Diels-Alder reactions organocatalysed

DFT has been used to investigate the Diels-Alder reactions of cyclopentadiene with a,/S-unsaturated aldehydes and ketones organocatalysed by MacMillan s chiral... 

MacMillan s imidazolidinone salts, used successfully in the organocatalysed Diels-Alder reaction (see Section 8.1) also function as effective catalysts in the asymmetric nitrone cycloaddition with simple monodentate dipolarophiles. Thus acrolein (8.63) and crotonaldehyde (8.99) both react with acyclic C-aryl, N-benzyl nitrones and C-aryl N-alkyl nitrones such as (8.198) with high ees ranging from 90 to 99% in the presence of the perchlorate salt of imidazolidinone (8.91). 

As an extension of the organocatalysed Diels-Alder reaction, the List group developed a three-component domino Knoevenagel-hetero-Diels-Alder using ketones, aldehydes and Meldrum s acid (Scheme 5.42). ... 

Wilson RM, Jen WS, MacMillan DWC (2005) Enantioselective organocatalysed intramolecular Diels-Alder reaction. The asymmetric synthesis of solanapyrone. J Am Chem Soc 127 11616-11617. doi 10.1021/ja054008q... 

The organocatalysed asymmetric cycloaddition reaction of a,p-unsaturated ketones and aldehydes is scarcely studied, especially for fluorine-containing substrates. In this area, Liu et al. have reported unusual inverse-electron-demand oxa-Diels-Alder reactions of a,p-unsaturated trifluoromethyl ketones with aldehydes catalysed by chiral a,a-diphenylprolinol trimethylsilyl ether. It was shown that the addition of pura-fluorophenol and silica gel along with this catalyst was necessary, otherwise the reaction was very slow and a poor yield was obtained. Under these optimal conditions, the expected cyclic adducts were obtained in good yields and high fl n-diastereo- and enantioselectivities, as shown in Scheme 6.11. 

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