In this work, six novel axially unfixed biaryl-based water-compatible bifunctional organocatalysts were designed and synthesized for the organocatalytic access to a variety of 3-alkyl-3-hydroxy-2-oxindole derivatives via aldol reactions in water. Organocatalyzed by 5a, the direct aldol reactions of isatins with enolisable ketones underwent readily in water, furnishing the structurally diverse 3-alkyl-3-hydroxy-2-oxindoles in various stereoselectivities (up to >99% dr and > 99% ee). Moreover, a plausible transition state of the conducted aldol reactions was hypothesized to shed light on the observed stereoselectivities of the obtained 3-alkyl-3-hydroxy-2-oxindoles.