Novel biomimetic, aerobic oxidation with an organocatalyst was performed. The oxidations of organic substrates such as sulfides, secondary amines, N-hydroxylamines, and tertiary amines molecular oxygen (1 atm) or even in air the presence 5-ethyl-3-methyllumiflavinium perchlorate catalyst hydrazine monohydrate 2,2,2-trifluoroethanol occur highly efficiently to give corresponding oxidized compounds excellent yields along water nitrogen, which are environmentally benign. TON sulfides amounts 19 000.

A series of novel helical poly(phenylacetylene)s bearing amino-functionalized cinchona alkaloid pendant groups connecting to the phenyl rings through an amide linkage were prepared by polymerization corresponding phenylacetylenes using a rhodium catalyst. All polymers formed preferred-handed conformation biased optically active pendants, resulting in induced circular dichroism their π-conjugated polymer backbone regions. The efficiently catalyzed asymmetric Henry reaction benzaldehydes with...

Novel polyacetylenes bearing an optically active or racemic [6]helicene unit as the pendant groups directly bonded to main-chain (poly-1s) were prepared by polymerisation of corresponding acetylenes (1-rac, 1-P and 1-M) using a rhodium catalyst. The (poly-1-P poly-1-M) formed preferred-handed helical conformation biased helicene pendants, resulting in induced circular dichroism (ICD) their π-conjugated polymer backbone regions. polymers, when employed enantioselective adsorbent, showed high...

Empfindliche Substrate wie Alkohole, Olefine und Sulfide, die unter gewöhnlichen Baeyer-Villiger-Bedingungen elektrophile Oxidationen eingehen würden, bleiben in einer hoch chemoselektiven katalytischen Baeyer-Villiger-Oxidation unversehrt (siehe Schema). Die Flavin-Verbindung [DMRFlEt]+[ClO4]− (blau) katalysiert aerobe Gegenwart von Zinkstaub. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2005/z462429_s.pdf or from author....

We report the first enantioselective reductive aldol couplings of vinyl ketones, which were achieved through design a novel monodentate TADDOL-like phosphonite ligand. Specifically, hydrogenation commercially available methyl ketone (MVK) or ethyl (EVK) in presence aldehydes 1a−7a using cationic rhodium catalysts modified by chiral ligands AP-I and AP-IV produces adducts 1b−7b 1c−7c with excellent control relative absolute stereochemistry. The stereochemical assignments are made analogy to...

An optically inactive poly(4-carboxyphenyl isocyanide) (poly-1-H) changed its structure into the prevailing, one-handed helical upon complexation with active amines in dimethylsulfoxide (DMSO) and water, complexes show a characteristic induced circular dichroism polymer backbone region. Moreover, macromolecular helicity water aqueous organic solutions containing more than 50 vol % could be "memorized" even after complete removal of chiral (h-poly-1b-H), while that DMSO DMSO−water mixtures...

Flavin of the month! Triazolium-derived N-heterocyclic carbenes (NHCs) and a flavin catalyzed oxidative esterification, thioesterification, amidation aldehydes with various alcohols, thiols, amines, respectively, O2 as terminal oxidant (see scheme; R1=aryl; R2, R3=alkyl or aryl). By using chiral NHC catalyst, enantioselective acylation promoted kinetic resolution racemic alcohols desymmetrization meso-diol. Detailed facts importance to specialist readers are published ”Supporting...

A novel optically active polymer consisting of riboflavin units as the main chain (poly-1) was prepared from naturally occurring (vitamin B(2)) in three steps. The residues poly-1 were converted to 5-ethylriboflavinium cations (giving poly-2), which could be reversibly transformed into corresponding 4a-hydroxyriboflavins poly-2OH) through hydroxylation/dehydroxylation reactions. This reversible structural change accompanied by a visible color along with significant changes absorption and...

A bioinspired two-component redox organocatalyst system using 1,10-bridged flavinium and NH4I was developed to perform environmentally friendly aerobic oxidative ring formation of 1,2,3-thiadiazoles from N-tosylhydrazones sulfur. The organocatalysis the promoted iodine-catalyzed without use any sacrificial reagents, except for benign molecular oxygen.

