Amines ketimines

A number of studies have been directed specifically at the acridine nucleus. The effect of substituents in the 9-position in acridine (V-oxides on Rf values for thin-layer chromatography (TLC) is measured by ap,198 and there is also a relation between this parameter and the N—O stretching frequencies. The effect of substituents on the basicity of acridine and the possibility of amine-ketimine tautomerism in 9-aminoacridines have been evaluated, taking quinoline as a model... 

The cyclization of the amine-ketimine, F3CN=CFNH2, with COF occurs through the amine groups, according to Equation (13.23) [1131],... 

Methyl isobutyl ketone has become increasingly important as a chemical feedstock. The oxime is used as an antiskinning agent in oxidatively drying paints, and the peroxide is used to cure unsaturated polyester resins. Methyl isobutyl ketone is an intermediate in the preparation of imidazolones and acetal esters. It is also used to block amines (ketimines) that act as moisture-initiated latent epoxy resin hardeners. Finally, alkaline autocondensation at elevated temperature yields higher molecular mass products that are employed as fragrances and perfumes. 

The acid-catalyzed reaction of acetophenone with acyclic secondary amines results in the formation of the expected enamine and a rearrangement product. The latter product arises from the transfer of one of the amino N-alkyl groups to the cnamine s carbon to produce a ketimine (53a). 

Recent efforts in the development of efficient routes to highly substituted yS-ami-no acids based on asymmetric Mannich reactions with enantiopure sulfmyl imine are worthy of mention. Following the pioneering work of Davis on p-tolu-enesulfmyl imines [116], Ellman and coworkers have recently developed a new and efficient approach to enantiomerically pure N-tert-butanesulfmyl imines and have reported their use as versatile intermediates for the asymmetric synthesis of amines [91]. Addition of titanium enolates to tert-butane sulfmyl aldimines and ketimines 31 proceeds in high yields and diastereoselectivities, thus providing general access to yS -amino acids 32 (Scheme 2.5)... 

Rather than preforming the a-amino ketimines to be reduced, it is often advantageous to form in situ the more reactive iminium ions from a-aminoketones and primary amines or ammonium salts in the presence of the reducing agent, e.g., sodium cyanoborohydride. Use of this procedure (reductive amination) with the enantiopure a-aminoketone 214 and benzylamine allowed the preparation of the syn diamines 215 with high yields and (almost) complete diastereoselectivities [100] (Scheme 32). Then, the primary diamines 216 were obtained by routine N-debenzylation. Similarly, the diamine 217 was prepared using ammonium acetate. In... 

C. Reactions not involving P=0 or P=S Groups.—Enamine phosphine oxides (45) have been prepared by the addition of amines to 1-alkynyl-phosphine oxides, and the reactions of their anions with various electrophiles have been reported. - With ketones a Wittig-type reaction leads to the formation of a/3-unsaturated ketones, in 53—70% yield, while with epoxides cyclopropyl ketimines are formed. A Diels-Alder reaction of l-phenyl-A -phospholen-l-oxide (46) with 1,4-diacetoxybutadiene has been used in the preparation of l-phenyl-benzo[/>]phosphole (47), as... 

In 1994, the scope of this p-hydroxy sulfoximine ligand was extended to the borane reduction of ketimine derivatives by these workers. The corresponding chiral amines were formed with enantioselectivities of up to 72% ee, as shown in Scheme 10.57. It was found that the A -substituent of the ketimine had a major influence on the asymmetric induction, with a ketoxime thioether (SPh) being the most successful substrate. 

FAB-MS has been used for the analysis of lubricant additives, thermally labile or involatile organic compounds, such as macromolecules and dyes, and inorganic compounds. Cationic dyes and dye intermediates, which are typically acid salts, readily yield preformed ions in the FAB matrix solution. They are also very difficult to address by other MS ionisation methods due to their involatility. Lay and Chang [85] used positive ion FAB to characterise a mixture of amine and ketimine cross-linking agents for polymer coatings. Bentz et al. 

