Palladium migration along linear carbon chains: The detection of η1-η2-enyl intermediates and the study of their rearrangement

Article abstract of DOI:10.1021/om9703907

The reactions of [PdPfBr(NCMe)₂] (Pf = C₆F₅) with stoichiometric amounts of 1,5-hexadiene, 1,6-heptadiene, or 1,7-octadiene at low temperature result in the formation of several (η¹-η²-enyl)palladium complexes that isomerize sequentially at different temperatures depending on the ring size of the palladacycles (T_isom: 7.5- < 6.5- < 5.5-membered). These (η¹-η²-enyl)palladium derivatives are intermediates in the Pd-migration process, arrested by coordination of the unattacked double bond. The final products of their isomerization are several isomeric Pf-(η³-allyl)palladium complexes (Pf = C₆F₅). The major allylic derivative in each case arises from Pd migration to the terminal double bond. Minor amounts of (η³-allyl)palladium complexes formed by double bond switches in the process of Pd migration are also seen, but this occurs only on putative 1,5- or 1,6-diene-hydrido-palladium intermediates. A small amount of cyclic organic derivatives coming from the cyclization of (η¹-η²-enyl)palladium intermediates is detected in each case. The use of excess diolefin gives rise to additional (η³-allyl)palladium complexes without the Pf group and to the corresponding Pf-substituted linear dienes. These arise via displacement of the Pf dienes by the starting diolefin in a hydrido-palladium intermediate during the Pd-migration process.

