Unsaturated nitriles, epoxidation

Although hydrogenation of A-benzylideneaniline in the presence of 11 afforded the corresponding product (eq. 1 in Scheme 11), the a,(3-unsaturated ketone was converted into a mixture of unsaturated and saturated alcohols in the 42 56 ratio (eq. 2 in Scheme 11). Several substrates (nitrile derivatives, epoxides, esters, internal alkynes, and terminal alkenes), which are shown in Fig. 4, are not hydrogenated in this catalytic system. 

Cyclization of epoxy alkenes.2 The reaction of 8,e-unsaturated epoxides with 2 equiv. of Cp2TiCl in THF results in cyclization to cyclopentanemethanols. The reaction is compatible with keto and nitrile groups but not aldehyde groups. 

Unsaturated nitriles are epoxidized with hydrogen peroxide- Tetra-cyanoethylene, after treatment with 30% hydrogen peroxide in acetonitrile at 10-12 °C, furnishes tetracyanoepoxyethane in 59-68% yield [750]. A similar treatment of acrylonitrile gives a 62% yield of glycidamide (epoxy-propionamide) [747]. 

Titanium alkyls, known as tamed Grignard reagents, do not add to esters, nitriles, epoxides, or nitroalkanes at low temperatures. Rather, they add exclusively ia a 1,2 fashion to unsaturated aldehydes (208—210). 

The formation of unsaturated cyanohydrins (from a, -unsaturated aldehydes) is of further advantage as these products possess an additional synthetic potential. As in the saturated cyanohydrins (above in Scheme 6) they possess the same opportunities for elaboration of the hydroxyl or nitrile moiety, although the presence of the carbon-carbon double bond offers the possibility for additional transformations to be performed such as additions [108], oxidative cleavage [117,118] and epoxidation [119] (Scheme 7). Thus, these highly functionalised chiral units can be of greater importance to an organic chemist. 

All of the stereoisomerie methyl 2,3-anhvdro-6-deoxy-DL-hexo-pyranosides have been prepared by epoxidation of 2,3-unsaturated pyranosides (328-331, R = Me) with hydrogen peroxide-benzo-nitrile. The H-n.m.r. data of their 4-O-acetyl derivatives were reported, and discussed in connection with configurational and conformational assignments.223 The1 regio- and stereo-selectivity of the... 

Cleavage of epoxidesThe aiiion (2) of 1 reacts with carbonyl compounds to give a,/(-unsaturated nitriles and LiOSi(CH3)3, as expected.2 The reaction with epoxides is unexpected the products are y-trimethylsilyloxynitriles, which are useful precursors to -/-lactones (equation I). The formulation indicates that a 1,4-migration of the trimethylsilyl group is involved.2... 

CARBON SKELETON. The technique of precolumn catalytic hydrogenation can be applied to reduce certain unsaturated compounds to their parent hydrocarbons. Compounds analyzed by this technique include esters, ketones, aldehydes, amines, epoxides, nitriles, halides, sulfides, and fatty acids. Fatty acids usually give a hydrocarbon that, is the next lower homolag than the parent acid. For most systems utilizing hydrogenation, hydrogen is also used as the carrier gas. Usually 1% palladium or platinum on a non-adsorptive porous support such as AW-Chromosorb P is used as the catalytic packing material. 

Other c,/3-unsaturated nitriles (Eq. 68) converted into the corresponding epoxides by hydrogen peroxide oxidation under controlled pH include a-phenykiimamomtrile, a-oyano-/3-methylcrotorKH)itril and ethyl a-cyano- -methylcrotonftte.mj-1817... 

Epoxides react with cyanide under basic reaction conditions to yield 3-hydroxypro-pionitriles by nucleophilic attack at the sterically less demanding carbon atom (Scheme4.86). Me3SiCN can also be used as reagent, but trimethylsilyl ethers will be the main products. With some types of epoxide (e.g. styrene oxide [372]) the products readily dehydrate to yield ,/i-unsaturated nitriles [373] (Scheme4.86). 

Under alkaline conditions, H202 produces perhydroxide anion, which playing the role of the intermediate substance epoxidizes a-unsaturated ketones and interacts with nitriles giving amides and 02 [59], In the two latter cases, the perhydroxide anion helps in setting the inter-reaction communication required for conjugation. 

Reduction of diphenyl diselenide with the Sm-Me3SiCl-H20 system also leads to a benzeneselenolate, which reacts with organic halides, epoxides, a, -un-saturated esters or cr, -unsaturated nitriles to afford unsymmetrical phenyl selenides in good yields under mild and neutral conditions as shown in Scheme 13 [19]. This method is easier to handle than the use of air-sensitive Sml2. 

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