Where the Synthon Supplies Three or More Ring Atoms

Where the Synthon supplies Three or More Ring Atoms 

Of the possibilities, only N1 + C2 + C3, C2 + C3 + C4, N6 + C7 + C8, N1 + C2 + C3 + C4, and C5 + N6 + C7 + C8 have been supplied by the synthon in this category of primary synthesis. Such cyclocondensations are illustrated here by typical classified examples. Fused 1,6-naphthyridines may also be made by analogous procedures.169 

5-Dibenzylidene-l-isopropyl-4-piperidinone (108) (or tautomer) with 2-cya-no(thioacetamide) gave 8-benzylidene-6-isopropyl-4-phenyl-2-thioxo-l,2,5,6,7,8-hexahydro-l,6-naphthyridine-3-carbonitrile (109) (or tautomer) (reactants, MeONa, MeOH, 50°C, 8 h 55%).946 

3-Iodo-4-pyridinamine (112) with allyl alcohol also gave 1,6-naphthyridine (111) [reactants, PdCl2, NaHC03, Pd(/ -MeC6H4)3, OP(ONMe2)3, 140°C. 4h 51%].165 

4-Amino-6-hydroxy-2(l//)-pyridinone (113) with l-benoyl-2-dimethylami-noethylene gave 4-phenyl-1,6-naphthyridine-5,7(l//,6//)-dione (114) (reactants, AcOH, reflux, 5 min 95%) 757 analogs likewise.469,757,1310 

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