References and Notes
<A NAME="RU11107ST-1A">1a</A>
Silvestri G.
Gambino S.
Filardo G.
Gulotta A.
Angew. Chem., Int. Ed. Engl.
1984,
23:
979
<A NAME="RU11107ST-1B">1b</A>
Silvestri G.
Gambino S.
Filardo G.
Acta Chem. Scand.
1991,
45:
987
<A NAME="RU11107ST-2A">2a</A>
Sock O.
Troupel M.
Périchon J.
Tetrahedron Lett.
1985,
26:
1509
<A NAME="RU11107ST-2B">2b</A>
Chaussard J.
Folest JC.
Nédélec JY.
Périchon J.
Sibille S.
Troupel M.
Synthesis
1990,
369
<A NAME="RU11107ST-3">3</A>
Saboureau C.
Troupel M.
Sibille S.
Périchon J.
J. Chem. Soc., Chem. Commun.
1989,
1138
<A NAME="RU11107ST-4">4</A>
Chiozza E.
Desigaud M.
Greiner J.
Dunach E.
Tetrahedron Lett.
1998,
39:
4831
<A NAME="RU11107ST-5">5</A>
Kamekawa H.
Senboku H.
Tokuda M.
Electrochim. Acta
1997,
42:
2117
<A NAME="RU11107ST-6">6</A>
Tokuda M.
Yoshikawa A.
Suginome H.
Senboku H.
Synthesis
1997,
1143
<A NAME="RU11107ST-7">7</A>
Kamekawa H.
Kudo H.
Senboku H.
Tokuda M.
Chem. Lett.
1997,
26:
917
<A NAME="RU11107ST-8">8</A>
Kamekawa H.
Senboku H.
Tokuda M.
Tetrahedron Lett.
1998,
39:
1591
<A NAME="RU11107ST-9">9</A>
Senboku H.
Fujimura Y.
Kamekawa H.
Tokuda M.
Electrochim. Acta
2000,
45:
2995
<A NAME="RU11107ST-10">10</A>
Senboku H.
Kanaya H.
Fujimura Y.
Tokuda M.
J. Electroanal. Chem.
2001,
507:
82
<A NAME="RU11107ST-11">11</A>
Senboku H.
Komatsu H.
Fujimura Y.
Tokuda M.
Synlett
2001,
418
<A NAME="RU11107ST-12">12</A>
Senboku H.
Kanaya H.
Tokuda M.
Synlett
2002,
140
<A NAME="RU11107ST-13">13</A>
Chowdhury MA.
Senboku H.
Tokuda M.
Tetrahedron
2004,
60:
475
<A NAME="RU11107ST-14">14</A>
Kuang C.
Yang Q.
Senboku H.
Tokuda M.
Chem. Lett.
2005,
34:
528
<A NAME="RU11107ST-15">15</A>
Senboku H.
Yamauchi Y.
Fukuhara T.
Hara S.
Electrochemistry
2006,
74:
612
<A NAME="RU11107ST-16">16</A>
Furuya T.
Fukuhara T.
Hara S.
J. Fluorine Chem.
2005,
126:
721
<A NAME="RU11107ST-17">17</A>
Schlosser M.
Michel D.
Guo Z.-W.
Sih CJ.
Tetrahedron
1996,
52:
8257
<A NAME="RU11107ST-18">18</A>
Goj O.
Kotila S.
Haufe G.
Tetrahedron
1996,
52:
12761
<A NAME="RU11107ST-19">19</A>
Rozen S.
Hagooly A.
Harduf R.
J. Org. Chem.
2001,
66:
7464
<A NAME="RU11107ST-20">20</A>
Laurent E.
Marquet B.
Roze C.
Ventalon F.
J. Fluorine Chem.
1998,
87:
215
<A NAME="RU11107ST-21">21</A>
Fujisawa H.
Fujiwara T.
Takeuchi Y.
Omata K.
Chem. Pharm. Bull.
2005,
53:
524
<A NAME="RU11107ST-22">22</A>
Bellezza F.
Cipiciani A.
Ricci G.
Ruzziconi R.
Tetrahedron
2005,
61:
8005
<A NAME="RU11107ST-23">23</A>
Takeuchi Y.
