A Squaramide‐Tagged Proline‐Mediated Direct Asymmetric Aldol Addition in the Presence of Water

Abstract A squaramide moiety introduced at the C‐4 position of proline produced an organocatalyst that promoted the direct asymmetric aldol addition in the presence of water. A variety of aldol adducts, majorly from the reaction cyclohexanone with aldehydes, were obtained in yields generally in the range of 53–99 %, accompanied by 71–99 % ee and 83 : 17 to >99 : 1 diastereomeric ratios. An asymmetric desymmetrization of 4‐alkyl cyclohexanones was also achieved using the transformation.