Opening of epoxides with aromatic amines promoted by indium tribromide: a mild and efficient method for the synthesis of β-amino alcohols

A mild and efficient synthesis of β-amino alcohols by aminolysis of epoxides promoted by indium tribromide is described. The methodology is regio- and chemoselective and works well with independence of the epoxide or the aromatic amine used. In addition, the reaction can be carried out in a wide variety of undried solvents under air.     

Large second-order optical nonlinearities of s-triazine derivatives: View from micro molecules to macro crystals

Organic nonlinear optics (NLO) is also called mo-lecular nonlinear optics. In recent years organic mate-rials have been intensively studied because of their large NLO coefficients and structural diversities[1―3]. Second harmonic generation (SHG) is a bas…     

Palladium-catalyzed C-N bond formation: synthesis of 1-aryl-1H-pyrazoles from β-bromovinyl aldehydes and arylhydrazines

Cyclic and acyclic β-bromovinyl aldehydes are cyclized with an array of arylhydrazines in toluene at 125 °C in the presence of a palladium catalyst and a phosphorus chelating ligand together with NaO^tBu to give 1-aryl-1H-pyrazoles in moderate to good yields.     

Synthesis and biological evaluation of 6-oxa-nor-tropane glycomimetics as glycosidase inhibitors

The preparation of polyhydroxylated 6-oxa-nor-tropane glycomimetics structurally related to the glycosidase inhibitor family of the calystegines is reported. The synthetic strategy involves the furanose→piperidine rearrangement of 5-deoxy-5-ureido-l-idose precursors, followed by intramolecular glycosylation involving the primary hydroxyl group. Inversion of the configuration at C-3 in the resulting 6-oxa-(+)-calystegine B₂ analogue allows accessing the elusive 3-epi-6-oxa-(+)-calystegine B₂ skeleton. Acid-catalyzed opening of the nor-tropane bicycle was observed, however, which could be avoided by careful neutralization of the reaction mixture. The inhibition results suggest that (+)-calystegine B₂ derivatives and the corresponding C-3 epimers can be seen as glucomimetics and galactomimetics, respectively, pointing to a 1-azasugar mode of action for this family of alkaloids.     

Recent studies on phosphorus-bridging carbonyl derivatives: organophosphorus analogs of aldehydes and ketones

Reactions of disodium tetracarbonylferrate, Na₂Fe(CO)₄, with sterically hindered dialkylaminodichlorophosphines, R₂NPCl₂ (R₂N=diisopropylamino, dicyclohexylamino, and 2,2, 6, 6-tetramethylpiperidino) in diethyl ether lead to the air-stable phosphorus-bridging carbonyl derivatives (R₂NP)₂COFe₂(CO)₆ as the major products. The phosphorus-bridging carbonyl group in (i-Pr₂NP)₂COFe₂(CO)₆ has been found to undergo the following types of reactions: 1)Reduction, 2)Acylation, 3)Extrusion of the carbonyl group. The mechanisms of the reactions have been considered.This work was presented at the Workshop «The Modern Problems of Heteroorganic Chemistry» held on the ship «Nikolai Bauman» during the period May 8–13, 1993.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1858–1867, November, 1993.     

N-α-Benzyloxyacetyl derivatives of (S)-4-benzyl-5,5-dimethyloxazolidin-2-one for the asymmetric synthesis of differentially protected α,β-dihydroxyaldehydes

α-Dibenzylamino- and α-benzyloxy- derivatives of N-acetyl-(S)-4-benzyl-5,5-dimethyloxazolidin-2-one readily undergo highly stereoselective boron mediated syn-aldol reactions with a range of aromatic and aliphatic aldehydes, generating the syn-aldol products in good to excellent yields as single diastereoisomers after purification. In the α-dibenzylamino series, deprotection of the functionalised aldol fragments to the corresponding α-amino-β-hydroxy methyl ester or α-amino-β-hydroxyaldehyde proved problematic, with a range of N- and O-protecting groups giving mixtures of products arising from endocyclic and exocyclic cleavage pathways. However, in the α-benzyloxy series, O-silyl protection of the aldol products, and subsequent DIBAL reduction gives stereoselectively the corresponding N-1′-hydroxyalkyloxazolidin-2-ones, which undergo base promoted fragmentation to the desired highly functionalised and differentially protected α,β-dihydroxyaldehydes in good yields and without loss of stereochemical integrity.     

Unprecedented intermolecular aldol-type condensation involving CH-acid and the nitro group

The first evidence that α-acylnitrone is an intermediate in the base-promoted reaction of 4-nitro-N,N-diethylaniline with aceptophenome to give an enaminoketone was obtained. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1645–1647, August, 1998.     

制备参数对β-Mo2N0.78催化剂加氢脱硫活性影响的研究

以N2与H2的混合气为反应气，和三氧化钼进行多段程序升温反应，制得一种β晶型的氮化钼。以噻吩为模型化合物的常压加氢脱硫反应表明，β-Mo2N0.78具有较强的加氢脱硫活性和强的抗硫化性能。同时考察了预还原、反应温度以及氮化末温、升温速率、反应气中N2-H2比及氮化时间等制备参数对β-Mo2N0.78加氢脱硫活性的影响。研究发现，β-Mo2N0.78的加氢脱硫活性在320 ℃～400 ℃随反应温度的升高增强，而还原预处理会降低催化剂的活性。氮化末温、氮化时间、反应气组成和升温速率等制备参数对催化剂的活性有明显的影响：随着氮化末温的升高，所制备的催化剂催化加氢脱硫活性降低；在氮化末温恒温较长时间，可以引起制备催化剂的加氢脱硫活性下降；存在最佳的反应气组成和各段升温速率。小晶粒的β-Mo2N0.78具有强的加氢脱硫活性。     

Synthesis of new α,α,β,β-tetrafluoroesters

Substituted phenyl iodides or diiodides reacted with ethyl iodotetrafluoroproponylate ICF₂CF₂CO₂Et, 1 in the presence of copper powder to give the coupled products 2 or 3 in good yields. Addition of 1 to ethylene and allyl acetate proceeded smoothly under thermal and radical conditions to give the corresponding adducts, which underwent elimination reaction to give β-vinyl and β-allyl α,α,β,β-tetrafluoroesters, CH₂CHCF₂CF₂CO₂Et, 4 and CH₂CHCH₂CF₂CF₂CO₂Et, 5, respectively. 1 also readily reacted with 1,5-hexadiene and 1-hexene with copper or palladium complex, followed by reduction to remove iodine to produce ω-alkenyl-α,α,β,β-tetrafluoroester CH₂CH(CH₂)₄CF₂CF₂CO₂Et 6 and α,α,β,β-tetrafluoroester C₄H₉CH₂CHICF₂CF₂CO₂Et.