Water mediated synthesis of various [1,3]oxazine compounds using alum as a catalyst

Abstract

A simple, efficient, and practical procedure for the synthesis of various substituted 2,3-dihydro-2-phenyl-1H-naphtho[1,2-e][1,3]oxazines and 3,4-dihydro-3-phenyl-2H-naphtho[2,1-e][1,3]oxazines using KAl(SO₄)₂ 12H₂O (alum) as a non-toxic, reusable, inexpensive, and easily available catalyst is described using water as a solvent. These improved reaction conditions allow the preparation of a wide variety of substituted [1,3]oxazines in high yields and purity under mild reaction conditions.     

Biosynthesis and antioxidant activity of 4NRC β-glycoside

This Letter describes glycosylation of 4-Nerolidylcatechol (4-NRC) the major secondary metabolite from Pothomorphe peltata and Pothomorphe umbellata showing remarkable antioxidant, antimalarial, anti-inflammatory, and anti-HIV activities. One step biosynthesis was catalyzed by Cunninghamella echinulata ATCC 9245 and the reaction was undertaken in PDSM medium at 27 °C, 200 rpm for 96 h. After purification by silica gel flash column chromatography the 4-NRC β-glycoside was identified by ultrahigh resolution mass spectrometry and ¹H NMR. The antioxidant activity was evaluated by differential pulse voltammetry.     

钒取代的杂多酸催化一锅四组分Dakin-West反应合成β-乙酰氨基酮(英文)

The multicomponent condensation of an aryl aldehyde,acetyl chloride,acetonitrile,and enolizable ketone as one-pot synthesis of β-acetamido ketones in high yields was investigated using commercial,non-corrosive,and environmentally benign Keggin and Wells-Dawson heteropolyacid catalysts.The best catalyst was H5PW10V2O40.The methodology used simple experimental conditions,and the short reaction times and high yields indicate it is a useful strategy for the large scale synthesis of β-acetamido ketones.     

Chemoselective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst

Selective hydrogenation of α, β-unsaturated aldehydes with modified Pd/C catalyst was developed.The reduction of C=O bond could be efficiently inhibited by the addition of carbonates,and high selectivity to the corresponding saturated aldehydes was achieved under mild conditions.This protocol provides an alternative for efficient preparation of saturated aldehydes.     

Inclusion Modes of Berberine with β-Cyclodextrin in Aqueous Solution

The possible inclusion modes of berberine(Berb)with β-cyclodextrin(BCD)in aqueous solution were predicted by molecular docking,molecular dynamics(MD)simulation and binding free energy calculations.Firs...     

Crystal structures of chloro-, bromo-, and nitro-substituted chromium(III) acetylacetonates

The molecular and crystal structures of chlorine-, bromine-, and nitro-substituted chromium(III) acetylacetonate are determined. Connecting the substituent to the central atom does not change bond lengths and valence angles in metal chelate rings. Studied chromium complexes are characterized by greater intermolecular interactions compared with analogous metal acetylacetonates. In some cases, intermolecular interactions increase the bend of chelate rings along the O?O line. Substituents do not interact with chromium ions of neighboring molecules because metal is blocked by three ligands.     

An efficient method for the synthesis of gem-difluoroolefins

A series of gem-difluoroolefin derivatives were synthesized in moderate to good yields by the reaction of α,α-difluoro-β-carbonyl benzothiazol-2-yl sulfones (DFBTs) with various carbon nucleophiles. Using dl-proline as organocatalyst, the reaction of DFBT with acetone gave a tertiary alcohol, which could be further converted to the corresponding difluoroolefin by LDA.     

Encapsulation of nanocrystals with responsive gels for spatial optical identification

A tripeptide (β-AspFF) gelator was designed and synthesised using solid-phase peptide synthesis. The as-prepared gelator formed a stable and clear multi-responsive gel in toluene solution. Encapsulating the quantum dots with β-AspFF effectively increased stability and antioxidisation ability which are beneficial for optical identification.     

TBAI/K2S2O8-facilitated reaction of sulfonylhydrazides with alkynes: Facile synthesis of (E)-β-iodovinyl sulfones

An efficient and convenient approach for the construction of various (E)-β-iodovinyl sulfones has been developed through potassium persulfate/tetrabutylammonium iodide-facilitated reaction of sulfonylhydrazides with alkynes. The products were obtained in good to excellent yields. The salient features of this reaction are the applications of a new iodine source, environmentally benign, safer solid oxidant, and shorter reaction time.     

H-β-zeolite catalyzed synthesis of β-bromostyrenes from styrene bromohydrins

Synthesis of β-bromostyrenes from styrene bromohydrins using H-β-zeolite as catalyst under moderate conditions is reported. The catalyst could be regenerated and reused up to three consecutive cycles.