Synthesis of Mannich bases of 4-hydroxyacetophenone

Abstract

Mannich bases are the products of Mannich reactions which involve aldehyde, ketone and primary or secondary amine. Mannich bases are widely studied as they possess important diverse activities such as antibacterial, anticancer and analgesics. Apart from that, they are also being used in detergent additives, resins and polymers. In this study, a series of Mannich bases were synthesized by using 4-hydroxyacetophenone as the precursor. The initial step in the synthesis was to prepare 4-methoxyacetophenone by methylation of phenolic hydroxyl group of 4-hydroxyacetophenone. Both 4-hydroxyacetophenone and 4-methoxyacetophenone were refluxed separately with piperidine and formaldehyde by using absolute ethanol as the solvent to produce 4-hydroxy-3,5-(dipiperidin-1-ylmethyl)acetophenone and 4-methoxy-3-(piperidin-1-ylmethyl)acetophenone respectively. The reactions were monitored by using thin layer chromatography and purified by column chromatography. The structures of the final compounds obtained were elucidated by using several spectroscopic techniques which were IR, ¹H NMR and ¹³C NMR. Both reactions produced Mannich bases as yellowish brown liquid.