A Facile Solvent-Free Synthesis of 1-Alkyl/Aralkyl-2-(1-arylsulfonyl alkyl) Benzimidazoles Using TBAB as Surface Catalyst

Reaction 2-(alpha-chloroalkyl)benzimidazoles 1 with aryl sulphinate sodium salt 2 under solvent-free conditions in the presence of tetrabutylammonium bromide as surface catalyst, by simple physical grinding using mortar and pestle, gives 1H-2-(alpha-arylsulfonylalkyl)benzimidazoles 3. The latter on treatment with alkylating agents under solvent-free conditions results in 1-alkyl/aralkyl-2-(alpha-arylsulfonylalkyl)benzimidazoles 4. Alternatively, 4 can also be prepared directly from 1-alkyl/aralkyl-2-(alpha-chloroalkyl)benzimidazoles 5 by reaction with 2, which in turn could be prepared by reaction of 1 with alkylating agents under solvent-free conditions and all these reactions are free from organic solvents including experimental procedures.