Pyrrolo[2,3-C]pyridines as imaging agents for neurofibrillary

A compound of formula (I):

• or a pharmaceutically acceptable salt thereof wherein;
• X represents CH, or N;
• R represents hydrogen, or —C1-6alkyl, said alkyl optionally substituted with 1 to 3 groups of Ra;
• R1 represents hydrogen, —C1-6alkyl, —CN, —(CH2)nNH(CH2)nN(R)2, —C2-6alkenyl, —(CH2)nOR, or —(CH2)nhalogen;
• R2 represents —OC1-6 alkyl, —C2-6alkenylR3—(CH2)nOR, —(CH2)nhalogen, —O(CH2)nhalogen, —C6-10 aryl, —C5-10 heterocyclyl, —O(CH2)nRa, —N(CH3)(CH2)nOR, —NRC(O)R, —NH(CH2)nhalo, —NC(O)C6-10 aryl, —NC(O)C5-10 heterocyclyl, —N(CH3)(CH2)nhalogen, —C(O)NC6-10 aryl, said alkyl, aryl, and heterocyclyl optionally substituted with 1 to 3 groups of Ra;
• or an adjacent R1 can combine with R2 to form a nine to ten membered bicyclic ring together with the ring to which R1 and R2 are attached, optionally interrupted with N, S, and/or O, said bicyclic ring optionally substituted with 1 to 3 groups of Ra;
• R3 represents hydrogen, —C1-6alkyl, —(CH2)nhalogen, —(CH2)nN(R)2, —(CH2)nNR(CH2)nN(R)2, —C6-10 aryl, —C5-10 heteroaryl, said alkyl, aryl, and heteroaryl optionally substituted with 1 to 3 groups of Ra;
• Ra represents —CN, CF3, —C1-6alkyl, —C2-6alkenyl, —C2-6alkynyl, C6-10 aryl, —C5-10 heterocyclyl, —CN, NO2, (CH2) halogen, —O(CH2)nhalogen, (CH2)nOR, —O(CH2)nC6-10 aryl, —(CH2)nN(R)2, —C(O)N(R)2, —N(CH3)(CH2)nOR, —NRCOR, —COR, —NH(CH2)nhalo, —N(CH3)(CH2)nhalogen, C(O)C6-10 aryl, or —CO2R, said alkyl, alkenyl, alkynyl, aryl, and heterocyclyl optionally substituted with 1 to 3 groups of Rb;
• R represents hydrogen, —C1-6alkyl, —OR, —(CH2)nN(R)2, or halogen;
• and
• n represents 0-4.