Diels catalyzed asymmetric

Metal-catalyzed asymmetric hetero Diels-Alder reactions of unactivated dienes with glyoxylates 98PAC1117. 

Lewis-acid-catalyzed asymmetric hetero-Diels-Alder cycloaddition of a 1-thiabuta-1,3-diene with chiral A/-acryloyl and A/-crotonyl oxazolidinone dienophile [105]... 

A new chiral ligand for the Fe-Lewis-acid catalyzed asymmetric Diels-Alder reaction [117]... 

Clay-catalyzed asymmetric Diels-Alder reactions were investigated by using chiral acrylates [10]. Zn(II)- and Ti(IV)-K-10 montmorillonite, calcined at 55 °C, did not efficiently catalyze the cycloadditions of cyclopentadiene (1) with acrylates that incorporate large-size chiral auxiliaries such as cA-3-neopentoxyisobornyl acrylate (2) and (-)-menthyl acrylate (3, R = H) (Figure 4.1). This result was probably due to diffusion problems. 

Johannsen M., Yao S., Graven A., Jorgensen K. A. Metal-Catalyzed Asymmetric Hetero-Diels-Alder Reactions of Unactivated Dienes With Glyoxylates Pure Appl. Chem. 1998 70 1117-1122... 

Hiroi K. Transition Metal or Lewis Acid-Catalyzed Asymmetric Reactions With Chiral Organosulfur Eunctionahty Rev. Heteroat. Chem. 1996 14 21-57 Keywords hefero-Diels-Alder reactions, asymmetric synthesis, chiral organosulfur functionality... 

Zeijden [112] used chiral M-functionalized cyclopentadiene ligands to prepare a series of transition metal complexes. The zirconium derivative (82 in Scheme 46), as a moderate Lewis acid, catalyzed the Diels-Alder reaction between methacroleine and cyclopentadiene, with 72% de but no measurable enantiomeric excess. Nakagawa [113] reported l,T-(2,2 -bis-acylamino)binaphthalene (83 in Scheme 46) to be effective in the ytterbium-catalyzed asymmetric Diels-Alder reaction between cyclopentadiene and crotonyl-l,3-oxazolidin-2-one. The adduct was obtained with high yield and enantioselectivity (97% yield, endo/exo = 91/9, > 98% ee for the endo adduct). The addition of diisopropylethylamine was necessary to afford high enantioselectivities, since without this additive, the product was essentially... 

Scheme 2.182. Amino acid-catalyzed asymmetric three-component Knoevenagel/Diels-Alder reactions.

Chiral (Acyloxy)borane Complex Catalyzed Asymmetric Diels-Alder Reaction (1 R)-1,3,4-Trimethyl-3-cyclohexene-1-carboxaldehyde. 

Scheme 7. Cu-catalyzed asymmetric Diels-Alder used by Evans in the total synthesis of isopulo upone (1997).

Taguchi and coworkers175 studied the Lewis acid catalyzed asymmetric Diels-Alder reactions of chiral 2-fluoroacrylic acid derivatives with isoprene and cyclopentadiene. When a chiral l,3-oxazolidin-2-one and diethylaluminum chloride were used as the chiral auxiliary and the Lewis acid catalyst, respectively, a de of 90% was observed for the reaction with isoprene. The reaction with cyclopentadiene afforded a 1 1 mixture of endo and exo isomers with de values of 95% and 96%, respectively. The endo/exo selectivity was improved by using 8-phenylmenthol as the chiral auxiliary. Thus, the reaction... 

CHIRAL (ACYLOXY)BORANE COMPLEX-CATALYZED ASYMMETRIC DIELS-ALDER REACTION (1R)-1,3,4-TRIMETHYL-3-CYCLOHEXENE-1-CAR BOX ALDEHYDE (3-Cyclohexene-1-carboxaldehyda, 1,3,4-trlmethyl-, (-)-)... 

CHIRAL ACYLOXVBORANIE CATALYZED ASYMMETRIC DIELS-ALDER REACTION... 

PEG-supported bix(oxazoline) ligands (12) were prepared and tested as ligands in homogeneous Gu-catalyzed asymmetric transformations (Fig. 5.4) [73]. The Diels-Alder reaction proceeded in poor ee, while cyclopropanation and ene reac-... 

Yamamoto reported an aluminum complex-catalyzed asymmetric hetero Diels-Alder reaction (Scheme 9.19) [36]. Chiral ketone d-3-bromocamphor discriminates (R)-organoaluminum complex 34 from (S)-complex 34 by diastereoselective complexation, whereas the remaining (S)-isomer 34 catalyzes the enantioselective cycloaddition of an activated diene to benzaldehyde. 

