Mild and regioselective oxidative bromination of anilines using potassium bromide and sodium perborate

Artificial sugar saccharin and its derivatives: role as a catalyst

The primary objective of this review was to demonstrate the significance of artificial sugar saccharin and its derivatives as catalysts for a wide variety of organic transformations. The application of saccharin and its derivatives represents a greener and superior catalytic approach for reactions. In particular, we were interested in bringing together the literature pertaining to these saccharin derivatives from a catalysis perspective. The present review reports synthesis of saccharin and its derivatives such as saccharin-N-sulfonic acid, sodium saccharin, N-halo saccharin, saccharin lithium-bromide, N-formyl saccharin, N-acyl saccharin, N-nitrosaccharin, N-SCF₃ saccharin, N-fluorosultam, N-phenylselenosaccharin, N-thiocyanatosaccharin palladium saccharin, DMAP-saccharin, and [Bmim]Sac. This catalytic application of saccharin and its derivatives includes reactions such as the Biginelli reaction, Paal-Knorr pyrrole synthesis, azo-coupling reaction, halogenations, domino Knoevenagel, Michael, deoximation reaction, catalytic condensation, functional group protection and oxidation etc. Also, these saccharin derivatives act as a source of CO, NH₂, SCN, SCF₃ and nitro groups. We reported all the available data on saccharin and its derivatives acting as a catalyst from 1957 to date.

A New Ring Bromination Method for Aromatic Compounds under Solvent-Free Conditions with Nbs/Al2O3

Alumina supported N-bromosuccinimide was found to be an efficient reagent for ring bromination of a number of aromatic compounds under solvent-free conditions. In the absence of the alumina the reactions are slow and some of the substrates are recovered unchanged. Under the reaction conditions aromatic oximes are converted into the corresponding carbonyl compounds. The method is simple, safe and rapid.

Reconstitution of Vanadium Haloperoxidase's Catalytic Activity by Boric Acid-Towards a Potential Biocatalytic Role of Boron

Boron's unusual properties inspired major advances in chemistry. In nature, the existence and importance of boron has been fairly explored (e.g. bacterial signaling, plant development) but its role as biological catalyst was never reported. Here, we show that boric acid [B(OH)₃ ] can restore chloroperoxidase activity of Curvularia inaequalis recombinant apo-haloperoxidase's (HPO) in the presence of hydrogen peroxide and chloride ions. Molecular modeling and semi-empirical PM7 calculations support a thermodynamically highly favored (bio)catalytic mechanism similarly to vanadium haloperoxidases (V-HPO) in which [B(OH)₃ ] is assumedly located in apo-HPO's active site and a monoperoxyborate [B(OH)₃ (OOH)^- ] intermediate is formed and stabilized by interaction with specific active site amino acids leading ultimately to the formation of HOCl. Thus, B(OH)₃ -HPO provides the first evidence towards the future exploitation of boron's role in biological systems.

Efficient, versatile and practical palladium-catalyzed highly regioselective ortho-halogenation of azoxybenzenes

A highly efficient and practical strategy of regio-selective ortho-halogenation of azoxybenzenes with NXS in the presence of palladium catalysts has been developed in good to excellent yields.

Extending the biocatalytic scope of regiocomplementary flavin-dependent halogenase enzymes

Flavin-dependent halogenases are potentially valuable biocatalysts for the regioselective halogenation of aromatic compounds. These enzymes, utilising benign inorganic halides, offer potential advantages over traditional non-enzymatic halogenation chemistry that often lacks regiocontrol and requires deleterious reagents. Here we extend the biocatalytic repertoire of the tryptophan halogenases, demonstrating how these enzymes can halogenate a range of alternative aryl substrates. Using structure guided mutagenesis we also show that it is possible to alter the regioselectivity as well as increase the activity of the halogenases with non-native substrates including anthranilic acid; an important intermediate in the synthesis and biosynthesis of pharmaceuticals and other valuable products.

Nonanebis(peroxoic acid): a stable peracid for oxidative bromination of aminoanthracene-9,10-dione

A new protocol for the oxidative bromination of aminoanthracene-9,10-dione, which is highly deactivated towards the electrophilic substitution is investigated. The peracid, nonanebis(peroxoic acid), possesses advantages such as better stability at room temperature, it is easy to prepare and non-shock sensitiv as compared to the conventional peracids. The present protocol has a broad scope for the bromination of various substituted and unsubstituted aminoanthracene-9,10-diones.

