Introduction:
Mannich reaction is a typical example of a three-component condensation reaction and the chemistry of
Mannich bases has been the matter of search by researchers. Here an efficient procedure for the synthesis of some new Mannich
derivatives of simple phenols is described.
Methods:
In this procedure a microwave-assisted and solvent less condensation were done
between different phenols, secondary amines and paraformaldehyde. The reactions proceed in the presence of catalytic amount of
nano ZnO and tetrabutylammonium bromide (TBAB) in excellent yields. 10 new compounds were synthesized (A1-A10). Chemical
structures of all new compounds were confirmed by different spectroscopic methods. We optimized the chemical reactions in
different conditions. Optimization reactions were done in the presence of different mineral oxides, different amount of TBAB and also
different solvents. Nano ZnO and TBAB in catalytic amounts and solvent free conditions were the best conditions. All the synthesized
compounds were screened for their antimicrobial activities. Antifungal and antibacterial activities of the synthesized compounds were
evaluated against some Candida, filaments fungi, gram positive and gram negative bacteria by broth micro dilution method as
recommended by CLSI.
Results:
The result showed that compounds A2, A3 and A4 against most of the tested Candida species and
compounds A5 and A7 against C. parapsilosis and C. tropicalis, exhibited considerable antifungal activities. Also Compounds A8 and
A10 showed desirable antifungal activities against C. neoformance and C. parapsilosis, respectively. The antibacterial activities of the
synthesized compounds were also evaluated. Compounds A6 - A10 against E. Fecalis and compounds A5, A7, A9 and A10 against P.
aeruginosa showed desirable antibacterial activities.
Discussion:
We have synthesized some new Mannich adducts of poly-hydroxyl
phenols in the presence of nano-ZnO as a reusable catalyst, with the hope of discovering new lead compounds serving as potent
antimicrobial agents. The advantages of this method are generality, high yields with short reaction times, simplicity, low cost and
matching with green chemistry protocols. The antimicriobial studies of Mannich derivatives of phenols showed desirable results in
vitro.
