Imines, phenol-derived

For determination of phenolic derivative of P-lactam analog (cefadroxil) measurement of absorption of formed product in the reaction between it and 4-aminoantipyrine in the presence of alkaline potassium hexacyanoferrate(III) at 510 nm was also proposed (Fig. 16). Potassium hexacyanoferrate(III), being oxidant in this reaction, yielding N-substituted quinine imines and in the result was responsible for formation of red-colored antipyrine dye. Additionally, a sequential injection analysis (SIA) spectrophotometric procedure for the determination was reported [52]. 

Ellipticine (E) 1 is an indolic alkaloid with antitumor activity. Some of its phenolic derivatives as N-methyl-9-hydroxyellipticine (Celiptinium), obtained from 9-hydroxy ellipticine (9-OH E), exhibit high cytotoxicity. 38 Syntheses of 9-OH E are not satisfactory considering yields and cost, justifying the attempts at the direct conversion of E to 9-OH E via 9-oxoellipticine (9-0X0 E). Potassium nitrosodisulfonate (Fremy s salt), a valuable oxidant for the synthesis of quinone-imine from heterocyclic amines,139 was used. Under these conditions the conversion of E to 9-0X0 E was observed for the first time. Its reduction to 9-OH E is then easily achieved with ascorbic acid. The radical nature of Fremy s salt [ 0-N(S03K)2] led us to carry out the oxidation reaction under sonication in order to increase the yields via an easier electron transfer.1 1... 

Chelation-assisted ortho arylation of aromatic imines with aryl halides was reported by Oi and Inoue [10b] and Ackermann [14b] (Scheme 17.5). In 2003, Bedford [15a,b] demonstrated the C-H arylation of phenol derivatives at their ortho position using various aryl halides in the presence of a rhodium catalyst. Subsequently, Oi [15c] also reported a similar rhodium-catalyzed C-H arylation of phenols. In 2008, Bedford [15d] reported conditions for the C-H/C-X couphng of simple phenol derivatives. 

Later, an enantioselective one-pot tandem Mannich-hydroamination reaction was reported by Liu and co-workers on the basis of a sequential organo- and gold catalysis.The proeess involved propargylated malonitrile and oxindole imine derivatives as substrates and employed a chiral cinchona alkaloid, such as a quinidine phenol derivative, to induce the enantioselective Mannich reaction and a gold catalyst, such as XPhosAuNTfa... 

Scheme 1.12 Enantioselective allylation of phenol-derived imines by Leighton group.

In hydrogenation, early transition-metal catalysts are mainly based on metallocene complexes, and particularly the Group IV metallocenes. Nonetheless, Group III, lanthanide and even actinide complexes as well as later metals (Groups V-VII) have also been used. The active species can be stabilized by other bulky ligands such as those derived from 2,6-disubstituted phenols (aryl-oxy) or silica (siloxy) (vide infra). Moreover, the catalytic activity of these systems is not limited to the hydrogenation of alkenes, but can be used for the hydrogenation of aromatics, alkynes and imines. These systems have also been developed very successfully into their enantioselective versions. 

M. Shi and Y.-L. Shi reported the synthesis and application of new bifunctional axially chiral (thio) urea-phosphine organocatalysts in the asymmetric aza-Morita-Baylis-Hillman (MBH) reaction [176, 177] of N-sulfonated imines with methyl vinyl ketone (MVK), phenyl vinyl ketone (PVK), ethyl vinyl ketone (EVK) or acrolein [316]. The design of the catalyst structure is based on axially chiral BINOL-derived phosphines [317, 318] that have already been successfully utilized as bifunctional catalysts in asymmetric aza-MBH reactions. The formal replacement of the hydrogen-bonding phenol group with a (thio)urea functionality led to catalysts 166-168 (Figure 6.51). 

Oxidation of Phenol Ether Derivatives to Biaryls, Quinone-Imine... 

Hence, the initial reactions were conducted using BINOL-phosphate 5 in combination with various achiral Brpnsted acids, including pro-tonated pyridine derivatives, alcohols and acids. Best enantioselectiv-ities were observed with the addition of carbonic acids, phenol and hexafluoro isopropanol which provided the isoquinuclidines 28 with up to 88% ee. Further explorations concentrated on varying the reaction parameters including different protected imines, catalyst load-... 

Phenol imine derivatives, (I), prepared by the author [1] in an earlier investigation were used to polymerize styrene when activated with 2,2 -azobis (2-methylpropanenitrile). 

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