1,8-Naphthyridine, reaction with metal

The activated methyl groups of 5,7-dimethyl-l,8-naphthyridin-2-one (106) can be selectively metallated, reaction with two equivalents of butyllithium giving (107), while with two equivalents of sodamide in liquid ammonia (108) is obtained. Both (107) and (108) gave appropriate products on treatment with electrophiles (81JOM(213)405>. A possible explanation of this result involves a coordination mechanism for the formation of (107) and an acid-base mechanism giving (108). 

Luminescent trigonal gold(I) metallocryptates have been obtained by reaction of 2,9-bis(diphenylphosphino)-l,8-naphthyridine or 2,9-bis(diphenylphosphino)-l,10-phananthroline PPh2(phen)PPh2 with [AuCl(tht)] (molar ratio 3 2) and in the presence of a cation Na+, Tl+ or Hg°, which is encapsulated in the cavity making Au-M interactions [207]. Similar mixed metal metallocryptands with Pd(0) or Pt(0) have been reported (Figure 1.29) [208]. 

Complexes 431 of Group IB or VIII metals with 1,5-naphthyridine derivatives 432 were synthesized (1993GEP4105386). Compounds 431 are used for the preparation of singlet oxygen. These serve as sensitizers in photoinitiation of polymerases and electrophotography and as redox catalysts in organic reactions. 

The high reactivity is also understandable from the mild reaction conditions under which many cyclometalation reactions proceed with many kinds of metal elements, such as Ti, Fe, Ru, Os, Rh, Ir, Ni, Pd, Pt, B, and Cu, and with many kinds of substrates, such as amines, imines, 2-phenylpyridines, benzo[/ ]quinones, quinolines, diarylpyridines, naphthyridines, azobenzenes, oxazolines, aldehydes, ketones, amides, phosphines, phosphites, and alkyl sulfides, as shown in Figs. 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, and 5.9. 

Guillier, F., Nivoliers, F., Godard, A., Marsais, F., and Queguiner, G. (1994) An original one-pot synthesis of 5-(4-pyridyl)-benzo[c]-2,7-naphthyridine as key intermediate in the synthesis of amphimedine by metalation connected with cross-coupling reaction. Tetrahedron Lett., 35, 6489-6492. 

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