Schiff bases reactions

Reactions with Amines and Amides. Hydroxybenzaldehydes undergo the normal reactions with aUphatic and aromatic primary amines to form imines and Schiff bases reaction with hydroxylamine gives an oxime, reaction with hydrazines gives hydrazones, and reactions with semicarbazide give semicarbazones. The reaction of 4-hydroxybenzaldehyde with hydroxylamine hydrochloride is a convenient method for the preparation of 4-cyanophenol (52,53). 

Formation of Schiff-Bases. Reaction of an amino acid and an aldehyde oi ketone gives a Schiff-base in neutral or alkaline solution, and following reduction gives the corresponding Ai-alkylamino acid. 

The NMR spectra have shown the formation of Schiff base as an intermediate product in the synthesis of the fully N-deacetylated oligomers from chitosan.32 The mechanism of the Schiff base reaction leading to chain cleavage and formation of 5-hydroxymethyl-2-furfural has been proposed. 

Figure 15.1 Reactions of formaldehyde with peptides and amino acids. Shown are the four types of reaction products seen when peptides or amino acids are treated with formaldehyde in aqueous solution. These reaction products are methylol (hydroxymethyl) adduct (reaction 15.1), Schiff-base (reaction 15.2), 4-imidazolidinone adduct (reaction 15.3), and one type of methylene bridge [cross-link] (reaction 15.4).

Pyrrolidine alkaloids have a pyrrolidine (C4N skeleton) nucleus. The structural a of these alkaloids is L-ornithine (in plants) and L-arginine (in animals). The pyrro-line skeleton is synthesized after /3 (putrescine) and

pyrroline alkaloids are (-)- and (-1-)- hygrines (Figure 56). 

J. Zhu, B.A. Price, J. Walker, S.X. Zhao, Catalytic hydrogenation of ethyl 2-amino-2-difluoromethyl-4-cyanobutanoate and its Schiff base reaction modes. Tetrahedron Lett. 46 (2005) 2795-2797. 

The enzymes commonly used as labels in ELISA and other immunochemical reactions include horse radish peroxidase (HRP) and alkaline phosphatase (AP). The enzyme can be covalently coupled to the antibody using glutaraldehyde conjugation to reactive amino groups on the enzyme (lysines) in a phosphate buffered aqueous solution at neutral pH, as shown in Fig. 19 (103). Alternatively, carbohydrates present in the immunoglobulin structure can be cleaved by periodate treatment (see Fig. 20) and bound to free amino groups on the enzyme through a Schiff base reaction (103). 

Piperidine that is typically used for this purpose has a double function. As a nucleophile, it releases the damaged base (denoted as HNR2) and assists in the acidification of the H2 by forming a positively charged Schiff base [reaction (8)]. 

Scheme 3.22 Schiff base reactions (a) 1 1 cyclocondensation templated by small metal ions (b) larger macrocycles are obtained with larger templates.

The sulfhydryl proposal did not gain support and has disappeared from the literature. More recent investigations have generally assumed the association is by way of a Schiff Base reaction. 

Keywords Cage compounds Coordination Encapsulation SCHIFF base reaction Supramolecular chemistry... 

Chunhua Yan and coworkers designed metal-tuneable M4L6 tetrahedra. For the synthesis of these cages the group uses two different Cj-symmetric facial ligands. Both could be synthesised via a Schiff base reaction. The first is made by the... 

The imine mechanism for both acetoacetate decarboxylase132 and class I aldolases131 is also supported by the finding that the substrates that have lsO in their keto groups that undergo the putative Schiff base reaction lose this oxygen to solvent and introduce 160 from solvent water at the corresponding positions in the products. 

Compartmental ligands (16) are derived from diketonates and triketonates and are usually synthesized from Schiff base reactions of the ketone with a diamine. ... 

A second mechanism, the possible interaction of aldehydes with amino acids or peptides forming Schiff base reaction products, was also studied. Initial results (Hansen, A. P. Heinis J. J., North Carolina State University, Raleigh, unpublished data) showed a decrease in the aldehyde concentration when model systems containing various aldehydes and amino acids were heat processed. Losses ranging from 8 to 50% of various aldehydes have been observed in the pasteurization of aldehydes and amino acids mixtures in simulated milk ultrafiltrate. 

Polystyrenes have also been used to support chromophores useful in organic light-emitting diodes (OLEDs). Week and coworkers have attached tris(2-phenylpyridine) iridium complexes to aminomethylated polystyrene using a Schiff base reaction, 4 [21]. There was no major diminution of the desirable luminescence properties of the iridium complexes (high emission quantum yields of 0.23 and lifetimes of about a microsecond). Similar results have been reported for aluminum and boron 8-hydroxy quinoline complexes tethered to polystyrene using Schiff base condensation [22]. 

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