A method for the [2 + 2] cycloaddition of aryl ketenes and alkenes is presented. The process involves the in situ generation of a ketene in the presence of a Lewis acid. The utility of products is demonstrated towards the synthesis of a common scaffold found in several natural product families.
![Graphical abstract: Lewis acid-promoted [2 + 2] cycloadditions of alkenes with aryl ketenes](http://hg.y866.cn/compound/lib/scimg/usr/1/C5OB01837D.jpg)
