Hydrogen atom storage upon Z-class borane ligand functions: an alternative approach to ligand cooperation

Ligand cooperation has become an important strategy in the development of new transition metal based transformations. By using this approach some remarkable new catalytic transformations have been achieved, all in the space of only a few years. The purpose of this tutorial review is to explore the potential utilisation of ligands containing borohydride and borane functionalities as reversible hydrogen atom stores. At the heart of this review will be a discussion on hydrogen transfer reactions and the transformation between borohydride and borane moieties. An outline of the various synthetic routes to metal-borane (metallaboratrane) complexes will be provided together with a discussion of their further reactivity including key transformations such as 1,2 additions across the metal-boron bond and 'recharging' the borane functional group back to borohydride. Finally, an evaluation of the potential future applications of such reactivity will be provided.     

Facile domino access to chiral mono-, bi-, and tricyclic 2,3-dihydrofurans

The asymmetric domino Michael-S(N)2 reaction of various 1,3-dicarbonyl compounds to α-bromonitroalkenes is described for the first time, employing readily available cinchona-derived bifunctional thioureas as organocatalysts. The novel transformations were highly regio-, chemo-, diastereo-, and enantioselective, which simultaneously gave the chiral tricyclic 2,3-dihydrofurans, bicyclic 2,3-dihydrofurans, and tetrasubstituted 2,3-dihydrofurans with two vicinal chiral carbon centers.     

Synthesis of annulated oxa-triquinanes and oxa-diquinanes via cascade Michael addition-intramolecular alkylation involving α-halodicyclopentadienones

Base Mediated Michael addition of 1,3-dicarbonyl compounds to α-halodicyclopentadienones followed by cyclization of the intermediate Michael adducts leads to novel annulated dihydrofurans as single diastereomers. Such fused dihydrofurans, which are also oxa-triquinanes and oxa-diquinanes, undergo retro-Diels-Alder reaction to give cyclopentadiene-eliminated products in excellent yield. Certain 1,3-dicarbonyl compounds exhibited a different reactivity profile with α-halodicyclopentadienones leading to spiro-cyclopropanes fused to dicyclopentadiene skeleton.     

Reactions of azidoazolopyridazines with 1,3-dicarbonyl compounds

Azidoazoloazines react with 1,3-dicarbonyl compounds to give cycloaddition products, 1,2,3-triazole derivatives, whose structures have been established by chemical transformations and spectroscopic data.     

Synthesis of highly functionalized piperidines by one-pot multicomponent reaction using tetrabutylammonium tribromide (TBATB)

Tetrabutylammonium tribromide (TBATB) has been found to be an efficient catalyst for the one-pot synthesis of highly substituted piperidines through a combination of 1,3-dicarbonyl compounds, aromatic aldehydes, and various amines in ethanol at room temperature. Atom economy, good yields, environmentally benign, and mild reaction conditions are some of the important features of this protocol.     

Nickelacyclobutanes: Versatile Reactivity and Role as Catalytic Intermediates

Metallacyclobutanes are intermediates in several catalytic cycles such as olefin metathesis and cyclopropanation. Furthermore, nickel is attracting attention as a versatile, earth-abundant metal in developing new homogeneous catalytic transformations. In this context, the current literature on nickelacyclobutanes and their role in catalysis is reviewed. First, catalytic reactions involving a (putative) nickelacyclobutane intermediate are discussed, including cyclopropanations and various transformations of methylenecyclopropane. Second, studies of the stoichiometric reactivity of nickelacyclobutanes relying on their direct observation or even isolation are detailed. In particular, the relationship between the structure of nickelacyclobutanes and their reactivity is highlighted. Finally, future prospects for the development of new catalytic transformations relying on nickelacyclobutane intermediates are briefly outlined.     

