Homologation of aldehydes

A convenient way of six-carbon homologation of aldehydes and ketones is the nucleophilic addition of the dianion generated from sorbic acid, (2 ,4 )-hexa-2,4-dienoic acid and subsequent dehydration to form the corresponding trienoic acid (equation 43)81. The 3-methyl analogue of sorbic acid has been used in a similar fashion for a short synthesis of vitamin A carboxylic acid (equation 44)82. 

Dondoni pioneered the use of 2-(trimethylsilyl)thiazole (71) as a formyl anion equivalent for the homologation of aldehydes. Extension of this reaction to ketones would be very useful, but has thus far been restricted to tritluoromethyl cases. However, it has now been widened to include several a, a -alkoxy ketones, as demonstrated in a new route to branched-chain monosaccharides. Aldehydes catalyse the reaction, although the scope is still limited electrophilic aldehydes, such as 2-fluorobenzaldehyde, promote the addition of (71) to electrophilic ketones. 

PhenyUhlo)nitromethane is a convenient reagent for the synthesis of derivatives of 3-methylfuranfor the preparation of a-substituted phenylthio esters via the homologation of aldehydes, and for the preparation of bicyclic... 

Terminal alkenylstannanes can be prepared after homologation of aldehydes via the Corey-Fuchs reaction.95... 

Dienones.5 The cleavage by n-BuLi of an Se—C bond with generation of a furfuryllithium has been used for homologation of aldehydes to 2,4-dienones (equation I). 

A general method for the homologation of aldehydes to benzylic ketones makes use of the Bamford-Stevens approach, via intermediate aryldiazomethanes ... 

Diethyl N-benzylideneaminomethylphosphonate (5) has been previously employed as an intermediate in the synthesis of B-lactam antibiotics6 and as a reagent for the homologation of aldehydes and ketones via intermediate 2-azadienesJ Other derivatives of dialkyl am1nom thylphoxphon t. s hav alio... 

Hoppe, D. Follmann, R. Homologization of aldehydes and ketones to fhiiranes or S-vinyl thiocarbamates via 2-alkylimino-l,3-oxafhio-lanes. Angew. Chem. Int. Ed. 1977, 36, 462-463. 

A mild oxidative one-carbon homologation of aldehyde to amide has been reported.326... 

We have developed a straightforward strategy for the synthesis of an important class of lepidopteran sex pheromones starting from simple dialdehydes. The combination of a Wittig reaction and an organocatalytic reduction represents a useful sequence for the nontrivial two-carbon homologation of aldehydes. 

Homologation of aldehydes or ketones. These reagents react with aldehydes or ketones to form homologated ketones. 

Homologation of aldehydes, ketones, acyl chlondes, two caitwn homologation via 2-(tnmethylsilyl)thiazole... 

It was pointed out that the ylide 20 can be regarded as a j5-formylvinyl anion equivalent 21 it reacts with aldehydes to give oxiranes, which can readily be converted under mild conditions into 4-hydroxy-2-( )-enals (equation 7). A vinylogue of 20 has been converted in the same way into a 6-hydroxy-2, 4-( , F)-dienal this reaction enables a five carbon atom homologation of aldehydes to be achieved. ... 

Corey-Fuchs alkyne synthesis One-carbon homologation of aldehydes to form the corresponding terminal alkynes. 104... 

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