Cooperative Dienamine/Hydrogen‐Bonding Catalysis: Enantioselective Formal [2+2] Cycloaddition of Enals with Nitroalkenes

Two can play this game: The title reaction is catalyzed by a chiral secondary amine in the presence of an achiral thiourea for the enantio- and diastereoselective synthesis of highly functionalized cyclobutanes (see scheme; TMS=trimethylsilyl). Mechanistically, two consecutive Michael reactions proceed through an unprecedented combination of an dienamine/iminium activation mode. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.