Chiral 2,2‘-Bipyridines, 1,10-Phenanthrolines, and 2,2‘:6‘,2‘ ‘-Terpyridines:  Syntheses and Applications in Asymmetric Homogeneous Catalysis

“Rollover” cyclometalation – early history, recent developments, mechanistic insights and application aspects

“…43,44 The attractiveness of this ligand is certainly a consequence of i) its rich and intriguing coordination chemistry, ii) the easiness of functionalization of the pyridine rings and iii) the high stability of many of its transition-metal complexes against moisture and oxygen.…”

First metal complexes of 6,6′-dihydroxy-2,2′-bipyridine: from molecular wires to applications in carbonylation catalysis

“…Metal complexes with bipy ligands have been prepared, probably of all metals known, and numerous variations on the basic ligand 15 framework have been made. [1][2][3] However, one remarkably simple derivative that has been elusive so far is 6,6'-dihydroxy-2,2'-bipyridine (1). A few metal complexes of bipy ligands with hydroxy substituents at other positions have been reported, for example 3,3'-and 4,4'-dihydroxy-2,2'-bipyridine 4,5 and also 6-20 hydroxy-2,2'-bipyridine 6 has been coordinated to a metal centre but, to the best of our knowledge, no reports have appeared on the synthesis of a metal complex containing the 6,6'-dihydroxy-2,2'-bipyridine ligand.…”

Design and synthesis of new bis-hydrazones and pyridine bis-hydrazones: application in the asymmetric Diels-Alder reaction

“…Taking this limitation into account, we decided to use the reaction of N-crotonyloxazolidin-2-one 8 with cyclopentadiene 9 as the model system. The preliminary results of the model reaction were collected using [M(bis-hydrazone)(OTf) x ], generated in situ by stirring a solution of the corresponding ligand (5 or 7; 11 mol%) with the desired metal triflate [Sc(OTf) 3 , Mg(OTf) 2 , Zn(OTf) 2 , Cu(OTf) 2 ; 10 mol%], in dry toluene at room temperature (Table 1). Under these conditions, bis-hydrazones 5 afforded disappointing results.…”

“…Moreover, they are in general easy to synthesize and manipulate, and possess fair stability, for instance against the oxidation that is a common problem in phosphines, and this stability also provides recycling opportunities by different methods. In particular, the chiral N(sp 2 )-based privileged bipyridine (I), 3 bis-imine (II), 4 bis-oxazoline (III), 5 or pyridine bisoxazoline (IV) 6 ligands ( Figure 1) have enabled the development of a vast number of asymmetric reactions. During the last few years we have accumulated some knowledge about the synthesis, reactivity and structural aspects of the chemistry of N,N-dialkylhydrazones.…”