalysts. Herein, we report the synthesis of a novel planar-chiral rhodium catalyst [(C5H2tBu2CH2tBu)RhI2]2 in two steps from commercially available [(cod)RhCl]2 and tert-butylacetylene. Pure enantiomers of the catalyst were obtained through separation of its diastereomeric adducts with natural (S)-proline. The catalyst promoted enantioselective reactions of aryl hydroxamic acids with strained alkenes to give dihydroisoquinolones in high yields (up to 97 %) and with good stereoselectivity (up to 95 % ee).
- Trifonova, Evgeniya A.,Ankudinov, Nikita M.,Mikhaylov, Andrey A.,Chusov, Denis A.,Nelyubina, Yulia V.,Perekalin, Dmitry S.
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supporting information
p. 7714 - 7718
(2018/04/25)
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- Rhodium(III)-Catalyzed Controllable C?H Bond Functionalization of Benzamides and Vinylidenecyclopropanes: A Directing Group Determined Reaction Pathway
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A controllable rhodium(III)-catalyzed C?H bond activation of benzamides and vinylidenecyclopropanes (VDCPs) by changing the directing group from C(O)NH–OPiv to C(O)NH–OBoc has been disclosed, affording two different major products in good yields under mild condition, respectively. The substrate scope has been investigated and a plausible reaction mechanism has been also proposed on the basis of previous literature. (Figure presented.).
- Ji, Cheng,Xu, Qin,Shi, Min
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supporting information
p. 974 - 983
(2017/03/27)
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- Rhodium(III)-catalyzed heterocycle synthesis using an internal oxidant: Improved reactivity and mechanistic studies
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Directing groups that can act as internal oxidants have recently been shown to be beneficial in metal-catalyzed heterocycle syntheses that undergo C-H functionalization. Pursuant to the rhodium(III)-catalyzed redox-neutral isoquinolone synthesis that we recently reported, we present in this article the development of a more reactive internal oxidant/directing group that can promote the formation of a wide variety of isoquinolones at room temperature while employing low catalyst loadings (0.5 mol %). In contrast to previously reported oxidative rhodium(III)-catalyzed heterocycle syntheses, the new conditions allow for the first time the use of terminal alkynes. Also, it is shown that the use of alkenes, including ethylene, instead of alkynes leads to the room temperature formation of 3,4-dihydroisoquinolones. Mechanistic investigations of this new system point to a change in the turnover limiting step of the catalytic cycle relative to the previously reported conditions. Concerted metalation-deprotonation (CMD) is now proposed to be the turnover limiting step. In addition, DFT calculations conducted on this system agree with a stepwise C-N bond reductive elimination/N-O bond oxidative addition mechanism to afford the desired heterocycle. Concepts highlighted by the calculations were found to be consistent with experimental results.
- Guimond, Nicolas,Gorelsky, Serge I.,Fagnou, Keith
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supporting information; experimental part
p. 6449 - 6457
(2011/06/16)
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