Dipeptides ball milling

Reproduced from HemMez JG, Juaristi E Efficient ball-mill procedure in the green asymmetric aldol reaction organocatalyzed by (S)-proline-containing dIpeptides in the presence of water. Tetrahedron 2011 67 6953-9. Copyright (2011), with permission from Elsevier. 

Reproduced with permission from Machuca E, Rojas Y, Juarlsti E Synthesis and evaluation of (S)-prolhe-contalnlng a. p-dipeptides as organocatalysts In solvent-free asymmetric aldol reactions under ball-milling conditions. Asian J Org Chem 2015 4 46-53. Copyright (2015), Wiley. 

Scheme 21.30 Dipeptide catalyzed ball-milled aldol reaction with acetone. ...

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... 

Figure 21.6 Scope of ball-mill assisted asymmetric aldol reaction catalyzed by dipeptides...

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