Fujisawa H.
Fujiwara T.
Matsuura M.
Komatsu H.
Ueno S.
Matsuzaki T.
Chem. Pharm. Bull.
2005,
53:
1062
<A NAME="RU11107ST-24">24</A>
Corey EJ.
Fuchs PL.
Tetrahedron Lett.
1972,
3769
<A NAME="RU11107ST-25">25</A>
Olah GA.
Nojima M.
Kerekes I.
Synthesis
1973,
779
<A NAME="RU11107ST-26">26</A>
The structures of compounds were determined by 1H NMR, 13C NMR, and 19F NMR and HRMS. Spectral data are shown in ref. 33.
<A NAME="RU11107ST-27">27</A>
General Procedure for the Electrochemical Carboxylation of α,α-Difluoroethylarenes: A solution of difluoroethylarene (1.0 mmol) in DMF (10 mL) containing Bu4NBF4 (0.1 M) was electrolyzed at 0 °C with a constant current (15 mA/cm2) under an atmospheric pressure of bubbling carbon dioxide. An undivided cell equipped
with a Pt plate cathode (2 × 2 cm2) and a Mg rod anode (φ 6 mm) was used for electrolysis. After an appropriate amount
of electricity was passed (shown in schemes), the electrolyzed solution was poured
into 1 M HCl (100 mL) and then extracted with Et2O (3 × 30 mL). In the case of 15 and 16, 6 M HCl, instead of 1 M HCl, was used and the resulting mixture was stirred for
2 h at r.t. before extraction. The combined ethereal solution was washed with sat.
NaHCO3 (3 × 40 mL). The resulting aqueous solution was acidified with 3 M HCl, and then
extracted with Et2O (3 × 30 mL). The combined ethereal solution was washed with sat. brine and dried
over MgSO4. Evaporation of the solvent gave an almost pure 2-fluoro-2-arylpropanoic acid. Spectral
data of the products were in good agreement with the data reported in ref. 21 in every
respect, except for the new compound 21.
<A NAME="RU11107ST-28">28</A>
Hiyama T.
Wakasa N.
Ueda T.
Kusumoto T.
Bull. Chem. Soc. Jpn.
1990,
63:
640
<A NAME="RU11107ST-29A">29a</A>
Silvestri G.
Gambino S.
Filardo G.
Tetrahedron Lett.
1986,
27:
3429
<A NAME="RU11107ST-29B">29b</A>
Mcharek S.
Heintz M.
Troupel M.
Périchon J.
Bull. Soc. Chim. Fr.
1989,
95
<A NAME="RU11107ST-29C">29c</A>
Chan ASC.
Huang TT.
Wagenknecht JH.
Miller RE.
J. Org. Chem.
1995,
60:
742
<A NAME="RU11107ST-30">30</A>
Karimi B.
Golshani B.
Synthesis
2002,
784
<A NAME="RU11107ST-31">31</A>
There would be some possible explanations for this overcarboxylation in EC of 14a although they are not fully examined at this stage. Since biphenyl is known to work
as an electron-transfer mediator (see ref. 34), biphenyl moiety in the reaction medium
is likely to work as an electron-transfer mediator to induce the over-reduction producing
dicarboxylic acid 18. Similarly to the substrate 14a, products 17 and 18, which exist as a mixture of magnesium salts in the reaction medium, also have a
biphenyl moiety that would work as a mediator.
<A NAME="RU11107ST-32">32</A>
Terao Y.
Ijima Y.
Kakidani H.
Ohta H.
Bull. Chem. Soc. Jpn.
2003,
76:
2395
<A NAME="RU11107ST-33">33</A>
4-(1,1-Difluoroethyl)isobutylbenzene (9): 1H NMR (400 MHz, CDCl3): δ = 0.90 (d, J = 6.6 Hz, 6 H), 1.80-2.08 (m, 1 H), 1.92 (t, J = 18.1 Hz, 3 H), 2.50 (d, J = 6.6 Hz, 2 H), 7.19 (d, J = 7.9 Hz, 2 H), 7.41 (d, J = 7.9 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ = 22.3, 25.9 (t, J = 30.0 Hz), 30.2, 45.1, 122.0 (t, J = 238.5 Hz), 124.4 (t, J = 6.0 Hz), 129.1, 135.6 (t, J = 26.7 Hz), 143.4 (t, J = 1.7 Hz). 19F NMR (372.5 MHz, CDCl3): δ = -87.31 (q, J = 18.1 Hz, 2 F). HRMS (EI): m/z calcd for C12H16F2: 198.1220; found: 198.1220.
