Ball Milling University of Massachusetts Bostonball milling Ar c Franziska Schneider Org Proc Res Develop 2009 13 44 Up to 96% yield Entry Rpm T min Yield% 1 400 10 92 2 800 5 94 Aldol Condensation 17 B Rodr´ıguez Angew Chem Int Ed 2006 45 6924 O H O R S proline 10 mol% Ball milling A or stirring B H R Entry R= Method t/h Yield% anti/syn ee% 1 4 NO 2 A 99 89 11 94 2 4 NO 2 B 24 95 89 11 94 3 3 NO 2 A 7