Influence of ultraviolet light on some copper chelates of β-dicarbonyl compounds : Spectral evidence for a photoactivated metallotropy

The influence of ultraviolet light on heptane solutions of the copper chelates of several β-dicarbonyl compounds has been followed by spectroscopy. Reversible transformations are apparent, leading us to assume the presence of a photoactivated metalotropy.     

K2CO3-promoted domino reactions: construction of functionalized 2,3-dihydrobenzofurans and clofibrate analogues

The K(2)CO(3)-catalyzed domino reactions (Michael alkylation, Mannich alkylation, and aldol alkylation) of salicylic aldehyde derivatives (2-hydroxyaryl-α,β-unsaturated ketones, 2-hydroxyarylnitroalkenes, 2-hydroxyarylimines, and salicylic aldehydes) and 2-halo-1,3-dicarbonyl compounds (diethyl α-bromomalonate, diethyl α-chloromalonate, ethyl 2-chloroacetoacetate, and 3-chloropentane-2,4-dione) were carried out under mild conditions to provide a series of functionalized 2,3-dihydrobenzofurans in moderate to excellent yields. The novel transformations simultaneously gave a series of clofibrate analogues, which possess various substitution patterns.     

New generation of nucleophilic glycine equivalents

A new generation of nucleophilic glycine equivalents, designed to contain a functional framework, that allows control over the physical properties as well as the reactivity, is described. The reactivity of these nucleophilic glycine equivalents have been compared to previously described examples with the application of various transformations such as alkyl halide alkylations, Michael additions, and aldol condensations.     

Acyl pyruvates as synthons in the Biginelli reaction

Chlorotrimethylsilane-promoted Biginelli-type reaction of ethyl 2,4-dioxo-4-phenylbutanoate, benzaldehyde, and various (thio)ureas is explored. The outcome of the reaction depends on the structure of the (thio)urea used and is strongly affected by the acceptor electronic properties of the COOEt substituent in the molecule of the starting β-dicarbonyl compound. The di- and tetrahydropyrimidine derivatives obtained possess two functional groups with orthogonal reactivity, and thus represent promising building blocks for drug discovery.     

Anilinomethylidene derivatives of cyclic 1,3-dicarbonyl compounds in the synthesis of new sulfur-containing pyridines and quinolines

Simple methods for the synthesis of previously unknown sulfur-containing pyridin-2-ones and 5,6,7,8-tetrahydroquinolines from cyanothioacetamide and anilinomethylidene derivatives of cyclic 1,3-dicarbonyl compounds were developed. Structures and chemical transformations of compounds obtained were studied.     

Tandem conjugate addition-elimination reaction promoted by chiral pyrrolidinyl sulfonamide (CPS)

Chiral pyrrolidinyl sulfonamides have been found to promote the conjugate addition-elimination reaction between activated allylic bromides and 1,3-dicarbonyl compounds with high enantioselectivities and the highly functionalised products can be used to generate a variety of interesting enantiomerically pure compounds via simple transformations.     

Annelation of perfluorinated heteroaromatic systems by 1,3-dicarbonyl derivatives

Reactions of various perfluorinated heteroaromatic substrates such as tetrafluoro-4-cyanopyridine, tetrafluoropyrazine and tetrafluoropyridazine with 1,3-dicarbonyl systems gave corresponding [5,6]-ring fused furo derivatives. Subsequent reactions of the [5,6] bicyclic scaffolds with nucleophiles gave some highly functionalised heteroaromatic systems.     

Ultrasound promoted three-component synthesis of dihydroindeno[1,2-b]pyrrole derivatives

In this work, a one-pot three-component reaction of ninhydrin, primary amines, and 1,3-dicarbonyl compounds was investigated under various conditions to synthesis of diverse derivatives of dihydroindeno[1,2-b]pyrroles. Catalyst-free conditions in EtOH under ultrasound irradiation (45% of amplitude) were selected as a novel and efficient method for synthesis of these fused structures. The reactivity of different primary amines was then investigated for steric and electronic effects. Two examples of difunctional structures were also synthesized by using of 1,4-diaminobenzene under optimum conditions with high yields. The structure of all products was characterized by spectroscopic methods and elemental analysis.     

