Trans-chalcone

The Robinson annulation of ethyl acetoacetate and trans-chalcone proceeded smoothly to give 6-ethoxycarbonyl-3,5-diphenyl-2-cyclohexenone in 48 % yield. The product was separated from the ionic liquid by solvent extraction with toluene. In both these reactions, the ionic liquid [HMIM][PF6] was recycled and reused with no reduction in the product yield. 

A series of chiral phosphinous amides bearing pendant oxazoline rings (50, Ri=H,Tr R2=H,Tr, 51, Ri=H,Tr R2=H,Tr and 54, Ri=H,Tr R2=H,Tr in Scheme 41) have been used as ligands in the copper-catalyzed 1,4-addition of diethylzinc to enones. Two model substrates have been investigated, the cyclic 2-cyclohexenone and the acyclic trans-chalcone. The addition products are obtained quantitatively in up to 67% ee [171]. 

Table 3 summarizes the scope and limitation of substrates for this hydrogenation. Complex 5 acts as a highly effective catalyst for functionalized olefins with unprotected amines (the order of activity tertiary > secondary primary), ethers, esters, fluorinated aryl groups, and others [27, 30]. However, in contrast to the reduction of a,p-unsaturated esters decomposition of 5 was observed when a,p-unsaturated ketones (e.g., trans-chalcone, trans-4-hexen-3-one, tra s-4-phenyl-3-buten-2-one, 2-cyclohexanone, carvone) were used (Fig. 3) [30],... 

Scheme 6.119 Michael adducts from the asymmetric addition of nitromethane to trans-chalcones catalyzed by 122.

In 2007, Chen and co-workers reported the 122-catalyzed (10mol% loading) enantioselective Michael addition [149-152] of ethyl a-cyanoacetate to various electron-rich and electron-deficient trans-chalcones [283]. The reaction was performed for a broad spectrum of chalcones and gave the corresponding adducts in yields of 80-95% and in ee values of 83-95%, but at low sy /a ti-diastereoselectiv-ities as shown for representative products 1-8 in Scheme 6.125. 

Quite recently, one of the most efficient phase-transfer-catalyzed epoxidation methods for chalcone-type enones was developed by the Park-Jew group [11], A series of meta-dimeric cinchona PTCs with modified phenyl linkers were prepared. Among this series, the 2-fluoro substituted catalyst 5, exhibited unprecedented activity and enantioselectivity for the epoxidation of various trans-chalcones in the... 

The first catalytic asymmetric version of the Darzens reaction was achieved in 1978 by J. Hummelen and H. Wynberg [41]. The treatment of p-chlorobenzaldeh ydc and phenacylchloride with the strong base NaOH in the presence of the benzyl quini-nium chloride 86 as a chiral catalyst (6 mol%) afforded the trans-chalcone epoxide 98 in 68% yield. However, the optical yield achieved was only in the range of 7-9% ee (Scheme 8.33). 

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... 

A solution of trans-chalcone oxide (fra s-l -benzoyl-2-phenyloxirane) (0.5 g) in anhydrous ether (25 ml) is heated at the b.p. with boron trifluoride etherate (5 ml) for 30 min. The mixture is then shaken with water and the a-formyldeoxybenzoin that is formed quantitatively is precipitated as copper salt. 

Trans-chalcone Precito atos Gelucire 50/13 315-325 12 2-7 pm de Sousa (2009) ... 

Scheme 7.8 Enantioselective Michael addition of malononitrile to trans-chalcones catalysed by prolinol Ij.

Scheme 19.24 As mimetric addition of nitromethane to trans-chalcones utilising Cinchona-thiourea 17 as catalyst.

Nucleophilic epoxidation (Julia-Colonna epoxidation) of trans-chalcone and derivatives with hydrogen peroxide catalysed by Nagasawa-G (Scheme 23.1) was shown to proceed successfully with a biphasic system consisting of water and toluene. This is a highly atom economical reaction (92% for chalcone). 

The enantioselective Michael addition of malononitrile CH2(CN)2 to trans-chalcones R CH=CHCOR catalysed by diarylprolinols (151), has been studied in detail. Both experimental and computational results are consistent with a bifunctional non-covalent activation of the reactants (152). The latter mechanism correctly predicts formation of the (R)-configured products (<75% eef- but is in conflict with the generally accepted iminium mechanism. Furthermore, (151) is likely to form the corresponding oxazolidine derivative as an intermediate, which has not been taken into account. 

In addition, Schuetz et al. have prepared a samarium Schiff base alkox-ide complex, 74, which showed acceptable functionality in epoxidation of trans-chalcone, 75, to 2,3-epoxy-l,3-diphenyl propanone, 76, at ambient temperature by TBHP in THF [57]. 

Experiment 38 involves the reaction between ethyl acetoacetate and trans-chalcone in the presence of base. Under the conditions of this experiment, a sequence of three reactions takes place a Michael addition followed by an internal aldol reaction and a dehydration. 

The average of Ajp of benzophenone ( 32), ds-chalcone ( 33), trans-chalcone ( 34), cis-4-nitrochalcone ( 35), tranx-4-nitrochalcone ( 36), cis-4-methoxy-chalcone ( 37), trans-4-methoxychalcone ( 38), prednisone ( 39), hydrocortisone ( 40), flimitrazepam ( 43), and 5,5-diphenylhydantoin ( 44) as parameter S (steric hindrance to analyte insertion into the stationary phase). These substances differ from ethylbenzene ( 3) mainly through their molecular size. 

Michael Addition Reaction Involving trans-Chalcones... 

Enantioselective Michael reactions of thiols provide a convenient route to diverse chiral sulfides. Chen and coworkers have demonstrated that a chiral squaramide catalyst was effective in promoting a sulfa-Michael conjugated addition of various aromatic and aliphatic thiols to a wide range of trans-chalcones (Scheme 10.19) [97]. Moderate to excellent yields and enantioselectivities were achieved. Notably, the reactions between various benzylthiol and trans-chalcones bearing electron-donating or electron-withdrawing substituents proceeded with high enantioselectivities. 

Dai L, Wang S, Chen F. A bifunctional cinchona alkaloid-squaramide catalyst for the highly enantioselective addition of thiols to trans-chalcones. Adv. Synth. Catal. 2010 352 2137-2141. 

Catalyst 8 was also reported to be suitable for the enantioselective hydrophos-phonylation of ketimines (Scheme 6.8) [23] and the asymmetric conjugate addition of diarylphosphane oxides to trans-chalcones, affording adducts in up to 89%... 

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