Quaterpyridine derivative

The bis(ethylthio) species (83a,b) may be mono-oxidized with MMPP or m-CPBA to afford the thiones (82a,b). If these species are treated with methylmagnesium bromide, a ring-coupling reaction occurs to provide (83b,c) in yields of 56 and 3%, respectively (Scheme 15). Alternatively (82a,b) may be treated with 6-lithio-2,2 -bipyridine to provide the oligomers (84a,b).88 A similar reaction has been used to prepare a chiral quaterpyridine derivative employing the mono-sulfone of (84a).89... 

The non-symmetrical alkyl-substituted quaterpyridines 39 and 40 (Figure 6.21) also react with an excess of [Cu(MeCN)4](PF ) to yield the corresponding complexes of type [Cu2L2](PF )2. ° An analysis of the NMR spectra of each product indicated that, while the ligand derivative with R = Me (39) yields a 1 1 mixture of head-to-head and head-to-tail dimers (see Figure 6.21), the presence of the... 

The neurotoxic quaterpyridine natural product nemertelline was successfully synthesized by S. Rault et al. using a Suzuki cross-coupiing as the key step. The boronic acid coupling partner, required for the Suzuki reaction, was prepared by first subjecting 3-amino-2-chloropyridine to the conditions of the Sandmeyer reaction followed by a lithium-halogen exchange and trapping the lithiopyridine derivative with triisopropylborate. 

Double Krohnke reactions have been employed in the preparation of quaterpyridines and sexi-pyridines. Thus, the chalcone dimer (77a,b) reacts with the pyridinium salt (78) to provide (79a,b) (Scheme 13).84 An alternative approach involves a bischalcone species based on bpy that can be elaborated to (76c), as well as several 4, 4""-disubstituted derivatives.85 A dimeric analogue of (78), having a central bpy moiety, undergoes condensation with a Krohnke-type salt to provide the parent sexipyridine (76c).86... 

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