ZnFe2O4 nanoparticles: A green and recyclable magnetic catalyst for fast and regioselective conversion of epoxides to vicinal hydroxythiocyanates using NH4SCN under solvent-free conditions

ZnFe₂O₄ nanoparticles were synthesized and used as recyclable magnetic catalyst in the solvent-free conversion of different epoxides to vicinal hydroxythiocyanates with NH₄SCN at room temperature. The reactions were carried out by grinding in a mortar with perfect regioselectivity within short times (2-25 min) and with high to excellent yields (75–95%). The nanocatalyst was separated easily using an external magnet and reused for four consecutive cycles without any noticeable loss of efficiency or magnetic property.     

Coupling Titanium and Chromium Catalysis in a Reaction Network for the Reprogramming of [BH4]− as Electron Transfer and Hydrogen Atom Transfer Reagent for Radical Chemistry

We describe a unique catalytic system with an efficient coupling of Ti- and Cr-catalysis in a reaction network that allows the use of [BH₄]⁻ as stoichiometric hydrogen atom and electron donor in catalytic radical chemistry. The key feature is a relay hydrogen atom transfer from [BH₄]⁻ to Cr generating the active catalysts under mild conditions. This enables epoxide reductions, regiodivergent epoxide opening and radical cyclizations that are not possible with cooperative catalysis with radicals or by epoxide reductions via Meinwald rearrangement and ensuing carbonyl reduction. No typical S_N2-type reactivity of [BH₄]⁻ salts is observed.     

Microwave-enhanced bismuth triflate-catalyzed epoxide opening with aliphatic amines

In the presence of a catalytic amount of Bi(OTf)₃·4H₂O and under microwave irradiation, neat mixtures of epoxides and amines afforded smoothly the corresponding 2-amino alcohols. A wide variety of aliphatic amines were reacted with cycloalkene oxide, styrene oxide, and stilbene oxide. The reaction proceeded rapidly and afforded the 2-amino alcohols in high up to quantitative yields. All products could be obtained without aqueous work-up by simple filtration.     

Hydrolysis of epoxides and aziridines catalyzed by polymer-supported quarternary ammonium bisulfate

Macroporous resin （D201）-supported quartemary ammonium bisulfate （D201-HSO4） was prepared and effectively used in catalyzing the hydrolysis of epoxides or aziridines under mild and non-metal conditions to give the corresponding 1,2-diols and β-amino alcohols in high yields. The catalyst was facilely prepared and recyclable.     

2-Phenyl-2-(2-pyridyl)imidazolidine (PPI) as New Catalyst in the Efficient,Mild, and Regioselective Conversion of Epoxides to Thiocyanohydrines with Ammonium Thiocyanate

2-Phenyl-2-(2-pyridyl)imidazolidine (PPI) catalysis the addition of thiocyanate ion to epoxides to afford g -hydroxy thiocyanate in high yields, mild conditions, and regioselectivity. Thus, several 2-hydroxyethyl thiocyanates, which are useful intermediates toward biological active molecules, are obtained easily in very good yields.     

Grignard reagent induced tandem semipinacol rearrangement/ketone addition reaction of 20S-hydroxy-5α-pregnane-16(17)-epoxide

A Grignard reagent induced tandem semipinacol rearrangement/chelation-controlled ketone addition process, which converts 20S-hydroxy-5α-pregnane-16(17)-epoxide into an unusual C20-substituted 17S-pregnane-3S,16R,20S-triol, is described.     

Competing cyclopropane over epoxide formation from γ-halogeno-δ-hydroxy-ketones

Carbocyclization has been selectively achieved over epoxide formation from a γ-chloro-δ-hydroxy-ketone in the presence of a lithiumamide or using a different strategy in which the related silyloxyenol ether bearing an iodine atom at gamma-position and a silyloxy group in delta-position is reacted with tetrabutylammonium fluoride. These approaches take advantage of (i) the poor reactivity of the intermediate β-halogeno lithiumalkoxide first formed in the former case and (ii) the poorer ability of the fluoride ion to desilylate a silyl ether over a silylenol ether.