Highly enantioselective conjugate addition of thiols using mild scandium triflate catalysis.

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.

Novel crown ether and salen metal chelation driven molecular pincers.

The synthesis of novel metal chelation driven molecular pincers based on crown ether and salen ligand substructures are described. Their functionality was monitored by fluorescence spectroscopy using pyrene groups as fluorescence probes. The pincer was shown to function reversibly with respect to metal chelation with Zn2+ and also to chelate ditopically with 100 mol % of Zn2+ and 100 mol % Li+ or 200 mol % of Li+ ion.