Synfacts 2007(5): 0486-0486  
DOI: 10.1055/s-2007-968417
Synthesis of Materials and Unnatural Products
© Georg Thieme Verlag Stuttgart · New York

Planar-Chiral Arenes via Alkyne Cyclotrimerization

Contributor(s): Timothy M. Swager, Anne J. McNeil
K. Tanaka*, H. Sagae, K. Toyoda, K. Noguchi, M. Hirano
Tokyo University of Agriculture and Technology, Japan
Further Information

Publication History

Publication Date:
24 April 2007 (online)

Significance

Tanaka and co-workers report an enantioselective synthesis of planar-chiral arenes via an intramolecular alkyne cyclotrimerization using a cationic rhodium catalyst and (R)-(H8)-BINAP. Although the desired chiral metacyclophane is formed in low yields due to the competing formation of an achiral orthocyclophane, the observed enantioselectivies are high. Remarkably, the yield and enantioselectivity are independent of the ansa-bridge length; [7]- to [10]metacyclophanes were easily synthesized using this method. An intermolecular variant using di-tert-butyl acetylenedicarboxylate gave the desired metacyclophane in 15% yield and 92% ee, further demonstrating the versatility of this approach.