Winding vine-shaped bithiophene was synthesized through the nosyl (2-nitorobenzene sulfonyl) cyclization protocol. The reaction of bithiophene bearing bromomethyl groups at the 3,3'-positions with nosylated 1,2-ethylenediamine in the presence of potassium carbonate afforded the annulated product in excellent yield. The obtained bithiophene was found to contain a 10-membered ring, which was confirmed by X-ray analysis. The related nosyldiamine bearing a tri-or tetramethylene group also reacted in a similar manner, affording 11-or 12-membered macrocycle, respectively.

No abstract

Preparation of 2,2¤-bithiophene derivatives bearing ω-alkenyl groups at the 3,3¤-positions and ring-closing metathesis reactions of the obtained compound were performed. The reaction of bithiophene bearing 3-butenyl substituents 1 with 5 mol % Grubbs 1st generation catalyst underwent ring-closing metathesis (RCM) to afford the cyclized product 7 showing winding vine-shaped molecular asymmetry in up to 88% yield. Enantioselective RCM was also achieved by the use of chiral Schrock Hoveyda molybdenum-alkylidene catalyst in up to 87% ee.

The chirality of winding vine-shaped heterobiaryls with molecular asymmetry is recognized by a sugar-based chiral oxidant. Kinetic resolution of (±)-bisbenzoimidazole bearing an olefin moiety takes place with Shi’s asymmetric epoxidation to observe krel value up to ca. 35 affording the corresponding epoxide. The reaction of a (±)-bithiophene derivative also recognized the chirality to give the corresponding epoxide with er of 96:4 at 39% conversion. Dynamic kinetic resolution is found to take place when unsymmetrical biaryl composed of benzoimidazole/thiophene is subjected to Shi’s epoxidation, whose conversion of the racemic substrate exceeds to 50%.

Oxidative condensation of N-(3-buten-1-yl)-1,2-phenylenediamine with a formylated heteroarene bearing 3-buten-1-yl substituent gives unsymmetrical heterobiaryl in 42-86% yields. Ring-closing metathesis of the thus obtained product affords the cyclized product, which resulted in separation of each enantiomer by HPLC with a chiral column showing molecular asymmetry.