Unusual behavior of the anionic species from (E)-1-chloro-3,3,3- trifluoropropene(HCFC-1233t)

Article abstract of DOI:10.1002/ejoc.200900370

(E)-1-Chloro-3,3,3-trifluoropropene was smoothly deprotonated by MeLi at the position β to the CF₃ group, and exclusive formation of propargylic alcohols was observed by addition of appropriate carbonyl compounds as long as up to 1.6 equiv. of

Full text of DOI:10.1002/ejoc.200900370

SHORT COMMUNICATION
DOI: 10.1002/ejoc.200900370
Unusual Behavior of the Anionic Species from
(E)-1-Chloro-3,3,3-trifluoropropene (HCFC-1233t)
Akiko Miyagawa,[a] Motoki Naka,[a] Takashi Yamazaki,*[a] and
Tomoko Kawasaki-Takasuka[a]
Keywords: Fluorine / Rearrangement / Alcohols / Alkenes
(E)-1-Chloro-3,3,3-trifluoropropene was smoothly deproton-
ated by MeLi at the position β to the CF3 group, and exclus-
ive formation of propargylic alcohols was observed by ad-
dition of appropriate carbonyl compounds as long as up to
1.6 equiv. of MeLi was used, whereas more than 1.7 equiv. of
this base led to selective construction of allylic alcohols.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
effect smooth removal of protons: thus, hexane afforded
products in very low yields irrespective of the base em-
ployed (Table 1, Entries 3, 6, and 11) but THF (Table 1, En-
tries 1, 4, 7, and 9) demonstrated excellent selectivity for
propargylic alcohol 4e[5] and also quite high chemical
yields.[6] In contrast, Et2O furnished a mixture of 4e and
allylic alcohol (E)-2e with the latter being preferred
(Table 1, Entries 2, 5, and 10), but this was not the case
when MeLi was used (Table 1, Entry 8).
Introduction
Nonozone depleting (E)-1-chloro-3,3,3-trifluoropropene
[(E)-1; abbreviated as HCFC-1233t], is manufactured as the
convenient intermediate for the preparation of 1,1,1,3,3-
pentafluoropropane (HFC-245fa) as the potent chlorofluo-
rocarbon substitute.[1] In addition to its usage for this pur-
pose, (E)-1 is also recognized as a useful CF3-containing
building unit by installation of a structurally defined (E)
olefin and a chlorine atom as the useful synthetic handles.[2]
Moreover, consideration of the characteristic nature of the
CF3 moiety leads to the expectation that two hydrogen
atoms in (E)-1 are likely to be removed by treatment with
an adequate base, such as the various types of RLi: Ha
would be acidic enough, as the resulting anion would be
inductively stabilized by the CF3 group,[3] and abstraction
of Hb would furnish vinyllithium species Int-1 containing
firm and energetically favorable intramolecular five-mem-
bered Li···F chelation (Scheme 1).[4] Then, we started to in-
vestigate the behavior of versatile substrate (E)-1 towards
various bases and utilization of the resultant anionic inter-
mediates.
Table 1. Investigation of reaction conditions.[a]
Entry
Base (equiv.)
Solvent
19F NMR yield [%]
(E)-2e
4e
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
sBuLi (1.2)
sBuLi (1.2)
sBuLi (1.2)
BuLi (1.2)
BuLi (1.2)
BuLi (1.2)
MeLi (1.2)
MeLi (1.2)
LDA (1.2)
LDA (1.2)
LDA (1.2)
tBuOK (1.2)
sBuLi (2.2)
BuLi (2.2)
MeLi (2.2)
LDA (2.2)
THF
Et2O
hexane
THF
Et2O
hexane
THF
Et2O
THF
Et2O
hexane
THF
THF
THF
THF
THF
5
44
0
0
76
0
0
0
0
59
38
0
55
21
1
52
0
55
8
Results and Discussion
First of all, our attention has been focused on finding
appropriate conditions for deprotonation of (E)-1 and for
nucleophilic attack of the resultant anion towards a repre-
sentative electrophile, benzaldehyde (Table 1). Requirement
of relatively higher polarity was apparent for solvents to
24
11
0
7
0
45
55
[b]
[b]
–
–
[a] Department of Applied Chemistry, Graduate School of Engi-
neering, Tokyo University of Agriculture and Technology,
2-24-16 Nakamachi, Koganei 184-8588, Japan
Fax: +81-42-388-7038
90
75
5
25
[a] RLi reagents were titrated prior to use. [b] No reproducible re-
sults were obtained (constant product selectivity was not obtained
and sometimes the major product was switched).
