Of N-imines

Since then, the thermolysis or photolysis of azides in the presence of pyridines has been developed into a widely applicable synthesis of N-imines, albeit in most cases in small yields (5-30%). Numerous sulfonyl... 

Benzophenone Process. Benzophenone, (CgH5 )2C=0, reacts with ammonia to form diphenylmethanimine, (CgHg )2C=NH. In the presence of copper catalysts, this is oxidized with oxygen to benzophenone azine, (CgHg )2C=N—N=C(CgHg The formation of the imine and its... 

When additional substituents ate bonded to other ahcycHc carbons, geometric isomers result. Table 2 fists primary (1°), secondary (2°), and tertiary (3°) amine derivatives of cyclohexane and includes CAS Registry Numbers for cis and trans isomers of the 2-, 3-, and 4-methylcyclohexylamines in addition to identification of the isomer mixtures usually sold commercially. For the 1,2- and 1,3-isomers, the racemic mixture of optical isomers is specified ultimate identification by CAS Registry Number is fisted for the (+) and (—) enantiomers of /n t-2-methylcyclohexylamine. The 1,4-isomer has a plane of symmetry and hence no chiral centers and no stereoisomers. The methylcyclohexylamine geometric isomers have different physical properties and are interconvertible by dehydrogenation—hydrogenation through the imine. 

IR spectra of 2-substituted 1-azetines show the expected trends in the frequency of the imine absorption thus 2-aryl-l-azetines generally show vq=n at ca. 1550-1580 cm while 2-ethylthio and 2-alkoxy-1-azetines show absorptions at ca. 1535 and 1620 cm respectively (79CB3914, 67JHC619, 69LA(725)124). The parent 1-azetine shows vc=n at 1570 cm ... 

The hydrolysis of simple imines occurs readily in aqueous acid and has been studied in great detail by kinetic methods. The precise mechanism is a fimction of the reactant structure and the pH of the solution. The overall mechanism consists of an addition of water to the C=N bond, followed by expulsion of the amine from a tetrahedral intermediate. ... 

One of the biological pathways by which an amine is converted to a ketone involves two steps (1) oxidation of the amine by N.AD+ to give an imine, and (2) hydrolysis of the imine to give a ketone plus ammonia. Glutamate, for instance, is converted by this process into a-ketoglutarate. Show the structure of the imine intermediate, and propose mechanisms for both steps. 

Reductive amination takes place by the pathway shown in Figure 24.4. An imine intermediate is first formed by a nucleophilic addition reaction (Section 19.8), and the C=N bond of the imine is then reduced. 

The mechanism of the first part of transamination is shown in Figure 29.14. The process begins with reaction between the a-amino acid and pyridoxal phosphate, which is covalently bonded to the aminotransferase by an iminc linkage between the side-chain -NTI2 group of a lysine residue and the PLP aldehyde group. Deprotonation/reprotonation of the PLP-amino acid imine in steps 2 and 3 effects tautomerization of the imine C=N bond, and hydrolysis of the tautomerized imine in step 4 gives an -keto acid plus pyridoxamine... 

Q An amino acid reacts with the enzyme-bound PLP inline by nucleophilic addition of its -NH2 group to the C=N bond of the imine, giving a PLP-amino acid imine and releasing the enzyme amino group. 

The mechanism of attack of 1,3-dipolar reagents on fluoroalkenes can be considered to be either stepwise or concerted. Heteroaromatic N-imines react by a stepwise 1,3 addition to perfluoroalkenes and -alkynes to give fluorinated pyrazolo[l,5-a]pyridines [82JCS(P1)1593]. Pyridinium /-butoxycarbonylmethylide with fluoroalkenes gave pyrrolo[l,2-a]pyri-dines [86JCS(P 1) 1769] and indolizines (22) are obtained with pyridinium phenacylide [91JFC(51)407]. 

Davis has also employed a similar procedure for the synthesis of aziridine-2-phosphonoates, involving the addition of N-(2,4,6-trimethylphenylsulfinyl)imine to anions of diethyl a-halomethyl phosphonates (Scheme 1.29) [53, 54], Aziridines... 

Reductive Dimerization2 5,6 can be competitive with the addition of Grignard reagents to the C —N double bond of nonenolizable imines, especially with increasing size and branching of the carbanion,... 

After recrystallization from hexane, the major diastereomer is obtained in a 71 % yield. Although interpretation of the steric course of the reaction is difficult25, the preferred formation of the (6S )-diastereomer may be rationalized in terms of an imine conformation which is favored according to the Felkin-Anh model (vicinal C-O orthogonal to C = N)26 and by chelation21. 

The diastereofacial selectivity of this asymmetric [3C+2S] process is explained following a model similar to that described in Sect. 2.6.4.4 for the reaction of chiral alkenylcarbene complexes and 1,3-dienes. Thus, the proposed mechanism that explains the stereochemistry observed assumes a [4+2] cycloaddition reaction between the chromadiene system and the C=N double bond of the imine. The necessary s-cis conformation of the complex makes the imine... 

In the presence of N,N,N, N",N"-pentamethyldiethylenetriamine ( = PMDETA), monomeric lithium complexes of bulky formamidinate ligands can be isolated. The compounds (Scheme 12) comprise a Li(PMDETA) center coordinated by a bulky formamidinate in either the E-syn- or E-anti-isomeric form. Two of the structures display coordination of the pendant amidinate imine, and can therefore be considered the first examples of if. r -C = N,N metal amidinate coordination. ... 

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