Amines with aldehydes

Aliphatic ketones react more slowly than aldehydes with amines to form imines (see Table VII). Higher reaction temperatures, longer reaction times, and the removal of water aid in giving high yields of imines (80-95 %). Steric-ally hindered ketones react slowly. Methyl ketones require mild acid catalyst and are more prone to aldol condensation by-products than are methylene ketones [3]. 

The addition of nucleophiles to the carbonyl group may be catalysed by acids obtained by the protonation of the carbonyl oxygen (equilibrium 26). Acid catalysis can also occur during the elimination step which follows the addition step. For example, the reactions of aldehydes with amines (and of all the ammonia derivatives) to form imines are generally assumed to occur in two steps the first is the addition of nucleophile to yield a gem amino alcohol, the second includes the elimination of water from the tetrahedral adduct 138 (see Scheme 45). This elimination is usually thought to be catalysed by electrophiles171,212. 

Fig i Reactions of a NHS ester, b isothiocyanate and c aldehyde with amines, and d iodoacetamide and e maleimide with sulfhydryls... 

To prove that all side arms of the dendrimer were reduced to the amine by our DIBAH reduction method and to demonstrate the possibility of synthesizing new, functionalized (in this case complexing, Section IV.B) dendrimers, we attempted a Schiff base formation.15 On account of the stability of salicyl imines and their cation-complexing abilities, we chose to react salicylic aldehyde with amine 47. 

Anionic bridged bis(amidinate) lithium lanthanide complexes have been found to be efficient catalysts for the amidahon of aldehydes with amines under mild conditions (Scheme 56). The achvity was found to follow the order of yttrium < neodymium < europium ytterbium. The catalysts are available for the formahon of benzamides derived from pyrrolidine, piperidine, and morpholine with good to excellent yields. In comparison with the corresponding neutral complexes, the anionic complexes showed higher achvity and a wider range of scope for the amines. A cooperation of the lanthanide and lithium metals in this process was proposed to contribute to the high activity of these catalysts [66,67]. 

Schiff Bases and Oximes Schiff bases and oximes formed from ketones or aldehydes with amines or hydroxyl amines are chemically reversible under acidic or basic conditions. They could be used as prodrugs of compounds containing either an amine or carbonyl functionality. 

Scheme 6.5 Strecker-type condensation of aldehydes with amines and TMSCN...

Oxidative amidation of aromatic aldehydes with amines. 

Mannich condensation reaction can occur between nitroalkanes and aldehydes with amines, r-nitroalkane does not have a-hydrogen atoms and can not have the Mannich condensation reaction. 

Urea-Formaldehyde and Related Adhesives. Urea-formaldehydes (UF) are the most significant members of the class of materials known as the Amino Resins or aminopolymers. These are the polymeric condensation products of the reaction of aldehydes with amines or amides. A molar excess of formaldehyde is used, and this along with the temperature and the pH dictate the properties of the final product. The initial reactions of urea and formaldehyde to form mono- and dimethylolureas can be catalyzed by either acids or bases, but the final condensation reactions will proceed only under acid conditions. These adhesives are widely used to make plywood and particleboard in processes utilizing heated hydraulic presses with multiple outlets for water vapor release. Temperatures up to 200°C... 

Organolanthanide complexes are known to be highly active catalysts for a variety of organic transformations, which can be either intramolecular or intermolecular in character. Successful intramolecular transformations include hydroelementation processes, which is the addition of a H-E (E = N, O, P, Si, S, H) bond across unsaturated C-C bonds, such as hydroamination, hydroalkoxylation, and hydrophosphination. Intermolecular transformations include a series of asymmetric syntheses, the amidation of aldehydes with amines, Tishchenko reaction, addition of amines to nitriles, aUcyne dimerization, and guanylation of terminal aUcynes, amines, and phosphines with carbodiimides. 

The amide group is an essential motif in biological systems as well as in important molecules in the areas of polymers, natural products, and pharmaceuticals. Direct amidation of aldehydes with amines is the most desired approach to amides because of economics and the availability of starting materials. Various efficient catalysts have been... 

Scheme 8 Several efficient catalysts for amidation of aldehydes with amines...

Lanthanide amides Ln[N(SiMe3)2]3()tt-Cl)Li(THF)3 or Ln[N(SiMe3)2]3 have been reported to be efficient catalysts for amidation of aldehydes with amines under mild conditions without the use of peroxide and base. But this kind of catalyst is not suitable for the amidation of aldehydes with secondary cycUc amines. Heterobimetallic lanthanide/alkali metal complexes stabilized by phenolate ligand are new classes of bimetallic catalysts for amidation of... 

The proposed mechanism for organolanthanide amido-mediated amidation of aldehydes with amines is shown in Scheme 9. The addition of Ln-N bond to a carbonyl group gave the intermediate, an organolanthanide alkoxide, which... 

Elimination reactions following a hydroformylation step are quite common. In particular, in sequential reactions the condensation of aldehydes with amines plays a crucial role for the production of imines (see Section 5.4). Here only those reactions will be considered in which, immediately after the hydroformylation reaction, parts of the newly formed aldehyde are split off. 

Peng L, Zhang X, Ma J et al (2007) 1,2-Sulfanyl group migration as a driving force new approach to p5uroles by reaction of allenic aldehydes with amines. Org Lett 9 1445-1448... 

Muthaiah S, Ghosh SC, Jee JE, Chen C, Zhang J, Hong SH (2010) Direct amides synthesis from either alcohols or aldehydes with amines activity of Ru(II) hydride and Ru(0) complexes. J Org Chem 75 3002... 

Kegnaes S, Mielby J, Mentzel UV, Jensen T, Fristrup P, Riisager A (2012) One-pot synthesis of amides by aerobic oxidative coupling of alcohols or aldehydes with amines using supported gold and base as catalysts. Chem Commun 48(18) 2427-2429... 

Fu R, Yang Y, Zhang J, Shao J, Xia X, Ma Y, Yuan R (2016) Direct oxidative amidation of aldehydes with amines catalyzed by heteropolyanion-based ionic liquids under solvent-free conditions via a dual-catalysis process. Org Biomol Chem 14(5) 1784—1793... 

Saberi D, Heydari A (2014) Oxidative amidation of aromatic aldehydes with amine hydrochloride salts catalyzed by silica-coated magnetic carbon nanotubes (MagCNTs Si02)-immobilized imine—Cu(I). Appl Oiganomet Chem 28(2) 101-108... 

Ghosh SC, Ngiam JSY, Seayad AM, Tuan DT, Chai CLL, Chen A (2012) Copper-catalyzed oxidative amidation of aldehydes with amine salts synthesis of primary, secondary, and tertiary amides. J Org Chem 77(18) 8007-8015... 

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