E-mail: tyamazak@cc.tuat.ac.jp
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200900370.
Eur. J. Org. Chem. 2009, 4395–4399
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4395

A. Miyagawa, M. Naka, T. Yamazaki, T. Kawasaki-Takasuka
SHORT COMMUNICATION
These results allowed us to propose the brief mechanism
(Scheme 1). Thus, contrary to the computational results de-
scribed below (see Scheme 3), a base in THF would select
Ha, α to the strongly electron-withdrawing CF3 group, and
its removal would be followed by elimination of a chlorine
atom to furnish 3,3,3-trifluorinated propyne 3. Then, the
second base molecule might successfully convert this inter-
mediate into 4 by reaction of the corresponding acetylide
and an appropriate carbonyl compound. In contrast, depro-
tonation at the β position to the CF3 moiety seemed to
compete to some extent in a less coordinating solvent like
Et2O. These experimental results suggested that Int-2 was
more energetically stable than Int-1, and the aggregation
state of RLi species would affect the reaction course signifi-
cantly.
Figure 1. Relationship between the amount of MeLi employed and
the product selectivity [(E)-2e: ᭿, 4e: ᭹].
system completely altered the situation to afford 4e selec-
tively [72% yield without formation of (E)-2e; condi-
tions d]. Combination of these results led to speculation
that (1) production of 4e in an excellent conversion yield by
the action of LDA (1.2 equiv.) suggested the initial forma-
tion of the vinylic anion β to a CF3 group (Int-1 in
Scheme 1), which would be then transformed into the corre-
sponding acetylide before reaction with PhCHO and (2) the
quite sharp effect of HMPA as an additive would assume
an appropriate intermolecular interaction between Int-1
and the excess amount of MeLi.
Scheme 1. Possible routes to allylic alcohols (E)-2 and propargylic
alcohols 4.
On the basis of this analysis, 2.2 equivalents of a base
was employed in THF with the aim to produce 4e in high-
yield. However, a totally unexpected outcome resulted:
thus, especially as shown in Entries 15 and 16 in Table 1,
allylic alcohol (E)-2e was actually obtained as the major
product and 4e was formed only in low yield. sBuLi did not
give the good (E)-2e/4e selectivity that we expected
(Table 1Entry 13). To solve this puzzling question, (E)-1
was treated with varying amounts of MeLi[7] as the model
base, and it is quite intriguing to note that the chemical
yields of (E)-2e and 4e were highly dependent on the quan-
tity of MeLi, and their selectivity clearly and drastically
changed between 1.6 and 1.7 equivalents (Figure 1). A
unique point was also found between 1.4 and 1.5 equiva-
lents.
For acquiring further information about the present reac-
tion mechanism, a couple of additional experiments were
performed (Scheme 2). At first, in an attempt to spontane-
ously capture the anionic species initially generated from
(E)-1, this substrate was subjected to a THF solution of
LDA (1.2 equiv.)[8] containing PhCHO to furnish a mixture
of (E)-2e and 4e in 18 and 8% yield, respectively (condi-
Scheme 2. Syntheses of (E)-2e and 4e by various methods.
