A Sc complex of (4S,5S)-diphenyl PYBOX 1 was found to serve as a catalyst for the asymmetric conjugate addition reactions between various thiols and 3-crotonoyl-2-oxazolidinone, affording the corresponding adducts in good yields and high enantioselectivies (up to 92% ee). A new improved method for making (4S,5S)-diphenyl PYBOX is presented.
Abe, A., Sauerland, S., & Koskinen, A. (2007). Highly Enantioselective Conjugate Addition of Thiols Using Mild Scandium Triflate Catalysis. Journal of organic chemistry, 72(14), 5411-5413. https://doi.org/10.1021/jo070492z