1,10-Phenanthroline, chlorination

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). 

There is a difference in the ease with which the two chlorine groups in 4,10-dichloro-l,7-phenanthroline are replaced by nucleophiles. For example, the 10-chloro substituent reacts with sodium ethoxide five hundred times faster than the 4-chloro substituent. Consequently, 4-chloro- 10-ethoxy, 4-chloro- 10-methoxy-, 4-chloro- 10-anilino, and 4-chloro-10-hydroxy-1,7-phenanthrolines can be prepared from 4,10-dichloro-l,7-phenanthroline.97, 171,172,336 The exceptional reactivity of the 10-chloro group is attributed to relief of strain in the transition state in its reaction with nucleophilic reagents.336 With excess of the nucleophilic reagents, both chlorines in 4,10-dichloro-l,7-phenanthroline are replaced.171, 172,336... 

Chlorine substituents may be replaced by hydrogen by reductive dehalogenation with, for example, Raney nickel or palladium-charcoal catalyst. The 1,7-phenanthroline skeleton is not reduced under these conditions.96,171,172 The bromine group in 4-bromo-2-trifluoromethyl-... 

Chlorine groups in chloro- and dichlorobenzo[6][l,8]phenanthrolines have likewise been replaced by a variety of amines.180... 

The chlorine groups in 4-chloro-1,10-phenanthroline and 4,7-dichloro-1,10-phenanthroline are replaced by cyano groups on fusion with potassium cyanide342 while 2-cyano- and 5-cyano- 1,10-phenanthrolines have been obtained from 2-chloro and 5-bromo-l,10-phenanthrolines, respectively, by reaction with cuprous cyanide.267... 

Although aryl chlorides are not usually reactive enough to couple efficiently with alkyl-coppers, heteroaryl chlorides often couple quite well. For example, the most efficient way of alkylating chlorinated phenanthrolines and quinolines, and both 2- and 3-substitued pyridines involves the use of Grignard reagents and copper salts (equation 51)73. 

The dimer (XXVI) yields the FeCla complex (XXVII) containing four coordinate rhodium, the fourth chlorine atom bridging rhodium and iron. XXVI also reacts with o-phenanthroline, pyridine, and carbon monoxide to give complexes of the type (TPPO)RhCl L or (TPPO)RhCl in which TPPO remains ly -bonded to the metal. 

The reaction of (1) with hypochlorous acid leads to chlorination at the 5- and 6-positions.30 Oxidative chlorination with phosphorus pentachloride gives the 2,9-dichloro-[l], as well as the 2,3,8,9-tetrachloro-[l]31 Chlorinated-[l] may be converted sequentially through the thiol-[l] to the sulfonato-[l] 32 Several trihalomethyl derivatives, particularly fluorinated phenanthrolines, have also been prepared 33-37... 

Oxygen and suitable catalysts can also be used for the conversion of phenol to ben-zoquinone. Thus, irradiation of phenol in the presence of [Cu(bpy)2] or [Cu(l,10-phenanthroline)] + brings about degradation by a path that shows both pH and solvent dependency . Thus in acetonitrile benzoquinone predominates, but in water carbon dioxide is the sole product. Benzoquinone can also be formed from phenol by continuous irradiation in the presence of the catalysts [Crfbpyfs] or less effectively with [Ru(bpz)3] + and [Ru(bpy)3] +. The reaction path involves 02( A ) as the oxidant . Porphyrins such as 5,10,15,20- tetrakis(2,6-dichlorophenyl)porphyrin and chlorins can also be used to convert naphthols and phenols to the corresponding quinones (Scheme 28) . Phthalocyanines immobilized on polymers have also been used as the catalyst system to effect photooxidation. ... 

The chlorine groups in 4-chloro-1,10-phenanthroline and 4,7-dichloro-1,10-phenanthroline are replaced by cyano groups on fusion with potassium cyanide while 2-cyano- and 5-cyano-1,10-phenanthrolines have been obtained from 2-chloro and 5-bromo-1,10-phenanthrolines, respectively, by reaction with cuprous cyanide. 2-Chloro-1,10-phenanthroline (69) reacts with the sodium salt of tert-butyl cyanoacetate to give the intermediate 105, which with cold hydrochloric acid affords 2-cyanomethyl-1,10-phenanthroline (106). 2-Chloro-1,10-phenanthroline also participates in the Ullmann reaction to afford 2,2 -bi-( 1,10-phenanthroline) (107). 5,5 -Bi-(l,10-phenanthroline) was also prepared, but by a different route starting from 8,8 -diamino-6,6 -biquinoline. 

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