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Correction for 'Professor (Dr) Sukh Dev: an iconic scientist with an innate sixth sense who radicalized natural product synthesis & organic chemistry' by Harry Kochat et al., Org. Biomol. Chem., 2024, 22, 5466-5469, https://doi.org/10.1039/D4OB90071E.
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We describe the first phosphine-promoted intramolecular Rauhut-Currier reaction that triggers an intramolecular Wittig process assembling new classes of diquinanes. The one-pot strategy provides ready access to simple diquinanes and various (hetero)arene-fused diquinanes incorporated with up to two contiguous all-carbon quaternary centers under metal-free and neutral conditions. We showcased the generality of the method on a broad range of substrates and demonstrated its synthetic utility in accessing various advanced intermediates relevant to natural product synthesis and material science.
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The Corey-Chaykovsky reaction is usually employed to synthesize cyclopropanes from activated olefins. We intercepted the intermediates prevailing during this transformation and diverted the process for the creation of intricate molecular motifs. We describe an unusual skeletal remodelling of tethered bis-enones to 2,3-epoxy-hexahydrofluoren-9-ones via an "interrupted Corey-Chaykovsky reaction". The strategy rationally merges the nucleophilic features of sulfur ylides with electronically biased olefins to achieve the regio- and stereoselective synthesis of several new classes of hydrofluorenones. We have demonstrated the synthetic utility of the products in accessing several highly functionalized molecules.
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We introduce an advancement in Morita-Baylis-Hillman (MBH) chemistry that provides access to α-spirannulated enones. The treatment of enone-tethered azaarenium salts with catalytic amounts of organophosphines provides spiroindenyl dihydropyridines. It represents the α-spirannulation of enones via an intramolecular MBH (IMBH) reaction utilizing dual phosphine- and anion-binding catalysis. The IMBH adducts were subjected to several post-synthetic modifications to access highly functionalized molecules.
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We describe a diversity-oriented one-pot telescopic synthesis of various benzo[b]carbazoles with the naphthannulation of indoles as the key step, enabled by an intramolecular furan-olefin Diels-Alder reaction. This strategy is general and efficient across a wide range of substrates. We applied this method to synthesize and characterize the first benzo[b]carbazole-based liquid crystalline materials, where the unique molecular design led to the formation of a rare nematic phase at room temperature.
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The ring-reorganizing transformations of activated cyclopropanes are typically achieved under acidic conditions. This Letter describes the first acid-free and Lewis base-mediated cascade ring opening/recyclization of designed cyclopropyl ketones to access tetrahydrofluorenones. We rationally merged the nucleophilic features of phosphines with the electronically biased cyclopropanes to synthesize several new classes of hydrofluorenones. We have also demonstrated the synthetic utility of the products in accessing highly functionalized molecular scaffolds.
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Rich in antioxidants with a variety of flavones and anthocyanins, passionflower/fruit has been extensively used in food, beverage, medicinal, and natural dyes industries. The individual components present in passionflower are identified by extracting them in methanol, partitioning them between ethyl acetate and aqueous layers, and recording their ESI mass spectrometric data. The steady-state absorption and fluorescence spectra of the extract in methanol and dimethyl sulfoxide are recorded and the lifetime of the fluorescing species is reported. The pH dependence of the absorption spectrum confirms the presence of the anthocyanins.
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Antocianinas , Flavonas , Passiflora , Antocianinas/química , Passiflora/química , Flavonas/química , Espectrometria de Massas por Ionização por Electrospray , Concentração de Íons de Hidrogênio , Espectrometria de Fluorescência , Antioxidantes/química , Extratos Vegetais/químicaRESUMO
Catalysis by trivalent nucleophilic organophosphines has emerged as an essential tool in organic synthesis. Several new organic transformations promoted by phosphines substantiate and complement the existing synthetic chemistry tools. Mere design of the substrate and reagent combinations has introduced new modes of reactivity patterns, which are otherwise difficult to achieve. These design considerations have led to the rapid build-up of complex molecular entities and laid a solid foundation to synthesise bioactive natural products and pharmaceuticals. This article presents an overview of some of the conceptual advances, including our contributions to nucleophilic organophosphine chemistry. The scope, limitations, mechanistic insights, and applications of these metal-free transformations are discussed elaborately.
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Simultaneous dearomatizing spirannulation of pyridinium salts is still in its infancy. Here, we present an organized skeletal remodeling of designed pyridinium salts by utilizing an interrupted Corey-Chaykovsky reaction to access unprecedented and structurally intriguing molecular architectures such as the vicinal bis-spirocyclic indanones and spirannulated benzocycloheptanones. This hybrid strategy rationally merges the nucleophilic features of sulfur ylides with the electrophilic pyridinium salts to achieve the regio- and stereoselective synthesis of new classes of cyclopropanoids. The plausible mechanistic pathways were derived from experimental results and control experiments.
