Cross-aldol and Reformatsky-type reactions

The aldolisation reaction is one of the most popular carbon-carbon bond formation reactions as it involves carbonylated chemicals that are widely available from numerous industrial processes. In its simpler type, it is performed directly from the carbonylated substrates under acidic or basic 

The hydroxyketones that are provided by the aldolisation process can exist in two diastereoisomeric forms syn and anti) based on the transition-state geometry. 

In an intramolecular case, it was shown that, in an aqueous medium, the nature of the acidic or basic catalyst had a dramatic effect on the outcome of the aldolisation (Denmark and Lee, 1992). Acid-induced aldol condensation of ketoaldehyde 1 provided the syn hydroxyketone 2, while the anti isomer 3 arose from base-catalyzed reactions  

Neutral aldol condensation of 77-nitrobenzaldehyde with acetone was reported (Nakagawa et ai, 1985) to be catalyzed by Zr complexes of a-amino acid esters  

The reaction was performed mostly in methanol and led to some asymmetric induction due to the chirality of the catalysts. Water was also used, providing quantitative aldol condensation, although no optical activity could be obtained in this case (Buonora et al, 1995). The influence of pH on this system was measured in order to minimize undesired dehydration of aldol 

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