Formation of Allenyl Ketones, 3‑Ethynylcoumarins, and Arylfurans, Furylfurans, and Furylthiophenes by Flash Vacuum Thermolysis of 3‑Methylidenefuran-2(3H)‑ones

Posted on 03.01.2014 - 00:00
Flash vacuum thermolysis (FVT) of 3-methylidenefuran-2­(3H)-ones 3 causes cheletropic extrusion of CO with formation of allenyl ketones 4. o-Chloro- and o-bromophenylmethylidenefuranones also afford allenyl ketones upon flash vacuum thermolysis, but in addition, 3-ethynylcoumarins 6 are formed via E/Z isomerization of the methylidenefuranones, cyclization, halogen atom migration, and HCl (HBr) elimination. The presence of strongly electron-withdrawing groups (nitroaryl or acetyl) on the acylallene moiety causes rearrangement to give 2-arylfurans 10 and 13 as well as 2-furylfurans and 2-furylthiophenes 16 by cyclization of the allenyl ketones. The reaction mechanisms are supported by calculations at the M06-2X/6-311+G­(d,p) level of theory.

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Koch, Rainer; Berstermann, Hans Michael; Wentrup, Curt (2016): Formation of Allenyl Ketones, 3‑Ethynylcoumarins, and Arylfurans, Furylfurans, and Furylthiophenes by Flash Vacuum Thermolysis of 3‑Methylidenefuran-2(3H)‑ones. ACS Publications. Collection. https://doi.org/10.1021/jo402139a
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