Chiral phase transfer catalysts enable the synthesis of diverse chiral N-heterocycles through a combination of asymmetric cascade reactions

The effectiveness of a series of chiral phase transfer catalysts in cascade reactions of active methylene compounds with 2-cyanobenzaldehyde leading to chiral 3-substituted isoindolinones and fused benzoindolizidinones has been investigated. High yields and moderate enantiomeric excesses (e.e.s) were achieved employing a chiral phase-transfer catalyst derived from bifunctional urea–quinine. Moreover, an efficient process of heterochiral crystallization, performed on moderately enantioenriched compounds, led to an impressive increase of the enantiopurity up to 93% e.e.s.