Indanes and indenes are among the most important carbocycles. Many indane and indene derivatives have shown important pharmacological activities, and the indane and indene nuclei are structural ...motifs present in several natural products of biological relevance. In spite of their importance, only a few reviews on their preparation methods have appeared so far in the literature, the most recent ones being published about ten years ago. The present Review is aimed at filling this gap, presenting some of the most important and innovative approaches to indanes and indenes that have been published in the course of the last ten years (coverage: from 2005 to May, 2015).
Doing the rounds: Indanes and indenes are among the most important carbocycles, but few reviews on their preparation methods have appeared in the literature (see scheme). In this Review an overview of the recently developed synthetic methods for the preparation of indane and indene derivatives is presented. The coverage will concentrate on the period between 2005 and May 2015.
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Recent advances in the field of oxidative carbonylation reactions leading to carbonylated heterocyclic derivatives are presented (coverage: 2006 to the beginning of 2012).
Recent developments in the ...application of oxidative carbonylation to the synthesis of carbonylated heterocycles are reviewed (coverage: 2006 to the beginning of 2012).
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This review is intended to highlight some recent and particularly interesting examples of the synthesis of thiophene derivatives by heterocyclization of readily available S-containing alkyne ...substrates.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This review focuses on contaminant removal from water using hydrogel-based materials. It highlights the recent results achieved, unresolved problems, and possible developments. Polymer and graphene ...hydrogels are promising new materials for removing inorganic (e.g., metals and metalloids) and organic (e.g., dyes) trace contaminants from water. They can be prepared as composites with practically any desired conventional or innovative adsorbent, to enhance the removal efficiency. Obtaining a three-dimensional highly effective network is one of the significant features of hydrogels, which confer specific characteristics on them. There are number of benefits of using hydrogels: easy separation and handling, the facility for large-scale application, and the ability to regenerate and reuse the hydrogels. At present, the experiments based on hydrogels for water purification are mostly limited to the laboratory scale and further research needed to move toward large-scale industrial applications. Moreover, the present studies are currently limited to a few types of contaminants, so that further experiments needed for removal of more contaminant types and mixtures of contaminants, considering that in practical situations. All these features are described and discussed in this review, which, to the best of our knowledge, is the first comprehensive review on hydrogel applications for contaminant removal from water.
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In this minireview, we discuss some recently reported methods for the synthesis of polycyclic heterocycles by palladium‐catalyzed double cyclization processes. Paradigmatic examples taken by the most ...recent literature (from 2014 to the beginning of 2019) are presented. Only transformations in which palladium is involved in at least one cyclization stage are taken into consideration. The first part deals will Pd(0)‐catalyzed processes. Double cyclizations initiated by the oxidative addition of an Ar–X bond or other functional groups are treated first, followed by processes beginning with carbopalladation by Pd(0) attack to unsaturated bonds. The second part concerns Pd(II)‐catalyzed reactions, and begins with double cyclizations initiated by intramolecular nucleophilic attack to unsaturated bonds coordinated to Pd(II), followed by processes initiated by aromatic palladation.
This minireview highlights recent progress in the synthesis of polycyclic heterocycles involving a double cyclization process, in which at least one cyclization is promoted by palladium. It is shown how different kinds of palladium catalysts can efficiently be employed for realizing this important synthetic transformation in one step, starting from suitably functionalized starting materials.
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Ruthenium PNP pincer complexes bearing supplementary cyclometalated C,N‐bound ligands have been prepared and fully characterized for the first time. By replacing CO and H− as ancillary ligands in ...such complexes, additional electronic and steric modifications of this topical class of catalysts are possible. The advantages of the new catalysts are demonstrated in the general α‐alkylation of ketones with alcohols following a hydrogen autotransfer protocol. Herein, various aliphatic and benzylic alcohols were applied as green alkylating agents for ketones bearing aromatic, heteroaromatic or aliphatic substituents as well as cyclic ones. Mechanistic investigations revealed that during catalysis, Ru carboxylate complexes are predominantly formed whereas neither the PNP nor the CN ligand are released from the catalyst in significant amounts.
