Anionic cycloaromatization of 1-aryl-3-hexen-1,5-diynes initiated by methoxide addition: synthesis of phenanthridinones, benzo[c]phenanthridinones, and biaryls.
Treatment of 2-((Z)-6-substituted-3-hexene-1,5-diynyl)benzonitriles with sodium methoxide in refluxing methanol in the presence of a polar aprotic solvent, such as DMSO, HMPA, THF, or 18-crown-6, gave phenanthridinones in 21-77% yields. In these cases, addition of 10% DMSO into the reaction mixture gave the highest yield. On the other hand, methanolysis of 2-(2-(2-alkynylphenyl)ethynyl)benzonitriles under the same reaction conditions gave benzo[c]phenanthridinones in 31-57% yields. Methanolysis of (Z)-1-aryl-3-hexen-1,5-diynes in the presence of 2 equiv of tetrabutylammonium iodide gave biaryls in 14-64% yields. It is found that the reactions with aryl groups bearing electron-withdrawing groups proceeded at greater rates and gave better yields.
School of Chemistry, Kaohsiung Medical University, Kaohsiung, Taiwan. mijuwu@cc.kmu.edu.tw
Ming-Jung
MJ
Wu
Chi-Fong
CF
Lin
Wen-Der
WD
Lu