Karnam Jayaramapillai Rajendra Prasad

Synthesis of novel phenyl substituted dibenzonaphthyridines

The reaction of 2,4-dichloroquinolines with 2-amino-5-chlorobenzophenone yielded 2-[(2-benzoyl-4-chlorophenyl) amino]-4-chloroquinolines which with sodium methoxide afforded 2-[(2-benzoyl-4-chlorophenyl)amino]-4-methoxyquinolines. These on PPA-catalysed cyclisation gave 2-chloro-12-phenyldibenzo[b,g][1,8]naphthyridin-11(6H)-ones. Temperature differences for the formation of the final products were due to the in situ formation of the 2-[(2-benzoyl-4-chlorophenyl)amino]quinolin-4-ones from the chloro and methoxy intermediates. The dibenzonaphthyridin-11-ones were N-methylated at N(6); a methyl group at C(7) was found to hinder the methylation reaction sterically, when a considerably longer reaction time was needed.

An efficient synthesis of phenyl-substituted dibenzonaphthyridines

A one-pot synthesis of 9-chloro-6-methyl-7-phenyldibenzo[b,h][1,6]naphthyridines from 4-chloro-2-methylquinolines is reported. Since the yield of the dibenzonaphthyridine was low, in an alternative method the title compounds were prepared from the 4-chloro-2-methylquinolines via 2-methyl-4-[(4-chlorophenyl)amino]quinolines as intermediates, which provided improved yields.

Synthesis and Spectroscopic Distinction of Benzonaphthonaphthyridine and Its Isomer

Abstract Distinction of benzo[h]naphtho[1,2-b][1,6]naphthyridine and its isomeric benzo[b]naphtho[1,2-h][1,6]naphthyridine is well explained on the basis of various spectroscopic techniques. Initially these isomers were prepared from their respective chloroquinolines via anilinoquinolines as potential intermediates. Spectroscopic dissimilarities of their precursors and intermediates have also been considered and compared with the final benzonaphthonaphthyridine isomers. GRAPHICAL ABSTRACT

2,9-Dimethyl-7-phenyl-N-(4-methyl­phen­yl)dibenzo[b,h][1,6]naphthyridin-6-amine

The title compound, C31H25N3, was synthesized from 6,4′,4′′-trimethyl-2,4-bis(N-phenylamino)quinoline and is the first structural example containing a phenyl and phenylamino fragment attached to a fused dibenzo[1,6]naphthyridine moiety. The fused tetracyclic ring system is essentially planar [r.m.s. deviation = 0.08 (3) Å]. The phenyl ring and the phenylamino group are inclined by 82.68 (6) and 35.31 (5)°, respectively, to the mean plane of the fused tetracyclic ring system. A weak intramolecular N—H⋯π(arene) interaction may in part influence the conformation of the molecule. In the crystal, molecules are linked by weak intermolecular C—H⋯N hydrogen bonds into centrosymmetric dimers. Additional stabilization is provided by weak C—H⋯π and π–π stacking interactions [centroid–centroid distances = 3.834 (2) and 3.898 (1) Å].

7-(2-Chloro­phen­yl)-2,6,9-trimethyl­dibenzo[b,h][1,6]naphthyridine

In the title compound, C25H19ClN2, the dibenzo[b,h][1,6]naphthyridine system is planar to within 0.16 (2) Å, and the chlorophenyl ring is inclined to it by 82.53 (7)°. In the crystal, molecules are linked by C—H⋯N hydrogen bonds, forming chains propagating in [100]. There are also a number of weak π–π stacking interactions present [centroid–centroid distances = 3.8531 (1) and 3.7631 (1) Å].

2-Chloro-7-methyl-12-phenyldibenzo[b,g][1,8]naphthyridin-11(6H)-one.

In the title compound, C23H15ClN2O, the fused ring system is planar: the deviation of all the non-H atoms from the plane through all four fused rings is less than 0.31 Å. The plane of the phenyl ring is inclined at 71.78 (5)° to the mean plane of the 1,8-naphthrydine ring system. The crystal structure is devoid of any classical hydrogen bonds but π–π interactions are present.

7-(4-Meth-oxy-phen-yl)-4,9-dimethyl-N-(4-methyl-phen-yl)-5,12-diaza-tetra-phen-6-amine.

In the title compound, C32H27N3O, the fused tetracycilc ring system is essentially planar [r.m.s. deviation = 0.07 (7) Å]. An intramolecular N—H⋯π(arene) interaction and a weak intramolecular C—H⋯N hydrogen bond may influence the molecular conformation. In the crystal, weak intermolecular C—H⋯N hydrogen bonds link the molecules into centrosymmetric dimers, forming R 2 2(14) motifs. In addition, weak π–π stacking interactions with centroid–centroid distances in the range 3.578 (1)–3.739 (1) Å provide further stabilization.

4-Chloro-6-methyl-N-(4-methyl-phen-yl)quinolin-2-amine.

In the title compound C17H15ClN2, the dihedral angle between the quinoline ring system and the phenyl ring is 50.18 (6)°. In the crystal, molecules are linked into chains running along the c axis by N—H⋯N hydrogen bonds.