5.6- Dimethyl-1,10-phenanthroline, reaction

The silver-silver distance is 3.386 A, indicating a weak silver-silver interaction (Fig. 6.3). Observing the disilver structure for the second time, the authors studied the importance of the disilver structure on reactivity. By testing different phenanthrolines, they found that 2,9-substituted phenanthrolines did not catalyze the amination reaction. This result was supported by structural evidence—the silver-2,9-dimethyl-phenanthroline complex did not form disilver structure two ligands coordinated one silver in a tetrahedral geometry, blocking the approach of any other molecule to the silver center. Even one bulky mesityl group in the 2 position inhibits the reactivity completely (Scheme 6.6). 

Oxidative Heck arylation of enamides with arylboronic acids, using oxygen gas as a reoxidant for Pd(0) and 2,9-dimethyl-1,10-phenanthroline as a chelating regiocontrolling ligand, yielded a (= internally) arylated reaction product as the major compound with a very good a//3 selectivity [92]. Microwave irradiation with prepressurized sealed vials proved useful in reducing the reaction time (Scheme 82). 

A stopped flow technique coupled with spectrophotometric analysis of the iron (II) complex formed has been used to investigate - the reactions of some organic complexes of iron(III) with the ion Fe ". The iron(III) was complexed with 1,10-phenanthroline, various substituted 1,10-phenanthrolines (5-methyl-, 5-nitro-, 5-chloro-, 5-phenyl-, 5,6-dimethyl-, 4,7-diphenyl-, and 3,4,7,8-tetramethyl-) and 2,2 -dipyridine, 4,4 -dimethyl-2,2 -dipyridine, and 2,2, 2"-tripyridine. The wavelengths used for the analysis lay in the region 500-552 m/i. 

A related entry to the 1,7-phenanthroline ring system involves reaction of m-phenylenediamine with dimethyl acetylenedicarboxylate in methanol at ambient temperature.177 This affords the intermediate bis-fumarate which cyclizes in diphenyl ether at 250° giving, in 95% yield, 2,8-dicarbomethoxy-4,10-dihydroxy-1,7-phenanthroline. The angular... 

The presence of l,2,3,4-tetrahydro-3,4,7,8-tetramethyl-l,10-phen-anthroline as a coproduct with 3,4,7,8-tetramethyl-l,10-phenanthroline from the reaction of 3,4-dimethyl-8-aminoquinoline with 3-methylbut-3-en-2-one is explained by disproportionation of the intermediate 1,2-dihydrophenanthroline.206... 

The first synthesis of a derivative of 2,8-phenanthroline was reported by Merz, Weidlich, and Fink13 in 1964. They prepared 5,6-dimethoxy-2,8-phenanthroline (34) (isolated as the dipicrate) in very low yield by conducting a double Pomeranz-Fritsch isoquinoline synthesis on 4,5-dimethoxyisophthalaldehyde. The parent compound was prepared 2 years later12 in 25-35% yield, along with 1,9-phenanthroline (4%), by the photocyclization of trans-1 (3-pyridyl)-2-(4-pyridyl)ethylene in benzene. This reaction was used by Hiinig and his colleagues15 to prepare an N,N -dimethyl diquaternary salt of 2,8-phenanthroline by methylating the crude product from the irradiation reaction. 

Phenanthroline was first claimed to have been synthesized by a double Pomeranz-Fritsch isoquinoline synthesis.11 It has recently been prepared12 in about 12% yield by the irradiation of trans-l,2-di(3-pyridyl)ethylene in benzene, along with 1,8-phenanthroline (12-20%) and 1,10-phenanthroline (1-2%). The melting point is quite different from that recorded earlier by Ruggli and Schetty.11 This latter method has subsequently been used15 to prepare an AT, AT -dimethyl diquaternary salt of 3,8-phenanthroline by methylating the crude product from the irradiation reaction. 

Applications of the Conrad-Limpach reaction to the synthesis of 1-hydroxy-4,7-phenanthrolines or, more correctly, l-oxo-l,4-dihydro-4,7-phenanthrolines, from p-phenylenediamine or 6-aminoquinolines continue to be reported. l,10-Dihydroxy-3,8-dimethyl-4,7-phenanthroline has again been prepared from p-phenylenediamine,234 hot diphenyl ether being used to effect the cyclization. Other examples include the new or improved preparations of l-hydroxy-3-methyl-, 10-amino-l-hydroxy-3-methyl-,232 2-(y-chlorocrotonyl)- l,10-dihydroxy-3,8-dimethyl-, and 2,9-bis (y- chlorocrotonyl)-1,10- dihydroxy - 3,8 - dimethyl - 4,7 - phenanthro-lines.235 Compounds prepared in this way have been patented as antiasthmatic agents.178 A closely related synthesis employing poly-phosphoric acid as cyclizing agent has yielded l-hydroxy-3-phenyl-4,7-phenanthroline.236... 

