Iodine-mediated formal [3 + 2] annulation for synthesis of furocoumarin from oxime esters
作者:Quyen T. Pham、Phong Q. Le、Ha V. Dang、Hiep Q. Ha、Huong T. D. Nguyen、Thanh Truong、Tri Minh Le
DOI:10.1039/d0ra07566c
日期:——
A novel synthesis of furocoumarins was developed by a reaction between oxime esters and 4-hydroxycoumarins. The reaction was proposed to undergo radical mechanism mediated by iodine, a cheap and common laboratory reagent. Mechanistic studies showed the key for the successful transformation was the presence of α-iodoimine intermediate which facilitated the ring-closing step. The developed conditions
Metal-Free Synthesis of Furocoumarins: An Approach via Iodine-Promoted One-Pot Cyclization between 4-Hydroxycoumarins and Acetophenones
作者:Phuc H. Pham、Que T. D. Nguyen、Nhu K. Q. Tran、Vu H. H. Nguyen、Son. H. Doan、Hiep Q. Ha、Thanh Truong、Nam T. S. Phan
DOI:10.1002/ejoc.201800983
日期:2018.8.31
An iodine‐mediated one‐pot synthesis of furocoumarins has been developed. The furocoumarins were obtained in high yields in the presence of NH4OAc as an additive, whereas neither acidic nor basic additives were effective.
Abstract Facile synthesis of furo[3,2-c]coumarins (2a–g) via cyclocondensation of 4-hydroxycoumarin and α-tosyloxyketones (1a–g) is described. A plausible mechanism involving C-C bond formation followed by 5-exo-tet cyclization is suggested. GRAPHICAL ABSTRACT
Modular access to furo[3,2-c]chromen-4-ones via Yb(OTf)3-catalyzed [3 + 2] annulation of 4-hydroxycoumarins with β-nitroalkenes
作者:Hua Wang、Qin Ma、Yifei Xu、Yanyan Sun、Siyuan Zhao、Shaoyin Wang、Xinwei He
DOI:10.1039/d4ra03962a
日期:——
A facile and efficient strategy for modular access to furo[3,2-c]chromen-4-ones using 4-hydroxycoumarin and β-nitroalkenes via Lewis acid-catalyzed formal [3 + 2] annulation protocol is described. This reaction proceeds via cascade Michaeladdition/nucleophilic addition/elimination in the presence of Yb(OTf)3, which involves the formation of two new σ (C-C and C-O) bonds for the construction of a novel
(2-chloro-2-nitroethenyl)benzenes as synthons: a general method for the preparation of 2,3-dihydro- 2-nitro-3-phenyl-4H-furo [3,2-c] [1]benzopyran-4-ones and 3-phenyl-4H-furo[3,2-c][1]benzopyran-4-ones