A compound of formula wherein n is 0 or 1; m is 0 or 1; p is 0 or 1; X is oxygen or sulfur; Y is CH, N or NO; W is oxygen, H2 or F2; A is N or C(R2); G is N or C(R3); D is N or C(R4); with the proviso that no more than one of A, G, and D is nitrogen, but at least one of Y, A, G, and D is nitrogen or NO; R1 is hydrogen or C1 to C4 alkyl; R2, R3, and R4 are independently hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, aryl, heteroaryl, OH, OC1-C4 alkyl, CO2R1, —CN, —NO2, —NR5R6, —CF3, —OSO2CF3 or R2 and R3, or R3 and R4, respectively, may together form another six membered aromatic or heteroaromatic ring sharing A and G, or G and D, respectively, containing between zero and two nitrogen atoms, and substituted with one to two of the following substituents: independently hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, aryl, heteroaryl, OH, OC1-C4 alkyl, CO2R1, —CN, —NO2, —NR5R6, —CF3, —OSO2CF3; R5 and R6 are independently hydrogen, C1-C4 alkyl, C(O)R7, C(O)NHR8, C(O)OR9, SO2R10 or may together be (CH2)jQ(CH2)k where Q is O, S, NR11, or a bond; j is 2 to 7, k is 0 to 2; R7, R8, R9, R10, and R11 are independently C1-C4 alkyl, aryl, or heteroaryl, or an enantiomer thereof, and the pharmaceutically acceptable salts thereof, processes for preparing them, composition containing them, and their use in therapy, especially in the treatment or prophylaxis of psychotic disorders and intellectual impairment disorders.