(E)-2-(fluoro(phenyl)methylene)cyclopentan-1-one

Silver-initiated radical ring expansion/fluorination of ethynyl cyclobutanols: efficient synthesis of monofluoroethenyl cyclopentanones

Green Chem., 2016, Advance Article
DOI: 10.1039/C6GC02656G, Communication

Qingshan Tian, Bin Chen, Guozhu Zhang
A stereoselective synthesis of [small beta]-halogenated 2-methylenecyclopentanones via silver-catalyzed formal ring expansion using water as the cosolvent is described.

Silver-initiated radical ring expansion/fluorination of ethynyl cyclobutanols: efficient synthesis of monofluoroethenyl cyclopentanones

Qingshan Tian,^a   Bin Chen^a and   Guozhu Zhang*^a  

*

Corresponding authors

^a

State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, P. R. China
E-mail: guozhuzhang@sioc.ac.cn

Green Chem., 2016, Advance Article

DOI: 10.1039/C6GC02656G

A stereoselective synthesis of β-halogenated 2-methylenecyclopentanones via silver-catalyzed formal ring expansion using water as the cosolvent is described. A variety of 2-methylenecyclopentanones with fluoro, chloro and bromo functionalities are efficiently prepared from 1-alkynyl cyclobutanols. This method offers facile access to halogenated complex molecules which are not only useful chemicals but also valuable building blocks for further derivatizations.

1-(m-tolylethynyl)cyclobutan-1-ol (1b) Yield: 89%; Yellow oil;

1H NMR (400 MHz, CDCl3)

δ 7.25 (s, 1H), 7.23 (d, J = 8.1 Hz, 1H), 7.18 (t, J = 7.5 Hz, 1H), 7.10 (d, J = 7.5 Hz, 1H), 2.51 (dt, J = 15.8, 6.3 Hz, 2H), 2.34 (t, J = 9.3 Hz, 2H), 2.30 (s, 3H), 1.85 (m, 2H);

13C NMR (100 MHz, CDCl3)

δ 137.94, 132.27, 129.19, 128.72, 128.17, 122.49, 92.16, 83.58, 68.31, 38.64, 21.20, 12.98; HRMS (EI+ , 70 eV): C13H14O [M]+ : calcd. 186.1045, found 186.1047

(E)-2-(fluoro(phenyl)methylene)cyclopentan-1-one (2a) Yield: 85%; Colorless oil;

1H NMR (400 MHz, CDCl3) δ 7.79 (dd, J = 8.0, 1.5 Hz, 2H), 7.46-7.40 (m, 3H), 2.94 (td, J = 7.3, 3.3 Hz, 2H), 2.43 (td, J = 7.9, 1.2 Hz, 2H),1.99 (m, 2H);

13C NMR (100 MHz, CDCl3) δ 204.7 (d, J = 14.4 Hz), 162.4 (d, J = 270.7 Hz), 131.1, 130.0, 129.7, 128.7 (d, J = 7.0 Hz), 127.8, 117.3 (d, J = 19.4 Hz), 40.7 (d, J = 4.3 Hz), 27.6 (d, J = 3.9 Hz), 19.4;

19F (376 MHz, CDCl3) δ -76.9;

HRMS (EI+ , 70 eV): C12H11FO [M]+ : calcd. 190.0794, found 190.0795.

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