Mn-Catalyzed Ligand-Free One-Pot Synthesis of (E)-6,7-Dihydrodibenzo[b,j][1,7]phenanthrolines and (E)-1,2,3,4-Tetrahydrobenzo[b][1,6]naphthyridines through Dehydrogenative Friedlander Annulation/C(sp3)-H Functionalization

An efficient, MnO2-catalyzed ligand-free synthesis of (E)-6,7-dihydrodibenzo[b,j][1,7]phenanthrolines, 13, and (E)-1,2,3,4-tetrahydrobenzo[b][1,6]naphthyridines, 15, utilizing, 2-amino-5-chloro-benzhydrol, 9, acridinol, 10, or 1-benzyl-4-piperidinol, 14, and benzyl alcohols, 11, is reported. The MnO2-catalyzed dehydrogenative Friedlander annulation utilizing ChCl/p-TSA (DES-1) and subsequent C(sp(3))-H functionalization with TBAB/p-TSA (DES-2) was effected at 100 degrees C. The optimized reaction conditions gave excellent product yields, and the products were evaluated for their by UV absorption and fluorescence emission studies.