Compounds of formula (a), (b), (c), or (d), or any mixture thereof, or a pharmaceutically-acceptable salt thereof;wherein R is 
hydrogen, 
alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl or 2-hydroxyethyl; R3 is -CH2-X-R', wherein X is O, S or NR'', wherein R'' is 
hydrogen or 
alkyl and R' is 
alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, or -CO-alkyl; R4 is phenyl optionally substituted with 
halogen, CF3, CN, alkoxy, cycloalkoxy, alkyl, cycloalkyl, alkenyl, alkynyl, amino, nitro, heteroaryl, or 
aryl; 3,4-methylenedioxyphenyl; benzyl optionally substituted with 
halogen, CF3, CH, alkoxy, cycloalkoxy, alkyl, cycloalkyl, alkenyl, alkynyl, amino nitro, heteroaryl, or 
aryl; heteroaryl optionally substituted with 
halogen, CF3, CN, alkoxy, cycloalkoxy, alkyl, cycloalkyl, alkenyl, alkynyl, amino, nitro, heteroaryl, or 
aryl; or naphthyl optionally substituted with halogen, CF3, CN, alkoxy, cycloalkoxy, alkyl, cycloalkyl, alkenyl, alkynyl, amino, nitro, heteroaryl, or aryl. The compounds are 
monoamine neurotransmitter, i.e., 
dopamine, 
serotonin, noradrenaline, 
reuptake inhibitors.