The discovery and unique pharmacological profile of RO4938581 and RO4882224 as potent and selective GABAA alpha5 inverse agonists for the treatment of cognitive dysfunction

Lead optimisation of the imidazo[1,5-a][1,2,4]-triazolo[1,5-d][1,4]benzodiazepine class led to the identification of two clinical leads [RO4882224 (11) and RO4938581 (44)] functioning as novel potent and selective GABAA alpha5 inverse agonists. The unique pharmacological profiles and optimal pharmacokinetic profiles resulted in in vivo activity in selected cognition models.

Synthesis and evaluation as MRI probe of the trifluoromethylated p-boronophenylalanine and its alcohol derivative

Boron-neutron capture therapy (BNCT) and magnetic resonance imaging (MRI) are quite attractive techniques for treatment and diagnosis of cancer, respectively. In order to develop practical tools for BNCT and MRI, novel compounds containing both the trifluoromethyl group and 10B atom in a single molecule were designed. In the present study, p-boronophenylalanine and p-boronophenylalaninol with the trifluoromethyl group were synthesized, and 19F NMR measurements of these compounds were carried out.

A Simple Catalytic Method for the Regioselective Halogenation of Arenes

This paper describes a mild palladium-catalyzed method for the regioselective chlorination, bromination, and iodination of arene C-H bonds using N-halosuccinimides as oxidants. These transformations have been applied to a wide array of substrates and can provide products that are complementary to those obtained via conventional electrophilic aromatic substitution reactions. [reaction: see text]

A new recyclable ditribromide reagent for efficient bromination under solvent free condition

1,2-Dipyridiniumditribromide-ethane (DPTBE) has been synthesized and explored as a new efficient brominating agent. The crystalline ditribromide reagent is stable for months and acts as a safe source of bromine requiring just 0.5 equiv for complete bromination. It has high active bromine content per molecule and shows a remarkable reactivity compared to other tribromide reagents toward various substrates by just grinding the reagent and substrates in a porcelain mortar at room temperature. No organic solvent has been used during any stage of the reaction for substrates giving product as solid. Product can easily be isolated by just washing the highly water soluble 1,2-dipyridiniumdibromide-ethane (DPDBE) from the brominated product. The spent reagent can be recovered, regenerated, and reused without any significant loss.

Synthesis of 5-Substituted-1H-indol-2-yl-1H-quinolin-2-ones: A Novel Class of KDR Kinase Inhibitors

[reaction: see text] A number of approaches for the synthesis of the 1H-indol-2-yl-1H-quinolin-2-one ring system found in the potent and selective KDR kinase inhibitor 1 are described. The preparation and reaction of trimethylsilylnitrobenzene 26 with 2-methoxy-3-quinolinecarboxaldehyde 28 afforded alcohol 30, which was the key intermediate for the preparation of the target compounds. Conversion of alcohol 30 to either nitroketone 36 or nitrostyrene 45 set the stage for reductive cyclization and the formation of indole 25. The quinolin-2-one functionality was unmasked in the last step to provide compound 1 in 56-60% overall yield from readily available starting materials.

Syntheses and DNA-binding studies of a series of unsymmetrical cyanine dyes: structural influence on the degree of minor groove binding to natural DNA

Twelve crescent-shaped unsymmetrical dyes have been synthesized and their interactions with DNA have been investigated by spectroscopic methods. A new facile synthetic route to this type of cyanine dyes has been developed, involving the preparation of 6-substituted 2-thiomethyl-benzothiazoles in good yields. The new dyes are analogues to the minor groove binding unsymmetrical cyanine dye, BEBO, recently reported by us. In this dye, the structure of the known intercalating cyanine dye BO was extended with a 6-methylbenzothiazole substituent. Herein we further investigate the role of the extending benzazole heterocycle, as well as of the pyridine or quinoline moiety of the cyanine chromophore, for the binding mode of these crescent-shaped dyes to calf thymus DNA. Flow LD and CD studies of the 12 dyes show that the extent of minor groove binding to mixed sequence DNA varies significantly between the dyes. We find that hydrophobicity and size are the crucial parameters for recognition of the minor groove. The relatively high fluorescence quantum yield of many of these cyanines bound to DNA, combined with their absorption at long wavelengths, may render them useful in biological applications. In particular, two of the benzoxazole containing dyes BOXTO and 2-BOXTO show a high degree of minor groove binding and quantum yields of 0.52 and 0.32, respectively, when bound to DNA.

Hydrogen bond-stabilized helix formation of a m-phenylene ethynylene oligomer

[reaction: see text] Incorporation of a single hydrogen bonded beta-turn mimic in the backbone of a m-phenylene ethynylene oligomer is shown to affect the thermodynamic properties of the folding reaction. Oligomers 1 and 2 both undergo solvophobic helix formation, but hydrogen bonded oligomer 1 was found to form a more stable helix with a higher tolerance to solvent denaturation than isomeric, non-hydrogen bonded oligomer 2.