Protecting group-free concise synthesis of (RS)/(S)-lubeluzole.

Three new, concise, and protecting group-free synthetic routes for (RS)- and (S)-lubeluzole are reported in higher (46-62%) overall yields compared to the reported procedures (6-35%). The key steps involve C-N bond formation via epoxide aminolysis and nucleophilic substitution of 2-chlorobenzothiazole with suitably designed precursor amines and are performed in aqueous medium. Water offers an advantage in promoting the reactions compared to organic solvents and its role is envisaged as hydrogen-bond mediated electrophile-nucleophile dual activation.