Aqueous synthesis of 2-aryl-3-nitro-2Hchromenes via l-prolinamide mediated tandem oxa-Michael Henry reactions

• Published in: Journal of molecular structure Vol. 1265
• Main Authors: Rani, Dixita, Gulati, Vinny, Guleria, Mamta, Singh, Satya Prakash, Agarwal, Jyoti
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.10.2022
• Subjects: Chromene, Oxa-Michael Henry reaction; Heterogeneous catalysis; L-prolinamide; Water reaction; β-nitrostyrenes; Heterogeneous catalysis; L-prolinamide; Water reaction; β-nitrostyrenes; Chromene, Oxa-Michael Henry reaction
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2022.133341

•Aqueous protocol for the synthesis of 2-aryl-3-nitro-2H-chromenes has been developed.•Simple and easily accessible l-prolinamide catalyst were used to produce the chromenes in high yields.•The efficiency of the protocol was compared in both organic and aqueous solvents.•Better efficiency was observed in aqueous medium in terms of rate of reaction and chemical yields of the products. An efficient and aqueous protocol has been developed for the synthesis of 2-aryl-3-nitro-2H-chromene derivatives. This protocol involves the l-prolinamide mediated tandem oxa-Michael Henry reaction between a variety of β-nitrostyrenes and salicylaldehyde. Among the screened solvents, the catalytic efficiency of prolinamides was found to be high in chloroform, but the best results were obtained in water to provide the 2-phenyl-3-nitro-2H-chromene in excellent yields. Substrate scope was also investigated using various substituted β-Nitrostyrenes. All reactions worked well to provide the corresponding products in very high yields. Theoretical calculations were performed to find out the reaction pathways and nature of transition state at 3–21G* basis set and TS1 corresponding to the product (S)-3a, was found favorable by 1.13 kcal/mol over TS2 corresponding to the product (R)-3a. [Display omitted]