Solvent‐Dependent Divergent Cyclization of Bicyclo[1.1.0]butanes.

Bicyclo[1.1.0]butanes (BCBs) have recently garnered significant research interest as versatile precursors for synthesizing potential [n.1.1] bioisosteres and multi‐functionalized cyclobutanes in a straightforward and atom‐economical manner. Here, we report a solvent‐dependent divergent cyclization of BCBs that provides highly diastereospecific decorated cyclobutanes and oxygen‐containing bicyclo[3.1.1]heptanes (BCHeps), which serve as bioisosteres of <italic>meta</italic>‐substituted arenes. Additionally, an unprecedented 1,2‐difunctionalization reaction mode for BCBs was explored, thus expanding the chemical space of arene bioisosteres and highly functionalized cyclobutanes. [ABSTRACT FROM AUTHOR]