Hydroxy amines imines

A comparison of the tautomeric constants in the series of N4-substituted cytosines indicates an interesting trend. As seen above, in the case of cytosine itself, the ratio of the tautomers of the amine type 2 to those of the imine type 6 is about 105. In the case of jV4-amino-cytosine134 the amine form 22 predominates by a factor of about 30, while N4-hydroxy compounds have mainly the imine form 21 with tautomeric constant 10 [i.e., Kt (amine/imine) = — 10 1]. Another study136 of this constant gave the value of 25 [Kt (amine/imine) = 4 x 10-2] in favor of the imine. 

The formation of imine or Schiff base metal complexes can be effected very readily by arranging for reaction of the amine with the carbonyl compound to take place in the presence of the metal ion. Nucleophilic attack of the amine on the carbonyl group is enhanced by polarization of the carbonyl group by coordination of the oxygen atom to the metal ion. Furthermore, the reaction is reversible unless steps are taken to effect dehydration of the intermediate hydroxy amine, and coordination of the product imine is an important factor in the promotion of the reaction by suitable metal ions. 

From a.-Amino Acid Amides and Amidines a-Amino acid amides, which fall into the amine-imine class according to the general model (beginning of Section II,B), are converted to 3-alkyl-4-hydroxy-l,2,5-thiadiazoles by reaction with sulfur mono-chloride, thionyl chloride, or thionyl aniline. A large number of -amino acid amides were employed in the synthesis (see Table I)... 

Originally, a C-20 amine (prepared from a bisnorcholanic acid) was converted into its 7V-chloro derivative, dehydrohalogenated to the imine, converted into the A-acetylenanime, reacted with perbenzoic acid, then hydrolyzed to the 17a-hydroxy-20-ketone ... 

Several methods for asymmetric C —C bond formation have been developed based on the 1,4-addition of chiral nonracemic azaenolates derived from optically active imines or enamines. These methods are closely related to the Enders and Schollkopf procedures. A notable advantage of all these methods is the ready removal of the auxiliary group. Two types of auxiliaries were generally used to prepare the Michael donor chiral ketones, such as camphor or 2-hydroxy-3-pinanone chiral amines, in particular 1-phenylethanamine, and amino alcohol and amino acid derivatives. 

The reactivity of epoxides can be modified by various proximal functionality. For example, 2,3-epoxy sulfides 118 are converted to the corresponding TMS-thiiranium species 119 upon treatment with TMS triflate. This intermediate reacts with O-silyl amides regiospecifically to form l-substituted-3-hydroxy-2-thioethers (e.g., 120). Simple primary amines undergo polyalkylation, but imines can be used as an indirect amine equivalent <96TET3609>. 

Polar C=Y double bonds (Y = NR, O, S) with electrophilic carbon have been added to suifinic acids under formation of sulfones. As in the preceding section one must distinguish between carbonyl groups and their derivatives on the one hand, and carboxylic acids (possessing leaving groups at the electrophilic carbon) on the other. Aldehydes " of sufficient reactivity—especially mono-substituted glyoxals - —and their aryl or arylsulfonyl imines have been added to suifinic acids (in a reversible equilibrium) to yield a-hydroxy or a-amino sulfones the latter could also be obtained from the former in the presence of primary amines (equation 26). 

Unsymmetric compartmental ligands that allow for the controlled synthesis of unsymmetric Ni2 or heterobimetallic NiM complexes have received particular attention.1876,1892 A wide range of such ligands derived particularly from 2-hydroxy-3-hydroxymethyl-5-methylbenzaldehyde and 2-hydroxy-3-hydroxymethyl-bromo-benzaldehyde has now been prepared and used for Ni com-plexation. These ligands have monopodal iminic pendent arms and either mono- or dipodal aminic pendent arms and the terminal donors of the pendent arms can be provided by pyridine, imidazole, and tertiary amino groups.1893-1897 Complexes are usually prepared by reaction of the requisite Ni11 salts with the preformed ligand. 

Vogtle et al. have prepared chiral poly(imine) dendrimers of various generations by condensation of non-racemic 5-formyl-4-hydroxy[2.2]paracyclophane moieties with poly(amine) dendrimers [71]. They have found that the optical activity of these dendrimers was nearly constant with increasing generation number. 

The plausible mechanism of the reaction is shown in Fig. 25. The reaction probably proceeds through the activation of imine (formed in situ from the o-hydroxy benzaldehyde and the aromatic amine) by the catalyst followed by the addition and subsequent cyclization of the enol ether, resulting in the formation of the fused acetal. Ionic liquids are stable enough with amines and water and also effectively activate the imines to undergo cyclization. The recovered ionic liquid can be re-used with gradual decrease in the efficiency of the method. The hydro-phobic nature of the ionic liquid also helps in recovery of the catalyst. 

Therefore, in principal, condensation of a primary amine with an enantiomerically pure ketone should allow asymmetric synthesis of a-substituted primary amines. This approach has been applied to the synthesis of a-amino acids, for example, using the imine prepared from a-amino esters and (l.S, 2,S ,5,S )-2-hydroxy-3-pinanone, via an amino-substituted ester enolate anion with some success39 40. Application of this approach to simple primary amines has seldom been reported. 

The alkylation of metalated imines, hydrazones, 4,5-dihydrooxazoles, 4,5-dihydroisoxazoles, 5,6-dihydro-4/7-1,2-oxazines and 2,5-dialkoxy-3,6-dihydropyrazines (i.e., azaenolates) is a commonly used method in asymmetric synthesis of enantiomerically enriched aldehydes, ketones, spiroacetals, amines, /J-oxo esters, carboxylic acids, lactones, 1,3-amino alcohols, /(-hydroxy ketones and amino acids. 

Polyolefins with vinyl end groups can be readily transformed into end-functionalized polyolefins by post-polymerization functionalization to yield a wide variety of end-functionalized polyolefins, which include epoxy-, amine-, and hydroxy-terminated polyolefins. Brookhart, Gibson, and co-workers reported on diimine-pyridine-ligated Fe complexes incorporating sterically less hindered alkyl substituents such as a methyl group ortho to the imine-A s, F12-1, that selectively converted ethylene to oligomers, affording linear a-olefin mixtures (>99%) (see also Section... 

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