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: A phosphine-catalyzed enantioselective (3+2) annulation reaction between allenes and isoindigos, containing either two identical or different oxindole moieties, is introduced as a powerful strategy for the construction of spirocyclic bisindoline alkaloid core structures.
Abstract: Construction of contiguous all-carbon quaternary stereogenic centers is a long-standing challenge in synthetic organic chemistry. In this report, a phosphine-catalyzed enantioselective (3+2) annulation reaction between allenes and isoindigos, containing either two identical or different oxindole moieties, is introduced as a powerful strategy for the construction of spirocyclic bisindoline alkaloid core structures. The reported reactions feature high chemical yields, excellent enantioselectivities, and very good regioselectivities, and are highly useful for creating structurally challenging bisindoline natural products.
67 citations
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TL;DR: The mechanism of the [(Cp*MCl(2))(2)] (M = Rh, Ir)-catalyzed oxidative annulation reaction of isoquinolones with alkynes was investigated in detail and a Rh(III)→Rh(I)→ Rh( III) catalytic cycle was proposed for this reaction.
Abstract: The mechanism of the [(Cp*MCl(2))(2)] (M = Rh, Ir)-catalyzed oxidative annulation reaction of isoquinolones with alkynes was investigated in detail. In the first acetate-assisted C-H-activation process (cyclometalated step) and the subsequent mono-alkyne insertion into the M-C bonds of the cyclometalated compounds, both Rh and Ir complexes participated well. However, the desired final products, dibenzo[a,g]quinolizin-8-one derivatives, were only formed in high yield when the Rh species participated in the final oxidative coupling of the C-N bond. Moreover, a Rh(I) sandwich intermediate was isolated during this transformation. The iridium complexes were found to be inactive in the oxidative coupling processes. All of the relevant intermediates were fully characterized and determined by single-crystal X-ray diffraction analysis. Based on this mechanistic study, a Rh(III)→Rh(I)→Rh(III) catalytic cycle was proposed for this reaction.
67 citations
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TL;DR: A novel Pd-catalyzed intermolecular dehydrogenative annulation of aryl iodides and aryL carbamic chlorides for the efficient synthesis of phenanthridinone derivatives was developed.
Abstract: A novel Pd-catalyzed intermolecular dehydrogenative annulation of aryl iodides and aryl carbamic chlorides for the efficient synthesis of phenanthridinone derivatives was developed. Simple aryl iodides and carbamic chlorides readily made from various anilines, a broad substrate scope with hetero/polycycles, as well as high-value products, make this direct dehydrogenative annulation approach very practical and attractive.
67 citations
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TL;DR: These procedures constitute efficient methods for rapid carbocyclization and annulation of carbohydrates to produce a variety of functionalized five- and six-membered ring systems.
Abstract: Methyl 5-deoxy-5-iodo-pentofuranosides are reductively ring-opened and propargylated in a tandem fashion in the presence of zinc. The 1,7-enynes thus obtained are subjected to ring-closing enyne metathesis with catalyst B to produce functionalized 1-vinyl cyclohexenes. By adding BnNH2 to the tandem reaction, an amino group can be introduced in the 1,7-enyne products. Addition of 2-TMS-ethynylcerium(III) chloride after the reductive ring-opening produces the corresponding 1,6-enynes. Further annulation of the product 1,3-dienes can be achieved through a Diels−Alder reaction with good control of stereochemistry. These procedures constitute efficient methods for rapid carbocyclization and annulation of carbohydrates to produce a variety of functionalized five- and six-membered ring systems.
67 citations
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TL;DR: In this paper, a variety of indoles, all bearing a methyl group in the 3-position, underwent smooth reaction with 1,1-cyclopropanediesters to yield annulated adducts in fair to excellent yield.
67 citations