Cis-chalcone

Brouillard, R. and Lang, J., The hemiacetal-cis-chalcone equilibrium of malvin, a natural anthocyanin. Can. J. Chem. 68, 755, 1990. 

Mono- and disubstituted 4,4 -chalcones were the focus of two extensive studies [613]. A total of 48 E-S-cis- and Z-S-cis-chalcones were chromatographed on aminopropyl, diol, cyanopropyl, Cig, and Cg columns (2 = 270 nm) using a 97/3 heptane/THF mobile phase. Capacity factors for all compounds on all columns are... 

Brouillard R, Lang J (1990) The hcaniacetal-cis-chalcone equilibrium of malvidin, a natural anthocyanin. Can J Chem - Revue Canadienne De Chimie 68 755-761... 

The first enantioselective synthesis of cis- and trans- 3-hydroxyflavanones is based on the Lewis-acid-catalysed reaction of phenylmethanethiol with chalcone epoxides <96CC2747>. Further support for the intermediacy of epoxides in the Algar-Flynn-Oyamada flavone synthesis has been provided by the isolation of epoxides in the corresponding preparation of 3-hydroxy-2-phenylquinol-4-ones <96JCS(P2)269>. 

See also Epoxy coatings Epoxy chalcone, 10 450 12,13-Epoxy-cis-9-octadecenoic (vernolic) acid, physical properties, 5 35t Epoxy coatings, 10 436 450 17 845. See also Epoxy can coatings for corrosion protection, 7 199 markets for, 10 442-449 performance of, 10 423 waterborne, 10 439 Epoxy composites, 10 450, 451 Epoxy compounds, photoinitiated polymerization of, 23 716 Epoxy content analysis, 10 385 Epoxy cresol novolac (ECN) resins, 10 367, 369... 

The stereoselective epoxidation of chalcones, followed by acid-catalysed ring closure and concomitant cleavage of the epoxide ring, provides a very efficient route to chiral flavon-3-ols and, subsequently, by borohydride reduction to produce flavan-3,4-diols [13, 14], It has been shown that diastereoselective reduction of the chiral flavon-3-ols by sodium borohydride in methanol yields the trans-2,3-dihydroxy compounds, whereas borohydride reduction in dioxan produces the cis-isomers [14] the synthetic procedure confirms the cis configuration of the 2,3-hydroxy groups of naturally occurring leucodelphinidins [14]. 

Bode and co-workers rendered this transformation asymmetric allowing access to a>cyclopentenes 244 with high enantioselectivity (Table 19) [128], Optimized reaction conditions include the use of A-mesityl substituted aminoindanol derived triazo-lium catalyst 214. When chalcone and derivatives we re subjected to the reaction conditions, ax-cyclopentenes were formed selectively. Although the substrate scope is also limited to P-aryl substituted enals, cis. trans ratios of up to >20 1 are observed. 

Each anthocyanidin is involved in a series of equilibria giving rise to different forms, which exhibit their own properties including color. One- and two-dimensional NMR have been used to characterize the various forms of malvidin 3,5-diglucoside present in aqueous solution in the pH range 0.3 to 4.5 and to determine their molar fractions as a function of pH. In addition to the flavylium cation, two hemiacetal forms and both the cis and trans forms of chalcone were firmly identified. In a reexamination, the intricate pH-dependent set of chemical reactions involving synthetic flavylium compounds (e.g., 4 -hydroxyflavylium) was confirmed to be basically identical to those of natural anthocyanins (e.g., malvidin 3,5-diglucoside) in... 

Block, A., Dangl, J.L., Hahlbrock, K. Schulze, L.P. (1990). Functional borders, genetic fine structure, and distance rquirements of cis elements mediating light responsiveness of the parsley chalcone synthase promoter. Proceedings of the National Academy of Sciences (USA) 87, 5387-91. 

In contrast to the reaction products of the 1,3-dipolar cycloaddition to linear enones (chalcones and their derivatives), spiro- 1-pyrazolines 25-28 are stable heterocycles. Their isomerization into spiro-2-pyrazolines 29-31 can be carried out under acidic conditions at room temperature for 24 h in the case of the cis isomers, and for more than 1 month in the case of trans isomers [30, 41, 42, 43]. 

Optically pure (+)-(i )-3-phenylsulfanyl-l,3-diarylpropan-l-ones are readily available by the enantioselective Michael addition of thiophenols to chalcones. After reduction, acidic dehydration of the racemic alcohol affords a mixture of the racemic cis- and trans- 2,4-disubstituted thiochromans (Scheme 164). A detailed consideration of the stereochemical outcome of the reaction with unsymmetrically substituted diaryl derivatives suggests the involvement of a [1,3] PhS shift via a four-membered sulfonium intermediate and this is backed up by theoretical calculations <2003T3621>. 

A binaphthol-based chirally modified acetylide 116 was shown to undergo conjugate addition to chalcone 40 to give adduct 117 in 90% ee (Scheme 14) [63], Enones capable of achieving an s-cis conformation are claimed to be suitable substrates for this addition reaction. 

