This invention is directed to compounds of the following formula: ##STR00001## wherein when a is 0, b is 1 or 2; when a is 1, b is 1, m is from 0-3, X is O or S, Y is halogeno, R.sub.1 is hydrogen C.sub.1-4 alkyl, R.sub.2 is hydrogen, C.sub.1-4 alkyl, or optionally substituted propargyl and R.sub.3 and R.sub.4 are each independently hydrogen, C.sub.1-6 alkyl, C.sub.6-12 aryl, C.sub.6-12 aralkyl each optionally substituted.This invention is also directed to the use of these compounds for treating depression, Attention Deficit Disorder (ADD), Attention Deficit and Hyperactivity Disorder (ADHD), Tourette's Syndrome, Alzheimer's Disease and other dementia's such as senile dementia, dementia of the Parkinson's type, vascular dementia and Lewy body dementia.This invention is further directed to a pharmaceutical composition comprising a therapeutically effective amount of the above-defined compounds and a pharmaceutically acceptable carrier.