Tishchenko reaction crossed

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. 

In mixed Tishchenko reactions using benzaldehyde combined with fural or 2,3-dimethyoxybenzaldehyde in a 1 1 ratio (Scheme 12.24/b), the Sm-supported material 17 gave a better selectivity in cross products P (53-67%) than the molecular Sm[N(SiMe3)2]3 (36-51%). Again, the changed selectivity was attributed to phenomena like spatial restriction and diffusion controlled surface confine-... 

Modern Aldol Reactions contains several pertinent reviews (i) catalytic enantiose-lective aldols with chiral Lewis bases 97 (ii) the aldol-Tishchenko reaction 98 (iii) titanium—enolate aldols 99 (iv) crossed aldols mediated by boron and silicon enolates 100 (v) amine-catalysed aldols 101 and (vi) aldols catalysed by antibodies.102... 

Additionally, a nickel-catalyzed Tishchenko reaction has been developed, where the selective crossed addition of two different aldehydes to generate a single ester product is possible (Scheme 3-76). By employing an aromatic aldehyde with a nonaromatic aldehyde, a metallacycle derived from heterocoupling is formed, followed by its decomposition to the ester product. 

The first highly enantioselective cross-aldol-Tishchenko reaction of alkyl aryl ketones 28 and aldehydes was developed by the group of Shibasaki et al. [15]. With a chiral heterobimetallic lanthanide-based catalyst, this reaction was shown to proceed in typically very good enantioselectivity to furnish, after saponification of... 

Inspired by the earliest report of a Sml2-catalyzed Tishchenko reaction of P-hydroxyketones by Evans [150], and anyttrium-salen-complex-catalyzed asymmetric cross aldol-Tishchenko reaction by Morken and coworkers (Scheme 13.48) [151]. LLB catalyst was applied to direct catalytic asymmetric aldol-Tishchenko reactions. 

Scheme 13.48 Catalytic asymmetric cross aldol-Tishchenko reaction with Y-salen complex.

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