A solvent-dependent, divergent synthesis of highly functionalized N,S-heterocycles presenting a thiazoline and an isoquinuclidine (DCE as solvent) or tetrahydroisoquinoline (DMF as solvent) scaffolds by cyclization reactions of isoquinolinium 1,4-zwitterionic thiolates is reported. The robustness and applicability of the method are also demonstrated by an efficient 6-times upscaling of the reaction and derivatization of the thiazoline-isoquinuclidine derivatives.