One-pot construction of spirooxindole backbone via biocatalytic domino reaction

A simple and environmentally friendly method to synthesize spiropyrazolo[3,4-b]pyridines derivatives starting from isatin, cyclic-1,3-diketone and 3-methyl-5-aminopyrazole was developed. With the optimized conditions for enzymes, solvents, enzyme loading and reaction time in hand, 9 compounds were obtained in acceptable yields. Moreover, the investigation in fluorescent properties of these products showed their potential application in the field of new fluorescent material.     

Asymmetric aziridination of chalcones catalyzed by a novel backbone 1,8-bisoxazolinylanthracene (AnBOX)-copper complex

Highly enantioselective aziridination of chalcones catalyzed by a novel backbone 1,8-bisoxazolidinylanthracene (AnBOX) and CuOTf with up to >99% ee and the opposite enantioselectivity compared with the ligands of Evans are described.     

One-pot conversion of allyl alcohols into selenochroman derivatives

A one-pot conversion of allyl alcohols into selenochroman derivatives was achieved by treatment with a phenyl trimethylsilyl selenide (TMSSePh)-AIBr3 reagent system.     

One-pot transformation of trichloroacetamide into readily deprotectable carbamates

[Structure: see text] A trichloroacetamide group was converted to an isocyanate, which was in situ captured by a variety of alcohols in the presence of CuCl and n-BuN4Cl to afford the corresponding carbamates. The scope and limitation of this transformation are also described.     

One-pot N-dealkylation and acid-catalyzed rearrangement of morphinans into aporphines

The one-pot N-demethylation and acid-catalyzed rearrangement of morphinan-N-oxides offers a new, shorter and more efficient route to neuropharmacologically important N-substituted aporphines. An improved procedure is described for the preparation of the starting alkaloid N-oxides using Na₂WO₄ as catalyst. The transetherification during the rearrangement of codeinone into 2-O-alkyl-norapocodeines is documented.     

Catechol-Mediated Redox-Neutral One-pot Transformation of SiO2 into SiPh4

Organosilanes range among the most important products in chemical industries. Unfortunately, their bulk production starting from silicon oxides has a substantial ecological footprint due to the immense energy consumption and the numerous hazardous by-products imposed by the redox cycling between Si(0) and Si(IV). Herein, we report the first redox-neutral, one-pot silicon−carbon bond formation starting from silica gel by combining catechol-mediated SiO₂ depolymerization and nucleophilic substitution of the tris(catecholato)silicate dianion intermediates. Screening and optimization of the individual steps enables a 76 % yield of SiPh₄ on a preparative scale. Non-rationalizable effects of solvents, nucleophiles, and countercations are identified, rendering suitable for statistical optimization approaches such as “design-of-experiments” in future studies. The general success of such process encourages the search for more energy- and waste-effective organosilane production.     

Facile One-pot Transformation of 2,3-Epoxy Alcohols into Allylic Alcohols

Optically-active allylic alcohols have been frequently used as chiral building blocks for the preparation of optically pure compounds.¹ There are at present various methods for the synthesis of optically active allylic alcohols including the kinetic resolution racemic allylic alcohols,² reductive rearrangement of 2,3-epoxy alcohol by metal, halide and telluium-based chemistry.³ To our knowledge, One-pot Transformation of 2,3-epoxy alcohols into allylic alcohols, especially via epoxy iodides,is limited to Dorta's method³ using a Ph₃P,iodine, imidazole,2,6-lutidine and water system. The original Dorta's method can be successfully applied to the formation of tertiary allylic alcohols, but give unsatisfactory results in formation of secondary allylic alcohols.     

Epoxidation of chalcones

Previously undescribed aromatic -keto oxides have been obtained by the epoxidation of chalcones with alkaline hydrogen peroxide in methanolic solution.     

Nickel-catalysed intramolecular alkene insertion into cyclobutanones

A nickel(0) catalyst converted 3-styrylcyclobutanones into benzobicyclo[2.2.2]octenones by an intramolecular insertion of the vinyl moiety into the cyclobutanone skeleton.     

Palladium-catalyzed carbene insertion into benzyl bromides

Palladium can catalyze the insertion of ethyl diazoacetate into benzyl bromides. The key step in the catalytic cycle is the migratory insertion of a carbene, derived from ethyl diazoacetate, into a Pd-C bond.     

Nickel-catalyzed intermolecular alkyne insertion into cyclobutanones

Cyclobutanones reacted with alkynes in the presence of nickel(0) catalysts to produce cyclohexenones. Oxidative cyclization of the carbonyl group of the cyclobutanone and the alkyne with the nickel(0) was followed by beta-carbon elimination from the resulting oxanickelacyclopentene and subsequent reductive elimination. This reaction achieves a formal alkyne insertion between the carbonyl carbon and the alpha-carbon, providing a six-membered carbocyclic skeleton.     

