Solvent-dependent self-discrimination of Bis(2-hydroxyphenyl)diamides

摘要

Solvent-dependent, self-dis-crimination of diamides is described. Mixing a solution of (A)-1a and (S)-1a, which are valine-derived, bis(2-hy-droxyphenyl) diamide-bearing, multiple hydrogen-bonding modules, in di-chloromethane immediately led to the formation of a thick suspension com-prising a 1: 1 heterochiral aggregate of la. The solubility of heterochiral la was substantially lower in halogenated solvents than in ethyl acetate. A perus-al of racemic crystal structures ob-tained from chloroform and ethyl ace-tate revealed a significant difference in the crystal-packing pattern, which is likely to be the basis for the pro-nounced difference in solubility. Specif-ic self-discrimination of la in an en-semble of eight structurally related molecules showcased the specific ag-gregation through the hydrogen-bond-ing network of the bis(2-hydroxyphe-nyl)diamide framework. The low solu-bility of heterochiral la in halogenated solvent was exploited to achieve high stereoselectivity in a catalytic asymmet-ric reaction by using a low enantiomer-ic excess sample of la.