A Lewis acid-catalyzed divergent synthesis of cyclobutyl and biscyclobutenyl amines is realized by exploiting the distinct reactivity exhibited by bicyclo[1.1.0]butane (BCB) ketones and esters with triazinanes. The first (2+2+3) cycloaddition of BCB ketones with triazinanes yields 2,4-diazabicyclo[4.1.1]octanes (aza-BCOs) under B(C6F5)3 catalysis, and a direct acidic treatment efficiently cleaves the aminal moiety, resulting in cis-cyclobutyl diamines. In contrast, the reaction of BCB esters with triazinanes produces butterflyshaped biscyclobutenyl amines under In(OTf)3 catalysis. Mechanistic studies reveal that the distinct reaction pathways originate from the different activation modes of BCBs by Lewis acid.