Additional reactions were also carried out to verify the
tions b). In contrast, 4e was obtained in 55% yield as the possible production of propargylic alcohol 4e by formal de-
sole product by the deprotonation sequence with LDA at hydrochlorination of allylic alcohol (E)-2e. In the event,
–80 °C for 0.5 h, followed by the addition of PhCHO smooth and quantitative conversion of (E)-2e to 4e via Int-
(Table 1, Entry 9; conditions a). Moreover, apparent from 3 was substantiated by 2.2 equivalents of BuLi, whereas
Figure 1, treatment of (E)-1 with MeLi (1.7 equiv.) led to with the same quantity of MeLi only 20% conversion to 4e
exclusive formation of (E)-2e (97% yield with 2% of 4e; was realized along with 75% recovery of (E)-2e (condi-
conditions c), whereas addition of HMPA (1 equiv.) to this tions e and f), which led to the conclusion that (3) this was
4396
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 4395–4399

Unusual Behavior of the Anionic Species from HCFC-1233t
not the major route to yield 4e as long as MeLi was em- Entries 2 and 5 in Table 1, different from THF, the lower
ployed. With these additional data in hand, we revised the Lewis basic solvent Et2O allowed formation of (E)-2e to
mechanism to that shown in Scheme 3, which also includes some extent, which would be as a result of favorable con-
the relative energy by DFT calculations[9] in parentheses. struction of complexes by interaction of Int-1 and sBuLi or
Thus, the first proton abstraction by MeLi would regiose- BuLi like the case of MeLi.
lectively occur at the β position to the CF3 group so as to
To obtain further experimental proof, we performed the
form the computationally more stable intermediate Int-1, deuteration reaction of the resultant possible anionic spe-
which would constitute complexes like Int-4[10] or its oligo- cies, thus Int-1 or 2. Because it has already known that (E)-
meric forms with an excess amount of MeLi for gaining 1 readily undergoes nucleophilic attack of secondary amines
further stabilization.[11] In contrast, because MeLi under by way of an addition–elimination sequence,[16,17] the in situ
such a situation still retained its ability as a base, it would conversion of regenerated (E)-1 to (E)-6 was investigated as
abstract Hb from another (E)-1 molecule to furnish Int-1, a result of the low boiling point of (E)-1 of 21 °C
which by losing an extra stabilizing factor, would further (Scheme 4). At first, for confirmation of the applicability of
release LiCl by the α elimination pathway when less than the original method[18] with a slight modification, the an-
1.6 equivalents of MeLi was employed.
ionic species from the reaction of (E)-1 and 1.7 equivalents
of MeLi at –80 °C was quenched with CH3OH and addition
of piperidine to this mixture afforded (E)-6a in 32% yield.
Then, the same process was repeated by using the same base
in amounts of 1.2 and 1.7 equivalents with CD3OD as the
deuterium source. The former conditions furnished (E)-6a
in 16% yield without any sign of deuterium incorporation,
but the product of the latter was found to possess 54% D
only at the N-attached carbon atom. The fact that the prod-
uct obtained under conditions c in Scheme 4 did not con-
tain any deuterium seemed consistent with our proposed
mechanism, because this pathway would furnish 0.6 equiva-
lents of Int-5 and 0.4 equivalents of (E)-1 and the latter led
to formation of (E)-6a and deuterated 3 from Int-5 would
be vaporized (boiling point: ca. –40 °C). The use of
1.7 equivalents of MeLi furnished a mixture of (E)-6a and
6b in a ratio of 46:54, indicating the presence of vinyl an-
ionic intermediates possibly like Int-4, which nicely com-
pared with the result when 1.2 equivalents of MeLi was em-
ployed.
Scheme 3. The proposed mechanism of the present reaction {in the
parenthesis is shown the calculated relative energy [kcalmol–1] by
the B3LYP/6-311++G** level of theory with considering the effect
of THF (SCIPCM)}.
Subsequent hydride migration[12] would convert carbene
5 into F3-propyne 3, which underwent deprotonation to
give the corresponding acetylide Int-5 by another Int-1
molecule or MeLi itself. This interesting reaction course is
already known as the Fritsch–Buttenberg–Wiechell (FBW)
rearrangement.[13,14] Eventually, final intermediates Int-4
and Int-5 would directly correspond to products (E)-2 and
4, respectively. This scheme would at least qualitatively ex-
plain the behavior of (E)-1 after lithiation: for example, ad-
dition of HMPA (1 equiv.) would be effective for decompo-
Scheme 4. Reaction of (E)-1 with piperidine under various condi-
tions.