Epoxidation of chalcones

Previously undescribed aromatic α-keto oxides have been obtained by the epoxidation of chalcones with alkaline hydrogen peroxide in methanolic solution.     

Influence of solvents on the insertion of methacrolein into zirconacyclopropenes

The reaction of Cp₂Zr(L)(η²-Me₃SiC₂) (L = THF, py) with equimolar amounts of H₂C = CMe-CHO at room temperature depends strongly on the ligands L and the solvents that are used. With L = THF, in the THF solution the insertion product

Full-size image

1 was isolated, whereas by conducting the reaction in n-hexane solution an alkyne substitution with 1,4-coordination of the methacrolein takes place and the binuclear complex [

Full-size image

2 was obtained. In conttrast, with L = py (a stronger ligand) only a 1:1 ratio of 1 and 2 was observed in both THF and in n-hexane. At 50°C complex 1 was converted into 2 and the alkyne was eliminated quantitatively.

Complexes 1 and 2 were characterized by IR and NMR spectroscopical measurements and 1 by an additional X-ray structure determination.     

Proton dissociation constants of benzoylacetone and isonitrosobenzoylacetone in aqueous dioxane media

Thermodynamic proton dissociation constants,TpKa of benzoylacetone(HBA) as well as isonitrosobenzoylacetone (HINBA) have been determinedpH-metrically in 10–50% (v/v) dioxane-water mixtures at 25 and 35±0.01°C applying an empiricalpH correction for mixed aqueous media. ThepKa's in aqueous medium (at 0% dioxane) are obtained following the method of extrapolation and least-squares. BothHBA andHINBA are very weak monoprotic acids withTpKa between 7.0 and 10.0.TpKa's do not vary linearly with the reciprocal of the dielectric constant of the medium, but a plot ofTpKa vs. the mole fraction of dioxane is linear at a given temperature. The true constantKa' and solvation number,n, in the expression (H⁺)(A ^–)/(HA)=Ka' (S) ⁿ =Ka* for these reagents have been evaluated by analysing the experimental data mathematically. Values of G ⁰, H ⁰, and S ⁰ are also computed. Temperature and medium effects are briefly discussed.

---

Protonen-Dissoziationskonstanten von Benzoylaceton und Isonitrosobenzoylaceton in wäßrigem Dioxan

Zusammenfassung Es wurden die thermodynamischen Protonen-Dissoziationskonstanten (TpKa) von Benzoylaceton (HBA) und Isonitrosobenzoylaceton (HINBA)pH-metrisch in 10–50% (v/v) Dioxan-Wasser-Mischungen bei 25 und 35 ± 0.01°C bestimmt, wobei eine empirischepH-Korrektur für das gemischt-wäßrige Medium angewendet wurde. DiepKa-Werte in wäßrigem Medium (0% Dioxan) folgen aus der Extrapolation und der Methode kleinster Fehlerquadrate. SowohlHBA als auchHINBA sind sehr schwache monoprotische Säuren mitTpKa zwischen 7.0 und 10.0. DieTpKa's variieren nicht linear mit der reziproken Dielektrizitätskonstante des Mediums, ein DiagrammTpKa gegen Molenbruch Dioxan ergibt jedoch für eine konstante Temperatur eine Gerade. Die wahre KonstanteKa' und die Solvatationszahln des Ausdrucks (H⁺)(A ^–)/(HA)=Ka'(S) ⁿ =Ka* wurde aus den experimentellen Daten für beide Reagentien errechnet. Die thermodynamischen Parameter G°, H° und S° wurden ebenfalls bestimmt, Temperatur- und Lösungsmitteleffekte werden diskutiert.

     

Catalytic diboration of aldehydes via insertion into the copper-boron bond

Mesitaldehyde reacts cleanly with (IPr)CuB(pin) [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene); pin = 2,3-dimethyl-2,3-butanediolate] to afford the product complex 1, the first well-defined product of carbonyl group insertion into a metal-boron bond. Analysis of 1 by NMR spectroscopy and single-crystal X-ray diffraction indicates the formation of a copper-carbon and a boron-oxygen bond. A copper(I) precatalyst supported by the less sterically demanding ligand ICy (1,3-dicyclohexylimidazol-2-ylidene) achieves the efficient 1,2-diboration of aryl-, heteroaryl-, and alkyl-substituted aldehydes at room temperature.     

Isocyanide insertion into platinumoxygen bonds

The reaction of isocyanides, CNR, with hydroxy- and methoxy-alkyl complexes of platinum(II), PtOH(R)(Ph₂ PCHCHPPh₂)_and PtOCH₃(R)(Ph₂PCHCHPPh₂) (R  CF₃, CH₂ CN) affords insertion products Pt(CONHR)(R)(Ph₂PCHCHPPh₂) and Pt[C(OCH₃)NR] (R)(Ph₂PCHCHPPh₂) containing the carboxamido and imidoyl moiety, respectively.