Full text of DOI:10.1021/om9703907

4138
Organometallics 1997, 16, 4138-4144
P a lla d iu m Migr a tion a lon g Lin ea r Ca r bon Ch a in s: Th e
Detection of η1-η2-En yl In ter m ed ia tes a n d th e Stu d y of
Th eir Rea r r a n gem en t
Ana C. Albe´niz, Pablo Espinet,* and Yong-Shou Lin
Departamento de Quı´mica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid,
47005 Valladolid, Spain
Received May 12, 1997X
The reactions of [PdPfBr(NCMe)2] (Pf ) C6F5) with stoichiometric amounts of 1,5-
hexadiene, 1,6-heptadiene, or 1,7-octadiene at low temperature result in the formation of
several (η1-η2-enyl)palladium complexes that isomerize sequentially at different temperatures
depending on the ring size of the palladacycles (Tisom: 7.5- < 6.5- < 5.5-membered). These
(η1-η2-enyl)palladium derivatives are intermediates in the Pd-migration process, arrested
by coordination of the unattacked double bond. The final products of their isomerization
are several isomeric Pf-(η3-allyl)palladium complexes (Pf ) C6F5). The major allylic
derivative in each case arises from Pd migration to the terminal double bond. Minor amounts
of (η3-allyl)palladium complexes formed by double bond switches in the process of Pd
migration are also seen, but this occurs only on putative 1,5- or 1,6-diene-hydrido-palladium
intermediates. A small amount of cyclic organic derivatives coming from the cyclization of
(η1-η2-enyl)palladium intermediates is detected in each case. The use of excess diolefin gives
rise to additional (η3-allyl)palladium complexes without the Pf group and to the corresponding
Pf-substituted linear dienes. These arise via displacement of the Pf dienes by the starting
diolefin in a hydrido-palladium intermediate during the Pd-migration process.
In tr od u ction
process of Pd migration between distant carbons. For
instance, quite stable η1-η2-enyl complexes are formed
by insertion of 1,5-cyclooctadiene in Pd-R,9 and other
η1-η2-enyls with the same type of palladacycle are
obtained by other methods.10,11 Less stable η1-η2-enyl
compounds have also been identified and/or isolated,
and Pd migration to form the corresponding η3-allyls is
a more facile process in these systems.7,12-15
This suggests that, starting from linear nonconju-
gated dienes with long spacers between the double
bonds, different (η1-η2-enyl)palladium complexes of me-
dium stability might be formed and the Pd-migration
process could be followed step by step, through the
isolation or detection of the η1-η2-enyl intermediates,
which would be snapshots in the migration of palladium.
Here we report this study made on the following
linear terminal dienes: 1,5-hexadiene; 1,6-heptadiene;
and 1,7-octadiene. They react with [PdPfBr(NCMe)2]
(Pf ) C6F5) to give insertion into the Pd-Pf bond. The
possibility of monitoring the reactions by 19F NMR
(clean spectra with chemical shifts very sensitive to
small changes in the molecule) greatly facilitates the
study.16 Preliminary results on 1,5-hexadiene were
previously reported;13 the use of a higher field instru-
Conjugated and nonconjugated dienes have been used
to prepare (η3-allyl)palladium derivatives by insertion
of one double bond into a Pd-R bond, or by attack of
an external nucleophile on the coordinated diene.1,2 The
formation of the palladium allyl is straightforward in a
conjugated diene. For nonconjugated dienes Pd migra-
tion (via sequential Pd-H elimination-readdition) has
to follow insertion or nucleophilic attack in order to
reach the second double bond. It has been shown that
the Pd atom can migrate efficiently quite “long dis-
tances”,3 and this has been used in the catalytic
transformation of nonconjugated dienes.3a,4 Nonetheless
it is becoming more evident that other mechanisms,
such as intramolecular insertion into the newly formed
Pd-R bond (cyclization), can compete with migration
in Pd-mediated reactions.2,5-8
η1-η2-Enyl derivatives forming specially favorable
palladacycles can be isolated as intermediates in the
* E-mail: espinet@cpd.uva.es.
X Abstract published in Advance ACS Abstracts, August 15, 1997.
(1) Maitlis, P. M.; Espinet, P.; Russell, M. J . H. In Comprehensive
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds.; Pergamon Press: Oxford, 1982; Vol. 6, p 385.
(2) Davies, J . A. In Comprehensive Organometallic Chemistry:
A
Review of the Literature 1982-1994; Abel, E. W., Stone, F. G. A.,
Wilkinson, G., Eds.; Pergamon Press: Oxford, 1995; Vol. 9, p 291.
(3) (a) Larock, R. C.; Lu, Y.; Bain, A. C.; Russell, C. E. J . Org. Chem.
1991, 56, 4589 and references therein. (b) Larock, R. C.; Takagi, K. J .
Org. Chem. 1984, 49, 2701. (c) Larock, R. C.; Takagi, K. Tetrahedron
Lett. 1983, 24 (33), 3457.
(4) Larock, R. C.; Wang, Y.; Lu, Y.; Russell, C. E. J . Org. Chem.
1994, 59, 8107.
(5) De Meijere, A.; Meyer, F. E. Angew. Chem., Int. Ed. Engl. 1994,
33, 2379.
(9) Albe´niz, A. C.; Espinet, P.; J eannin, Y.; Philoche-Levisalles, M.;
Mann, B. E. J . Am. Chem. Soc. 1990, 112, 6594.
(10) Parra-Hake, M.; Rettig, M. F.; Wing, R. M. Organometallics
1983, 2, 1013.
(11) Peuckert, M.; Keim, W. Organometallics 1983, 2, 594.
(12) Albe´niz, A. C.; Espinet, P; Lin, Y.-S. Organometallics 1995, 14,
2977-2986.
(13) Albe´niz A. C.; Espinet, P. Organometallics 1991, 10, 2987-2988.
(14) Goddard, R.; Green, M.; Hughes, R. P; Woodward, P. J . Chem.
Soc., Dalton Trans. 1976, 1890-1899.
(6) Trost, B. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 259-281.
(7) Albe´niz, A. C.; Espinet, P.; Lin, Y.-S. J . Am. Chem. Soc. 1996,
118, 7145.
(15) Parra-Hake, M.; Rettig, M. F.; Williams, J . L.; Wing, R. M.
Organometallics 1986, 5, 1032.
(8) Negishi, E.; Cope´ret, C.; Ma, S.; Liou, S.-Y.; Liu, F. Chem. Rev.
1996, 96, 365.
(16) Albe´niz, A. C.; Espinet, P.; Foces-Foces, C.; Cano, F. H.
Organometallics 1990, 9, 1079.
S0276-7333(97)00390-7 CCC: $14.00 © 1997 American Chemical Society

