The cycloaddition reaction of BCB ketones with triazinanes leads to aza-BCOs, and a direct acidic treatment efficiently cleaves the aminal moiety, resulting in cis-cyclobutyl diamines. Either a stepwise or one-pot manner is suitable for the "cycloaddition/ringopening" strategy. In contrast, the reaction of BCB esters with triazinanes yields a series of beautiful butterfly-shaped biscyclobutenyl amines under In(OTf)3 catalysis. Mechanistic studies indicate that the distinct reaction pathways originate from the different activation modes of BCBs by Lewis acid, the cycloaddition of BCB ketones with triazinanes proceeds via a stepwise (2+2+3) rather than (4+3) pathway, and the reaction of BCB esters with triazinanes involves a Leitch's carbocation intermediate. The obtained two series of products provide a unique platform for exploration of new cyclobutane-based drug candidates, especially given the cis-configuration of cyclobutyl diamines and the functional group compatibility of both products.