N-(2-arylethyl)benzylamines as antagonists of the 5-HT6 receptor

A method of treating Alzheimer's disease comprising administering to a patient in need thereof an effective amount of a combination of a 5-HT6 receptor antagonist and a cholinesterase inhibitor, or pharmaceutically acceptable salts thereof, wherin the 5-HT6 receptor antagonist is of structural formula I:

• wherein X is selected from the group consisting of —O—, —NH—, —S—, —SO2—, —CH2—, —CH(F)—, —CH (OH)—, and —C(O)—;
• R1 is selected from the group consisting of optionally substituted phenyl, optionally substituted naphthyl, optionally substituted 5 to 6 membered monocyclic aromatic heterocycle having one heteroatom selected from the group consisting of nitrogen, oxygen, and sulfur and which 5 to 6 membered monocyclic aromatic heterocycle is optionally benzofused;
• R2 is selected from the group consisting of hydrogen and C1-C3 alkyl;
• R3 is selected from the group consisting of hydrogen, fluoro, and methyl;
• and
• R4 is selected from the group consisting of hydrogen, allyl, C2-C4 alkyl, fluorinated C2-C4 alkyl, optionally substituted phenyl, optionally substituted phenylsulfonyl, optionally substituted benzyl, and optionally substituted 5 to 6 membered monocyclic aromatic heterocycle having one or two heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur, provided that R4 is not optionally substituted phenylsulfonyl when X is —SO2—, —CH2—, —CH(F)—, —CH(OH)—, or —C(O)—.