Catalyst-free and atom-economical 1,3-dipolar cycloaddition of C,N-cyclic azomethine imines: Facile synthesis of isoquinoline-fused spirocycles

A highly efficient and environmentally benign 1,3-dipolar cycloaddition of C, N - cyclic azomethine imines with 5-alkenyl thiazolones and 2-arylidenindane-1,3-diones is developed for the construction of congested quaternary spiro-carbon centers. All these transformations can be smoothly performed in ethanol at room temperature, providing a catalyst-free and atom-economical access to diversely substituted novel isoquinoline-fused spirocycles in almost quantitative yields with high diastereoselectivities. The promising anti-tumor activity of these structurally novel spirocyclic compounds is reported as well.