Basic Behavior of Epoxides in the Presence of Halide Ions

Epoxides behave as bases in the presence of catalytic quantities of halide ions. They convert halogenated hydrocarbons into olefins, suitable phosphonium salts into ylides, and haloforms into dihalocarbenes. Kinetic studies with the aid of JR and NMR spectroscopy show that the species that functions as the proton acceptor is neither the epoxide ion nor the halide ion, but the 2-haloethoxide ion.     

Regio- and stereoselective synthesis of vicinal fluorohydrins

Vicinal fluorohydrins are useful building blocks as well as important targets for synthesis of bioactive compounds or new materials. This review gives an overview on regio- and stereoselective, particularly enantioselective, syntheses of such compounds by building block methods, reduction of α-fluoro carbonyl compounds and ring opening of epoxides with hydrofluorinating reagents. Resolution of racemic vicinal fluorohydrins using enzyme-catalyzed reactions will also be discussed in detail.     

STUDY OF THE PHOTOINITIATED CATIONIC POLYMERIZATION OF 3,4-EPOXY-1-BUTENE

The photopolymerization of 3,4-epoxy-1-butene (1) was investigated using Fourier transform real-time infrared spectroscopy (FT-RTIR). The effects of photoinitiator structure and concentration and light intensity on the photopolymerization were investigated. Compared to related epoxide monomers, 1 was shown to be more reactive and this was ascribed to stabilization of the growing cationic chain end by the double bond during the ring-opening polymerization. Epoxide 1 was also shown to be useful as a reactive diluent in the photopolymerization of multifunctional epoxides and was observed to accelerate the polymerization of less reactive epoxy monomers.     

Oxorhenium-catalyzed deoxydehydration of glycols and epoxides

The conversion of renewable cellulosic biomass into hydrocarbons has attracted significant attention with a growing demand of sustainability. MeReO₃ catalyzes the deoxydehydration (DODH) of glycols and epoxides to alkenes by primary and secondary alcohols (5-nonanol, 3-octanol, 1-butanol) in the benzene solvent. The product yield range from moderate to excellent.     

Regioselective ring-opening of epoxides with amines using Zn(ClO4)2-Al2O3 as a heterogeneous and recyclable catalyst

A simple and efficient method has been developed for the synthesis of β-amino alcohols by regioselective ring-opening of epoxides with amines in the presence of zinc perchlorate-neutral alumina as a heterogeneous recyclable catalyst at room temperature in high yields.     

Controlling the Fluorescence Performance of AIE Polymers by Controlling the Polymer Microstructure

Aggregation-induced emission (AIE) polymers with expected emission wavelength/color and fluorescence efficiency are valuable in applications. However, most AIE polymers exhibit irregular emission wavelength/color changes compared to the original AIE monomers. Here, we report the synthesis of AIE polymers with unchanged emission wavelength by ring-opening (co)polymerizations of 4-(triphenylethenyl)phenoxymethyloxirane (TPEO) and other epoxides or phthalic anhydride. The chemical structures/physical properties of all (co)polymers were characterized by NMR, SEC, MALDI-TOF, and DSC. The co-polyether microstructures were revealed by calculating the reactivity ratios and visualized by Monte Carlo simulation. The photoluminescence quantum yields of all the (co)polymers were determined in the solid state. We systematically correlated the fluorescence performance with molecular weights, crystallinity, monomer compositions, glass transition temperatures, side lengths, and flexibility/rigidity.     

A catalytic approach to the base-promoted reaction of epoxides with activated methylenes

This contribution reports the results obtained in the definition of a catalytic method for the nucleophilic ring opening of epoxides by activated methylenes promoted by a polymer-supported base. The attention has been focused on the use of polymer supported bases and the best results have been obtained by using 4-(dimethylamino)pyridine (PS-DMAP) and 2-tert-butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorine both on polystyrene (PS-BEMP). Solvent-free conditions has been essential for reaching a sufficient reactivity to realize this process, in fact when a reaction medium is used, the processes are almost unfeasible.