SEARCH Articles Figures Tables 1,3-Cyclopentadiene, cycloaddition with Cycloaddition with Cycloaddition with ketenes Cycloadditions cyclopentadienes Cyclopentadiene cycloaddition Cyclopentadienes 2 + 2]cycloaddition Cyclopentadienes cycloaddition with Ketene 2 + 2] cycloadditions Ketene cycloaddition Ketenes cycloaddition Ketenes, cycloadditions