Syntheses and Structural Properties of Cyclic Tetrathiadiynes

The four‐component cyclization of dilithium acetylide with dithiocyanatoalkanes yielded the hitherto unknown tetrathiacyclodiynes 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.