Crotonic acid derivatives

Asymmetric 1,3-dipolar cycloaddition of cyclic nitrones to crotonic acid derivatives bearing chiral auxiliaries in the presence of zinc iodide gives bicyclic isoxazolidines with high stereoselectivity (Eq. 8.51). The products are good precursors of (3-amino acids such as (+)sedridine.73 Many papers concerning 1,3-dipolar cycloaddition of nitrones to chiral alkenes have been reported, and they are well documented (see Ref. 63). 

SCHEME 5. Screening of catalysts and crotonic acid derivatives in the copper-catalyzed Grignard addition. Adapted with permission from Acc. Chem. Res., 40, 179-188 (2007). Copyright 2007 American Chemical Society... 

Reactions of j8-halovinylacetic acid derivatives (266) with nucleophiles give crotonic acid derivatives (274) (Vcssiere, 1949 Theron, 1967) by prototropy either preceding the substitution step, or following it. 

However, the results should be taken as an exception, since in our understanding of enantioface differentiating transformations enantioselectivity is obtained by discrimination of one of the two enantiofaces of a molecule usually due to steric hindrance. Since under high pressure the sterically more crowded transition structure is preferred, a decrease in enantioselectivity should be observed under high pressure. This indeed was found for the intermolecular all-carbon Diels-Alder reaction of 2-methyl-1,3-butadiene to a crotonic acid derivative [552], A divergent result may be obtained if the differentiation is caused by electrostatic reasons. 

JCS(P1)1153>. On the other hand, compounds (294) give the expected 5-substituted thiazoles (296) when are treated with y-bromo crotonic acid derivatives (Scheme 74) <92LA415>. 

A recent synthesis of (+)-sedridine (167) was reported in which a key step was the asymmetric cycloaddition of the nitrone 2,3,4,5-tetrahydropyridine A-oxide with an asymmetric crotonic acid derivative containing a chiral auxilliary [439], Sedridine has recently been isolated from the bark of Punica granatum [440],... 

The above sequence was adapted to an asymmetric Diels-Alder reaction. The reaction of 3>3 dimethylacrylic acid derivative 12, derived from ( )-2-amino-2-phenylethanol, afforded preferentially one diastereomer in good yield, as did the crotonic acid derivative. 

Crotonic acid derived dienophiies 15.1.6.1 Acyclic dienes ... 

Poly(vinyl alcohol) has the structure 10.67. Poly(vinyl acetate) is the fully esterified derivative of polyfvinyl alcohol), in which the -OH groups are replaced by -OCOCH3 groups. As indicated in Table 10.5, commercial polyvinyl sizes are effectively copolymers of polyfvinyl acetate) and polyfvinyl alcohol) that vary in the degree of saponification of the ester groups. These products may comprise 100% of either polymer, or combinations of the two monomers in any proportions. Crotonic acid (2-butenoic acid), widely used in the preparation of resins, may also be a component. This compound exhibits cis-trans isomerism (Scheme 10.17). The solid trans form is produced readily by catalysed rearrangement of the liquid cis isomer. 

A derivative from trans-crotonic acid via quinine salt resolution... 

Saito et al. (32) developed a tartaric acid derived chiral nitrone 18. In the reaction of 18 with methyl crotonate 19, the 1,3-dipolar cycloaddition product 20 was obtained in an endo/exo ratio of 10 1 and with high diastereofacial induction to give the endo-isomer (Scheme 12.9). 

Crotonic acid and derivs 3 C562—C563 crotonyl azide 3 C563... 

Reaction of 2-aminopyridines with acrylic acid or methacrylic acid in boiling water for 2-20 hours gave betaine hydrates 262 (R3 = H) in 11-88% yields (Scheme 20) (92KGS80). When 2-aminopyridine reacted with methyl metharylate in acetic acid for 24 hours or 2-aminopyridine and its 5-bromo and 5-chloro derivatives reacted with acrylic acid in boiling toluene for 24 hours or 2-aminopyridine reacted with crotonic acid in boiling toluene for 20 hours, 3-(2-pyridylamino)propionic acid derivatives 263 were the products. When 5-chloro-2-aminopyridine reacted with acrylic... 

Iodonium salts 60 react with cyanide anion affording the cyano derivatives of crotonic acid 61 as single isomers retaining the initial configuration of the phenyliodonium tosylate (Scheme 28) [51]. 

Metalated enones and related compounds are usually alkylated at the position a to the electron-withdrawing group [109-113], but the precise structure of the electrophile can also have an impact on regioselectivity (Scheme5.10). Certain substrates, such as crotonic acid dianions [111], crotonamide dianions [114, 115], or certain enones [116] can also give mixtures of a- and y-alkylatcd products, whereas metalated -oxy [117-119] or /i-amino [120, 121] acrylic acid derivatives often yield pure products of y-alkylation. 

These materials are the reaction product of a primary amine and either acrylic acid, an ester of acrylic acid such as methyl acrylate, ethyl acrylate or crotonic acid. Either 1 or 2 mol of acrylate is used. If 1 mol is added, an N-alkyl (3-alanine is produced (Figure 6.6) and if 2 mol of acrylate per mole of amine is used, the corresponding carboxyethyl (3 -alanine derivative is produced (Figure 6.7). 

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