Amines aldehyde with primary

Aldehydes undergo condensation with primary amines with the elimination of water to give compounds known as SchifF s Bases, which can also be used to characterise aldehydes. Benzaldehyde for example condenses readily with... 

A number of compounds of the general type H2NZ react with aldehydes and ketones m a manner analogous to that of primary amines The carbonyl group (C=0) IS converted to C=NZ and a molecule of water is formed Table 17 4 presents exam pies of some of these reactions The mechanism by which each proceeds is similar to the nucleophilic addition-elimination mechanism described for the reaction of primary amines with aldehydes and ketones... 

Reaction of primary amines with aldehydes and ketones (Section... 

Reaction of primary amines with aldehydes and ketones (Section 17.10) Imines are formed by nucleophilic addition of a primary amine to the carbonyl group of an aldehyde or a ketone. The key step is formation of a carbinolamine intermediate, which then dehydrates to the imine. 

Preparation of the key tropine is achieved by any one of several variations on the method first developed by Robinson, which involves reaction of a primary amine with dihydroxyacetone and glyoxal. Reduction of the carbonyl group in the product (86) followed by acylation affords the aminoester (88). Transesterification with ester aldehyde 89... 

A method for the synthesis of long-chain aminophosphinic acids having surface-active and antibacterial activity followed the procedure developed by Schmidt [182]. It is based on the condensation of the hypophosphite salt of a primary amine with an aldehyde or ketone [183], as shown in Eq. (108) ... 

The nitrogen analogs of ketones and aldehydes are called imines, azomethines, or Schiff bases, but imine is the preferred name and we use it here. These compounds can be prepared by condensation of primary amines with ketones or aldehydes.102 The equilibrium constants are unfavorable, so the reaction is usually driven forward by removal of water. 

Reductive amination of an aldehyde with excess primary amine, using a support-bound borohy-dride, provides the desired secondary amine contaminated with the primary amine precursor. Covalent capture of the primary amine with a support-bound aldehyde provides the pure secondary amine. Treatment with excess isocyanate yields the final urea product, which is purified by reaction with a support-bound amine to remove unreacted isocyanate. For the full potential of this method to be realized, further development of support-bound reagents and scavengers for most of the important chemical transformations will be necessary. Al-... 

The three-component reaction of sodium ethyl oxalacetate with ammonia or primary amines with an aromatic aldehyde in ethanol or acetic acid results in the... 

Ir and nmr analysis of the condensation products of primary amines with aldehydes and ketones are in favor of the Schiff-base structure (46a). Nevertheless, these substances react with aryl azides in chloroform solution in the tautomeric enamine form (46b) yielding aminotriaiolines.206 225- 227 It proves that the dipolarophilic activity of an enamine olefin bond is much greater than that of an azomethine bond. 

The reaction of furans with ammonia and its derivatives is of considerable synthetic utility (B-73MI31 too). Substituted furan-2-carbaldehydes and 2-acylfurans on heating with ammonia and ammonium salts, often under pressure, yield 3-hydroxypyridines. The mechanism of this reaction is thought to involve nucleophilic attack of ammonia at the 2-position. Ring opening affords an amino aldehyde or ketone and thence, by reclosure, the 3-hydroxy-pyridine (Scheme 29). A wide range of substitutents is tolerated. Primary amines with furan-2-carbaldehydes yield A-substituted pyrroles, the closure of the intermediate... 

The condensation of primary amines with aldehydes and ketones gives products known as imines which contain a C=N double bond. These compounds rapidly decompose or polymerize unless there is at least an aryl group bonded to the nitrogen or to the carbon atom. The latter imines are called Schiff bases, since their synthesis was first reported by Schiff.1 The most common method of obtaining a Schiff base (4) is straightforward, as indicated in the condensation reaction (1) between (1) and (2) with the formation of an intermediate hemiaminal (3). 

Melt poly condensation is also the most popular method for other thermotropic condensation polymers, including the polyazomethines where the reaction between aromatic aldehydes or ketones and primary amines with elimination of water leads to azomethine (Schiffs base) formation 48). 

