Do the electronic effects of sulfur indeed control the pi-selectivity of gamma-sulfenyl enones? Further evidence

摘要

The reductions of gamma-sulfenyl and gamma-sulfenyl enones with NaBH4 and LiAlH4 lead to highly reduced anti-to-S selectivity. The selectivity turns even syn-to-S in some instances. These results underline the significance of steric effects arising from the bulk of the reducing agent and the substituent on S, on one hand, and negate any substantial role of the electronic effects of S on the observed diastereocontrol as reported previously, on the other hand.