The Lewis acid-mediated reactions of allene-ene compounds, derived from 3- methylcitronellal or dimethyl malonate, were carried out using various Lewis acids such as ethylaluminum dichloride, diethylaluminum chloride, titanium chloride, zinc chloride etherate, or boron trifluoride etherate, affording unexpectedly intramolecular [2+ 2] cycloaddition products under some particular reaction conditions without any formation of ...
