Microwave Synthesis and Preliminary Antibacterial Activities of New Imidazolidines Derived from 2-Aminobenzothiazole

2-aminobenzothiazole 1 was converted to the corresponding diazonium salt which was introduced in coupling reaction with alkaline solution of 2-hydroxybenzaldehyde as coupling reagent to give azo-benzothiazole derivative 2 bearing aldehyde group. The resulting aldehyde 2 was introduced in condensation reactions with the primary aromatic amines including (4-nitroaniline, 3-nitroaniline, 4-hydroxyaniline, 4-methoxyaniline, 2-methoxyaniline, 4-bromoaniline, 4-chloroaniline and 2,4-dichloroaniline) using microwave irradiation technique in absolute ethanol to produce eight imine derivatives of benzothiazole 3a-h, respectively. Treatment of the resulting imines 3a-h with L-alanine using microwave irradiation in tetrahydrofuran afforded eight new imidazolidines 4a-h substituted with benzothiazole moiety, respectively. Preliminary in vitro antibacterial activity of the target compounds were investigated using two types of bacteria, Staphylococcus aurous (Gram-positive) and Escherichia coli (Gram-negative). The results indicated that the newly synthesized imidazolidines (compounds 4c, 4d, 4f, 4g, and 4h) exhibited greater activities than gentamycin against Gram-positive bacteria. On the other hand, compounds 4c and 4f were also showed better activities against Gram-negative bacteria when compared with that of the control drug (Gentamycin).