Scheme 9.21. DMTC-catalyzed asymmetric three-component domino-Knoevenagel-Diels—Alder reaction.

Furuta, K. Gao, Q.-Z. Yamamoto, H. Chiral (acyloxy)borane complex catalyzed asymmetric Diels-Alder reaction (lR)-l,3,4-trimethyl-3-cyclohexene-l-carboxaldehyde. Org. Synth. 1998, Coll. Vol. IX, 722-727. 

Asymmetric Diels-AUer reactions The observation that simple acyloxy-boranes such as H2BOCOCH=CH2, prepared by reaction of BH3 with acrylic acid, can serve as Lewis acid catalysts for reactions of the a,P-unsaturated acids with cyclopentadiene (15, 2) has been extended to the preparation of chiral acyloxy-boranes derived from tartaric acid. The complex formulated as 3, prepared by reaction of BH3 with the monoacylated tartaric acid 2, catalyzes asymmetric Diels-Alder reactions of a,P-enals with cyclopentadiene with high enantioselectivity. The process is applicable to various dienes and aldehydes with enantioselectivities generally of 80-97 % ee. 

FIGURE 1 7.4 Proposed transition states for the copper- and magnesium-catalyzed asymmetric Diels-Alder reaction. 

Fig. 10 BINOL units attached to polyaryl cores used as ligands for Al111-catalyzed asymmetric Diels-Alder reactions...

Enantioselective silver-catalyzed aza-Diels-Alder reactions have also been described. Whereas the use of BINAP as the chiral ligand gave only unsatisfactory enantioselectivities,367,367a Hoveyda etal 6 used the peptidic phosphine 373 which has already been used for silver-catalyzed asymmetric Mannich reactions (see Scheme 108) in the efficient Ag(i)-catalyzed cycloaddition of arylimines 449 with Danishefsky s diene (Scheme 135). After acidic work-up, the chiral pyridones 450 were obtained with excellent yields and enantioselectivities. The presence of isopropanol as a proton source is essential for obtaining high conversions and stereoselectivities. Similar to the Mannich reactions, the cycloaddition is not affected by the presence of air or the use of undistilled THF. 

Wilson RM, Jen WS, MacMillan DWC (2005) Enantioselective organocatalytic intramolecular Diels-Alder reactions. The asymmetric synthesis of solana-pyrone D. J Am Chem Soc 127 11616-11617 Xie JH, Zhou ZT, Kong WL, Zhou QL (2007) Ru-catalyzed asymmetric hydrogenation of racemic aldehydes via dynamic kinetic resolution efficient synthesis of optically active primary alcohols. J Am Chem Soc 129 1868-1869... 

A chiral Lewis acid prepared in situ from magnesium iodide and (/ ,f )-DPEN efficiently catalyzes asymmetric aza-Diels-Alder reaction of a methyl glyoxylate/p-anisidine derived imine with the Danishefsky diene to give the cyclic adduct in 97% ee (eq 11). ... 

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. 

A chiral zirconium bis(triflate) complex has been found to catalyze asymmetric Diels-Alder reactions (Eq. 25) [25]. 

Heterobimetallic complexes 2 and 22 catalyze asymmetric Diels-Alder reactions of some dienophiles with cyclopentadiene [110]. Use of 6,6 -dibromo-substituted BINOL ligands led to significantly improved yield, endo.exo ratio, and enantioselectivity. 

White, J. D., Choi, Y. Catalyzed Asymmetric Diels-Alder Reaction of Benzoquinone. Total Synthesis of (-)-lbogamine. Org. Lett. 2000, 2, 2373-2376. 

Johannsen, M., Yao, S., Graven, A., Jorgensen, K. A. Metal-catalyzed asymmetric hetero-Diels-Alder reactions of unactivated dienes with glyoxylates. PureAppl. Chem. 1998, 70,1117-1122. 

During recent years, the homogeneous Lewis acid-catalyzed asymmetric Diels-Alder reactions and hetero-Diels-Alder (HDA) reactions have each undergone extensive study. Various chiral Lewis acids including aluminum, titanium or boron, and chiral ligands such as chiral amino alcohols, diols, salen, bisoxazoline or N-sulfonylamino acids have been used as the catalysts [84]. Much efforts have also been made in the investigation of heterogeneous diastereoselective Diels-Alder reactions. 

Fukuzawa and coworkers reported the rare earth (III) salt-catalyzed asymmetric Diels-Alder reaction of cyclopentadiene with a chiral dienophile in SCCO2 [112]. The Diels-Alder reaction in SCCO2 proceeded rapidly to give the corresponding adducts with higher diastereoselectivities than those in CH2CI2 (Scheme 7.41). 

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