Scheme 1.

General procedure for the synthesis of target compounds 5, 6, and 7a-l. Reagents and conditions: (i) thionyl chloride (SOCl₂), dicloroethane, reflux, 2 h; (ii) 4-aminibenzoic acid, triethylamine (TEA), acetonitrile, stirring, rt; (iii) thionyl chloride (SOCl₂), dichloroethane, reflux, 2 h; (iv) cyclohexylamine, treithylamine (TEA), acetonitrile, reflux, 2 h; (v) benzylamine, treithylamine (TEA), acetonitrile, reflux, 2 h; (vi) app. amine, treithylamine (TEA), acetonitrile, reflux, 2 h.