Scheme 1.

Reagents and conditions: (i) (COCl)₂ (3 equiv), CH₂Cl₂, DMF (one drop), stirring at room temperature for 4 h; (ii) the corresponding amine (1.2 equiv), K₂CO₃ (4 equiv), KI (1 equiv), CH₃CN, room temperature or slight heating for 12–48 h, yields 32–91%; (iii) excess of dimethylamine (40% wt. solution in ethanol) or diethylamine, K₂CO₃ (2 equiv), CH₃CN, room temperature or reflux for 12 h, yields 35–53%; (iv) the corresponding amine (1.5 equiv), Et₃N (1 equiv), CH₂Cl₂, room temperature or slight heating for 12–48 h, yields 32–91%. * Compound 1a was used as a commercial reagent.