2-Fluoro-4-(1,1-difluoroethyl)biphenyl (14a): 1H NMR (400 MHz, CDCl3): δ = 1.96 (t, J = 18.1 Hz, 3 H), 7.28-7.58 (m, 8 H). 13C NMR (100 MHz, CDCl3): δ = 25.8 (d, J = 29.6 Hz), 112.9 (dt, J = 6.2, 25.3 Hz), 120.5-120.7 (m), 121.0 (dt, J = 1.9, 239.0 Hz), 128.1, 128.6, 129.0 (d, J = 3.1 Hz), 130.5 (dt, J = 1.7, 13.6 Hz), 131.0 (d, J = 3.8 Hz), 134.9 (d, J = 1.2 Hz), 159.4 (d, J = 248.9 Hz). 19F NMR (372.5 MHz, CDCl3): δ = -117.33 (m, 1 F), -88.24 (q, J = 18.1 Hz, 2 F). HRMS (EI): m/z calcd for C14H11F3: 236.0813; found: 236.0819.
3-(1,1-Difluoroethyl)diphenylether (14b): 1H NMR (400 MHz, CDCl3): δ = 1.90 (t, J = 18.2 Hz, 3 H), 6.96-7.46 (m, 9 H). 13C NMR (100 MHz, CDCl3): δ = 25.9 (t, J = 29.8 Hz), 115.1 (t, J = 6.2 Hz), 119.1, 119.3 (t, J = 6.0 Hz), 119.7 (t, J = 1.7 Hz), 121.4 (t, J = 239.4 Hz), 123.7, 129.9, 129.9, 140.0 (t, J = 27.0 Hz), 156.6, 157.5. 19F NMR (372.5 MHz, CDCl3): δ = -88.26 (q, J = 18.2 Hz, 2 F). HRMS (EI): m/z calcd for C14H12F2O: 234.0856; found: 234.0857.
3-(1,1-Difluoroethyl)benzophenone (14c): 1H NMR (400 MHz, CDCl3): δ = 1.96 (t, J = 18.1 Hz, 3 H), 7.46-7.66 (m, 4 H), 7.72-7.77 (m, 1 H), 7.78-7.88 (m, 3 H), 7.96
(s, 1 H). 13C NMR (100 MHz, CDCl3): δ = 25.9 (t, J = 30.0 Hz), 121.4 (t, J = 239.4 Hz), 126.1 (t, J = 6.0 Hz), 128.4 (t, J = 5.8 Hz), 128.7, 130.0, 131.3 (t, J = 1.7 Hz), 137.1, 132.8, 137.9, 138.5 (t, J = 27.2 Hz), 195.9. 19F NMR (372.5 MHz, CDCl3): δ = -88.37 (q, J = 18.1 Hz, 2 F). HRMS (EI): m/z calcd for C15H12F2O: 246.0856; found: 246.0856.
2-[4-(1,1-Difluoroethyl)benzyl]cyclopentanone (14d): 1H NMR (400 MHz, CDCl3): δ = 1.47-1.61 (m, 1 H), 1.67-1.82 (m, 1 H), 1.90-2.02 (m, 1 H), 1.91 (t, J = 18.1 Hz, 3 H), 2.04-2.17 (m, 2 H), 2.30-2.42 (m, 2 H), 2.58 (dd, J = 9.5, 13.9 Hz, 1 H), 3.17 (dd, J = 4.0, 13.9 Hz, 1 H), 7.22 (d, J = 8.0 Hz, 2 H), 7.42 (d, J = 8.0 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ = 20.5, 25.8 (t, J = 30.1 Hz), 29.1, 35.2, 38.1, 50.8, 121.8 (t, J = 238.5 Hz), 124.7 (t, J = 6.0 Hz), 128.9, 136.1 (t, J = 26.7 Hz), 141.8 (t, J = 1.7 Hz), 219.8. 19F NMR (372.5 MHz, CDCl3): δ = -87.57 (q, J = 18.1 Hz, 2 F). HRMS (EI): m/z calcd for C14H16F2O: 238.1169; found: 238.1172.
