Compounds of the general formula are described: wherein R1 is hydrogen or halogen; R2 is hydrogen, halogen, lower alkyl or lower alkoxy; R3 is halogen, trifluoromethyl, lower alkoxy or lower alkyl; R4/R4′are each independently hydrogen or lower alkyl; R5 is lower alkyl, lower alkoxy, amino, hydroxy, hydroxy-lower alkyl, —(CH2)n-piperazinyl, optionally substituted by lower alkyl, —(CH2)n-morpholinyl, —(CH2)n+1-imidazolyl, —O—(CH2)n+1-morpholinyl, —O—(CH2)n+1-piperidinyl, lower alkyl-sulfanyl, lower alkyl-sulfonyl, benzylamino, —NH—(CH2)n+1N(R4″)2, —(CH2)n—NH—(CH2)n+1N(R4″)2, —(CH2)n+1N(R4″)2, or —O—(CH2)n+1N(R4″)2, wherein R4″ is hydrogen or lower alkyl; R6 is hydrogen; R2 and R6 or R1 and R6 may together be —CH═CH—CH═CH—, wherein R2 and R6 or R1 and R6, respectively, together with the two carbon ring atoms to which they are attached form a fused ring, with the proviso that n for R1 is 1; n is independently 0-2; and X is —C(O)N(R4″)— or —N(R4″)C(O)—; and pharmaceutically acceptable acid addition salts thereof.