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We describe a metal-free strategy to access various α-arylidene cyclopenta[b]indoles via phosphine-catalysed (3 + 2) annulation of α,ß-ynones and 3-nitroindoles. For the first time, the rearomatisation of the indole nucleus was observed in such an annulative transformation. The method was extended to the synthesis of an antimalarial natural product, bruceolline E.
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3-Hydroxyquinoline-4(1H)-ones (3HQs) are privileged structural motifs. The current methods for their synthesis necessitate strongly acidic or basic conditions, which hamper the generality and practicality. Here, we describe phosphine-mediated redox transformation of easily accessible 1-(2-nitroaryl)prop-2-ynones to 3HQs. Besides establishing a new entry to the synthesis of 3HQs under neutral conditions, this method is the first formal intramolecular oxyamination of α,ß-ynones. The synthetic utility of this method is demonstrated in the total synthesis of japonine, its analogs, and rare quinoline derivatives.
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We describe the palladium-catalyzed Nazarov-type cyclization of easily accessible (hetero)arylallyl acetates to pentannulated (hetero)arenes. This method provides ready access to various types of bi-, tri-, tetra-, and pentacyclic cyclopentanoids under neutral conditions. The synthetic utility is further demonstrated in the first total synthesis of ß-diasarone and several other complex cyclopentanoids relevant to medicinal chemistry and materials science.
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We demonstrate the first phosphine-catalyzed intramolecular vinylogous aldol reaction (IVAR) of α-substituted enones. This strategy provides access to various pentannulated (hetero)arenes and dibenzocycloheptanones incorporated with two contiguous stereocenters, one of which is an all-carbon quaternary center. The scope of this work is further broadened through elaborations of the IVAR adducts to (i) benzannulated nine-membered carbocyclic systems, (ii) interesting classes of 1,3-dienes, 1,3,5-trienes, and 1-yn-3,5-dienes, and (iii) the analogs of echinolactone D and russujaponol F.
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We describe the first metal-free and organocatalytic strategy to access highly functionalised dibenzocycloheptanes via a phosphine-promoted annulative Morita-Baylis-Hillman (MBH) reaction. The method is manipulated to access to chiral dibenzocycloheptanes as well. This work represents a rare entry for the construction of seven-membered carbocycles via the MBH route. The realisation of several bioactive molecules possessing the dibenzocycloheptane core makes this an attractive strategy.
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We describe the first atropselective Suzuki-Miyaura cross-coupling of ß-keto enol triflates to access axially chiral (Z)-diarylmethylidene indanones (DAIs). The chemical, physical, and biological properties of DAIs are unknown, despite their being structurally similar to arylidene indanones, primarily due to the lack of racemic or chiral methods. Through this work, we demonstrate a general and efficient protocol for the racemic as well as the atropselective synthesis of (Z)-DAIs. An unusual intramolecular Morita-Baylis-Hillman reaction is utilized for the Z-selective synthesis of ß-keto enol triflates.
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The development of new synthetic protocols to access diverse molecular scaffolds from readily available starting compounds is of significance in both academia and industry. Towards this, the catalysis by transition metals has been employed as a powerful tool to access molecules with broad structural and functional diversity. An overview of the recent literature manifested the tremendous potential of transition metal-catalyzed processes in advancing organic synthesis in a new direction. This account compiles new conceptual advancements in the palladium-catalyzed Alder-ene type cycloisomerization reactions, C-H functionalizations, and one-pot multicatalytic processes, which have become essential tools to access new classes of molecules.
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Paládio , Catálise , Técnicas de Química Sintética , EstereoisomerismoRESUMO
The synthesis of 3-acetoxyindanones and (hetero)arene-fused dihydrotropones was achieved via divergent annulation cascades. Under mild aqueous and basic conditions, α-substituted enone-aldehydes and 1,3-carbonyls undergo a Michael/aldol/hemiketalization/retro-aldol cascade for the formation of 3-acetoxyindanones possessing two contiguous stereogenic centers, one of which is an all-carbon quaternary center. On the other hand, the same enone-aldehydes generate new classes of fused-dihydrotropones upon reaction with 2,4-dioxobutanoates under merely the same reaction conditions via a Michael/aldol/lactonization/decarboxylation cascade.
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A conceptually novel intramolecular allylic alkylation strategy is developed for the synthesis of carbazoles and dibenzothiophenes. In an unusual event, palladium catalyses the formation of π-allylpalladium complexes of the respective (2-methylindol-3-yl)allyl acetates and subsequently facilitates the benzannulation process.
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An overview of the recent literature on palladium-catalyzed intramolecular Alder-ene (IMAE) reaction of a variety of 1,n-unsaturated systems is presented. The reaction which was first reported by Trost and Lautens provided an efficient alternative to the thermal or Lewis acid catalyzed cycloisomerizations involving ene-type reaction. The IMAE cyclization of enynes and dienes has emerged as an important area and found significant applications in building up of complex molecular architectures and in the synthesis of several bioactive natural products. Since highly impactful reviews on this subject have covered the literature till 2015, this article focuses on summarizing the works subsequent to 2015.