Intramolecular formal [4+2] cycloaddition between 3-ethoxycyclobutanones and a carbon-carbon double bond to the corresponding bicyclo[4.n.0]alkan-2-one derivatives proceeded effectively by using ethylaluminium dichloride.
School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan. jimatsuo@p.kanazawa-u.ac.jp