Alkylation with ruthenium: Eight new Ru pincer complexes were prepared by introduction of C,N‐bound phenyl heterocycle ligands. These complexes were applied as catalysts in the α‐alkylation of ketones with alcohols through hydrogen autotransfer. Here, superior yields in comparison to RuHCl(CO)(HN(CH2CH2PPh2)2) (Ru‐MACHO) were achieved and 21 different alkylated ketones were synthesized in up to 97 % yield. Moreover, investigations regarding the catalyst species present during the reaction were conducted.
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Cyclometalated ruthenium complexes
4-10
allow the effective methylation of anilines with methanol to selectively give
N
-methylanilines. This hydrogen autotransfer procedure proceeds under mild ...conditions (60 °C) in a practical manner (NaOH as base). Mechanistic investigations suggest an active homogenous ruthenium complex and β-hydride elimination of methanol as the rate determining step.
Cyclometalated ruthenium allow the effective and selective
N
-methylation of anilines under mild conditions.
Polycyclic heterocyclic derivatives have been synthesized in one step by a carbonylative double cyclization approach starting from readily available starting materials. The method is based on a ...regioselective 6‐endo‐dig heterocyclization – cyclocarbonylation sequence catalyzed by the PdI2/KI catalytic system under oxidative conditions, with CO (5–10 atm) as the carbonylating agent and O2 (from air, 35–70 atm) as the external oxidant and formation of water as benign coproduct. Starting from thiophenecarboxylic acids bearing an ω‐hydroxyalkynyl substituent in vicinal position, previously unknown 1H‐furo3,4‐bthieno3,2‐dpyran‐1,5(3H)‐diones, 4H‐furo3,4‐bthieno2,3‐dpyran‐4,8(6H)‐diones, 3,4‐dihydro‐1H,6H‐pyrano4,3‐bthieno3,2‐dpyran‐1,6‐diones, and 6,7‐dihydro‐4H,9H‐pyrano4,3‐bthieno2,3‐dpyran‐4,9‐diones were obtained in 45–86% yields over 21 examples. The structures of two representative products have been confirmed by X‐ray diffraction analysis.
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A catalytic carbonylative method for the direct, multicomponent synthesis of indolizine fluorophores has been developed. The process is based on the PdI2/KI‐catalyzed oxidative aminocarbonylation of ...2‐(pyridin‐2‐yl)pent‐4‐yn‐1‐carbonyl compounds leading to the corresponding 2‐ynamide intermediates, followed in situ by 5‐exo‐dig cyclization (by amine‐promoted conjugate addition of the pyridine ring nitrogen) and aromatization, to give the finally isolated N,N‐disubstituted 2‐(indolizin‐3‐yl)acetamides. Reactions are carried out under relatively mild conditions (100 °C under 20 atm of a 4 : 1 mixture CO−air for 6–15 h) in MeCN as the solvent and with a low catalyst loading (0.33 mol% PdI2), in the presence of 0.5 equiv. of KI and 3 equiv. of a secondary amine. The optical properties of representative 2‐(indolizin‐3‐yl)acetamide products have also been investigated.
N,N‐disubstituted 2‐(indolizin‐3‐yl)acetamides with fluorescent properties are obtained in a multicomponent fashion starting from simple building blocks (2‐(pyridin‐2‐yl)pent‐4‐yn‐1‐carbonyl compounds, CO, amines, and oxygen) through a sequential PdI2/KI‐catalyzed oxidative aminocarbonylation – cyclization – aromatization process. Initially formed 2‐ynamide intermediates, ensuing from Pd‐catalyzed triple bond oxidative aminocarbonylation, are converted in situ into the final products by amine‐promoted intramolecular dearomative conjugate addition followed by rearomatization.
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