Apart form the aforementioned highly enantioselective hetero-Diels-Alder reactions, that proceed with very low catalyst loadings, the catalytically accessible enolates have also been used for related intramolecular Michael reactions (Philips et al. 2007) and for the desym-metrization of 1,3-diketones yielding cyclopentenes via an intramolecular aldol reaction (Wadamoto et al. 2007). The formation of cyclopentenes, however, presents a special case, so—depending on the stereochemical nature of the enone substrates (s-cis or s-trans) and the stereochemistry of the final products—two different mechanisms are discussed in the literature. Whereas /ran.v-cycl open (cries are proposed to be available upon conjugate addition of a homoenolate to chalcones,... 

An account has also been given of the reaction between benzylmercaptan and cis-benzene trioxide.With a-mercapto esters, p-substituted phenyloxiranes undergo normal opening, without being affected by the substituents on the benzene ring. Chalcone oxides react with mercaptan with accompanying C-C bond cleavage (Eq. 308). ... 

Not only Cc,-0 and rarely Cg-O bond breaking but C -Cg bond splitting may be observed. A consequence of this is the very stereoselective epimerization of benzylidenecyclohexanone oxide.The stereochemistry of photolysis of optically active dypnone oxide has been studied and the possibility of C-C bond cleavage has likewise been proposed.C-C bond splitting has also been observed during examinations of chalcone oxides transformation to dibenzoylmethane, trans-cis isomerization, and photofragmentation occur via ylides and acylcarbene intermediates (Eq. 341). ... 

As described above, the stereochemistries of the mulberry Diels-Alder type adducts could be divided into the following two groups one is an all-trans in relative configuration and the other is a cis-trans configuration. All-trans type adduct may correspond to an exo-addition product in the Diels-Alder reaction of a chalcone and a dehydroprenylphenol, whereas a cis-trans type adduct corresponds to an endo-addition product in the reaction. 

Chalcone (100 g, 480 mmol) and hydrazine (29.8 g, 595 mmol) in EtOH (300 mL) were heated under reflux for 20 min. EtOH and excess hydrazine were removed under vacuum and the waxy residue (3,5-diphenyl-2,3-dihydro-l//-pyrazole) was pyrolyzed at 250°C. The crude product, mainly a mixture of cis- and trans-, l-diphenylcyclopropane, distilled out. Fractional distillation under vacuum (40-cm Vigreux column, reflux ratio 10 1, cooling water temperature 40°C) gave the pure m-l,2-diphenylcyclopropane at 120- 122 C/ O.Smbar yield 35.4 g (38%) mp 36-37°C. 

The catalysts leading to the higher trans and cis preferences, namely Cu(II)-bentonite and Cu(II)-K10, were tested in the reactions of ethyl diazoacetate (1) with different alkenes (Scheme 2). The results obtained (Table 2) show that the yield and the selectivities with regard to both reagents increase with the electron-donor ability of the substituents of the double bond, which indicates the electrophilic character of the reaction. Therefore the cyclopropanes coming from chalcone (10) could not be obtained. 

P, P] Although the stereochemistry of the process was not fully elucidated, Risaliti and co-workers examined the addition of the enamine derived from morpholine and cyclohexanone to cis- and trans-chalcone (23). In general, this process leads initially to dihydropyrans and the same product is obtained from either isomer of chalcone. Furthermore, ci s-chalcone is converted to the trans isomer under the reaction conditions, even though such cis-trans isomerization does not occur in the presence of a tertiary amine alone. Thus, the initial conjugate addition of the enamine to form the dipolar intermediate appears to be freely reversible under the reaction conditions. 

Carbon suboxide, 52 Carbonylation, 148, 149, 216 Carbonyl chlorofluoride, 48, 54 Carbonyl cyanide, 60-61 N,N -Carbonyldiimidazole, 61 1,1-Carbonyldi-l,2,4-triazole, 61 N-Carbonylsulfamic acid chloride (N-Carbonylsulfamyl chloride), 61 Carboxamides, 270 Carboxamine-N-sulfochlorides, 70 p-Carboxybenzenediazonium chloride, 62 p-Carboxybenzenesulfonazide, 62 Carboxylation, 15, 16 Carboxylic acid anhydrides, 133 Carboxylic acid N,N-dimethylamines, 153 Carboxylic anhydrides, 409-410 p-Carboxyphenylhydrazones, 62 Cardenolides, 130, 131 (S-Carotene, 19 /-Carvone, 451, 452 i//-Caryophyllene, 149, 150 Catechol, 65, 233 Catechol amines, 159 Catechyl phosphorus tribromide, 63 Catechyl phosphorus trichloride, 63 Cis-Cecropia juvenile hormone, 261 Cedrene, 234, 235 a-Cedrene, 349 /3-Cedrene, 349 Cendranoxide, 234, 235 Cephalosporin C, 48 Ceric ammonium nitrate, 63-65 Ceric sulfate. 65 Cesium fluoride, 346 trans-Chalcone oxide, 422 Chalcone phenylhydrazones, 257, 258 Chalcones, 406 Chloramine, 65-66, 69 Chloranil, 66-67, 113, 116, 401,454... 

Detailed studies of the cis-trans and trans-cis isomerization of chalcone and some of its derivatives and analogues (123) have been reported. Perkins and his co-workers have reported an irradiative method of reducing enone systems such as chalcone to the corresponding saturated compounds. The cis-trans isomerization of chalcone has been studied in CCI4 solution. ... 

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