Another intriguing point was the fairly contrasting reac-
sition of complexes like Int-4 and liberated Int-1 followed tivity between stereoisomers (E)- and (Z)-1. Thus, treat-
FBW rearrangement to give 4 (Scheme 2, conditions c vs. ment of (E)-1 with 1.7 equivalents of MeLi followed by
d). In contrast, the generation of the anionic species from trapping the resultant intermediate by PhCHO predomi-
(E)-1 in the presence of PhCHO furnished a mixture of (E)- nantly furnished allylic alcohol (E)-2e, whereas exclusive
2e and 4e, whereas the addition of PhCHO after 0.5 h mix- formation of propargylic alcohol 4e was realized by (Z)-1
ing of (E)-1 with MeLi predominantly afforded 4e (condi- (Scheme 5). The latter would be understood as a result of
tions a vs. b). The fact that the former “internal trap” ex- selective formation of Int-6 due to its electrostatic stability
periment furnished (E)-2e and 4e in 18 and 8% yield, and, at the same time, impossible intramolecular Li···F che-
respectively, would be a reflection of FBW rearrangement lation after deprotonation of Hb. In addition to our in-
as a relatively quick sequence.[15] As already described in terpretation described above, this conclusion also stemmed
Eur. J. Org. Chem. 2009, 4395–4399
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4397

A. Miyagawa, M. Naka, T. Yamazaki, T. Kawasaki-Takasuka
SHORT COMMUNICATION
from the inherently significant rate difference of this type the present method for the selective construction of either
of elimination between stereoisomers:[19] for example, elimi- alcohols (E)-2 or 4 just by controlling the amount of MeLi
nation of HBr from (Z)-2-bromo-p-nitrostyrene was re- employed. Further study in this area is underway in this
ported to proceed 2300 times faster than the corresponding laboratory.
(E) isomer.[19a]
Supporting Information (see footnote on the first page of this arti-
cle): Detailed experimental procedures for the preparation of allylic
and propargylic alcohols (E)-2 and 4, respectively, and characteri-
zation data of the new compounds.
Acknowledgments
The generous gift of both stereoisomers of HCFC-1233 from Cen-
tral Glass Co., Ltd. is gratefully acknowledged.
[1] a) T. Nakada, H. Aoyama, A. Yamamoto (Daikin Industries),
PCT Int. Appl. 9724307, 1997; b) S. Yoshikawa, R. Tamai, F.
Saku, Y. Hibino (Central glass), Jpn. Kokai Tokkyo Koho,
09241188, 1997; c) A. Lantz, B. Requieme, L. Wendlinger (Elf
Atochem), Ger. Offen. 19716337, 1997; d) M. Y. Elsheikh, B.
Chen (Elf Atochem North America), Jpn. Kokai Tokkyo Koho
2000336048, 2000; e) H.-S. Tung, R. C. Johnson, D. C. Merkel
(Honeywell International), U. S. Pat. Appl. Publ. 2005020862,
2005; f) H.-E. Yang, H.-D. Quan, M. Tamura, A. Sekiya, J.
Mol. Catal. A 2005, 233, 99–104; g) H.-D. Quan, H.-E. Yang,
M. Tamura, A. Sekiya, J. Fluorine Chem. 2007, 128, 190–195.
[2] a) T. Taguchi, G. Tomizawa, A. Kawara, M. Nakajima, Y. Ko-
bayashi, J. Fluorine Chem. 1988, 40, 171–182; b) M.
van der Puy, U. S. 6111139, 2000; c) H. K. Nair, D. Nalewajek,
A. Poss (Honeywell International), U. S. 6673976, 2004; d) T.
Komata, M. Fujiwara, S. Akiba, K. Hosoi, S. Narizuka (Cen-
tral glass), PCT Int. Appl. 2006046417, 2006; e) M. Fujiwara,
S. Narizuka (Central glass), Jpn. Kokai Tokkyo Koho
2006083066, 2006; f) T. Komata, K. Hosoi, S. Akiba (Central
glass), PCT Int. Appl. 2007037119, 2007; g) T. Komata, K.
Hosoi, S. Akiba (Central glass), PCT Int. Appl. 2007052492,
2007; h) T. Komata, S. Akiba, K. Hosoi, K. Ogura, J. Fluorine
Chem. 2008, 129, 35–39.
