Amine-carbonyl condensation products

Enamine A product of amine-carbonyl condensation having both a carbon-carbon double bond and an amino group. 

Oxaziridines are generally formed by the action of a peracid on a combination of a carbonyl compound and an amine, either as a Schiff base (243) or a simple mixture. Yields are between 65 and 90%. Although oxygenation of Schiff bases is formally analogous to epoxidation of alkenes, the true mechanism is still under discussion. More favored than an epoxidation-type mechanism is formation of a condensation product (244), from which an acyloxy group is displaced with formation of an O—N bond. 

Condensation of ethyl anthranHates with isothiocyanates provides entry to a closely related compound in which the carbonyl at the 2 position is replaced by a thione. The sequence starts with the alkylation of pyrrolidine nitrogen in (92-1) with 2-bromoethylamine. Reaction of the primary amine in the product (92-2) with thiophosgene leads to the isothiocyanate derivative (92-3). Reaction of that reactive intermediate with methyl anthranilate (92-4) leads initially to the transient... 

Mechanistically, this novel process is apparently a Type II MCR, characterized by complex equilibria among the three components and various intermediates, which give the amine condensation products 41 via an irreversible C-C bond-forming step (Scheme 7.7). Thus, condensation between the amine 38 and carbonyl 39... 

Cyclomethine Dyes can be prepared by condensing N-heterocyclic carbonyl compounds with secondary amines. Intensely colored products such as 4 are obtained by condensing 3-phenylpyrazoline with compounds such as /V-cthyl-naphtholactam. This compound dyes polyacrylonitrile a brilliant, lightfast yellow. Orange-red dyes are obtained by condensing acridone with secondary amines [6],... 

The Strecker reaction is defined as the addition of HCN to the condensation product of a carbonyl and amine component to give a-amino nitriles. Lipton and coworkers reported the first highly effective catalytic asymmetric Strecker reaction, using synthetic peptide 43, a modification of Inoue s catalyst (38), which was determined to be inactive for the Strecker reactions of aldimines (see Scheme 6.5) [62], Catalyst 43 provided chiral a-amino nitrile products for a number of N-benzhydryl imines (42) derived from substituted aromatic (71-97% yield 64->99% ee) and aliphatic (80-81% yield <10-17% ee) aldehydes, presumably through a similar mode of activation to that for hydrocyanations of aldehydes (Table 6.14). Electron-deficient aromatic imines were not suitable substrates for this catalyst, giving products in low optical purities (<10-32% ee). The a-amino nitrile product of benzaldehyde was converted to the corresponding a-amino acid in high yield (92%) and ee (>99%) via a one-step acid hydrolysis. 

Reductive alkylation of amines proceeds by the hydrogenation of the imine or enamine formed, in situ, by the condensation of the amine with a carbonyl compound. This reaction can give a mixture of products if the amine produced initially competes with the reactant amine in the carbonyl condensation step. The proper selection of reagent concentrations avoids this difficulty and leads to the formation of good yields of the desired product. 50 jhe use of a large excess of ammonia gives the primary amine as the predominant product (Eqn. 19.50). 51 An excess of a primary amine as the reactant leads to the preferential formation of the secondary amine product. An excess of the carbonyl compound gives the symmetrical secondary or tertiary amines (Eqn. 19.51). 50... 

The characteristic feature of the Ugi reaction s is the a-addition of an iminium ion (40) and the anion X of a suitable acid HX to an isocyanide, followed by a spontaneous rearrangement of the a-adduct (41) into a stable oi-aminocarboxamide derivative (42).2n 6. 6.37 Carbonyl compounds (4) and amines (43), or their condensation products, such as the imines, en-amines and aminals, in combination with the acid HX are generally the source of the iminium ion (40) and the anion. 

Hydrolysis of a Schiff base to carbonyl compound and amine occurs analogously to that of oximes and hydrazones. It is dependent on the basicity of the amine and the reactivity of the aldehyde into which the azomethine is cleaved. Hydrolysis can be achieved in relatively mild conditions, e.g., by short warming in dilute mineral acid, occasionally in dilute alcohol or acetic acid. The condensation products of amines and aldoses are decomposed by even traces of acid Schiff bases are generally resistant to alkali. As in oximes and hydrazones, the aldehyde residue of Schiff bases can be replaced by another aldehyde residue there is a preference for formaldehyde in this case.620... 

Indole alkaloids are derived mechanistically in a manner similar to that discussed for ipecacuanha alkaloids in Chapter 32. Schiff-base formation occurs between a carbonyl compound and an amine, but in this case, the amine is tryptamine (1) (instead of 3,4-dihydroxyphenylethyl amine), and the carbonyl-containing terpenoid unit is secologanin (2). The stereochemistry of the condensation products is identical to that of the ipecacuanha alkaloid series. The initial product of the condensation of secologanin (2) and tryptamine (1) in most, if not all, plants that produce monoterpenoid indole alkaloids is strictosidine (3) (Fig. 34.1) (formerly known as isovincoside). 

The Knoevenagel reaction in its simplest form is the condensation of malonic esters (or their analogues) with aldehydes or ketones in the presence of an amine base catalyst plus a small amount of a carboxylic add (or amino add) cocatalyst. The condensation products are often a,p-unsaturated carbonyl compounds. For example. 

JV Substitution considerably increases the thermodynamic stability of imines. Thus Schiff bases, as A substituted imines are commonly called, are generally obtained as the condensation products of the reaction of primary amines with carbonyl compounds (equation 2). 

IV. Ammoniiun salts of carboxylic adds, aldehyde-ammonias, amides, imides, nitriles. Acyl derivatives of bases (JV-substituted amides). Hydrazines, semicarbazide, hydroxyl-amine, their salts and carbonyl derivatives. Condensation products of aldehydes with ammonia or amines. 

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