Rhodium-Catalyzed Intermolecular [5+1] and [5+2] Cycloadditions Using 1,4-Enynes with an Electron-Donating Ester on the 3-Position.

Various 3-acyloxy-1,4-enynes could be employed in rhodium-catalyzed intermolecular [5+1] and [5+2] cycloadditions with CO or alkynes, respectively. The rate of these cycloadditions could be accelerated significantly by using 1,4-enynes with an electron-donating ester on the 3-position. The scope of rhodium-catalyzed [5+1] and [5+2] cycloadditions were examined by using 1,4-enynes bearing an electron-donating ester.