Oxime/hydrazone formation

Staudinger-based ligation techniques, oxime/hydrazone formation, or strain-promoted azide-allq ne cycloaddition reactions/ To be able to specifically address a particular protein target, or other moieties, these reactions use chemical groups that are not typically found in natural systems. 

The formation of oximes, hydrazones, and related imine derivatives is usually catalyzed by both general acids and general bases. General base catalysis of dehydration of the tetrahedral intermediate involves nitrogen deprotonation concerted with elimination of hydroxide ion. ... 

Schiff bases are obtained from 2-aminoimidazothiadiazoles with aldehydes (77M665). Hydrazones and oxime ether formation of imidazothia-diazole-5-carbaldehydes and -5-ketoesters was reported (84FES585 95EUP662477). Reduction of 122 with Al/FIg yields the tautomeric imine 128 of the corresponding amine (83JHC1003). 

The reaction is reversible, and the formation of all imines (Schiff s base, oxime, hydrazone and semicarbazide) follows the same mechanism. In aqueous acidic solution, imines are hydrolysed back to the parent aldehydes or ketones, and amines. 

Ligation Conditions of Peptide Dendrimer Formation through Oxime, Hydrazone, and Thiazolidine Ligations To Form 64, 66, or 70 [85 ... 

There are many examples of acid catalyzed carbonyl addition reactions, such as formation of hydrates (R2C(OH)2), hemiacetals, hemiketals, cyanohydrins, bisulfite compounds, azomethines, oximes, hydrazones, etc. These important reactions are discussed in Vol. 11. 

The relative rates of oxime and hydrazone formation parallel those... 

These derivatives are called oximes, hydrazones, phenylhydrazones, and 2,4-dinitro-phenylhydrazones, respectively. The mechanisms by which these C = N derivatives form are similar to the mechanism for imine formation from a primary amine. As with imines, the formation of ( ) and (Z) isomers is possible. 

The addition of nucleophilic reagents to the carbonyl group is of very common occurrence in organic chemistry. In many instances it is followed by loss of water, for example in the formation of oximes, hydrazones, and semicarbazones, frequently leading to rather complex kinetics. Similarly, if the carbon atom of the carbonyl group bears a group which can be readily lost, the formation of a tetrahedral intermediate often represents an intermediate stage in a replacement reaction of the type... 

Base-catalyzed dehydration has been observed in semicarbazone , oxime and hydrazone formation at pH values of 9 or... 

The formation of imines, oximes, hydrazones, and related derivatives from carbonyl compounds is reversible. Write a detailed mechanism for the acid-catalyzed hydrolysis of eyclohexanone semicarbazone to cyclohexanone and semicarbazide. 

Immobilization Through Formation of Oximes, Hydrazones, and Thiazolidines... 

---