Stereoselective synthesis of new vicinal diaminoalkyl naphthols by three component Mannich type reaction of α,β-unsaturated aldehydes

The application of the aromatic Mannich reaction to α,β-unsaturated aldehydes, affords a series of new diaminoalkyl naphthols, by a convenient solventless reaction, starting from inexpensive and easily available starting materials. The absolute configurations of the products obtained are attributed on the basis of the coupling constant values of 1H NMR spectra, joined with the conformational analysis of the molecules by molecular modelling. A mechanistic hypothesis is proposed, which involves an imino–amino intermediate.

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1-{(1R,3S)-1,3-Bis((R)-1-phenylethylamino)butyl}naphthalen-2-olC30H34N2O[α]D20=+35.4 (c 0.67, CHC13)Absolute configuration: (1R,3S,1′R,1″R)Source of chirality: (R)-(+)-1-phenylethylamine

1-((1R,3S)-1,3-Bis((R)-1-phenylethylamino)hexyl)naphthalen-2-olC32H38N2O[α]D20=+29.7 (c 1.07, CHC13)Absolute configuration: (1R,3S,1′R,1″R)Source of chirality: (R)-(+)-1-phenylethylamine

1-((1S,3R)-1,3-Bis((R)-1-phenylethylamino)hexyl)naphthalen-2-olC32H38N2O[α]D20=+37.4 (c 1.04, CHC13)Absolute configuration: (1S,3R,1′R,1″R)Source of chirality: (R)-(+)-1-phenylethylamine

1-((1R,3R)-1,3-Bis((R)-1-phenylethylamino)-3-phenylpropyl)naphthalen-2-olC35H36N2O[α]D20=+44.2 (c 2.19, CHCl3)Absolute configuration: (1R,3R,1′R,1″R)Source of chirality: (R)-(+)-1-phenylethylamine

1-((R)-1,3-Bis((R)-1-phenylethylamino)propyl)naphthalen-2-olC29H32N2O[α]D20=+28.85 (c 1.41 CHC13)Absolute configuration: (1R,1′R,1″R)Source of chirality: (R)-(+)-1-phenylethylamine

1-((S)-1,3-Bis((R)-1-phenylethylamino)propyl)naphthalen-2-olC35H36N2O[α]D20=+23.5 (c 1.15 CHC13)Absolute configuration: (1S,1′R,1″R)Source of chirality: (R)-(+)-1-phenylethylamine