Double anionic cycloaromatization of 2-(6-substituted-3-hexene-1,5-diynyl)benzonitriles initiated by methoxide addition

reaction: see text] Treatment of 2-((3Z)-undecene-1,5-diynyl)benzonitrile with 5 equiv of sodium methoxide in refluxing methanol for 16 h gave 1-pentyl-6-methoxyphenanthridine in 12% yield, 1-pentyl-6-phenanthridone in 6% yield, and 2-(2-pentyl-6-methoxyphenyl)benzonitrile in 4% yield. Under the same reaction conditions, methanolysis of several other benzonitriles gave similar results. Phenanthridine and biphenyl derivatives were obtained as the major products. A mechanism for this novel cycloaromatization reaction of enediynes is proposed.