Imines aryl-substituted

Scott et al. [45] prepared diimine derivatives of 2,2 -diamino-6,6 -dimethyl-biphenyl (as structure 37 in Scheme 19) as copper chelates for the catalyzed cyclopropanation reaction. All catalysts were active in this reaction but enan-tioselectivities varied importantly according to the substitution pattern of the imine aryl group only ortho-substituted ligands (by chloride or methyl groups) led to products with measurable enantioselectivity for the model test reaction (up to 57% ee with 37). 

Bode and co-workers have used NHCs to form y-butyrolactams 34 from enals 27 and saccharin-derived cyclic sulfonylimines 32. A range of [3-alkyl and [3-aryl substituted enals, and a variety of substituted imines, are tolerated in this reaction,... 

N-alkyl- and N-aryl-substituted acyclic or cyclic imines and the subsequent cycliza-tions providing the heterocyclic target compounds [74, 79]. ... 

Though the chemical oxidation of aryl-substituted ketene imines with various oxidizing agents [153-156] generally leads to cleavage products, anodic oxida-... 

Taking advantage of the acyl silane and imine methodologies, Scheidt and co-workers illustrated the use of acyl silanes 61 and iV-diarylphosphinoylimines 62 to form a-amino ketones 63 (Eq. 4) [55], Utilizing thiazolium pre-catalyst 64, a variety of acyl silanes, both alkyl and aryl, can be coupled efficiently. The reaction conditions are tolerant of various aryl substitutions, providing high yields. 

The preparation of thiiranes is most conveniently performed in solution. However, there are also protocols reported for reaction in the gas and solid phase. By using diazo and thiocarbonyl compounds in ether as solvent, both alkyl and aryl substituted thiiranes are accessible. As indicated earlier, aryl substituents destabilize the initially formed 2,5-dihydro-1,3,4-thiadiazole ring and, in general, thiiranes are readily obtained at low temperature (13,15,35). On the other hand, alkyl substituents, especially bulky ones, enhance the stability of the initial cycloadduct, and the formation of thiiranes requires elevated temperatures (36 1,88). Some examples of sterically crowded thiiranes prepared from thioketones and a macro-cyclic diazo compound have been published by Atzmiiller and Vbgtle (106). Diphenyldiazomethane reacts with (arylsulfonyl)isothiocyanates and this is followed by spontaneous N2 elimination to give thiirane-2-imines (60) (107,108). Under similar conditions, acyl-substituted isothiocyanates afforded 2 1-adducts 61 (109) (Scheme 5.23). It seems likely that the formation of 61 involves a thiirane intermediate analogous to 60, which subsequently reacts with a second equivalent... 

Fluorinated triazolines (Scheme 29) are particularly stable and require high temperatures for thermolysis when aziridines are obtained.145 Thermolysis of aryl-substituted triazolines is not well investigated144,175 the l-p-nitrophenyl-5-phenyl compound yields exclusively aziridine, whereas the 1,4-isomer gives the imine as the major product.175 1-Heterocyclic-substituted 5-vinyltri-azolines (Scheme 31) give S-vinylaziridines, which undergo thermal isomerization to azepine derivatives (e.g., 89).183... 

The nature of the iminic nitrogen substituent influences the cycloaddition pathway (4 + 2 versus 3 + 2) followed in the reactions of a-nitrosoalkenes with alkyl/aryl-substituted acyclic imines.4 The problem of rotamer control in Lewis acid-catalysed 3 + 2- and 4 + 2-cycloaddition reactions of a./S-disubstituted acryloylimides was solved by the use of N-H imide templates.5... 

When refluxed for 15 h in xylene, aryl-substituted /V-(trimethylsilylmethyl)imines rearrange to /V-tri methyl si I y lazi ridines with high c/s-selectivity. It has been demonstrated that the reaction proceeds via an ylid that can be trapped with diethylacetylene-dicarboxylate (DEAD), for example. The more stable frans-geometry of the ylid and conrotatory cyclization would be responsible for the c/.v-aziridines. The authors note that no reaction occurs when the reaction is run in a polar solvent such as THF or acetonitrile, and that treatment of the imine with cesium fluoride in THF leads to protodesilylation only, as does 1 equiv. of water in HMPA.329... 

Azomethine imines have been postulated as intermediates in the reaction of aryl-substituted diazo compounds with N-phenyltriazolinedione (PTAD) and DMAD, leading to pyrazolo[l,2-a][l,2,4]triazoles (Scheme 11) (81TL2535). 

The peptidic phosphine ligands that had been introduced by Hoveyda and co-workers271 for enantioselective copper-catalyzed Michael additions (see Section 9.12.2.2.1) were also employed successfully in silver-catalyzed asymmetric Mannich reactions.3 Thus, the aryl-substituted imines 372 reacted with various silyl enol ethers in the presence of stoichiometric amounts of isopropanol, as well as catalytic amounts of silver acetate and ligand 373 to... 

Before discussing structural effects on barrier heights, it is necessary to distinguish between the two processes planar nitrogen inversion and rotation about the C=N bond, which may both lead to interconversion of the isomers. Rotation about a non-activated C=N double bond is expected to be hindered by an energy barrier similar to the ethylene barrier, i.e. of the order of 50—60 kcal/mole 121.132) Thus, alkyl- and presumably also aryl-substituted imines, which show interconversion barriers below 30 kcal/mole (Table 6), undergo nitrogen inversion ). 

A. 15.1.2.2 Imines and Enamines. Primary amines react with aldehydes and ketones to form the corresponding A-alkyl- or A-aryl-substituted imines (R— CO—R + R"—NH2 R—C=(NR")—R + H2O). Imine formation is a... 

The l-aza-di-TT-methane rearrangement depends on the type of substitution of the nitrogen atom. For example, aza-di-ir-methane rearrangement occurs with aryl-substituted imines and with oxime acetates, but not with the oxime (23) or the nitrile (24). ... 

Becker, who intensively studied the anodic oxidation of heteroallenes, showed that electrooxidation of aryl-substituted ketene imines leads to mono- and multiannulated heterocyclic dimers [139]. 

Although N sulfinyl imines can be prepared by several other methods (oxidation of sulfenimines [12] and iminolysis of sulfinates [13]), they are most conveniently synthesized by condensing aldehydes with tert butanesulfinamide in the presence of copper(II) sulfate or magnesium sulfate/pyridinium p toluenesulfonate as a Lewis add catalyst and water scavenger (Scheme 1.4) [14]. When ketones, more sterically hindered aldehydes or even electronically deactivated aldehydes are used, titanium tetraethoxide is the preferred Lewis add and water scavenger. These methods are convenient to synthesize both alkyl and aryl substituted imines. 

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