The mol­ecule of the title compound, C34H36O6, is located on a twofold rotation axis. The two 4-but­oxy­benzoyl groups at the 1- and 8-positions of the naphthalene ring system are aligned almost anti­parallel. The dihedral angles between the benzene rings and the naphthalene ring system are 71.70 (4)°. In the crystal, the mol­ecules are connected via C—H⋯π inter­actions into a layer parallel to (010).

The title compound, C32H32O6, crystallized with two independent molecules in the asymmetric unit. Each molecule has essentially the same feature of non-coplanar aromatic rings whereby the two 4-isopropoxybenzoyl groups are twisted in a perpendicular manner to the naphthalene ring and oriented in the same direction (syn-orientation). The benzene rings of the aroyl groups make dihedral angles of 16.13 (7) and 25.31 (7)° in the two molecules. These benzene rings make dihedral angles of 88.38 (8) and 75.32 (7)° with the naphthalene ring system in one molecule, and 89.71 (7) and 82.11 (7)° in the other. In the crystal, mol­ecules are linked via C—H⋯O hydrogen bonds, forming a three-dimensional network. In one independent molecule, the 2-propyl groups of both isoprop­oxy groups are disordered over two positions with site occupancies of 0.512 (3) and 0.488 (3).

In the title compound, C32H32O4, the dihedral angle between the two benzene rings of the 2,4,6-trimethyl­benzoyl groups is 71.43 (7)°. The dihedral angles between the two benzene rings and the naphthalene ring system are 81.58 (5) and 84.92 (6)°. An intra­molecular C—H⋯O inter­action is observed.

In the title mol­ecule, C30H28O4, the inter­planar angle between the two benzene rings of the 3,5-dimethyl­benzoyl groups is 50.35 (7)°. The dihedral angles between the two benzene rings and the naphthalene ring system are 81.87 (6) and 83.55 (6)°. In addition, the conformations of the pairs of methyl groups and their counterparts differ from each other though their environment is very similar. In the crystal, weak C—H⋯O inter­actions occur.

In the title compound, C29H25ClO4, the dihedral angle between the benzene rings of the 2,4,6-trimethyl­benzoyl group and the 4-chloro­benzoyl group is 65.19 (9)°. The dihedral angles between the naphthalene ring system and the benzene rings of the 2,4,6-trimethyl­benzoyl group and the 4-chloro­benzoyl group are 85.66 (8) and 69.48 (8)°, respectively. In the crystal, two types of inter­molecular C—H⋯O inter­actions and an intra­molecular C—H⋯O inter­action are observed. Moreover, there is a short intra­molecular C=O⋯C=O contact of 2.614 (2) Å between the benzoyl substituents.