Substituted epoxides by lithiation of terminal epoxides

Diamine-ligand-assisted direct hydrogen-lithium exchange allows the generation of nonstabilized (H-substituted) oxiranyllithium species and their subsequent trapping by Bu(3)SnCl and carbonyl-based electrophiles. This reaction provides a new concise route to alpha,beta-epoxystannanes and substituted epoxides.     

Reaction of some trisubstituted steroid epoxides with triphenylphosphine - iodine complex. Deoxygenation of epoxides

Triphenylphosphine - iodine complex was found to be an effective reagent for deoxygenation of trisubstituted steroidal epoxides. The mechanism of the reaction is proposed.     

Enantioselective synthesis of epoxides by alpha-deprotonation--electrophile trapping of achiral epoxides

Enantioselective alpha-deprotonation of achiral epoxides 1, 21, and 26 using organolithiums in the presence of (-)-sparteine 2 and subsequent electrophile trapping gives access to enantioenriched trisubstituted epoxides 9-17, 22, 23, 27 and 28 (in up to 86% ee).     

生物催化合成光学活性环氧化物

手性环氧化物及其相应的邻二醇在合成上具有重要应用价值。近年来,制取这些手性合成块的合成方法得到了很的大发展。本文着重讨论当前国际上采用生物催化合成光学活性环氧化物的发展状况。     

Zinc-catalyzed aminolysis of epoxides

A series of amino alcohols has been prepared by a novel zinc-catalyzed nucleophilic opening of epoxide rings by amines.     

Flavanoid epoxides—XIII : Acid and base catalysed reactions of 2′-tosyloxychalcone epoxides. Mechanism of the algar-flynn-oyamada reaction

2′-Tosyloxychalcone epoxide (6a) on reaction with alkali gave flavonol (4a) while similar treatment of 6′-methoxy-2′-tosyloxychalcone epoxide (6b), both at room temperature and at the boiling point of the reaction medium, afforded 5-methoxyaurone (5b). The latter result indicates that an epoxide is not an intermediate in the production of flavanols from 2′-hydroxy-6′-methoxychalcone epoxides on treatment with alkaline hydrogen peroxide (AFO Reaction) at the higher temperature. Epoxide 6a on treatment with boron trifluoride etherate gave a mixture of flavanonol and flavonol while epoxide 6b gave formyldesoxybenzoin (9) under similar conditions.     

Synthesis of N-heterocycles via chalcone epoxides. 1. Amino and hydrazinopyrimidines

Chalcone epoxides have been used as precursors in the synthesis of 2-amino- and 2-hydrazinopyrimidines.     

Copper-catalysed reactions of grignard reagents with epoxides and oxetane.

The copper-catalysed ring opening of epoxides and oxetane by Grignard reagents proceeds in good yield under mild conditions.     

Synthesis of phytuberin. 4-endo-tet acid-catalyzed cyclization of alpha-hydroxy epoxides

The total synthesis of phytuberin, a phytoalexin of the Solanum genus, from (-)-alpha-santonin is reported. The key steps include (a) reductive cleavage of the C-O bond of the gamma-lactone with concomitant protection of the C1 double bond, (b) Sharpless stereocontrolled hydroxy-assisted epoxidation of allylic alcohol 6 and simultaneous deprotection of the C1 double bond, (c) a rare 4-endo-tet acid-catalyzed cyclization of an alpha-hydroxy epoxide, and (d) an unprecedented 4-exo selenocyclization of a homoallylic alcohol.     

Calcium trifluoromethanesulfonate-catalysed aminolysis of epoxides

Aminolysis of epoxides catalysed by calcium trifluoromethanesulfonate under mild reaction conditions is described. The novel method is very efficient in the synthesis of wide variety of β-amino alcohols with high regio- and stereoselectivity.     

Cationic copolymerization of tetrahydrofuran with epoxides. III. Synthesis of block copolymers

Polymerization of various cyclic ethers by BF₃·O(C₂H₅)₂ in the presence of polymeric glycol leads to the formation of hydroxyl terminated block copolymers. Where poly(oxyethylene glycol) is used as the polymeric glycol, fission of the poly(oxyethylene glycol) chain occurs, and block copolymers, containing shorter ethylene oxide unit sequences are obtained. With poly(oxypropylene glycol), on the other hand, the polymer chain remains intact. This may be due to the steric influence of the pendant methyl groups. The cyclic oligomers formed as by-products in the polymerizations are easily removed.     

Alkylation epoxide rearrangement. Application to stereoselective synthesis of chiral pheromone epoxides.

An approach is described for the stereospecific conversion of threo and erythro 1,2-epoxy-3-alkanol tosylates to cis and trans internal epoxides, respectively. The method is illustrated by the synthesis of chiral epoxides, including insect pheromones.     

Polymers from siloxane-containing epoxides

The synthesis and polymerization of seven epoxy polymer precursors which contained the siloxane linkage in varying structural arrangements was carried out. The polymers prepared from such precursors have utility as embedding compounds for electrical circuits. Polymerization of these epoxy intermediates with siloxane-containing diamines resulted in solid, thermosetting materials for which dielectric data were obtained. Dielectric constants of 3.1 were measured at 1 keps for polymers prepared by polymerization of 1,9-bis[p-(2,3-epoxypropyl)phenyl]decamethylpentasiloxane with 1,3-bis(p-am-inophenoxy)tetramethyldisiloxane, whereas polymers derived from 1,4-bis{[p-(2,3-epoxypropyl)phenyldimethylsiloxy]dimethylsilyl}benzene and the same diamine were characterized by slightly higher dielectric constants and a high degree of toughness, being nonbrittle at ?50°C.