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 novel and direct approach to synthesize 1-aminoindole derivatives by Rh(iii)-catalyzed cyclization of 2-acetyl-1-arylhydrazines with diazo compounds via aryl C-H activation has been developed that obviates the need of external oxidants and displays a broad substituent scope.
154 citations
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01 Jan 2020TL;DR: A catalytic system comprised of an N-heterocyclic carbene and an iridium complex can be used for the asymmetric, diastereodivergent synthesis of γ-butyrolactones and the synthetic utility was illustrated in the concise synthesis of the naturally occurring lignan (−)-hinokinin.
Abstract: The stereodivergent synthesis of natural product frameworks via a single transformation using simple starting materials is a significant challenge. The prevalence of γ-butyrolactones in biologically active natural products has long motivated the development of enantioselective strategies towards their synthesis. Herein, we report an enantio- and diastereodivergent [3 + 2] annulation reaction for the synthesis of α,β-disubstituted γ-butyrolactones through cooperative N-heterocyclic carbene organocatalysis and iridium catalysis. This method overcomes the challenges of merging N-heterocyclic carbene organocatalysis with iridium catalysis by the appropriate choice of ligands. The use of two chiral catalysts allowed control over the relative and absolute configuration of the two formed stereocentres, thereby providing selective access to all four possible stereoisomers of the γ-lactone products. The transformation could be extended to the synthesis of δ-lactams via [4 + 2] annulation. The synthetic utility of this methodology was illustrated in the concise synthesis of the naturally occurring lignan (−)-hinokinin. Methods to allow access to all isomers of a product are both valuable and challenging to achieve. Here the authors report a catalytic system comprised of an N-heterocyclic carbene and an iridium complex, and show that it can be used for the asymmetric, diastereodivergent synthesis of γ-butyrolactones.
154 citations
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TL;DR: A novel [5 + 1] annulation strategy is developed for the synthesis of highly substituted phenols and cyclohexenones from alpha-alkenoyl ketenedithioacetals and nitroalkanes.
Abstract: A novel [5 + 1] annulation strategy is developed for the synthesis of highly substituted phenols and cyclohexenones from α-alkenoyl ketenedithioacetals and nitroalkanes.
154 citations
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154 citations
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TL;DR: The transformation has demonstrated for the first time that Cu(OAc)2 can be renewable after undergoing an oxidative reaction, and offers a highly efficient approach to the 3-methyleneisoindolin-1-one scaffold.
153 citations