Manganese complexes chlorides

In other examples, compounds in which a metal atom is already coordinated in a molecule can be used as a comonomer in an addition polymerization. Two examples involve the ferrocenes discussed in Chapter 6. The vinyl ferrocene molecule is shown in 7.14, and a similar vinyl manganese complex in 7.15.30 An alternative approach involves condensation polymerization. For example, if the R group in the ferrocene unit shown in 7.16 contains a hydroxyl group, it can be copolymerized with a diacid chloride. If it is an acid chloride, it can be copolymerized with a diamine. (This type of polymer is called a heteroannular chain if only one of the rings in the repeat unit is in the backbone, the polymer is called homoannular.)7 Similarly, the titanium complex shown in 7.17 is copolymerized with diacids or diols.30 Numerous other examples involving ferrocenes are discussed in Chapter 6. 

The SjvAr reaction is another attractive method for diaryl ether synthesis, and reactions of o-nitro- and o-cyanofluorobenzenes with phenols were reported . 7r-Complexation of aryl halides with transition metals activates the aromatic nuclei toward S fAr. Segal employed a ruthenium chlorobenzene complex in the poly(aryl ether) synthesis , and the methodology was extensively studied by Pearson, Rich and their coworkers using manganese complex and later iron and ruthenium complexes in natural product synthesis " . The intramolecular substitution of an aromatic chloride with a phenylalanine derivative takes place at room temperature without racemization (equation 27). 

The catalyhc asymmetric epoxidation of alkenes offers a powerful strategy for the synthesis of enantiomerically enriched epoxides. Among the several existing catalyhc methods, the asymmetric epoxidahon of unfunctionalized alkenes catalyzed by chiral Mn(lll)(salen) complexes such as homochiral [( N.N )-bis(3,5-di-tert-butylsalicylidene)-l,2-cyclohexanediamine]manganese(lll) chloride (22) (Figure 7.7), as developed by Jacobsen and coworkers, represents one ofthe most reliable methods [39]. 

A wide variety of N-alkyl hydrazinedicarboxylic esters may be obtained in excellent yields by the hydrohydrazination reaction depicted in Eq. 49.215 Use of cobalt complexes results in more highly regioselective reactions at the cost of lower reaction rates as compared to additions where manganese complexes are employed. Di(fert-butyl) azodicarboxylate is the preferred azo ester reduction of the N=N double bond becomes more prominent when less hindered azo esters are used. Alcoholic solvents are essential the reaction fails when methylene chloride or THF is used. 

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