Scheme 5. Reaction of (Z)-1 with 1.7 equivalents of MeLi and
PhCHO.
The preparation of (E)-2 and 4 by adding 1.7 and
1.6 equivalents of MeLi to (E)-1, respectively, enabling the
selective formation of these two types of alcohols contain-
ing a variety of substituents is shown in Table 2.
Table 2. Reaction of (E)-1 with a variety of carbonyl compounds
in the presence of 1.6 or 1.7 equivalents. of MeLi.
Entry
R1
R2
Isolated yield [%]
(E)-2[a]
4[b]
[3] a) I. Ojima, Fluorine in Medicinal Chemistry and Chemical Bi-
ology, Wiley, New York, 2009; b) K. Uneyama, Organofluorine
Chemistry, Blackwell, Oxford, 2006, pp. 10–22.
1
2
3
4
5
6
7
8
9
C9H19
PhCH2CH2
p-CH3C6H4
p-CH3OC6H4
Ph
p-BrC6H4
p-NO2C6H4
Ph
H
H
H
H
H
H
H
CH3
94 (2a)
86 (2b)
88 (2c)
85 (2d)
97 (2e)
92 (2f)
84 (2g)
57 (2h)
85 (2i)
65 (4a)
59 (4b)
57 (4c)
[4] a) G. Sini, A. Tessier, J. Pytkowicz, T. Brigaud, Chem. Eur. J.
2008, 14, 3363–3370; b) M. Shimizu, T. Fujimoto, X.-Y. Liu,
H. Minezaki, T. Hata, T. Hiyama, Tetrahedron 2003, 59, 9811–
9823; c) T. Yamazaki, T. Kitazume in Enantiocontrolled Synthe-
sis of Fluoro-Organic Compounds: Stereochemical Challenges
and Biomedicinal Targets (Ed.: V. A. Soloshonok), John
Wiley & Sons, New York, 1999, pp. 575–600; d) T. Yamazaki,
M. Ando, T. Kitazume, T. Kubota, M. Omura, Org. Lett. 1999,
1, 905–908.
[5] a) S. Tajammal, A. E. Tipping, J. Fluorine Chem. 1990, 47, 45–
57; b) T. Yamazaki, K. Mizutani, T. Kitazume, J. Org. Chem.
1995, 60, 6046–6056; c) A. R. Katritzky, M. Qi, A. P. Wells, J.
Fluorine Chem. 1996, 80, 145–147; d) F.-L. Qing, W.-Z. Gao,
J.-W. Ying, J. Org. Chem. 2000, 65, 2003–2006; e) A. K. Bris-
don, I. R. Crossley, Chem. Commun. 2002, 2420–2421; f) M.
Shimizu, M. Higashi, Y. Takeda, G.-F. Jiang, M. Murai, T.
Hiyama, Synlett 2007, 1163–1165.
[6] Since 2 equiv. of a base is required for the formation of 4e on
the basis of the reaction mechanism shown in Scheme 1, 60%
is the theoretical yield.
[7] Each point was obtained by performing the experiments 2–3
times. MeLi was titrated by a literature method. See: B. H Lip-
shutz in Organometallics in Synthesis A Manual (Ed.: M.
Schlosser), John Wiley & Sons, New York, 1994, ch. 4, pp. 283–
382.
58 (4d)
72 (4e)
52 (4f)
[25][c] (4g)
56[d] (4h)
64 (4i)
(CH2)5
[a] 1.7 equiv. of MeLi was employed. [b] 1.6 equiv. of MeLi was
employed. [c] Yield in square brackets represents the yield when
2.2 equiv. of MeLi and 10 equiv. of HMPA were used. [d] Reaction
was carried out at –80 to –60 °C for 3 h.
Conclusions
As shown above, we have learned the interesting behavior
of anionic species Int-1 generated from (E)-1, which facili-
tated the formation of allylic alcohols (E)-2 possibly by way
of an energetically more stable complex with MeLi (MeLi
Ͼ 1.7 equiv.), whereas Int-1 itself would follow an FBW
rearrangement after α-elimination of LiCl to furnish the
corresponding propargylic alcohols 4 (MeLi Ͻ 1.6 equiv.).
