Catalytic Asymmetric Synthesis of β-Sultams as Precursors for Taurine Derivatives

摘要: Beta-sultams, biologically interesting sulfonyl analogues of beta-lactams, have been prepared by an organocatalytic asymmetric formal [2+2]-cycloaddition approach non-nucleophilic imines with alkyl chlorides. In the case very electron poor N-tosyl derived from chloral or ethylglyoxylate, this reaction type was catalyzed cinchona alkaloids providing heterocycles in high yield, good diastereoselectivity and up to 94% ee. Mechanistic investigations suggested that product formation proceeded via a zwitterionic imine-catalyst adduct. The scope significantly extended 2-pyridylsulfonyl non-activated aromatic aldehydes employing Yb(OTf)3 as Lewis acid cocatalyst. synthetic value strained enantioenriched beta-sultams demonstrated smooth nucleophilic ring opening reactions O-, N- C-nucleophiles yielding variety acyclic beta-aminosulfonyl (taurine) derivatives (sulfonates, sulfonamides, sulfones) without racemization epimerization.