Efficient and Mild Protocol for the Synthesis of 4(3)-Substituted 3(4)-Nitro-1H-pyrroles and 3-Substituted 4-Methyl-2-tosyl-1H-pyrroles from Nitroolefins and Tosylmethyl Isocyanide in Ionic Liquids

A mild and convenient method for the synthesis of 4(3)-substituted 3(4)-nitro-1H-pyrroles and 3-substituted 4-methyl-2-tosyl-1H-pyrroles from nitroolefins and tosylmethyl isocyanide (TosMIC) in ionic liquid 1-butyl-3-methylimidazolium bromide ([bmlm]Br) was developed. The reactions were performed at room temperature with KOH as base with good yields in a short time (about 2 h). Some tough conditions, such as absolutely anhydrous organic solvents, low temperature, hazardous and expensive strong base or organic base, were not needed. The yields of 4(3)-substituted 3(4)-nitro-1H-pyrroles were moderate, but excellent yields were achieved for the preparation of 3-substituted 4-methyl-2-tosyl-1H-pyrroles. This strategy was quite general and it worked in a broad range of nitroolefins with aromatic, aliphatic or heterocyclic substituents. The recovered ionic liquid could be reused as solvent for several times without significant decrease of reaction yields.