The application of chiral aminonaphthols in the enantioselective addition of diethylzinc to aryl aldehydes

Chiral phosphoric acid-catalyzed enantioselective aza-Friedel-Crafts reaction of naphthols and electron-rich phenols with 2-aryl-3H-indol-3-ones

The enantioselective aza-Friedel-Crafts reaction is one of the most straightforward and efficient strategies for constructing a new carbon-carbon bond bearing quaternary stereocenter in organic synthesis, but the catalytic asymmetric aza-Friedel-Crafts reaction of naphthols/phenols with cyclic-ketimines attached to a neutral functional group remains still relatively unexplored. Herein, a highly enantioselective aza-Friedel-Crafts reaction of cyclic-ketimines and naphthols/phenols has been realized using a chiral phosphoric acid catalyst. A variety of chiral aminonaphthols (chiral indolin-3-ones) containing a quaternary stereocenter at the C2 position were obtained with excellent outcomes (up to 97% yield, 98% ee). Moreover, the synthetic utility of the enantiomerically enriched chiral aminonaphthols was demonstrated in some efficient transformations. According to the experimental results, a possible transition state model has been proposed to rationalize the origin of asymmetric induction.

(S,S)-1-(Phenyl((1′-4-nitrophenyl-ethyl)amino)methyl)-2-naphthol

The Betti reaction of 2-naphthol, benzaldehyde and (S)-1-(4-nitrophenyl)ethylamine without any solvent gave the corresponding aminobenzylnaphthol, that is the (S,S)-1-(phenyl((1′-4-nitrophenyl-ethyl)amino)methyl)-2-naphthol, in good yield (56%). The absolute configuration of the title compound was attributed by NMR analysis, a procedure that is reliable if compared with the data obtained by X-ray diffraction experiments.

A combined structural and computational investigation of aminobenzylnaphthol compounds derived from the Betti reaction using valine methyl ester

We report CH⋯π interactions in aminobenzylnaphthol compounds that bear halogen atoms and amino acid residues (Hirshfeld surface/de, halogen = chlorine).

Estrone derived 2-naphthol analogue in the diastereoselective one-pot Betti-condensation

The utility of deoxy-isoequilenine synthesized from estrone as valuable 2-naphthol analogue is demonstrated in the three components Betti-condensation. A simple, efficient and green procedure for the synthesis of aminobenzylnaphthol analogues (so-called Betti bases) has been realized highly diastereoselectively by using (S)-phenylethylamine and 1- or 2-naphthaldehyde. The absolute configuration of the new chiral compounds obtained has been determined by means of NMR experiments and confirmed by X-ray crystallography. The chiral steroidal aminobenzylnaphthols have been evaluated as pre-catalysts for the addition of diethylzinc to aldehydes with enantioselectivities of up to 98% ee.

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

The multicomponent reaction between 2-naphthol, arylaldehydes and ammonia yields aminobenzylnaphthols in a process known as the Betti reaction, which was first uncovered at the beginning of the 20th century. Various methods have been reported for the synthesis of aminobenzylnaphthol (Betti base) and bis-Betti base derivatives using various types of naphthols, aromatic amines, heteroaromatic amines, and aliphatic and cyclic amines instead of ammonia or diamines and aliphatic and aromatic aldehydes or dialdehyde compounds under various conditions in recent years. The Betti reaction produces racemic and non-racemic aminobenzylnaphthol ligands. It is also clear that the most important area of application of the non-racemic aminonaphthols prepared in this manner is their use in asymmetric synthesis, either as chiral ligands or as chiral auxiliaries. The functional groups in these Mannich products offer many ring closure possibilities. Some of these products or the starting bifunctional compounds possess biological activity. Herein, we present a selection of the relevant studies on this topic.

Copper catalyzed oxidative deamination of Betti bases: an efficient approach for benzoylation/formylation of naphthols and phenols

A copper-catalyzed benzoylation/formylation of naphthols and phenols via oxidative deamination of Betti bases.

Organocatalytic enantioselective aza-Friedel–Crafts reaction of 2-naphthols with benzoxathiazine 2,2-dioxides

An organocatalytic enantioselective aza-Friedel–Crafts addition of 2-naphthols to benzoxathiazine 2,2-dioxides is described using a quinine-derived bifunctional catalyst.

1-{Phen-yl[1-(p-tol-yl)ethyl-amino]meth-yl}-2-naphthol

The title compound, C₂₆H₂₅NO, was obtained via a one-pot synthesis from the reaction of 2-naphthol, 1-(p-tol­yl)ethyl­amine, p-toluene­sulfonic acid and benzaldehyde. There are three mol­ecules per asymmetric unit, all having similar conformations. There are intra­molecular O—H⋯N and C—H⋯O hydrogen bonds, with only van der Waals forces found between mol­ecules.

Strontium(II) Triflate Catalysed Condensation of β-Naphthol, Aldehyde and Urea or Amides: A Facile Synthesis of Amidoalkyl Naphthols

A novel and efficient synthesis of amidoalkyl naphthols has been developed by one-pot condensation of β-naphthol, aromatic aldehydes and urea or amides in the presence of strontium(II) triflate as a catalyst in high yields.

The Reactions of the Betti Base with 1,3-Dicarbonyl Compounds

Reaction of the Betti base 1-(α-aminobenzyl)-2-naphthol with 1,3-dicarbonyl compounds at room temperature in CH3OH in the presence of p-toluenesulfonic acid leads to the corresponding enamino carbonyl products 3, in high yield and with high chemical purity. Among them, 3b was proven to be an enamine with cis-configuration by single crystal X-ray diffraction analysis.