High Quality Content by WIKIPEDIA articles! In chemistry, bisoxazoline ligands (BOX ligands for short) are chiral ligands based on a bis oxazoline skeleton and used in combination with a metal compound in asymmetric synthesis as a chiral catalyst . Three frequently encountered such ligands are PyBOX, tBuBOX and PhBOX. BOX ligands exist as organic compounds with the organometallic complex formed in-situ or as pre-prepared metal complexes.