And Mannich bases

Trimerization to isocyanurates (Scheme 4.14) is commonly used as a method for modifying the physical properties of both raw materials and polymeric products. For example, trimerization of aliphatic isocyanates is used to increase monomer functionality and reduce volatility (Section 4.2.2). This is especially important in raw materials for coatings applications where higher functionality is needed for crosslinking and decreased volatility is essential to reduce VOCs. Another application is rigid isocyanurate foams for insulation and structural support (Section 4.1.1) where trimerization is utilized to increase thermal stability and reduce combustibility and smoke formation. Effective trimer catalysts include potassium salts of carboxylic acids and quaternary ammonium salts for aliphatic isocyanates and Mannich bases for aromatic isocyanates. 

The literally thousands of examples involving the addition of stabilized nucleophiles to activated alkenes and alkynes have spawned many reviews over the years. The Michael reaction has been discussed in detail several times7 and reviews on other related topics, such as annulation8 and Mannich base meth-iodides,9 have also appeared, as have several reviews on nucleophilic additions to activated alkynes.10... 

Baldwin, J. M. and Robins, J., Epoxy Adhesive Composition Comprising a Calcium Salt and Mannich Base, U.S. Patent No. 5,629,380, 1997. 

Shalaby. A. F. A.. Daboun, H. A., and Aziz, M. A. A.. Reactions with 2-thiohydantoin synthesis of imidazothiazolone derivatives and Mannich bases of 5-arylidenc-2-thiohy-dantoin, Z. Numrforsch. Teil B, 3IB, 111,... 

Phenolic Mannich bases 526 and Mannich bases derived from hydrogen cyanide, precursors of a-amino acids 527 such as EDTA and similar derivatives,- - are largely used. The P-Mannich bases 528 may be also inserted into polymeric structures. - Structures represented by y-piperidone 529 and Mannich bases derived from phosphine (530) enable us to point out the wide possibility of synthesizing products having the chelating groups most suitably located for the best performance. 

To show the difference between the case of H-bonding with the chelate chain enabling ir-electron delocalization and without this possibility, let us discuss similarities and differences in the distant structural consequences of H-bonding in ortho-hydroxy Schiff and Mannich bases (Scheme 1). 

Scheme 1. Structural Schems of Schiff and Mannich bases.

The first observation is well shown in Fig. 2, where the energy of system is plotted against the elongation of the O-H bond for ortho-hydroxy Schiff and Mannich bases [19]. 

The amino group of Mannich bases can also be exchanged against sulfonamides,1128 hydroxylamines,1129 or phenylhydrazine.1130 Interaction of hydrazines and Mannich bases from ketones gives first the hydrazones and then pyrazolines by amine exchange involving cyclization 1131... 

Orio M, Jarjayes O, Philouze C et al (2010) Spin interaction in octahedral zinc complexes of mono- and diradical Schiff and Mannich bases. Inorg Chem 49 646-658... 

Tilak and co-workers have continued their investigations on the synthesis of 2-ethoxycarbonyl-3-hydroxythiophanes, through the base-catalysed condensation of methyl vinyl ketone, chalcones, ethyl 2-benzoyl-acrylate, and Mannich bases with ethyl thioglycollate. Dehydration of the thiophanes with polyphosphoric add followed by dehydrogenation using chloranil or diphenyl disulphide affords thiophens. 

Polymer (63) was produced in an 81% yield. This new condensation polymerization represents the first example of polymerization using the Stetter reaction. Since a variety of aromatic aldehydes and Mannich bases undergo the Stetter reaction, this procedure is useful for the preparation of new polymers. Ring closure of the polymer (63) by Lawesson s reagent gave the polymer (64), which showed a conductivity of 10 Scm after doping with AsFs. 

As shown, both alkyl halides and Mannich base quaternary salts have been used as alkylating reagents. With j -nitrobenzaldehyde and ammonium acetate in acetic acid a Mannich reaction occurs, the intermediate (37) so produced reacting further to give a pyrimidine ... 

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