1.10- Phenanthroline, reaction with

In the Meisenheimer reaction of quinoline 1-oxides chlorine atoms usually enter the 2-and 4-positions, but not exclusively. 2,4-Dibromoquinoline 1-oxide was 6-chlorinated (57MI1), and the 5- and 6-nitroquinoline 1-oxides were 3-chlorinated to some extent (44JOC302). This reaction with phosphoryl chloride-phosphorus pentachloride has also been used in the preparation of chlorinated phenanthrolines (88YZ1148). 

The pyridine ligand in the products shown in Scheme 126 is labile and can be readily replaced by bidentate ligands such as 1,10-phenanthroline (phen) or l,2-bis(diphenylphosphino)ethane (dppe). Scheme 127 illustrates the reaction with phen. ... 

Of interest to note is that in previous studies, the kinetics of the substitution reactions with bidentate ligands as shown in Eqs. (34) and (35) have been reported, with Pic = pyridine-2-carboxylate (83) and phen = 1,10-phenanthroline (84)... 

The amino acid derived chiral oxazolidinone 188 is a very commonly used auxiliary in Diels-Alder and aldol reactions. However, its use in diastereoselective 1,3-dipolar cycloadditions is less widespread. It has, however, been used with nitrile oxides, nitrones, and azomethine ylides. In reactions of 188 (R = Bn, R =Me, R = Me) with nitrile oxides, up to 92% de have been obtained when the reaction was performed in the presence of 1 equiv of MgBr2 (303). In the absence of a metal salt, much lower selectivities were obtained. The same observation was made for reactions of 188 (R = Bn, R = H, R = Me) with cyclic nitrones in an early study by Murahashi et al. (277). In the presence of Znl2, endo/exo selectivity of 89 11 and up to 92% de was observed, whereas in the absence of additives, low selectivities resulted. In more recent studies, it has been shown for 188 (R =/-Pr, R = H, R =Me) that, in the presence of catalytic amounts of Mgl2-phenanthroline (10%) (16) or Yb(OTf)3(20%) (304), the reaction with acyclic nitrones proceeded with high yields and stereoselectivity. Once again, the presence of the metal salt was crucial for the reaction no reaction was observed in their absence. Various derivatives of 188 were used in reactions with an unsubstituted azomethine ylide (305). This reaction proceeded in the absence of metal salts with up to 60% de. The presence of metal salts led to decomposition of the azomethine ylide. 

All possible isomers of the phenanthrolines are known and can be prepared by Skraup-type reactions, with the exception of the 2,8- and 3,8-phenanthrolines (which are structurally related to isoquinolines). Some of these compounds are commercially available. There have been no major advances in the synthesis of these compounds since CHEC-II(1996) <1996CHEC-II(7)921>. 

The oxidation of 1,7-phenanthrolines containing a hydroxy, methoxy, or amino group in the 5- or 6-position to 1,7 phenanthroline-5,6-dione (51) by nitric acid has been patented.249 250 Its monosemicarbazone has also been patented.251 l,7-Phenanthroline-5,6-dione (51) gives the diepoxide (52) on reaction with diazomethane.226... 

Reactions of 4,7-phenanthroline-5,6-dione have been the subject of considerable study. It is reduced to 5,6-dihydroxy-4,7-phenanthroline by Raney nickel hydrogenation226,249 or by aromatic thiols in benzene,262 and oxidized by permanganate to 3,3 -bipyridyl-2,2 -dicarboxylic acid.263 It forms bishemiketals with alcohols226 and diepoxides with diazomethane.226 The diepoxides by reaction with hydrochloric acid form diols of type 57, R = Cl, which on oxidation with lead tetraacetate give 3,3 -bipyridyl diketones of type 58, R = Cl. Methyl ketones of type 58, R = H, are also obtained by lead(IV) acetate oxidation of the diol 57, R = H, obtained by lithium aluminum hydride reduction of 57, R = Cl. With phenyldiazomethane and diphenyldiazomethane the dione forms 1,3-dioxole derivatives,264,265 which readily hydrolyze back to the dione with concomitant formation of benzaldehyde and benzophenone, respectively. 

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