Cannizzaro reaction internal

Cannizzaro reaction An internal oxidation-reduction reaction of aldehydes, carbamide Urea, carcinogenic Cancer causing. 

This is an internal crossed-Cannizzaro reaction the keto group is reduced and the —CHO is oxidized. 

Ethanedial undergoes an internal Cannizzaro reaction with alkali to give hydroxyethanoic (glycolic) acid ... 

Pretazettine (242) has a trans B-D ring juncture and seems a fairly strained molecule whereas tazettine (240) bears a cis B-D fusion allowing more flexibility, and the driving force for the B-ring opening is attributed to the relief of this internal strain. The reaction would be completed by an intramolecular crossed Cannizzaro reaction followed by hemiketal formation yielding the cis B-D fusion present in 242. 

The product is the lactone derived from the hydroxy acid that would result from a normal Cannizzaro reaction. Chiral additives have been used, but with bis(oxazo-lidine) derivatives the reaction proceeded with poor enantioselectivity. ° a-Keto aldehydes give internal Cannizzaro reactions ... 

Fiu. 9.—Internal Cannizzaro Reaction of the Dialdehyde from the Periodate Oxidation of Methyl /3-L-Rhamnopyranoside. 

In addition, it is known that a-ketoaldehydes undergo an internal Cannizzaro reaction to yield a-hydroxy carboxylic acids ... 

Propose a mechanism for the internal Cannizzaro reaction depicted below. 

On an alternative pathway, internal Cannizzaro reactions afford mandelic acid-type compounds from phenylglyoxal derivatives [152-156]. Copper complexes [153, 154], chromium perchlorate [154], cobalt Schiff s bases [155] and yttrium chloride [156] have been applied as catalysts. An asymmetric version [Eq. (7)] has been developed using phenylglyoxal (14) as substrate and a combination of Cu(OTf)2 and (S,S)-Ph-box 16 as the chiral catalyst [154]. After 24 h at room temperature isopropyl man-delate (15) was obtained with an enantioselectivity of 28% ee. 

Alkah-catalysed keto-enolic equilibrium c and internal Cannizzaro-type reaction f, represented in Scheme 13.5, should be taken into account when interpreting the experimental data. 

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