3-Acryloyl-l,3-oxazolidin-2-one

Aluminum-based catalyst (S,S)-diazaaluminolidine 54 promoted the cycloaddition [57] between 5-(benzyloxymethyl)-l,3-cyclopentadiene and 3-acryloyl-l, 3-oxazolidin-2-one, leading to the cycloadduct in high yield and high enantiomeric excess (94%) (Equation 3.14). 

Corey and colleagues215 prepared chiral aluminum complexes from chiral bis(sulfona-mides) and trimethylaluminum. These were successfully applied in the cycloadditions of 3-acryloyl-l,3-oxazolidin-2-one (17a) with substituted cyclopentadienes. Thus, the reaction of 3-acryloyl-l,3-oxazolidin-2-one with 5-(benzyloxymethyl)cyclopentadiene (331) afforded 332 with 94% ee (equation 93). A transition state was proposed based on the X-ray structure of the chiral catalyst and on NMR data of the 1 1 complex between 333... 

An example of the solvent effect is also seen in the reaction of 3-acryloyl-l,3-oxazolidin-2-one (15b) which did not give sufficient asymmetric induction by the previous method.(18) The reaction of 15b with butadiene in 1,3,5-TMB gives the 3-cyclohexenecarboxylic acid derivative 22 in 77% optical purity. 

Metal complexes of bis(oxazoline) ligands are excellent catalysts for the enantioselective Diels-Alder reaction of cyclopentadiene and 3-acryloyl-l,3-oxa-zolidin-2-one. This reaction was most commonly utilized for initial investigation of the catalytic system. The selectivity in this reaction can be twofold. Approach of the dienophile (in this case, 3-acryloyl-l,3-oxazolidin-2-one) can be from the endo or exo face and the orientation of the oxazolidinone ring can lead to formation of either enantiomer R or S) on each face. The ideal catalyst would offer control over both of these factors leading to reaction at exclusively one face (endo or exo) and yielding exclusively one enantiomer. Corey and co-workers first experimented with the use of bis(oxazoline)-metal complexes as catalysts in the Diels-Alder reaction between cyclopentadiene 68 and 3-acryloyl-l,3-oxazolidin-2-one 69 the results are summarized in Table 9.7 (Fig. 9.20). For this reaction, 10 mol% of various iron(III)-phe-box 6 complexes were utilized at a reaction temperature of —50 °C for 2-15 h. The yields of cycloadducts were 85%. The best selectivities were observed when iron(III) chloride was used as the metal source and the reaction was stirred at —50 °C for 15 h. Under these conditions the facial selectivity was determined to be 99 1 (endo/exo) with an endo ee of 84%. 

In 1993, Evans and co-workers examined phe-box 6, /-pr-box 45, and bu-box 3 ligands in the Diels-Alder reaction of cyclopentadiene 68 and 3-acryloyl-l,3-oxazolidin-2-one 69 using a weak Lewis acid such as copper(II) triflate." The results are summarized in Table 9.9. The reaction was carried out between —50 and —78 °C for 3-18 h and achieved selectivities of up to 98 2 (endo/exo) with an endo ee of >98% (using bu-box 3). Interestingly, the enantiomer produced in these reactions was the (25) configuration, compared to the (2K) isomer obtained with iron(III) and magnesium(II) as reported by Corey. This observed stereochemistry was explained by the chelation model of the copper(II) complex 74 (Fig. 9.23)... 

Diels-Alder reactions involving bis(oxazoline) ligands are not limited to the reaction between cyclopentadiene and 3-acryloyl-l,3,-oxazolidin-2-one they can be used with a wide variety of dienes and dienophiles. Evans demonstrated the utility of py-box ligand Id in the reaction between cyclopentadiene 68 and various... 

Enantioselective Diels-Alder reaction. Highly stereoselective Diels-Alder reactions can be achieved by use of the 4,4 -diphenylbis(oxazoline) 2b, prepared from (+)-phenylglycinol, as a chiral, bidentate ligand for iron salts. Thus reaction of Fel3 with 2b and I2 in CH3CN forms a complex presumed to be I-Fel3, which can catalyze reaction of 3-acryloyl-l,3-oxazolidin-2-one with cyclopentadiene at —50° to give the endo-adduct in 95% yield. The product is the 2R-enantiomer (82% ee). 

Much has been published on Lewis acid-catalyzed Diels-Alder reactions between the bidentate dienophile 3-acryloyl-l,3-oxazolidin-2-one and the prototypical diene component cyclopentadiene these afford the endo cycloaddition product with good selectivity. This reaction has become the prototype for two-point binding, Lewis acid catalyzed, asymmetric Diels-Alder reactions. For easier comparison, the data in Sch. 41 include. 

The N-Trifluoromethanesulfonyl group increases Lewis acidity of (S,S) diazaaluminolidine (85a), which associates with 3-acryloyl-l,3-oxazolidine-2-one conformationally tightly so as to control the preferred one-side access of the diene in the transition state 86 of the reaction of 87 with 88, as shown in Scheme 5.23 [8]. The same catalysts (85a-c) have been employed for asymmetric radical allylation on the quaternary carbon of coumarin derivatives [9]. Highly trifluoromethylated diols (90 and 91) have... 

The catalyst was also found to be effective for the Diels-Alder reactions of an acrylic acid derivative [77]. 3-Acryloyl-l,3-oxazolidin-2-one reacted with 2,3-dimethylbutadiene to afford the corresponding Diels-Alder adduct in a 78% yield and a 73% ee, whereas the reaction of 3-acryloyl-l,3-oxazolidin-2-one with cyclohexadiene gave a 72% ee for the endo adduct (88% yield, endo/exo=100/0). 

The catalyst was also found to be effective for the Diels-Alder reactions of an acrylic acid derivative (Narasaka et al. 1991). 3-Acryloyl-l,3-oxazolidin-2-one reacted with... 

A comparative study on the influence of different lanthanide cations and the substituents at the 4 and 5 -positions in the pybox ligands in the Diels-Alder reaction of cyclopentadiene with 3-acryloyl-l,3-oxazolidin-2-one was realized [135], Of the catalysts derived from (4 P,5 P)-4-Me-5-Ph-pybox, the Sc(III)-based one is both strongly endo selective (endo/exo = 97/3) and highly enantioselective (97% ee (endo)). Later, it was found that the scandium-(4 S,5 S)-4-CH20TIPS-5-Ph-pybox complex also gave endo selective (endo/exo = 92/8-96/4) and highly enantioselective (93-99% ee (endo)) for the Diels-Alder reactions of cyclopentadiene with 3-acryloyl-or 3-crotonoyloxazolidinones. 

Polymer-supported scandium-based Lewis acids are also active for the Diels-Alder reaction of 3-acryloyl-l,3-oxazolidin-2-one with cyclopentadiene. This reaction proceeded smoothly in the presence in water (Equation (8.46)) affording the corresponding adduct quantitatively [70]. 

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