Directionally Aligned Crown Ethers as Superactive Organocatalysts for Transition-metal Ion-free Arylation of Unactivated Arenes.

When one-dimensionally aligned to the same side, multiple non-covalently associated crown ether groups could act as a whole to yield a higher catalytic activity than an individual poorly active crown ether group, delivering the lowest catalyst loading of 1-2 mol % among all hitherto known organocatalysts for catalyzing direct arylation of unactivated arenes with haloarenes.