Imines, with carboxylic acids isocyanate

Over the last decade, a considerable number of reactions has been studied (11,35) (i) olefins oxidation (38,39), hydroboration, and halogenation (40) (ii) amines silylation (41,42), amidation (43), and imine formation (44) (iii) hydroxyl groups reaction with anhydrides (45), isocyanates (46), epichloro-hydrin and chlorosilanes (47) (iv) carboxylic acids formation of acid chlorides (48), mixed anhydrides (49) and activated esters (50) (v) carboxylic esters reduction and hydrolysis (51) (vi) aldehydes imine formation (52) (vii) epoxides reactions with amines (55), glycols (54) and carboxyl-terminated polymers (55). A list of all the major classes of reactions on SAMs plus relevant examples are discussed comprehensively elsewhere (//). The following sections will provide a more detailed look at reactions with some of the common functional SAMs, i.e hydroxyl and carboxyl terminated SAMs. 

Imines act as blocked amines because they hydrolyze to yield free amines, which react with an isocyanate. Ketimines also react directly with isocyanates to yield a variety of products, depending on the particular reactants and conditions. Aldimines react analogously with isocyanates to yield unsaturated substituted ureas. Since aldimines are more stable to hydrolysis than ketimines, the fraction undergoing direct reaction with isocyanate in the presence of water is greater than that with ketimines. Carboxylic acids react relatively slowly to form amides and CO2. Hindered carboxylic acid groups, such as in 2,2-dimethylolpropionic acid (3-hydroxy-2-(hydroxymethyl)-2-methylpropanoic acid) [4767-03-7], react very slowly. 

The synthesis of carboxylate-substituted imidazoline derivatives has previously been accomplished by the condensation of presynthesized 1,2-diamines with amides, or through the transition metal catalyzed aldol-type reaction between isocyanates and imines (4,5). We have recently communicated an alternative palladium catalyzed route to synthesize a new class of imidazoline carboxylates, utilizing acid chloride, imines and carbon monoxide as starting materials (see Table 1)... 

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