Reduction of cyclopropylmethylamines proceeded under mild reaction conditions in the presence of platinum (IV) oxide catalyst and hydrobromic acid at rt, providing isobutylamines and no linear butylamines. The ring cleavage reaction was widely applicable to cyclopropane rings in various compounds such as N-cyclopropylalkyl, O-cyclopropylalkyl, and C-cyclopropylalkyl derivatives. Although unactivated