Enantioselective Phase-Transfer Catalyzed α-Sulfanylation of Isoxazolidin-5-ones: An Entry to β 2,2 -Amino Acid Derivatives
Résumé
An unprecedented enantioselective α‐functionalization of C4‐substituted N‐alkoxycarbonyl isoxazolidin‐5‐ones, readily available platforms from Meldrum's acid derivatives, by N‐sulfanylphthalimide (PhthSR) electrophiles was achieved upon an efficient phase‐transfer catalytic approach, mediated by a commercial N‐spiro quaternary ammonium catalyst. Two catalytic activities of the in situ formed R4N+Phth− species were highlighted, the phtalimidate being involved in the anion metathesis event and likely as a Brønsted base. This sequence offers a straightforward access to α,α‐disubstituted isoxazolidinones, which turned out to be useful precursors of α‐sulfanyl‐β2,2‐amino acid derivatives.