Exploring Diversified Synthesis Pathways from Bicyclo[1.1.0]butanes (BCBs) and Benzoquinone Esters to Bicyclo[2.1.1]hexanes (BCHs) and Oxa-bicyclo[3.1.1]heptanes (Oxa-BCHeps)

Lewis acid-catalyzed diverse cyclizations of bicyclo[1.1.0]butanes (BCBs) with benzoquinone esters are reported. Yb(OTf)3 catalysis enabled a (3 + 2) cyclization to yield quinoid-fused BCHs. In contrast, NdCl3 catalysis led to the formation of spiro-cyclobutene-benzofuran-2(3H)-one skeletons. Notably, in the presence of Tf2NH, quinoid-fused bicyclo[2.1.1]hexanes (BCHs) rearranged to oxa-bicyclo[3.1.1]heptanes (oxa-BCHeps) in moderate to good yields. This (3 + 2) cyclization and rearrangement can be efficiently accomplished in a one-pot, two-step procedure.