Insight for the photochemical reaction of 4-aryl-4H-pyran: Experimental and theoretical studies. (26th January 2023)

• Record Type: Journal Article
• Authors: Wang, Shijie; Song, Xiuqing; Sun, Runzhi; Yan, Hong; Wang, Yeming
• Is Part Of: Tetrahedron. Volume 131(2023)
• Publication Date: 2023-01-26
• Subjects: 4-Aryl-4H-pyran -- Photocycloaddition -- Photochemical ring contraction -- Photocleavage -- Theoretical calculation; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2022.133212
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: In this article, we have investigated the photochemical reactions of 4-aryl-4 H -pyran and found that the structural symmetry had a significant influence on its photochemical behavior. When symmetric 4-aryl-4 H -pyran was used, such as diethyl 2, 6-dimethyl-4-aryl-4 H -pyran-3, 5-dicarboxylate, mainly underwent [2 + 2] photocycloaddition reaction. While asymmetric 4-aryl-4 H -pyran, such as 2-amino-3-cyano-4-aryl-4 H -pyrans, mainly underwent photocleavage reactions. To speculate the reaction mechanism, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were carried out at the B3LYP-D3/def2TZVP//B3LYP-D3/6-31G(d) level. The results showed that diethyl 2, 6-dimethyl-4-aryl-4 H -pyran-3, 5-dicarboxylate underwent a two-step [2 + 2] photocycloaddition to give 3, 9-dioxatetraasterane derivatives via an intermolecular and an intramolecular reaction. And the 2-amino-3-cyano-4-aryl-4 H -pyran underwent a ring cleavage to produce the conjugated diene derivatives. To explain the different photochemical behaviors of 4-aryl-4 H -pyrans, electron spin density, frontier molecular orbitals (FMOs) analysis, electron-hole analysis and root-mean-square-deviation (RMSD) analysis were performed. Graphical abstract: Image 1 Highlights: Symmetric 4-aryl-4 H -pyran underwent [2 + 2] photocycloaddition reaction produced 3, 9-dioxatetraasterane. Asymmetric 4-aryl-4 H -pyran underwent photocleavage reaction produced conjugated dienes. The reasons for the different photochemical behaviors of 4-aryl-4 H -pyran were discussed.