Scheme 6.148 Ketimines from ketones and primary amines.

Kinetic studies were carried out by Backvall and coworkers at -54 °C on the hydrogenation of a ketimine, which produces a ruthenium complex with a bound amine (Eq. (46)) [77]. 

Examination of a series of imines of differing electronic properties showed that a change in the rate-determining step of this stoichiometric C=N hydrogenation occurs as the imine becomes more electron-rich. Hydrogenation of N-iso-propyl-(4-methyl)benzilidene amine led to an amine complex of ruthenium. In addition, the C=N hydrogenation was accompanied by isomerization of the imine to a ketimine (Eq. (47)). 

Addition of RMgBr to nitriles. Grignard reagents react with nitriles slowly if at all, but even r-butylmagnesium chloride will add to nitriles in refluxing THF when catalyzed by a copper(I) salt. The adduct can be converted to a ketimine by anhydrous protonation, to a primary amine by reduction (Li/NH,), or to a ketone by hydrolysis. The actual reagent may be a cuprate such as R3Cu(MgX)2. 

Additives may exert not only a physical but also a chemical influence on the coupling suspension long-chain aliphatic or cycloaliphatic amines RNH2, which react partially with the pigment molecules, will enhace the effect of other additives. The carbonyl function of the acetyl group is converted to a ketimine (azomethine) or, in the presence of the enol form, it reacts to form an alkylammonium enolate [5],... 

More recently, an important chiral titanium catalyst for the asymmetric reduction with hydrogen of /V-substi luted dialkyl ketimines to enantioenriched amines has been... 

Essentially, aU studies have used acetophenone-based iV-aryl ketimines as substrates or derivatives thereof. Some of the iV-aryl groups are easily deprotected to yield branched a-aryl primary amines, which can be further functionalized. 

A-Acyl AAs, when transformed into a-acylaminoketones by the Dakin-West reaction, react with arylhydrazines, arylsulfonylhydrazines, or some primary amines to give the corresponding ketimines which undergo cyclodehydration with POCI3/PCI5 or TPP (Scheme 21) (78LA1916). 

Hydrolysis of the new imine then allows formation of a ketone as part of an a-keto acid, and an amine which is the previously mentioned pyridoxamine 5 -phosphate. Since this imine is the product from an amine and a ketone, it is termed a ketimine. These reactions are reversible in nature, allowing amino acids to be converted into keto acids, and keto acids to be converted into amino acids (see Section 15.6). 

Ketimines are reduced to amines very easily by catalytic hydrogenation, by complex hydrides and by formic acid. They are intermediates in reductive amination of ketones (p. 134). An example of the reduction of a ketimine is conversion of 3-aminocarbonyl-2,3-diphenylazirine to the corresponding aziridine by sodium borohydride (yield 73%), by potassium borohydride (yield 71%) and by sodium bis (2-methoxyethoxy) aluminum hydride (yield 71%) [939]. 

Hydrazones treated with alkalis decompose to nitrogen and hydrocarbons [845, 923] Woljf-Kizhner reduction) (p. 34), and p-toluenesulfonylhydra-zones are reduced to hydrocarbons by lithium aluminum hydride [812], sodium borohydride [785] or sodium cyanoborohydride [813]. Titanium trichloride hy-drogenolyzes the nitrogen-nitrogen bond in phenylhydrazones and forms amines and ketimines which are hydrolyzed to the parent ketones. Thus 2,4-dinitrophenylhydrazone of cycloheptanone afforded cycloheptanone in 90% yield [202]. 

An enzymatic reaction intermediate formed by nucleophilic attack by an amine on a carbonyl group of an aldehyde (forming an aldimine) or a ketone (forming a ketimine), followed by elimination of water. 

However, the syn and anti isomers of imines are easily thermally equilibrated. They cannot be prepared as single stereoisomers directly from ketones and amines so this method cannot be used to control regiochemistry of deprotonation. By allowing lithiated ketimines to come to room temperature, the thermodynamic composition is established. The most stable structures are those shown below, which in each case represent the less substituted isomer. 

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