Nitriles from epoxides

Scheme 4.8 Proposed mechanism for the synthesis of nitriles from epoxides...

Insertion of phenyl, trimethylsilyl, and nitrile-stabilized metalated epoxides into zircona-cyclcs gives the product 160, generally in good yield (Scheme 3.37). With trimethylsilyl-substituted epoxides, the insertion/elimination has been shown to be stereospecific, whereas with nitrile-substituted epoxides it is not, presumably due to isomerization of the lithiated epoxide prior to insertion [86]. With lithiated trimethylsilyl-substituted epoxides, up to 25 % of a double insertion product, e. g. 161, is formed in the reaction with zirconacyclopentanes. Surprisingly, the ratio of mono- to bis-inserted products is little affected by the quantity of the carbenoid used. In the case of insertion of trimethylsilyl-substituted epoxides into zirconacydopentenes, no double insertion product is formed, but product 162, derived from elimination of Me3SiO , is formed to an extent of up to 26%. 

POLYHYDROGEN FLUORIDE REAGENT 1-FLUORO-ADAMANTANE. Dichloroalkane synthesis is shown in cis-DI-CHLOROALKANES FROM EPOXIDES cis-1,2-DICHLORO-CYCLOHEXANE. Nitrile functionality can be introduced from a ketone, as in NITRILES FROM KETONES CYCLOHEXANENITRILE, or from a reactive diene, as shown in 2,3-DICYANOBUTADIENE AS A REACTIVE INTERMEDIATE BY in situ GENERATION FROM 1,2-DICYANO CYCLOBUTENE 2,3-DICYANO-1,4,4a,9a -TETRAHYDRO-FLUORENE. 

Epoxides (see also a,(3-Epoxy alcohols, etc., Glycidic acids, esters, nitriles) From alkenes by epoxidation Dimethyldioxirane, 120 Fluorine-Acetonitrile, 135 Potassium peroxomonosulfate, 259 From carbonyl compounds Alumina, 14... 

The use of a cationic aza-Cope rearrangement in concert with a Mannich cyclization has also been applied to the total synthesis of enantiomerically pure (—)-crinine (359) (205). In the event, nucleophilic opening of cyclopentenoxide with the aluminum amide that was formed on reaction of (/ )-a-methylbenzyl-amine and trimethylaluminum gave the amino alcohol 485 together with its (15,25) diastereomer. Although there was essentially no asymmetric induction in this process, the diastereomeric amino alcohols were readily separated by chromatography, and the overall procedure therefore constitutes an efficient means for the preparation of enantiomerically pure 2-amino alcohols from epoxides. When the hydrochloride salt derived from 485 was treated with paraformaldehyde and potassium cyanide, the amino nitrile 486 was formed. Subsequent Swem oxida-... 

Cross-coupling reactions of ArCOAr. Reaction of Yb(0) with diaryl ketones changes the reactivity of the carbonyl group from electrophilic to nucleophilic. Thus in the presence of this lanthanoid metal, diaryl ketones couple with other ketones, nitriles, and epoxides to give pinacols, a-hydroxy ketones, and 1,3-diols, respectively, via the intermediate a. 

SECTION 189 Nitriles from Ethers, Epoxides, and Thioethers... 

Openings of mcso-epoxides to obtain chiral P-hydroxy nitrile derivatives and of A -acylaziridines to afford A-(P-sulfenylalkyl) amides have enlisted the service of ligand 23 and dicyclohexyl L-(+)-tartrate, respectively. An efficient method for acquiring chiral azido silyl ethers from epoxides and Me SiN, employs a (salenlCr-N, complex 24. "... 

SECTION 189 NITRILES FROM ETHERS, EPOXIDES AND THIOETHERS... 

Scheme 6.43 Enantioselective trapping of a-nitrile carbanions generated via chirality transfer from epoxides.

It is known that trimethylsilyl ethers of p-hydroxy-nitriles may be obtained from epoxides and MesSiCN in the presence of AICI3 or Et2AlCl. It has now been shown that if zinc iodide is used in place of the aluminium reagent, iso-cyanides are obtained, e.g. (269) and (270). This transformation is highly... 

Epoxidized natural mbber is stiU a strain crystallising mbber and therefore retains the high tensile strength of natural mbber. However, as can be seen from Table 5, ia other respects they have very Httie ia common. The epoxidation renders a much higher dampiag mbber, a much-improved resistance to oil swelling (iasofar as a 50 mol % modified natural mbber has similar oil resistance to a 34% nitrile mbber), and much-reduced air permeabiUty. This latest form of modified natural mbber therefore widens the appHcations base of the natural material and enables it to seek markets hitherto the sole province of some specialty synthetic mbbers. 

Other modifications of the polyamines include limited addition of alkylene oxide to yield the corresponding hydroxyalkyl derivatives (225) and cyanoethylation of DETA or TETA, usuaHy by reaction with acrylonitrile [107-13-1/, to give derivatives providing longer pot Hfe and better wetting of glass (226). Also included are ketimines, made by the reaction of EDA with acetone for example. These derivatives can also be hydrogenated, as in the case of the equimolar adducts of DETA and methyl isobutyl ketone [108-10-1] or methyl isoamyl ketone [110-12-3] (221 or used as is to provide moisture cure performance. Mannich bases prepared from a phenol, formaldehyde and a polyamine are also used, such as the hardener prepared from cresol, DETA, and formaldehyde (228). Other modifications of polyamines for use as epoxy hardeners include reaction with aldehydes (229), epoxidized fatty nitriles (230), aromatic monoisocyanates (231), or propylene sulfide [1072-43-1] (232). 

A process that is effective for epoxidation and avoids acidic conditions involves reaction of an alkene, a nitrile, and hydrogen peroxide.82 The nitrile and hydrogen peroxide react, forming a peroxyimidic acid, which epoxidizes the alkene, by a mechanism similar to that for peroxyacids. An important contribution to the reactivity of the peroxyimidic acid comes from the formation of the stable amide carbonyl group. 

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