Alcohols can be oxidized with TPAP in the presence of tertiary amines.88 Secondary amines are transformed into imines under the action of TPAP.89 At the time of writing, the scientific literature contains no data regarding the possibility of performing selective oxidation of alcohols in the presence of secondary or primary amines, with the exception of the following example in which a secondary amine is trapped by reaction with an aldehyde, resulting from the selective oxidation of a primary alcohol.90... 

Imines (e.g. R CH2-CH=N R or R-CH2-C(R)=N-R) are derived from the reaction of primary amines with aldehydes or ketones respectively, and may exist in tautomeric equilibrium with the corresponding enamine form, but in which the imine form predominates. 

Imines are formed by the reaction of a primary amine with aldehydes or ketones with the simultaneous removal of water, for example by azeotropic distillation,213 by the addition of anhydrous sodium sulphate,214 by the addition of molecular sieves,215 or by the use of titanium(iv) chloride.216 When one, or both, of the reactants is aromatic, the imine is quite stable and usually known as a Schiff base (see Section 6.5.5, p. 902). In the case of wholly aliphatic reactants the imines tend to decompose or polymerise in these cases their further reaction is carried out without delay. 

Imines. Imines are usually prepared by acid-catalyzed condensation of aldehydes or ketones with primary amines with azeotropic removal of water. This method gives poor yields with low-boiling imines.2 A new method involves dehydrocyanation of a-cyanoamines with DCC and Dabco as catalyst (equation I).3... 

It has been well established that metal-directed condensation between metal-coordinated primary amines with aldehydes and dibasic acids such as nitroalkanes or primary amines provide a ready route to selected pendant arm maciocyclic ligands and their metal complexes [20], In such a reaction a new six-membered chelate ring is... 

N-Heterocyclics. The reaction of primary amines with the carbonyl products derived from lipid oxidation is a major pathway in lipid-protein interactions. Formation of Schiff s base intermediates followed by cyclization and rearrangement can yield imines, pyridines and pyrroles (5,15,30,31). For example, 2-pentylpyridine may result from the reaction of ammonia with 2,4-decadienal, one of the principle aldehydes from the autoxidation of linoleate (5). 

The formation of a Schiff base through condensation of a primary amine with an aldehyde or ketone has recently found application in the construction of... 

The reaction of primary amines with aldehydes and ketones do not give the products expected from nucleophilic addition alone. This is because of the further reaction taking place once nucleophilic addition occurs, e.g. consider the reaction of acetaldehyde (ethanal) with a primary amine methylamine (Following fig.). The product contains the methylamine skeleton, but there is no alcohol group and there is a double bond between the carbon and the nitrogen. This product is known as imine or a Scbiffbase. 

Alcohols and aldehydes are also suitable materials for the creation of an alkyl amine. In addition to the aforementioned formation of alkyl chloride as an intermediate, alcohols can be directly converted to amines under hydrogenation conditions in the presence of ammonia while aldehydes are prereacted to form imine followed by hydrogenation [13]. Selectivity of the primary amine with these techniques is difficult and this process is more typically utilized for the preparation of tertiary amines where the reaction can be driven to completion. In certain cases, alcohols and aldehydes provide structural elements which are not attainable from natural sources. An example is the formation of a hydrogenated tallow 2-ethyl hexyl amine. The amine is prepared as shown below in eqn 6.1.8 using a hydrogenated tallow amine reacted with 2-ethyl hexanal [14, 15] ... 

Winans (95) has studied the hydrogenation of aldehydes in the presence of Raney nickel in alcoholic ammonia solution. Aldehydes with no hydrogen on the a-carbons were used, and the amounts of ammonia were varied. When a 1 1 ratio of equivalents of ammonia to aldehyde was used, the main product was the primary amine. With a 1 2 ratio, a high yield of the secondary amine was obtained. In the former case o-chlorobenzaldehyde gave an 85% yield of the primary amine and a 7.6% yield of the secondary amine. In the latter case there was obtained a 3.6% yield of the primary and an 84.6% yield of the secondary amine. 

Secondary Amines Condensation of a primary amine with a ketone or aldehyde forms an /V-suhsti tuted imine (a Schiff base). Reduction of the imine, using either LiAlH4 or NaBH4, gives a secondary amine. 

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