Microwave-assisted synthesis of novel 2-naphthol bis-Mannich bases

Abstract

Mannich bases of 2-naphthol have the ability to chelate strongly to metal ions. Hence, they have great potential to be used as chiral catalysts, metallo-enzyme inhibitors and/or scavenger of heavy metal poisons. This paper deals with an efficient and expeditious microwave assistedsynthesis of novel bis-Mannich bases of 2-naphthols derived from aromatic aldehydes and diamines namely piperazine and N,N'-dialkylethylenediamines under solvent-free conditions. These compounds were also prepared under conventional reflux in ethanol. The compounds of this series displayed interesting NMR behaviour.

A Green Protocol for One‐Pot Pseudo Five‐Component Synthesis of a New Series of Bis‐Betti Bases Via Mannich‐Type Reaction

“…Decreasing (5 mol %) or increasing (15 and 20 mol %) the ratio of p-TSA at 90 °C under solvent-free conditions did not improve the product yield (Table 1, entries 10-12). When the reaction mixture was examined in the presence of various catalysts such as formic acid and guanidine hydrochloride at 90 °C under solvent-free conditions for 1.5 h, the product 4 a was furnished in 58 and 71 % yields, respectively (Table 1, entries [13][14]. Therefore, the entry 7 of Table 1 offered the optimum reaction condition for the one-pot synthesis of bis-Betti base derivative 4 a under solvent free conditions.…”

“…The synthetic routes for the synthesis of this scaffold have been reviewed. [5][6][7][8] Moreover, bis-aminomethylnaphthols (bis-Betti bases) have been synthesized using by the reaction of various types of dihydroxynaphthalens such as 2,6-dihydroxynaphthalene and 2,3-dihydroxynaphthalene with aldehydes and amines, [9][10][11][12][13] the reaction of diamines such as 2,6-diaminopyridine, piperazine and p-phenylenediamine with naphthols and aldehydes, [14][15] and the reaction of dialdehydes such as terephthaldehyde and isophthalaldehyde with naphthols and amines [16][17] and reduction of bisdihydrooxazine structures. [18] The Betti reaction produces racemic and nonracemic aminoalkylnaphthol ligands.…”

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“…[16] The compounds bearing nitrogen atom as hetero atom are playing unique role in medicinal chemistry; hence the combination of 4-nitrobenzaldehyde, morpholine and N-phenylurea was condensed as they were not yet reported. The amide unit present in the structural framework of the Mannich bases have strong ability to form metal complexes and enhance the absorption through bio-membranes by the disease causing microorganisms [17][18][19][20][21][22]. We aimed to link aldehyde and amide using morpholine by Mannich reaction.…”