A temperature study on a stereoselective organocatalyzed aldol reaction in water

We report the first temperature study on the stereoselectivity of the 'in-water' aldol reaction between nicotinaldehyde (3-pyridinecarbaldehyde) and cyclohexanone catalyzed by morpholine and trans-4-tert-butyldimethylsilyloxy-l-proline. Eyring plots of diastereomeric ratio anti/syn gave a constant diastereoselectivity with respect to reaction temperature using morpholine as catalyst. With O(TBS)-l-proline we observed a non-linear behaviour of the Eyring plot with the presence of an inversion temperature (Tinv), which disclosed dynamic solvation effects in water.