Catalyst‐free Synthesis of Betti bases in a Mannich‐Type Reaction

Abstract

Betti you can: An efficient, sustainable, and a catalyst‐free procedure for the synthesis of Betti bases by a one‐pot, three‐component, Mannich‐type condensation of secondary amines, aldehydes, and β‐naphthol in polyethylene glycol at room temperature has been developed. The products do not require purification by chromatography and the solvent was remarkably recyclable for up to four runs.

Prospects of practical application of hybrid membranes

“…Nafion exhibits catalytic activity in the dehydration of alcohols, Friedel-Crafts alkylation, isomerization, oligomerization, nitration, acylation, etc. [153][154][155][156][157]. It exhibits a number of advantages when used as a catalyst support [158].…”

Recent advances in the synthesis and synthetic applications of Betti base (aminoalkylnaphthol) and bis-Betti base derivatives

“…46 A one-pot procedure was reported by Foroughifar et al for the preparation of 4,9-dihydroxy-1,3diaryl-2,3-dihydro-2-zaphenalenes 70 in 78-92% yields aer 8-15 h from aromatic aldehydes, 2,7-naphthalenediol and ammonium hydrogen phosphate ((NH 4 ) 2 HPO 4 ) in a mixture of ethanol-water (3 : 1) under reux conditions (Scheme 38). 47 A self-catalytic protocol was developed using an aza-Friedel-Cras method to generate 1-naphthoyltetrahydroisoquinoline products 71 Addition of (R)-3-phenyl-3,4-dihydroisoquinoline to 2naphthols in water at 80 C overnight led to the formation of (S)-(R)-1,3-disubstituted tetrahydroisoquinolines 74 as chiral ligands in 40-69% yields (Scheme 41). 50 These chiral ligands were then used to catalyze asymmetric addition of diethylzinc to aldehydes in toluene at 0 C for 72 h and the desired Triton X-100 as a non-ionic surfactant catalyst was used for the synthesis of Betti bases 76 from secondary amine, aromatic aldehydes, and 2-naphthol using Mannich-type reaction in water at room temperature.…”

“…Betti bases 102 were obtained in 76-94% yields via the condensation reaction of aromatic aldehydes, secondary amines and 2-naphthol in PEG-400 as solvent in the absence of catalyst at room temperature aer 2-4 h. In this reaction, aromatic aldehydes and heteroaromatic carbaldehydes worked satisfactorily, but the reaction with aromatic amines was not successful (Scheme 62). 71 Song et al 72 developed a new method for the synthesis of enantiomerically pure Betti bases 103. By using triuoroacetic acid to replace the more traditionally used hydrochloric acid, the hydrolysis procedure used in the classical synthesis of racemic Betti base was carried out at 50 C in CH 2 Cl 2 /H 2 O with an improved yield (up to 96%), which was followed by a new and efficient resolution using recyclable (R)-1,1 0 -binaphthalene-2,2 0diyl sodium phosphate to provide enantiomerically pure (S)-Betti base 103a in 95% yield with up to 99% ee and (R)-Betti base 103b in 93% yield with 90% ee in one resolution step (Scheme 63).…”

Recyclable chiral dinuclear copper(II) complexes catalyzed asymmetric Friedel–Crafts alkylation of 1-naphthol using N-tosyl aldimine

“…Friedel-Crafts reaction of 1-naphthols with imines represents a direct and attractive approach for the synthesis of optically active amino arylnapthols known as Betti base [23,24]. The first asymmetric FC-type reaction of 2-naphthols and aldimines was reported by Hui [25] in 2010 using a stoichiometric amount of a chiral zinc complex.…”