Bifunctional acid–base ionic liquid for the one-pot synthesis of fine chemicals: Thioethers, 2H-chromenes and 2H-quinoline derivatives

• The bifunctional acid–base catalyst piperidinomethane piperidium tetrafluoroborate (A) catalyzes the Michael addition.
• Piperidinomethane piperidium tetrafluoroborate (A) catalyzes a condensation reaction and subsequent Michael addition in one-pot.
• A plausible cooperative effect between the acid and basic sites of the catalyst stabilizes the transition state.
• This bifunctional catalyst A has been extensively applied to the one-pot synthesis of thioethers, 2H-chromenes and 2H-quinolines.

A bifunctional organocatalyst with ionic liquid properties and with an optimized distance between the acid and basic sites efficiently activates electron deficient olefins for 1,4 conjugated addition, which can be incorporated in different one-pot transformations for the preparation of cyclic and acyclic compounds of biological and synthetic interest.More specifically, the catalyst can be successfully applied for different carbon–carbon (CC) and carbon–heteroatom (CN, CO, CS) bond forming reactions integrated in a cascade sequence. The activity of the organocatalyst has been compared with that of structurally related monofunctional and bifunctional catalysts.The most attractive features of this procedure are the high atom economy and the use of inexpensive starting materials as well as the use of an environmentally friendly catalyst that can be easily recovered due to its ionic liquid properties.

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