Cyclobutadiene Intermediates in Cycloaddition Reactions of 1-Alkynyl Sulfones with 1-Alkynylamines

Article abstract of DOI:10.1021/jo00013a005

The initially formed product from ynamines, such as diethyl(1-propynyl)amine, and 1-alkynyl sulfones is in fact the corresponding cyclobutadiene and not the 2-sulfinyl-4-aminofuran proposed by Himbert.The formation of the cyclobutadiene ring has been established by MS, IR, and 1H NMR data, as well as by chemical trapping experiments.