Allyl crotonate

Whereas monoallyl derivatives sdeld thermoplastic polymers, allyl esters containing two or more unsaturated groups yield thermosetting resins. Thus, monoallyl esters of unsaturated acids, e.g., allyl acrylate, allyl methacrylate, allyl crotonate, and allyl itaconate, and diallyl esters of dibasic acids, e.g., diallyl oxalate, diallyl phthalate, and diallyl itaconate, yield thermoset resins, which generally combine solvent resistance, toughness, hardness, transparency, and heat resistance. The cross-linking tendency of the allyl esters makes them useful in copolymerization wherein they impart these properties to normally linear polymers. 

Allyl vinylacetate is the main product in the reaction of allyl alcohol with carbon monoxide in the presence of tris-(tri-(p-fluorophenyl)-phosphine)-platinum at 200 °C without addition of another alcohol. At a reaction temperature of 250 °C allyl crotonate is obtained by thermal isomerization [551],... 

Allyl cyanide, CHg. CH CH. CN, occurs in some of the oils of the mustard type. It is a liquid of specific gravity 0 8365 boiling at 120° to 123°, and yields, on boiling with alcoholic potash solution, crotonic acid, melting at 72°. 

Bromide (6) is clearly needed and can be made by allylic bromination of ester (7), Crotonic acid (8) is... 

The Knoovenagol method (p T 161 ) gives high yields of crotonic acid. The allylic bromination uses N3S in CCl and the ylid (9) is stable enough to be isolated. 

Methyl crotonate reacts with NBS and brominates is allylic position giving methyl 3-bromocrotonate, a valuable synthetic reagent used in Reformatsky reaction. 

Another leading research theme was the migration of the double bond, for example, in the saponification of an allyl nitrile to crotonic acid. 36... 

When aqueous NaOH is given as a base, isomerization of the product butenoic acids can be extensive depending on the nature and concentration of base. In dilute aqueous solutions alcohols do not react to form the respective esters, however, the reactions are strongly accelerated due to the increased solubility of the substrates in the catalyst-containing aqueous-alcoholic phase. For example, with 23-33 % (v/v) ethanol in water the [PdCl2(TPPTS)2]-catalyzed hydroxycarbonylation of allyl chloride proceeded with TOF-s of 1850-2400 h and with a vinylacetic/crotonic acid ratio of 21 [16]. Addition of [CuCb] increased the overall conversion rate (by a factor of 2 at [Cu]/[Pd] = 8) but at the same time the side reactions... 

Dimerization of methyl crotonate has been carried out with alkaline earth metal oxides as basic catalysts 15). The reaction proceeds by Michael addition, which is initiated by abstraction of an allylic hydrogen of methyl crotonate by the basic site to form the allylic carbanion, which attacks a second methyl crotonate molecule at the jS-position to form a methyl diester of 3-methyl-2-vinylglutaric acid. The diester undergoes a double bond migration to form the final E- and Z- isomers of 3-ethylidene-3-methylglutaric acid dimethyl ester (MEG) (Scheme 22). 

Among the most commonly applied chiral moiety for nitrones (2) is the N-a-methylbenzyl substituent (Scheme 12.6) (18-25). The nitrones 8 with this substituent are available from 1 -phenethylamine, and the substituent has the advantage that it can be removed from the resulting isoxazolidine products 9 by hydrogeno-lysis. This type of 1,3-dipole has been applied in numerous 1,3-dipolar cycloadditions with alkenes such as styrenes (21,23), allyl alcohol (24), vinyl acetate (20), crotonates (22,25), and in a recent report with ketene acetals (26) for the synthesis of natural products. Reviewing these reactions shows that the a-methylbenzyl group... 

With the allylic intermediates, the introduction of oxygen is also possible and crotonaldehyde is one of the first oxygenated products to be formed. This molecule is not very stable, certainly not under reaction conditions, and will be further oxidized to crotonic acid or the relatively more stable furan. More severe oxidation will then result in the generation of maleic acid and its anhydride. 

The literature reports direct grafting by gamma-rays exposure of Nylon fibers or films to the following monomers carbon monoxide (/65), ethylene (157), propylene (157), acetylene (166), butadiene (157.162,163), styrene (158, 161,163,167,168), vinyl chloride (157,163), vinyl fluoride (169-172), vinyl acetate (161,163,173), vinyl propionate (161), vinyl butyrate (161), vinyl crotonate (161), vinyl 2-ethyl hexanoate (161), acrylic add (173,174), methyl acrylate (162, 163), ethyl acrylate (162,163), allyl acrylate (163), methyl methacrylate (28,161, 163,164), butyl methacrylate (161), acrylamide (158), methylol acrylamide (163), acrylonitrile (157,160-163, 167, 175-179), divinyl sulfone (161), vinyl pyridine (167,173), vinyl pyrrolidone (28) and triallyl cyanurate (158). 

The C—X reduction potentials of allylic halides and unsaturated a-haloesters are similar, and vary depending on their substitution pattern. The regioselectivity of the addition, therefore, is also influenced by the relative reduction potentials. l-Chloro-3-methyl-2-butene (41) reacts with diethyl fumarate (42) through attack from the primary carbon (equation 31), whereas with methyl crotonate (44) allylation takes place at the more highly substituted tertiary carbon (equation 32). 

The reduction potential of l-chloro-3-methyl-2-butene (41) is more positive than that of methyl crotonate which results in the initial 2-electron reduction of the allyl halide to give the allyl ion. This species subsequently undergoes Michael reaction through the tertiary... 

In addition to the above-mentioned monomers, various acrylic and methacrylic esters, methacrylonitrile, itaconic acid, crotonic acid, methyl vinyl ketone, allyl alcohol, allyl amine etc., have been studied by Fischer... 

Benzeneselenenyl azide adds to alkenes readily. The addition of the selenenyl azide always occurs with trans stereochemistry. The yield of adducts is reliably high with several different alkenes. Unlike benzeneselenenyl chloride, mixtures of regioisomers are found with simple primary alkenes. No addition occurs between benzeneselenenyl azide and ethyl crotonate. The reagent adds to conjugated dienes in a trans 1,4-fashion which is thought to be due to an initial trans 1,2-addition, followed by a facile 1,3-allylic azide shift (equation 19). Unfortunately, this reagent must be prepared and used in situ ... 

Beside the Grignard and other C-C bond-forming reactions, a number of functional group transformations may also serve as an entry into allylic systems. Some of them, namely the reduction of a, -unsaturated carbonyl compounds (products of crotonic condensation), halogenation of alkenes at the allylic position with Af-bromosuccinimide (NBS) and epoxide isomerization, are shown in Scheme 2.56. 

This is proven by the fact that allyl cyanide on hydrolysis yields crotonic acid in which the double bond is at carbon-2 (p. 173). Of the other cyanogen derivatives of propene the following are known though the position of the double bond is not established in all cases. 

In this series of reactions there occurs a shifting of the double bond from the first to the second carbon atom either in the allyl cyanide or when this is hydrolized to the acid for the acid obtained is crotonic acid which as we shall see has the constitution of A2-butenoic acid. 

While alcohol oxidations have been the most common metal promoted reactions involving molecular oxygen, a number of other metal catalyzed oxidations of potential synthetic interest have been reported. Supported palladium catalysts are comparable to many soluble palladium catalysts in promoting the selective oxidations of alkenes and aromatics. 2-Butene was oxidized primarily to crotonic acid over Pd/C in water but methyl vinyl ketone and crotonaldehyde were also formed in significant amounts. When this oxidation was run in acetic acid the allyl acetates were the major products, particularly when a Pd/Al203 catalyst... 

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