Manganese complexes salicylaldehyde

Several catalysts that can effect enantioselective epoxidation of unfunctionalized alkenes have been developed, most notably manganese complexes of diimines derived from salicylaldehyde and chiral diamines (salens).62... 

Asymmetric epoxidation of alkenes. Two groups have prepared chiral (salen)-manganese complexes such as 2 from ( + )- or (-)-l and salicylaldehyde derivatives... 

A similar strategy was developed by Kureshy et al. [45]. In 1998, Sherrington et al. [46] reported the application of polymer-bound Mn(lll)-salen catalyst in the epoxidation of 1-phenylcyclohex-l-ene, resulting in 49% yield and 91% ee, which are comparable to results obtained with the nonimmobilized Jacobsen catalyst. The synthesis of these catalysts started from polymer-bound salicy-laldehyde derivatives, which were first treated with 1,2-diamino cyclohexane and then with a second salicylaldehyde derivative. In the last step, the manganese complex was formed. Polymethacrylate was used as polymeric backbone. A similar approach was employed by Peukert and Jacobsen [47] to immobilize this catalyst to polystyrene. 

It has been known for many years that the rate of hydrolysis of a-amino acid esters is enhanced by a variety of metal ions such as copper(II), nickel(II), magnesium(H), manganese(II), cobalt(II) and zinc(II).338 Early studies showed that glycine ester hydrolysis can be promoted by a tridentate copper(II) complex coupled by coordination of the amino group and hydrolysis by external hydroxide ion (Scheme 88).339 Also, bis(salicylaldehyde)copper(II) promotes terminal hydrolysis of the tripeptide glycylglycylglycine (equation 73).340 In this case the iV-terminal dipeptide fragment... 

Preparative Methods over 100 chiral manganese(III) salen complexes have been reported the general procedure for their preparation involves condensation of a 1,2-diamine with 2 equiv of a salicylaldehyde derivative, followed by addition of Mn(OAc)2 in the presence of air. Yields of (salen)Mn complexes usually exceed 90%. 

In the case of sodium periodate as oxidant, manganese(III) complexes with a bis(salicylaldehyde)-4-methyl-l,2-phenyl-enediimine (BSMP) [249b] or tetrapyridylporphyrin supported on chloromethylated polystyrene (TPyP)-CMP [249a] have proven as the catalysts of choice (Scheme 13.143). 

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