Sulfinate‐Organocatalyzed (3+2) Annulation Reaction of Propargyl or Allenyl Sulfones with Activated Imines

An operationally simple methodology for the synthesis of 4‐sulfonyl‐3‐pyrrolines is described using a propargylic sulfone and N ‐sulfonyl imines as substrates. This annulation process is initiated by an arenesulfinate organocatalyst, which allows a smooth isomerization of the alkynyl precursor into the corresponding allene, followed by the generation of a highly reactive allyl sulfone anion. An asymmetric version involving an unprecedented enantiopure sulfinate–ammonium cooperative ion pair (PhSO 2 – R 4 N + *) was investigated. A proof‐of‐concept, with enantiomeric excesses of up to 41 %, was obtained according to a preliminary screening of commercially available chiral phase‐transfer catalysts.