Epoxy ethers, preparation

Tho well-known sugar derivative Brigl s anhydride, or 1,2-anhydro-3,4r6 tri-0-aoety]-a-D-glucopyranQge, is an epoxy ether prepared by the action of Ammonia on 3,4,6-tri-0-aoetyl-2-0-trichloro-acotyJ-o-n-glucopyranosyl chloride in benzene solution. 46 l2 6... 

Related to the epoxy ether preparations is another reaction, involving the same precursors and an essentially identical mechanism. When certain a-haloketones are treated -with potassium cyanide in aqueous alcoholic media, there are obtained, among other products, glycidonitriles. In this instance the carbonyl function suffers attack by a CN ion, rather than a methoxide, and the intermediate an kin collapses quickly to a glytddonitrile by ejecting a halide ion as shown in Eq. (228). 

Gel-permeation chromatography studies of epoxy resins prepared by the taffy process shown n values = 0, 1, 2, 3, etc, whereas only even-numbered repeat units are observed for resins prepared by the advancement process. This is a consequence of adding a difunctional phenol to a diglycidyl ether derivative of a difunctional phenol in the polymer-forming step. 

The procedure described here illustrates a general and inexpensive two-step method for the stereoselective preparation of new, variously substituted I-CF3 epoxy ethers from ethyl trifluoroacetate.2-3.4 The first step of this procedure is a Wittig olefination of ethyl trifluoroacetate in which sodium hydride is used for the generation... 

Recently 1-perfluoroalkyl epoxy ethers have been useful starting synthons for the preparation of various perfluoroalkylated organic compounds. For example, in the... 

The effect of varying the alkoxide ion was likewise invest ienmrl. several new epoxy ethers being prepared in this maimer1831 1441 (Eq. 222). 

The synthesis of epoxy ethers by peroxy acid treatment of suitable vinylic ethers, on the other hand, is complicated by the acid sensitivity of epoxy ethers. For example, Bergmann and Mk>keley1Ss claimed in 1921 to have prepared 1 -ethoxy-1 (2 -epoxyethane by the oxidation of ethyl vinyl ether with perbenzoic aoid, bat B years later modified their structure to a dioxone type of dimer.186 In 1 B0 Mous-seron and co-wcrkere1168-1184 reported the preparation of an epoxy ether from 1 -ethoxy-1 -eydohexene, but 4 years later Stevens and Taznma164 showed the compound obtained in this oxidation, not to have the structure initially assigned to it. 

Again in the carbohydrate field, Raphael and Roxburgh14 4 described the preparation of a labile intermediate assumed to possess a monomeric epoxy ether structure but too reactive to allow its isolation. Unsuccessful attempts by Huffman and Tarbcll 48 to prepare an epoxide from 2-benzhydrylidenetotrahydrctfuran constitute additional evidence of the instability of bicyolio epoxy ethers. 

Stevens and his co-workers report the preparation of 2-phenyl-3,3-dimethyl-3,4,5,6-tetrahydropyrazine (184) in 91% yield from the reaction of the epoxy ether (183) and ethylenediamine. The structural assignment is consistent with the observation of strong N-H and... 

Other carbon nucleophiles also tend to attack at the less substituted position of an unsymmetrical epoxide. This holds true for cyanide, which can be conveniently prepared in situ from methyllithium and acetone cyanohydrin 82. In a one-pot reaction, the epoxy ether 81 is... 

How are vegetable oil-based diglycidyl ether type epoxy resins prepared ... 

The dehydration of 3-hydroxyindolines (cf. 2 inSchane 2) was the tactic for indolization in other indole syntheses. For example, Boimet-Delpon s team prepared 3-trifluQro-methylindoles from the corresponding 3-hydroxyindoIines (SOCl, pyridine, 80%-87%), which were obtained from the reaction of aromatic amines and triflnoiomethyl epoxy ethers [13], and Swenton and cowoikers prepared 2,3-dime-thyl-5-methoxyindole by acid-catalyzed dehydration of the 3-hydroxyindoline, and they also effected loss of methanol from C-5 of quinone imine ketals to give, for example, 5,6-dimethoxyindole (73%) [14]. A more common indolization of indolines is the elimination of sulfinate from Al-substi-tuted-sulfonylindoles, and both base- and acid-catalyzed examples are known (Scheme 3, equations 1-3) [15-17]. 

Liquid crystals exhibit a partially ordered state (anisotropic) which falls in-between the completely ordered solid state and completely disordered liquid state. It is sometimes referred to as the fourth state of matter . In recent years, interest in liquid crystalline thermosets (especially liquid crystalline epoxy) has increased tremendously [33-44]. If the liquid crystal epoxy is cured in the mesophase, the liquid crystalline superstructure is fixed permanently in the polymer network, even at higher temperature. Liquid crystal epoxies are prepared using a liquid crystal monomer [33-38] or by chemical modification of epoxy resin [43] which incorporates liquid crystal unit in the epoxy structure. Liquid crystalline epoxy resins with different types of mesogen such as benzaldehyde azine [33], binaphthyl ether [34, 35], phenyl ester [36, 37] and azomethine ethers [38, 39] have been reported. Depending on the chemical nature of the mesogen, the related epoxies display a wide range of thermomechanical properties. The resins can be cured chemically with an acid or amine [40, 41] or by photochemical curing in the presence of a photo-initiator [3]. Broer and co-workers [42] demonstrated the fabrication of uniaxially oriented nematic networks from a diepoxy monomer in the presence of a photo-initiator. 

Polythiols as crosslinking agents for epoxy resins prepared from the reaction of l,5-dimercapto-3-oxapentane and pentaerythritol triallyl ether [163]. 

So, we were able to prepare selectively syn and anti trifluoromethyl amino alcohols. The next step was a search for a chiral approach to these compounds. Two approaches have been investigated to obtain chiral anti amino alcohols first we performed the reaction of epoxy ethers 3 with the chiral dimethylaluminum amide, prepared from the fi -phenethylamine and MeaAl (Scheme 5). From 3a, the reaction was effective leading, after reduction to the anti diastereoisomers 8a and 9a stereoselectively (Scheme 5). However, the chiral amine induced no selectivity anti amino alcohols 8a and 9a were obtained in a 50/50 mixture. Their separation was performed by crystallisation of the mandelate salts. Although this access to homochiral anti amino alcohols is somehow tedious, it is general since oxirane ring opening is efficient whatever the R substituent, and since epoxy ethers, substituted with various fluoroalkyl groups, are available. ... 

The preparation of an epoxy ether in high optical purity is not the sole condition for the success of this approach, seeing that a-amino ketones easily undergo enolization and consequently racemization. The stability of complex A of hemiketal form of amino ketone (fig. 1) should prevent from enolization. 

Reaction of 10a and 11a with the aluminum amide prepared from MejAl and the (R)-phenethylamine and subsequent reduction step occurred with the same excellent anti/syn diastereoselection as precedently, leading respectively to anti amino alcohols 8a and 9a. These amino alcohols were obtained in an excellent purity from 10a (8a/9a = 93/7) and from 11a (9a/8a = 90/10). The stereoisomeric excess is the same as the enantiomeric excess of starting epoxy ethers. No racemization occurred in the reaction ring opening does not involve a carbenium ion, and no enolization occurs from intermediate A or B. Both enantiommc amino alcohols 12a and 13a were obtained by debenzylation with palladium hydroxide imfortunately, we have not been able to assign the absolute configuration of the asymmetric carbons of 8a and 9a (Scheme 7). 

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