Syntheses and Structural Properties of Cyclic Tetrathiadiynes

摘要

The four-component cyclization of dilithium acetylide with dithiocyanatoalkanes yielded the hitherto unknown tetra-thiacyclodiynes 34, 38, 41, and 43 in moderate yields. The use of the trimethylsilyl protecting group allowed a more efficient and flexible stepwise approach with good yields. The resulting tetrathiacyclodiynes 25-44 were investigated by X-ray analysis. For ring systems with a twist-chair conformation the torsion angle between the CH_2-S σ-bonds of the CH_2-S-C≡C-S-CH_2 moiety adopts values between 75 ° and 110 °. These values are due to electronic effects, as shown by HF/6-31G~* calculations.