Aldol-Tishchenko reaction alkoxide

Zirconium alkoxide catalysts were used for the aldol-Tishchenko reaction shown in Equation 18 [23]. In the reaction, diacetone alcohol (55) is converted to the corresponding enol by removal of acetone, and adds to an aldehyde. Enantioselective version of the reaction was also examined [24]. 

When aldehydes, with or without a hydrogen, are treated with aluminum ethoxide, one molecule is oxidized and another reduced, as in 9-69, but here they are found as the ester. The process is called the Tishchenko reaction. Crossed Tishchenko reactions are also possible. With more strongly basic alkoxides, such as magnesium or sodium alkoxides, aldehydes with an a hydrogen give the aldol reaction. Like 9-69, this reaction has a mechanism that involves hydride transfer.751 The Tishchenko reaction can also be catalyzed752 by ruthenium complexes.753 by boric acid,754 and, for aromatic aldehydes, by disodium tetracarbonylferrate Na2Fe(CO)4,755 OS I, 104. 

Tishchenko reaction When aldehydes are treated with aluminium ethoxide, one molecule is reduced while the other is oxidised, and the product is the resulting ester.This reaction involves a hydride anion transfer. With more basic alkoxides, aldehydes with an a-hydrogen undergo the aldol reaction. 

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