Synthesis and Characterization of Cyclic Alkyl Tetraynes

Abstract

Cyclic (4a-e) and linear (10) tetraynes have been studied. Macrocycles 4a-e are unstable to isolation as neat compounds, but 4b-e have been characterized in solution. 13C NMR spectroscopy shows a consistent downfield shift of the acetylenic resonances of 4c-e as ring strain increases. UV-vis spectroscopy demonstrates that ring strain has little effect on the HOMO-LUMO gap. X-ray crystallography of tetrabromoolefin 6b confirms the monomeric constitution of the precursors.