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: P palladium-catalyzed, regiodivergent[5 + 4] and [5 + 2] annulations of vinylethylene carbonates and allylidenemalononitriles are reported, describing the production of over 50 examples of nine- and seven-membered heterocycles in high isolated yields and excellent regioselectivities.
Abstract: Medium-sized heterocycles exist in a broad spectrum of biologically active natural products and medicinally important synthetic compounds. The construction of medium-sized rings remains challenging, particularly the assembly of different ring sizes from the same type of substrate. Here we report palladium-catalyzed, regiodivergent [5 + 4] and [5 + 2] annulations of vinylethylene carbonates and allylidenemalononitriles. We describe the production of over 50 examples of nine- and seven-membered heterocycles in high isolated yields and excellent regioselectivities. We demonstrate the synthetic utility of this approach by converting a nine-membered ring product to an interesting polycyclic caged molecule via a [2 + 2] transannulation. Mechanistic studies suggest that the [5 + 2] annulation proceeds through palladium-catalyzed ring-opening/re-cyclization from the [5 + 4] adducts.
69 citations
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TL;DR: A palladium-catalyzed expeditious synthesis of dibenzofused carbazoles from readily available 2-arylindoles and diaryliodonium salts is reported, finding that an intramolecular cross-dehydrogenative coupling at the C2 position affords dibenzo[a,c]carbazoles in high yields.
Abstract: A palladium-catalyzed expeditious synthesis of dibenzofused carbazoles from readily available 2-arylindoles and diaryliodonium salts is reported. Interestingly, after the electrophilic C3 palladation of indole, an unexpected "through-space" 1,4-palladium migration to the 2-aryl moiety, by remote C-H bond activation followed by C-H arylation with diaryliodonium salt, and an unprecedented 1,2-aryl shift take place. Finally, an intramolecular cross-dehydrogenative coupling (CDC) at the C2 position affords dibenzo[a,c]carbazoles in high yields. Remarkably, the present migratory annulation occurs through three C-H bond activation one C-C bond cleavage, and the simultaneous construction of three new C-C bonds in a single operation.
69 citations
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TL;DR: A 4-HO-TEMPO-catalyzed redox strategy for the synthesis of pyridines through the annulation of cyclopropanols and oxime acetates has been developed in this article.
Abstract: A 4-HO-TEMPO-catalyzed redox strategy for the synthesis of pyridines through the annulation of cyclopropanols and oxime acetates has been developed. This protocol features good functional group tol...
69 citations
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TL;DR: In this article, the synthesis of indolocarbazoles was achieved via photochemical and thermal annulation reactions of chromium Fischer carbene complexes, which allows for facile incorporation of hydrogen bonding functionality which complements the pharmacophore contained within bioactive indolocal carbazole natural products.
68 citations
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TL;DR: In this article, primary and secondary alkylzinc reagents add to various aryldiazonium salts leading to polyfunctional indoles by means of a [3, 3]-sigmropic shift and subsequent aromatization.
Abstract: Primary and secondary alkylzinc reagents add to various aryldiazonium salts leading to polyfunctional indoles by means of a [3,3]-sigmatropic shift and subsequent aromatization.
68 citations