The chemistry of cyclopentyne is characterized by processes involving addition of nucleophiles across the in-plane π-bond. For example, 1-butanol and lithium chloride add to 1 providing 6a[3]a and 6b,[5]a respectively, after hydrolysis. Carbon-carbon π-bonds also function as nucleophiles toward 1, affording both [2+4]-[5] and [2+2]-cycloadducts,3 and 4 as illustrated in Equation 1. It is such cycloaddition reactions that are the subject of the present paper.
