We demonstrate a general method for conversion of various 5-oxopentanals to substituted δ- lactones and 1-oxa-2-decalones by the synergistic catalysis of samarium diiodide and 2- propanethiol (or disulfide). The deliberate use of mercaptan is advantageous to facilitate the catalytic cycle. This method shows high stereoselectivities, and an enantioselective procedure is feasible by using the chiral mercaptan (1 R, 2 S)-1-phenyl-2-(N-acetamido) ...
