CuOTf complexes tris ligands

Dissolution of the frans-cycloheptene-CuOTf complex in cycloheptene and evaporation of the solvent delivers a tris alkene complex of CuOTf containing one frans-cycloheptene and two cis-cycloheptene ligands. Heating frans-cycloheptene-CuOTf in neat c/s-cycloheptene delivers the trans,anti,trans,anti,trans trimer (eq 16). Experiments with c/s-cycloheptene-<4 show that the cyclotrimerization involves only frans-cycloheptene molecules, although the reaction is accelerated by the presence of cis-cycloheptene. A likely explanation for these observations is concerted template cyclotrimerization of a tns-trans-cycloheptene-CuOTf complex formed by ligand redistribution (eq 16). ... 

Tris(oxazoline) complexes have also been investigated as ligands in the allylic oxidation reaction. Katsuki and co-workers (116) observed that Cu(OTf)2 com-plexed to the tris(oxazoline) 160 is a more selective catalyst than one derived from CuOTf, Eq. 99, in direct contrast to results observed with bis(oxazohnes) or pyridyl bis(oxazohnes) as ligands (cf. Section III.A.3). When the reaction is conducted at -20°C, the cyclopentenyl benzoate is delivered in 88% ee albeit in only 11% yield after 111 h. Larger cycloalkenes are less selective (cyclohexene 56% ee, cyclohep-tene 14% ee, cyclooctene 54% ee). 

More recently, Burgess et al. (34) used the same approach in the synthesis of a constrained phenylalanine derivative, 3-phenyl-2,3-methanophenylalanine (123). Libraries of metal complexes were screened to determine the best combination for the asymmetric cyclopropanation reaction (35). The ligands shown below were combined with AgSbFg, (CuOTf)2 PhH, RuC12(C10H14)]2, Sc(OTf)3, where tri-... 

Structural variants of the chiral bis(oxazoline) ligands have been described for the CuOTf-catalyzed asymmetric JQiarasch reaction. Thus, a chiral CuOTf-tris(oxazoline) complex catalyzes the allylic oxidation of cyclopentene in 67% yield and with 66% ee. Cu(OTf)2 is, however, moderately more effective (68% yield, 74% ee). Ruorous bis(oxazolines), in which two... 

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