A green, aerobic sulfenylation of imidazo[1,2-a]pyridines was performed using thiols, a flavin-and-iodine dual catalytic system, and environmentally benign molecular oxygen as the only sacrificial reagent. The metal-free catalysts smoothly promote unique stepwise tandem process, beginning with oxidation thiol to afford disulfide that is utilized in oxidative imidazo[1,2-a]pyridine. This process has afforded diverse 3-sulfenylimidazo[1,2-a]pyridines biological interest friendly, H2O byproduct.

Abstract Self-recognition and self-discrimination within complex mixtures are of fundamental importance in biological systems, which entirely rely on the preprogrammed monomer sequences homochirality macromolecules. Here we report artificial chirality- sequence-selective successive self-sorting chiral dimeric strands bearing carboxylic acid or amidine groups joined by amide linkers with different through homo- complementary-duplex formations. A mixture dimers linked racemic -1,2-cyclohexane...

We report the unprecedented allosteric regulation of extension and contraction motions double-stranded spiroborate helicates composed 4,4′-linked 2,2′-bipyridine (bpy) its N,N′-dioxide units in middle ortho-linked tetraphenol strands. NMR circular dichroism measurements an X-ray crystallographic analysis along with theoretical calculations revealed that enantiomeric contract extend upon binding release protons and/or metal ions at covalently linked two bpy or moieties without racemization,...

The environmentally friendly direct sulfenylation of indoles with thiols was performed by a unique coupled redox organocatalysis system using flavin and iodine.

The first green and practical method for "aerobic hydrogenation" involving the use of hydrazine an organocatalyst is described. Olefins can be hydrogenated by treatment with in presence a 5-ethyl-3-methyllumiflavinium perchlorate (FlEt+.ClO4-) catalyst under O2 atmosphere to give corresponding products excellent yields along environmentally benign water molecular nitrogen as only waste products.

To develop a novel polymer-based asymmetric organocatalyst, series of helical poly(phenyl isocyanide)s with functional pendant groups were prepared by modifying the side optically active poly(4-carboxyphenyl isocyanide) macromolecular helicity memory. Helical polyisocyanides partially modified achiral amines, such as piperazine, maintained their chiral memory and enantioselectively catalyzed direct aldol reaction. Although enantioselectivity was low, original showed no catalytic activity....

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTSynthesis and Visualization of a Core Cross-Linked Star Polymer Carrying Optically Active Rigid-Rod Helical Polyisocyanide Arms Its Chiral Recognition AbilityToshitaka Miyabe, Hiroki Iida, Motonori Banno, Tomoko Yamaguchi, Eiji Yashima*View Author Information Department Molecular Design Engineering, Graduate School Nagoya University, Chikusa-ku, 464-8603, JapanE-mail: [email protected]Cite this: Macromolecules 2011, 44, 21, 8687–8692Publication Date...

A series of novel optically active poly(phenyl isocyanide)s bearing achiral benzanilide pendant groups was prepared based on the noncovalent "helicity induction and memory strategy". The polymers that exhibited an optical activity due to macromolecular helicity were immobilized 3-aminopropyl-silanized silica gel through chemical bonding or coated obtain chiral packing materials for high-performance liquid chromatography (HPLC). recognition abilities toward a variety racemic compounds with...

Abstract A versatile reducing agent, diimide, can be generated efficiently by the aerobic oxidation of hydrazine with neutral and cationic synthetic flavin catalysts 1 2 . This technique provides a convenient safe method for reduction olefins, which proceeds equiv under an atmosphere O or air. The advantage over conventional gas‐based has been illustrated through high efficiency, easy handling, characteristic chemoselectivity. Vitamin B derivative 6 acts as highly practical, robust catalyst...

Influential guests: The intercalation of an electron-deficient aromatic guest (shown in red) between the two porphyrin rings optically active, porphyrin-linked double-stranded spiroborate helicate triggered rotary motion one direction conjunction with a unidirectional twisting helix. This system has potential for development chirality-responsive molecular machines. As service to our authors and readers, this journal provides supporting information supplied by authors. Such materials are peer...

Diastereomeric left- and right-handed helical polyisocyanides composed of L-alanine-bound phenyl isocyanides were prepared. The polymers with a narrow molecular weight distribution immobilized on silica gel support via chemical bonding their optical resolution abilities evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). CSP prepared from the left-handed polyisocyanide resolved racemic cyclic ether carbonyl compounds dianilides dibenzamides,...

An efficient and practical catalytic method for the aerobic oxidative transformation of sulfides into sulfoxides, thiols disulfides with formic acid/TEA in presence a new, readily available, stable flavin catalyst 5d is described.