1
292
Sato et al.:
to give a m ixture of eth yl 2,2-difluoro-5-ph en ylpen tan oate (3), eth yl (E)-2,2-difluoro-
-ph en yl-4-pen ten oate (4) an d eth yl 4-brom o-2,2-difluoro-5-ph en ylpen tan oate (5). Yields of
5
th ese products were estim ated to be 17, 4 an d 40%, respectively, based on an alysis of th is
1
m ixture by H NMR spectroscopy usin g dioxan e as in tern al stan dard. Th is m ixture was fur-
th er separated by repeated colum n ch rom atograph y to give pure sam ples for an alysis.
+
Com poun d 3: A colorless oil. MS, m/z: 242 (M ). HRMS: calculated for C13H16F O :
2
2
+
1
2
2
–
42.112 (M ); foun d: 242.113. H NMR (CDCl ): 7.14–7.32 (m , 5 H); 4.30 (q, 2 H, J = 7.3);
3
.68 (t, 2 H, J = 7.8); 2.08 (m , 2 H); 1.82 (m , 2 H); 1.33 (t, 3 H, J = 7.3). F NMR (CDCl ):
1
9
3
3
+
40.3 (t, 2 F, JHF = 16.1). Com poun d 4: A colorless oil. MS, m/z: 240 (M ). HRMS: calculated
for C13H14F O : 240.096 (M ); foun d: 240.096. H NMR (CDCl ): 7.22–7.38 (m , 5 H); 6.56
d, 1 H, J = 15.6); 6.09 (dt, 1 H, J = 15.6, 7.3); 4.32 (q, 2 H, J = 7.3); 2.99 (td, 2 H, JHF =
6.1, J = 7.8); 1.32 (t, 3 H, J = 7.3). F NMR (CDCl ): –39.7 (t, 2 F, JHF = 16.1). Com poun d 5:
3
A colorless oil. MS, m/z: 275 (M – OEt), 241 (M – Br). HRMS: calculated for C11H10BrF O:
74.988 (M+ – OEt), C13H15F O : 241.104 (M – Br); found: 274.986 (M+ – OEt), 241.104 (M – Br).
H NMR (CDCl ): 7.18–7.37 (m , 5 H); 4.35 (m , 1 H); 4.33 (q, 2 H, J = 7.3); 3.22 (m , 2 H);
.61–2.88 (m , 2 H); 1.36 (t, 3 H, J = 7.3). F NMR (CDCl ): –35.3 (dt, 1 F, JFF = 263.7, JHF
+
1
2
2
3
3
(
1
1
9
3
+
+
2
+
+
2
1
2 2
3
1
9
2
3
2
1
=
3
4.7); –42.1 (dt, 1 F, 2JFF = 263.7, JHF = 16.1).
3
Reaction of Eth yl Brom odifluoroacetate with α-Meth ylstyren e (7)
In an atm osph ere of Ar, eth yl brom odifluoroacetate (1; 0.25 m l, 2.0 m m ol) an d
α-m eth ylstyren e (7; 0.26 m l, 2.0 m m ol) were added to a suspen sion of activated Cu powder
(
280 m g, 4.4 m m ol) in DMSO (2 m l), an d th e m ixture was stirred at 55 °C for 7 h . After th is
tim e, 1 was n ot detected by GLC. Th e m ixture was poured on to a m ixture of ice an d satu-
rated NH Cl solution , an d extracted with Et O. Th e Et O layer was wash ed with saturated
4
2
2
NH Cl solution an d saturated NaCl solution , an d dried over MgSO . After evaporation of th e
4
4
solven t, th e residue was purified by colum n ch rom atograph y (SiO , Et O–h exan e 1 : 4) to
2
2
give eth yl 2,2-difluoro-4-ph en ylpen tan oate (8, trace), eth yl 2,2-difluoro-4-ph en yl-
-pen ten oate (9, trace) an d dieth yl 2,2,5,5-tetrafluoro-3-m eth yl-3-ph en ylh exan edioate (10,
trace). Th e solven t was ch an ged to AcOEt–h exan e 2 : 3 to give dieth yl 2,2,7,7-tetrafluoro-
,5-dim eth yl-4,5-diph en yloctan edioate (11; 293 m g, 60%) as a m ixture of m eso form an d
4
4
racem ate (1 : 1). Each diastereom er of 11 could be purified by recrystallization from h exan e
or EtOH.
+
Com poun d 8: A colorless oil. MS, m/z: 242 (M ). HRMS: calculated for C13H16F O :
2
2
+
1
2
42.112 (M ); foun d: 242.112. H NMR (CDCl ): 7.30 (m , 2 H); 7.20 (m , 3 H); 4.04 (dq, 1 H,
3
J = 19.3, 7.0); 4.01 (dq, 1 H, J = 19.3, 7.0); 3.07 (m , 1 H); 2.49 (m , 1 H); 2.32 (m , 1 H); 1.34
1
9
2
3
(
1
(
d, 3 H, J = 7.0); 1.24 (t, 3 H, J = 7.0). F NMR (CDCl ): –35.3 (dt, 1 F, JFF = 259.3, JHF =
3
2
3
6.1); –41.6 (dt, 1 F, JFF = 259.3, JHF = 16.1). Com poun d 9: A colorless oil. MS, m/z: 240
M ). HRMS: calculated for C13H14F O : 240.096 (M ); foun d: 240.095. H NMR (CDCl ):
2 2 3
+
+
1
7
.27–7.39 (m , 5 H); 5.51 (t, 1 H, J = 1.0); 5.32 (s, 1 H); 4.05 (q, 2 H, J = 7.3); 3.30 (dt, 2 H,
3
19
3
JHF = 15.7, J = 1.0); 1.21 (t, 3 H, J = 7.3). F NMR (CDCl ): –38.0 (t, 2 F, JHF = 15.7). Com -
poun d 10: A colorless oil. MS, m/z: 364 (M ). HRMS: calculated for C17H20F O : 364.130
3
+
4
4
+
1
(
M ); foun d: 364.129. H NMR (CDCl ): 7.26–7.43 (m , 5 H); 4.01 (q, 1 H, J = 7.4); 4.00 (q,
3
3
1
2
3
2
H, J = 7.4); 3.76 (dq, 1 H, J = 34.2, 7.2); 3.74 (dq, 1 H, J = 34.2, 7.2); 3.19 (dt, 1 H, JHF
=
3
2.1, J =15.6); 2.77 (td, 1 H, J = 15.6, JHF = 12.0); 1.77 (bs, 3 H); 1.17 (t, 3H, J = 7.4); 1.00 (t,
1
9
2
3
2
H, J = 7.2); F NMR (CDCl ): –29.3 (dt, 1 F, JFF = 259.3,
J
= 12.0); –36.3 (dt, 1 F, JFF =
3
HF
3
2
2
59.3, JHF = 22.1); –43.4 (d, 1 F, JFF = 244.6); –48.0 (d, 1 F, JFF = 244.6). On e diastereom er
Collect. Czech. Chem. Commun. (Vol. 67) (2002)