2-[3-(1,1-Difluoroethyl)phenyl]-2-phenyl-1,3-dioxane (15): 1H NMR (400 MHz, CDCl3): δ = 1.68-1.98 (m, 2 H), 1.90 (t, J = 18.1 Hz, 3 H), 3.98-4.10 (m, 4 H), 7.23-7.29 (m, 1 H), 7.32-7.40 (m, 4 H), 7.50-7.58
(m, 3 H), 7.72 (s, 1 H). 13C NMR (100 MHz, CDCl3): δ = 25.5, 26.0 (t, J = 29.8 Hz), 61.6, 100.6, 121.8 (t, J = 239.2 Hz), 122.4 (t, J = 6.2 Hz), 124.0 (t, J = 6.0 Hz), 126.5, 127.7, 127.9, 128.6, 128.6, 138.3 (t, J = 26.7 Hz), 141.7, 143.4. 19F NMR (372.5 MHz, CDCl3): δ = -87.95 (q, J = 18.1 Hz, 2 F). HRMS (EI): m/z calcd for C18H18F2O2: 304.1275; found: 304.1281.
1-[4-(1,1-Difluoroethyl)benzyl]-6,10-dioxaspiro[4.5]de-cane (16): 1H NMR (400 MHz, CDCl3): δ = 1.30-1.48 (m, 2 H), 1.52-1.75 (m, 3 H), 1.80-1.98 (m, 1 H), 1.91 (t, J = 18.2 Hz, 3 H), 1.90-2.13 (m, 2 H), 2.14-2.23 (m, 1 H), 2.47 (dd, J = 11.1, 13.5 Hz, 1 H), 3.04 (dd, J = 4.0, 13.5 Hz, 1 H), 3.86-4.04 (m, 4 H), 7.25 (d, J = 7.9 Hz, 2 H), 7.40 (d, J = 7.9 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ = 20.6, 25.8 (t, J = 29.8 Hz), 25.9, 28.2, 30.3, 34.4, 50.6, 60.6, 62.1, 108.3, 122.0 (t, J = 237.9 Hz), 124.4 (t, J = 6.0 Hz), 129.0, 135.4 (t, J = 26.9 Hz), 143.9 (t, J = 1.9 Hz). 19F NMR (372.5 MHz, CDCl3)δ = -87.29 (q, J = 18.2 Hz, 2 F). HRMS (EI): m/z calcd for C17H22F2O2: 296.1588; found: 296.1580.
α-Fluoroloxoprofen (21): 1H NMR (400 MHz, CDCl3): δ = 1.51-1.58 (m, 1 H), 1.68-1.80 (m, 1 H), 1.90-2.03 (m, 1 H), 1.96 (d, J = 22.3 Hz, 3 H), 2.01-2.16 (m, 2 H), 2.30-2.39 (m, 2 H), 2.54 (dd, J = 9.5, 13.9 Hz, 1 H), 3.15 (dd, J = 4.1, 13.9 Hz, 1 H), 7.22 (d, J = 7.9 Hz, 2 H), 7.42 (d, J = 7.9 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ = 20.3, 24.2 (d, J = 23.9 Hz), 28.9, 34.9, 38.0, 50.8, 94.0 (d, J = 185.1 Hz), 124.8 (d, J = 8.5 Hz), 128.9, 136.4 (d, J = 22.8 Hz), 140.6, 174.9 (d, J = 28.3 Hz), 221.5. 19F NMR (372.5 MHz, CDCl3): δ = -151.09 (q, J = 22.3 Hz, 1 F). HRMS (EI): m/z calcd for C15H17FO3: 264.1162; found: 264.1162.
<A NAME="RU11107ST-34">34</A>
Simone J.
Pilard J.-F. In Organic Electrochemistry
4th ed.:
Lund H.
Hammerich O.
Marcel Dekker;
New York:
2001.
p.1163