Catalysts binaphthyl-based diamine

Maruoka, et al. reported unprecedented high exo-selectivity in the asymmetric Diels-Alder reaction of a, 3-unsaturated aldehydes by a protonic acid-(i )-binaphthyl-based diamine salt catalyst 48, Scheme 3.15 [27], On the other hand, the Diels-Alder reaction of cyclopentadiene and cinnamaldehyde via enantioselective catalysis over mesocellular foams was reported by Ying and his co-workers [28]. 

Figure 38.2 Binaphthyl-based diamine catalysts for Diels-Alder reactions a-substituted acroleins (Scheme 38.16).

MacMillan s group advanced the iminium activation strategy to intramolecular Diels-Alder reactions with good diastereoselectivity (up to 20 1) and enantioselectivity [61]. The strategy was applied in the total synthesis of (-i-)-hapalindole Q [62]. A novel binaphthyl-based diamine was utilized to catalyze Diels-Alder reaction of a,P-unsaturated aldehydes with unprecedented high exo selectivity [63]. It was reported that the same reaction was also catalyzed by diphenylprolinol silyl ether and an acid as cocatalyst [64]. However, with the same reactants and the same catalyst, an ene reaction took place instead without an acid additive. Diels-Alder reactions of 2-vinylindoles and a,p-unsaturated aldehydes were also developed [65]. 

Jurczak and co-workers reported hybrid diamines derived from l,r-binaphthyl-2,2 -diamine and a-amino acids as organocatalysts for 1,3-dipolar cycloaddition of aromatic nitrones 187 to ( )-crotonaldehyde 28b, Scheme 3.62 [79]. The L-phenylalanine-based l,r-binaphthyl-2,2 -diamine (BINAM) catalyst 194, with trifluoromethanesulfonic acid as an additive, afforded the optimal results with good endo-diastereoselectivity and enantioselectivity up to 95% ee. 

Another proUne-based catalyst was also tested in solvent-free aldol reactions under baU-miUing conditions, for example, derivatives of l,T-binaphthyl-2,2 -diamine or proUne-based dipeptides. Nijera [62] and coworkers used a combination of (SJ-binam-bis-L-prolinamide and benzoic acid to catalyze a direct aldol reaction under solvent-free conditions using conventional magnetic stirring. In addition, comparative studies with ball milling (400 rpm) were carried out for the reaction of cyclohexanone and 4-nitrobenzaldehyde but no improvement was observed. After 1.5 h quantitative conversion and similar diastereoselectivity and enantioselectivity were obtained using these methods [62]. Moreover, a study... 

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