Highly efficient methods for the preparation of shape-persistent macrocyclics

It has been about 25 years since Staab prepared a hexameric phenyl-ethynyl macrocycle by the statistical cyclization of the copper salt of m-iodo-phen ylacetylene in 4.6% yield. Since that time, different methodologies have be en investigated that allow not only the preparation of selectively function alized structures, but also their formation in high yields. The repetitive formation of precursors followed by an intramolecular cyclization is only o ne approach to these structures. Alternatives include the use of covalently or noncovalently bound templates, as well as cyclization under thermodynam ic control. (C) 1999 John Wiley & Sons, Inc.