Asymmetric reactions continued diastereoselectivity

The ene reaction of fuUerene (C o) with 3-methylene-2,3-dihydrofuran gives an easily isolated addition product in good yield <96JOC2559>. There is a continuous need for chiral acrylate esters for asymmetric Diels-Alder reactions with high diastereoselectivity. Lewis acid promoted Diels-Alder reactions of acrylate esters from monobenzylated isosorbide 28 (or isomannide) and cyclopentadiene provided exclusively e db-adducts with good yields and high diastereoselectivity <96TL7023>. 

The importance of the rigid aminoindanol backbone in asymmetric catalytic Diels-Alder reactions is a subject of continued interest.16 50 One example immobilized the copper-inda-box complex onto mesoporous silica in the context of continuous large-scale production of chiral compounds.16 Using 10 mol% of this catalyst (Figure 17.5), the Diels-Alder reaction between /V-acryoyloxazo-lidinone and cyclopentadiene proceeded in 99% yield, 17 1 endo. exo selectivity, and 78% ee of endo cycloadduct. The catalyst could easily be recovered and reused several times without significant loss of diastereoselectivity (15 1 endo. exo selectivity after the fifth reuse) or enantioselectivity (72% ee after the fifth reuse).16 The same remarkable reactivity was observed with a number of diene-dienophile partners. 

Sulfoximines are versatile reagents for diastereoselective and asymmetric synthesis. They continue to find many synthetic applications as both nucleophilic and electrophilic reagents. While the nucleophilic character of sulfoximine reagents has been well exploited,1 the use of the sulfoximine group as a nucleofuge is more recent and adds to the synthetic use of these compounds. The palladium(0)-catalyzed chemistry of allylic sulfoximines and the use of chiral sulfoximines as ligands in catalytic asymmetric synthesis are areas of recent development that have potentially useful applications. Further work is required to understand the factors that determine the diastereoselection and the stereochemical outcomes of these reactions. These studies will result in enhanced product diastereo- and enantioselectivities and make these reagents even more attractive to the wider synthetic chemistry community. 

To expand the scope of the diastereoselective C-C bond formation by the ester enolate Claisen rearrangement, the rearrangement of allylic esters of )S-hydroxy acids is noted to introduce three continuous asymmetric centers. Fujisawa et al. investigated the rearrangement of E- and Z-crotylesters 205 under different reaction conditions [119]. 

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