Cholesterol-appended aromatic imine organogelators: a case study of gelation-driven component selection.

This letter describes a novel approach for developing organogelators through the formation of reversible imine bonds from two molecular components and the enriching behavior of the gelating imines. Cholesterol-appended aniline 1 and 4-substituted benzaldehydes 2a-d did not gelate any solvents. Their condensation products, imines 3a-d, however, could gelate alcohols because of the enhanced stacking interaction of the imine unit. For a further component selectivity test, the reactions of the mixture of 1, 2b-d, and cholesterol-free aniline 7 (1:1:1) in different solvents were performed. The resulting imines were reduced to the corresponding amines and analyzed with 1H NMR. It was revealed that, for the reactions resulting in no formation of the gel phase, imines 8a-c formed from 2b-d and 7 were obtained as the major product (64-76%) and all of the reactions that led to the formation of the gel phase gave rise to 3b-d as the major product (55-61%).