Diphenyl-1,10-phenanthroline and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline give disulfonic acids on reaction with chloro-sulfonic acid at 25°. The position of substitution was not established, but presumably it occurs in the two phenyl rings.281 An improved method of sulfonation utilizes hot fuming sulfuric acid.282... 

Typical OH-scavengers suppress this reaction of (OP)2Cu+ (Que et al. 1980) yet, acetate and benzoate seem to be equally efficient, despite the fact that acetate is nearly two orders of magnitude less reactive towards OH than benzoate (k=7 X 107 dm3 mol-1 s 1 vs k = 5 X 109 dm3 mol-1 s 1 Buxton et al. 1988), and obviously it is not a freely diffusing OH that is responsible for the reaction. The reaction is also suppressed by Cu-complexing compounds and by transition metal ions such as Zn2+, Co2+, Cd2+ and Ni2+ that form stable complexes with 1,10-phenanthroline (Que et al. 1980) and also by competitive intercalators such as ethidium bromide and 2,9-dimethyl-l,10-phenanthroline (Reich et al. 1981). Interestingly, compared to its parent, the latter is inactive. NADH may serve as a reductant, but 02, seems to be a salient intermediate in this cleavage reaction, because cleavage is fully suppressed in the presence of SOD (Reich et al. 1981). 

EDTA has been assayed in foods through its reaction with Fe(III) [28]. Excess Fe(III) is removed by chloroform and N-benzoyl-iV-phenylhydroxylamine. The calibration graph was linear over the range of 0.5 - 40 pg/mL [28], A similar method for EDTA in food involving reaction with Cu(II) in Tris-HCl buffer at pH 8.5 has been reported [29]. The excess Cu(II) was been determined at 477 nm using 2,9-dimethyl-4,7-diphenyl-l,9-phenanthroline. This calibration curve was found to be linear over the range of 4-12 pM EDTA. 

Most ruthenium catalysts used in epoxidation reactions are based on bulky porphyrins or other amine ligands and require the use of PhIO and Cl2PyNO as oxidants. For examples see the reviews in Refs. [5,6,45] and some recent examples by Liu and coworkers [46,47] and Jitsukawa et al. [48]. Examples for the aerobic epoxidation of alkenes are the ruthenium mesityl porphyrin complex Ru(TMP)(0)2, where TMP is 5,10,15,20-tetramesitylporphyrinato, of Groves and Quinn [12] in 1985 (Eq. 7), the ruthenium dimethylphenanthroline complex, czs-[Ru(2,9-dimethyl-l,10-phenanthroline)(CH3CN)2]2+ published by Goldstein et al. [23] in 1994 (Eq. 8), and the ruthenium POM catalyst [WZnRu2(0H)(H20)](ZnW9034)2 n of Neumann and Dahan [49] in 1997 (Eq. 9). 

The first example of a chiral copper photosensitizer is [Cu(dmp)((R,R-diop))]+ [R,R-diop = (R,R)-2,3-0-isopropylidene-2,3-dihydroxy-1,4-bis(diphe-nylphosphino)-butane dmp = 2,9-dimethyl-1,10-phenanthroline], in which two chiral centers are introduced in the (R,R)-diop ligand. This complex was applied to the stereoselective photoreduction of [Co(edta)]- [25]. After the reaction, the CD spectrum exhibits a positive peak at 590 nm and a negative one at 515 nm, which indicates the presence of excess A-fCo(edta)]. This means that A-[Co(edta)] more rapidly reacts with the photoexcited copper complex than does the A-enantiomer, where the stereoselectivity, defined as the ratio of the conversion rate, is 1.17. However, the photoreduction of Co(acac)3 and [Co(bpy)3]3+ occurs without stereoselectivity. This is probably because the electrostatic attraction between [Cu(dmp)((R,R-diop))]+ and [Co(edta)] is favorable for the stereoselection, but such interaction does not exist between [Cu(dmp)((R,R-diop))]+ and the other cobalt(III) complexes. 

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