Recent Developments of Tellurium- and Selenium-Containing Iron Carbonyl Clusters

In recent years, quite a number of tellurium-or selenium-containing iron carbonyl clusters have been synthesized and structurally characterized, and some interesting structural transformations and reactivity of these clusters have been systematically investigated as well. The syntheses and reactivity of these clusters are reviewed and compared.     

Ceric ammonium nitrate (CAN) catalyzed synthesis and α-glucosidase activity of some novel tetrahydropyridine phosphonate derivatives

Abstract

A simple and highly efficient multicomponent one-pot synthesis of a series of pharmaceutically interesting functionalized tetrahydropyridine phosphonate derivatives has been developed based on low-cost and environmentally benign ceric ammonium nitrate (CAN) catalyst via tandem reactions of 1,3-dicarbonyl compounds, diethylphosphoramidate and various aromatic aldehydes in acetonitrile at room temperature. High atom economy, good yields, eco-friendliness and mild reaction conditions are some of the important features of this protocol.     

Cyclic Haloiodanes: Syntheses,Applications and Fundamental Studies

Hypervalent iodine reagents are powerful tools in contemporary organic synthesis. They have found numerous applications in modern oxidative transformations. The unique reactivity of hypervalent iodine allows access to unconventional electrophilic synthons. For example, electrophilic halogenation chemistry has been greatly expanded by the study of various haloiodanes. Cyclic λ³-haloiodanes are versatile reagents which can promote reactions such as halogenations, halocyclizations and oxidations. Their peculiar reactivity sets them apart from traditional sources of electrophilic halogens. Furthermore, they offer a broad range of reactivities which have been exploited in more diversified transformations. This review summarizes the different syntheses and derivatives of these cyclic haloiodanes, their applications and mechanistic insights as well as the relevant computational, structural and kinetic studies.     

Synthesis of new pyrazole and isoxazole derivatives based on products of condensation of β-dicarbonyl compounds with 1,2,3-trihalopropanes

The reaction of 2-(2-halo-3-propenyl)-1,3-dicarbonyl compounds, which are formed in the alkylation of -dicarbonyl compounds with 1,2,3-trihalopropanes in the presence of potassium carbonate in DMSO, with hydrazine and hydroxylamine derivatives was studied. The synthesis of new pyrazole and isoxazole derivatives on the basis of this reaction is described. Some chemical transformations of the 1,2-azoles obtained were investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 787–791, June, 1987.     

Axially chiral guanidine as highly active and enantioselective catalyst for electrophilic amination of unsymmetrically substituted 1,3-dicarbonyl compounds

A newly designed axially chiral guanidine is found to function as an effective platform for asymmetric induction at the alpha-carbon of unsymmetrically substituted 1,3-dicarbonyl compounds. Highly efficient and enantioselective electrophilic amination of various 1,3-dicarbonyl compounds with azodicarboxylate was successfully achieved using the present chiral guanidine catalyst, which provides efficient access to the construction of nitrogen-substituted quaternary stereocenters in an optically active form.     

Different Reactivity of Raw Starch from Diverse Potato Genotypes

Potato starch is one of the most important renewable sources for industrial manufacturing of organic compounds. Currently, it is produced from mixed potato varieties that often are harvested from different fields. Meanwhile, tuber starches of various potato breeds differ in their crystallinity, granule morphology, and other physical and chemical parameters. We studied the reactions of raw potato starches of different origins to chemical and biochemical reactions typically used for industrial starch modification. The results clearly demonstrate that there is a significant difference in the reactivity of the starches of different potato genotypes. While the main products of the transformations are the same, their preparative yields differ significantly. Thus, tuber starch of certain potato varieties may be more suitable for specific industrial purposes. Starch reactivity may potentially be a phenotypical trait for potato breeding to obtain potato starches for various industrial applications.