| abstract |
The invention provides compounds of formula I, <IMAGE> I wherein each of R1 and R4, which may be the same or different, is hydrogen, halogen, alkyl or alkoxy; each of R2 and R3 is hydrogen, or together, oxygen; B and D together with the carbon atoms to which they are bound may be a benzene ring or a substituted or unsubstituted thiophene ring and A may, for example, be oxygen, sulpur, -CH2-O-, -CH2-S, ethylene or vinylene, useful as psychostimulants and vigilance-increasing agents. |