Although the mechanism has not fully been clarified, we
successfully demonstrated the extraordinary convenience of
[8] Judging from Table 1, because LDA behaved basically in a sim-
ilar manner to MeLi at least in THF and spontaneous reaction
4398
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 4395–4399

Unusual Behavior of the Anionic Species from HCFC-1233t
was readily expected by mixing MeLi and PhCHO, we selected
the former base here.
1911–1913 (R = CH2OTBS); b) H. Uno, N. Nibu, N. Misobe,
Bull. Chem. Soc. Jpn. 1999, 72, 1365–1375 (R = Ph). For the
similar species with zinc instead of Li, see, S. W. Hansen, T. D.
Spawn, D. J. Burton, J. Fluorine Chem. 1987, 35, 415–420.
[13] a) W. A. Chalifoux, R. R. Tykwinski, Chem. Rec. 2006, 6, 169–
182; b) R. Knorr, Chem. Rev. 2004, 104, 3795–3849.
[14] One of the referees pointed out the possible equilibration be-
tween Int-1 and Int-2 in the presence of (E)-1, whereas our
experiment proved that this was not the case: To a solution of
(E)-1 was added MeLi (1.2 equiv.) at –80 °C and after 0.5 h,
another 0.8 equiv. of MeLi was added. When 2 equiv. of MeLi
was added all at once, (E)-2e was afforded in excellent selectiv-
ity by the addition of PhCHO (see Entry 15 in Table 1and Fig-
ure 1), whereas what was actually obtained was 4e only in 68%
yield.
[15] H2C=C was reported to rearrange into acetylene within a
period of picoseconds. G. A. Petersson, T. G. Tensfeldt, J. A.
Montgomery Jr, J. Am. Chem. Soc. 1992, 114, 6133–6138.
[16] T. Komata, M. Fujiwara, S. Akiba, K. Hosoi, S. Narizuka,
WO 2006/046417 A1.
[17] 1,2-Addition of amines to 3,3,3-trifluoropropyne was also re-
ported. N. P. Stepanova, V. B. Lebedev, N. A. Orlova, E. S. Tur-
banova, A. A. Petrov, Russ. J. Org. Chem. 1988, 24, 692–699.
[18] The original procedure, mixing 4 equiv. of piperidine with (E)-
1 at 0 °C for 3 h, allowed the isolation of (E)-6a in 73% yield.
[19] a) S. J. Cristol, A. Begoon, W. P. Norris, P. S. Ramey, J. Am.
Chem. Soc. 1954, 76, 4558–4561; b) O. M. Behr, G. Eglinton,
I. A. Lardy, R. A. Raphael, J. Chem. Soc. 1964, 1151–1154; c)
S. Miyano, Y. Izumi, K. Fujii, Y. Ohno, H. Hashimoto, Bull.
Chem. Soc. Jpn. 1979, 52, 1197–1202.
[9] Computation was carried out by Gaussian 03W using the
B3LYP/6-311++G** level of theory and the solvent effect
(SCIPCM) was estimated by single-point calculation. M. J.
Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A.
Robb, J. R. Cheeseman, J. A. Montgomery Jr, T. Vreven, K. N.
Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V.
Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.
Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pom-
elli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P.
Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich,
A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D.
Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui,
A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu,
A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W.
Wong, C. Gonzalez, J. A. Pople, Gaussian 03, Revision B.03,
Gaussian, Inc., Wallingford, CT, 2004.
[10] This is the species actually obtained by DFT optimization.
[11] Clear pictures of their structures have not been obtained yet.
[12] As a representative example of hydride migration in FBW re-
arrangement systems, see: T. Okuyama, S. Imamura, Y. Ishida,
Bull. Chem. Soc. Jpn. 2001, 74, 543–548. Very limited numbers
of substrates with a CF3 group were reported in related systems
and no migration from CF3CR=C(Br)Li was observed; a) J.-
M. Zhang, X.-M. Zhao, L. Lu, Tetrahedron Lett. 2007, 48,
Received: April 4, 2009
Published Online: July 24, 2009
Eur. J. Org. Chem. 2009, 4395–4399
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4399