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Zirconocene-mediated, high-yielding macrocyclizations of silyl-terminated diynes
Laurel L Schafer1, Jonathan R Nitschke, Shane S H Mao
1Center for New Directions in Organic Synthesis, Department of Chemistry, University of California, and Lawrence Berkeley National Laboratory, Berkeley 94720, USA.
Abstract:
A series of silyl-terminated diynes of varying lengths and substitution patterns have been prepared. These diynes undergo zirconocene coupling with selective formation of trimeric macrocycles from linear alkynes, while nonlinear diynes give cyclodimeric products. The length of the linear diynes can be increased for the preparation of macrocycles with large nanoscale cavities. Reaction of the zirconium-containing macrocycles with acid results in the synthesis of metal-free cyclophanes. All of these macrocycles were prepared in multigram quantities, in the absence of high-dilution conditions, to give products in > 75% yield that are easily purified as crystalline solids.