One-Pot Synthesis of Substituted Δ1-Pyrrolines Through the Michael Addition of Nitroalkanes to Chalcones and Subsequent Reductive Cyclization in Aqueous Media.

Abstract: A facile and efficient one-pot synthesis of substituted D 1 -pyrrolines in aqueous media has been developed. Upon treatmentwith aqueous sodium hydroxide in N , N -dimethylformamide, arange of chalcones underwent room temperature Michael additionreactions with nitroalkanes. The resulting adducts were directly re-duced in situ with Zn/HCl (aq) and subsequently underwent an in-tramolecular cyclization, affording the corresponding substitutedD 1 -pyrrolines in high yields. Key words: chalcones, cyclizations, Michael additions, hydroge-nations, pyrrolines Over the past few decades, the use of nitroalkanes as keybuilding blocks in organic synthesis has been steadilygrowing. They are easily available, versatile, and stabi-lized carbon nucleophiles that can react with commonelectrophiles such as haloalkanes, aldehydes, and Michaelacceptors, leading to carbon–carbon bond formation. 1,2 With regard to the Michael addition reactions of nitroal-kanes, the adducts obtained still retain the nitro functionand, therefore, are capable of undergoing subsequenttransformation of the nitro group after the main additionprocess. The nitro group can be removed from the mole-cule by two distinct strategies: 1) replacement of the nitrogroup with hydrogen through a nucleophilic addition-den-itration process