Cyclic Conjugated Diacetylenes

The synthesis of α-bisethynyl compounds, IV and VIII, and cyclic conjugated diacetylenes, V and IX, was performed according to Scheme 1. Bisethynyl compounds, IV and VIII, were prepared in good yields by ethynylation of bromides II, III and VII in N-ethyl-2-pyrrolidone with liquied ammonia solution of sodium acetylide at atmospheric pressure. The intramolecular cyclization of IV was carried out by the Eglinton's oxidative coupling¹with high-dilution technique under nitrogen atmosphere.