Synergistic Rhodium(II) Carboxylate and Brønsted Acid Catalyzed Multicomponent Reactions of Enalcarbenoids: Direct Synthesis of α‑Pyrrolylbenzylamines

The design of a synergistic rhodium­(II) carboxylate and BINOL phosphoric acid catalyzed efficient multicomponent reaction of enaldiazo compounds, arylamines, and aryl aldehydes leading to the first transition-metal-catalyzed direct synthesis of valuable α-pyrrolylbenzylamines is disclosed. The reaction is proposed to involve a transient ammonium ylide of a new class of electrophilic rhodium enalcarbenoid, its regioselective Mannich reaction, and a cyclocondensation cascade. The methodology was used in a highly diastereoselective synthesis of a binaphthyl based chiral pyrrole.