Do the electronic effects of sulfur indeed control theπ-selectivity of ´/-sulfenyl enones? Further evidence

Abstract

The reductions of ϒ-sulfenyl and ϒ-sulfonyl 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.