Activated Fuller’s earth: an efficient, inexpensive, environmentally benign, and reusable catalyst for rapid solvent-free synthesis of 1-(amido/amino)alkyl-2-naphthols

Catalyst‐Free Accelerated Three‐Component Synthesis of Betti Bases in Microdroplets

“…To facilitate the conversion smoothly, high temperature, [21] microwave [13,16b,22] and ultrasonic irradiation are typical strategies in combination with certain catalysts (Scheme 2b). In recent studies, many highly efficient catalysts with good stability and reusability such as clay, [23] activated Fuller's earth, [24] functionalized ionic liquid (3‐( N , N ‐dimethyldodecylammonium)propanesulfonic acid hydrogen sulfate), [25] porous carbon spheres (doped by nitrogen and sulfur, and ferric hydrogen sulfate), [26] and nanocatalysts (modified graphene oxide gold nanoparticles [27] and magnetic nanocrystallites strontium hexaferrite [28] ) (Scheme 2c) have been developed. However, in most cases, it usually took a long time for reaction completion under the assistance of catalysts at moderate to high temperatures.…”

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“…This method has some drawbacks including fast reaction rates and poor yields; making it inapplicable in a large scale production [7,8]. Thus, a series of methodologies have been explored to prepare aminoalkyl naphthols through more efficient procedures (especially one-pot multicomponent reactions) to overcome the drawbacks of classical synthetic routes [9][10][11][12]. The synthesis by using 2-naphthol, aldehydes, and amines has been performed by various catalytic systems including (+)-camphor-10sulfonic acid [13], Fe3O4@SiO2-ZrCl2-MNPs [14], maltose [15], oxalic acid [16], ionic liquid [17], aragonite [18], NH3(CH2)5NH3BiCl5 [19], and l-Valine [20].…”

Benzhydryl Amines: Synthesis and Their Biological Perspective

“…4 Interestingly, it was found that the reaction occurred at the N-methyl and/or cyclic Nmethylene positions through an aminium radical cation intermediate under SET catalysis only, whereas in contrast, synergistic SET and HAT catalysis reversed the regioselectivity. The reaction was finished within a very short time with 0.5 mol % of the Ir complex and 1 mol % of PhC(O)SH as a HAT catalyst, and diverse 1,1-diarylmethylamines (10) were synthesized in reasonable to excellent yields (56−98%). (11), salicylaldehydes (12), and secondary amines (13) to furnish alkylaminophenols ( 14) within a very short time period (Scheme 5).…”

“…In 2018, Rekunge et al reported a cost-effective, solvent-free, green protocol for the synthesis of 1-(amido/amino) alkyl-2naphthols ( 22) using activated Fuller's earth as a heterogeneous reusable catalyst via multicomponent reaction of an aldehyde, 2naphthol or phenol, and amides or amines with excellent to good yields (Scheme 10). 10 Afterward, in 2018 Patil et al (same group) reported an expeditious, practical, and environmentally benign approach for the synthesis of Betti bases (1-aminoalkyl-2-phenols) (23) via a multicomponent reaction using sulfated polyborate catalyst under solvent-free conditions (Scheme 11). 11 The catalyst was prepared by dehydration of boric acid followed by sulfonation, and the recovered catalyst was reused up to four times without loss of any catalytic activity.…”