Chiral solvating agents for carboxylic acids based on the salen moiety

A series of chiral salen C2-symmetric aminophenols 1–4, which were derived from (1R,2R)- or (1S,2S)-1,2-diphenylethane-1,2-diamine with the corresponding salicylic aldehyde through a [2+2] condensation reaction, have been prepared. The NMR studies demonstrated that they can function as chiral solvating agents for the determination of the enantiomeric purity of chiral carboxylic acids.

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(R,R)-N,N′-Bis(5-methylsalicyl)-1,2-diphenylethylenediamineC30H32N2O2[α]D25=+19.0 (c 0.0368, ethyl acetate)Source of chirality: the precursorAbsolute configuration: (R,R)

(R,R)-N,N′-Bis(4-methoxysalicyl)-1,2-diphenylethylenediamineC30H32N2O4[α]D25=-49.0 (c 0.0388, ethyl acetate)Source of chirality: the precursorAbsolute configuration: (R,R)

(S,S)-N,N′-Bis(5-chlorosalicyl)-1,2-diphenylethylenediamineC28H26Cl2N2O2[α]D25=-15.15 (c 0.0396, ethyl acetate)Source of chirality: the precursorAbsolute configuration: (S,S)

(R,R)-N,N′-Bis(5-fluorosalicyl)-1,2-diphenylethylenediamineC28H26F2N2O2[α]D25=+10.6 (c 0.0376, ethyl acetate)Source of chirality: the precursorAbsolute configuration: (R,R)

(1R,2R)-N,N′-Dibenzyl-1,2-diphenyl-ethane-1,2-diamineC28H28N2[α]D25=+74.4 (c 0.0336, ethyl acetate)Source of chirality: the precursorAbsolute configuration: (1R,2R)