Cannizzaro reaction aluminum alkoxides

In the general context of donor/acceptor formulation, the carbonyl derivatives (especially ketones) are utilized as electron acceptors in a wide variety of reactions such as additions with Grignard reagents, alkyl metals, enolates (aldol condensation), hydroxide (Cannizzaro reaction), alkoxides (Meerwein-Pondorff-Verley reduction), thiolates, phenolates, etc. reduction to alcohols with lithium aluminum hydride, sodium borohydride, trialkyltin hydrides, etc. and cyloadditions with electron-rich olefins (Paterno-Buchi reaction), acetylenes, and dienes.46... 

Both the Meerwein-Ponndorf-Verley reaction and the Cannizzaro reaction are hydride transfers in which a carbonyl group is reduced by an alkoxide group, which is oxidized. Note that each aluminum triisopropoxide molecule is capable of reducing three ketone molecules. 

The analogy has been drawn between the chemistry catalyzed by dehydrogenases and the base-catalyzed hydride transfer chemistry of Meerwein-Ponndon-Verley (MPV) reductions or the Cannizzaro reaction (for recent reviews of the chemistry of pyridine nucleotides see Refs. 1,3, and 5). In MPV reductions [reaction (2)] aluminum or lithium salts of the alkoxide activate the C-H bond for transfer of hydrogen to suitable acceptors. Both direct hydride transfer (52) and radical intermediates (55) have been suggested for this reac-... 

A modification of the Cannizzaro reaction was discovered by Claisen [158] and later extended by Tishchenko [159]. It involves the use of sodium or aluminum alkoxides in the conversion of aliphatic and aromatic aldehydes into the corresponding esters [160]. Other catalysts, such as boric add [161], superoxide ion/crown ether [162] and metal catalysts [163] have also been applied in this oxidation reaction. 

A special example of the Cannizzaro reaction results in the direct formation of an ester from two molecules of an aldehyde. The catalytic agent used here is an acid (aluminum alkoxide) according to the Lewis theory. This acid coordinates with a molecule of the aldehyde, acting as a base, and produces an acidic intermediate, as follows ... 

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