Acrylonitrile Michael-type reactions

The method is quite useful for particularly active alkyl halides such as allylic, benzylic, and propargylic halides, and for a-halo ethers and esters, but is not very serviceable for ordinary primary and secondary halides. Tertiary halides do not give the reaction at all since, with respect to the halide, this is nucleophilic substitution and elimination predominates. The reaction can also be applied to activated aryl halides (such as 2,4-dinitrochlorobenzene see Chapter 13), to epoxides, " and to activated alkenes such as acrylonitrile. The latter is a Michael type reaction (p. 976) with respect to the alkene. 

Cyclopropanation reactions of chloroalkanes with jt-deficient alkenes under basic phase-transfer catalysed conditions have been observed. Thus, for example, chloroacetic esters and chloroacetonitriles undergo Michael-type reactions with acrylic esters and acrylonitriles, the products of which cyclize to give cyclopropanes (see Section 6.4). 

Other reactions that show preference for the acidic N-3—H group include Mannich aminomethylation by treatment with formaldehyde and an amine (38) to yield compound (8), reaction with ethyleneimine (39) to give (9), and Michael-type additions (40) such as the one with acrylonitrile to give (10) ... 

Michael-Type Additions. Michael additions are generally used to prepare methyl 3-mercaptopropionate (eq. 10) and mercaptopropionitrile (eq. 11) by the reaction of methyl acrylate or acrylonitrile and hydrogen sulfide using a basic catalyst. This reaction proceeds as shown ... 

A Michael-type addition reaction of phosphine generated from red phosphorus in concentrated aqueous KOH solution has been noted to provide moderate isolable yields of pure organophosphorus products.27 For example, tris-(2-cyanoethyl)phosphine is produced in 45% isolable yield from acrylonitrile, and tris-(2-[y-pyridyl]ethyl) phosphine oxide is isolated in 40% yield from 4-vinylpyridine under these conditions. Excellent yields of the tertiary phosphine oxide, tris-(2-cyanoethyl)phosphine oxide, have been reported using white phosphorus in absolute ethanol with KOH at ice/salt-bath temperatures.28 A variety of solvent systems were examined for this reaction involving a Michael-type addition to acrylonitrile. Similarly, tris-(Z-styryl)phosphine is produced from phenylacetylene under these conditions in 55% isolated yield. It is noteworthy that this last cited reaction involves stereospecific syn- addition of the phosphine to the alkyne. 

Reaction of acrylonitrile with ketene acetals.3 Depending on the zinc salt and the solvent, ketene silyl acetals undergo [2+2]cycloaddition or a Michael-type addition with acrylonitrile. The former reaction occurs in CCU with ZnBr2, the latter in CH2C12 with Znl2, with no interconversion. 2-Chloroacrylonitrile can also be used in this way, but substituted acrylonitriles are inactive. 

Cyanoethylation Reactions (Michael-Type Additions). Most compoimds with a labile hydrogen atom can add on the double bond of acrylonitrile to form cyanoethyl groups that is, the primary products are 3-substituted propionitriles. 

In contrast to numerous novel reports on AT-substituted sulphimides, few papers have appeared on reactions of free sulphimides. These were concerned, for example, with the Michael-type addition of diphenylsulphimide PhaS=NH to acrylonitrile and phenyl vinyl sulphone to give the iV-(jS-substituted)alkyl-sulphimides (46) and (47), respectively. With carbonyl-activated alkenes. 

Cellulose Ethers. Cellulose ethers are formed when cellulose, in the presence of alkali or as alkali cellulose, is treated with alkyl or arylalkyl halides. Two types of reaction are employed in the preparation of cellulose ethers. The most common is nucleophilic substitution. Methylation of alkali cellulose with a methyl halide is an example of this type. The other type of etherification reaction is Michael addition. This reaction proceeds by way of an alkali-catalyzed addition of an activated vinyl group to the cellulose. The reaction of acrylonitrile with alkali cellulose is a typical example. The general reaction is outlined in Scheme 4. 

Almost all the catalysts presented up to this point have also been tested in the Michael reaction with acrylic acid derivatives, typically acrylate esters and acrylonitrile. The usual situation found is that these kinds of acceptors furnish similar results to those observed in the same reaction with vinyl ketones, although in some cases a different behavior is observed. On the other hand, there are also some catalytic systems which have been exclusively tested on acrylate-type electrophiles, as will be shown in the following. 

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