Palladium Migration along Linear Carbon Chains
Organometallics, Vol. 16, No. 19, 1997 4139
Sch em e 1
ment has allowed for the detection of some minor
products previously undetected.
ratio, along with a small amount of 3 (Scheme 1, n ) 1,
T3 ) 293 K). The molar ratio of 2-a n ti in the mixture
decreases significantly after 10 h. The isomerization
of 1 is complete after 32 h, and the final products 2-syn ,
2-a n ti, and 3 are produced in a 13:1:2 ratio. Phosphines
have been shown to promote syn-anti isomerization.18
Addition of a small amount of PPh3 to the mixture did
not change this ratio, thus supporting that it actually
corresponds to the equilibrium distribution of both
species, the less crowded syn isomer being more abun-
dant.
Resu lts
The reactions of [PdPfBr(NCMe)2] with stoichiometric
amounts of 1,5-hexadiene, 1,6-heptadiene, or 1,7-octa-
diene give several isomeric (η3-allyl)palladium com-
plexes for each diolefin. In addition, a small amount of
cyclic organic derivatives is identified in each case. The
formation of (η1-η2-enyl)palladium intermediates and
their isomerization was observed when the reactions
When [PdPfBr(NCMe)2] and 1,5-hexadiene are mixed
at room temperature and let stand for 32 h, so that
complete isomerization of the intermediate 1 occurs, the
following products result: 2 (70% based on the integra-
1
were monitored at low temperature by 19F and H NMR.
The products observed are collected in Scheme 1.
Rea ction w ith 1,5-Hexa d ien e. In the reaction of
[PdPfBr(NCMe)2] and 1,5-hexadiene an intermediate
5.5-membered η1-η2-enyl complex (1) is formed.17 1 can
be isolated as a white solid when the reaction is carried
1
tion of 19F and H NMR signals), which is a mixture of
2-syn and 2-a n ti in a 13:1 ratio; 3 (14%); 1-methyl-5-
(pentafluorophenyl)-1-cyclopentene (4, 8%); and PfH
(3%). 2-syn can be isolated by crystallization.13
Rea ction w ith 1,6-Hep ta d ien e. Insertion of 1,6-
heptadiene in [PdPfBr(NCMe)2] occurs efficiently at -30
°C (Scheme 1, n ) 2). After 1 h at this temperature
the insertion is complete, to give a 6.5-membered-ring
η1-η2-enyl complex (8), as shown by a new 19F resonance
(ca. -143 ppm) typical of a Pf-C moiety.16 Two small
out at 0 °C, and it isomerizes to the (η3-allyl)palladium
298K
species at room temperature (kobs
) 5.37 × 10-5
s-1).13
Isomerization of 1 in CDCl3 was monitored by 19F
NMR at 293 K. In the first hour the (η3-allyl)palladium
complexes 2-syn and 2-a n t i are formed in a ca. 1:1
(17) The size of the η1-η2-enyl palladacycles is referred to as n.5-
membered, n being the number of atoms in the cycle and 0.5 being
added to account for the π-coordination of the double bond to the metal
(see, for example: Omae, I. Angew. Chem., Int. Ed. Engl. 1982, 21,
889).
(18) Vrieze, K. In Dynamic Nuclear Magnetic Resonance Spectros-
copy; J ackman, L. M., Cotton, F. A., Eds.; Academic Press: New York,
1975; p 441.

4140 Organometallics, Vol. 16, No. 19, 1997
Albe´niz et al.
Sch em e 2
signals (-143.2 and -144.3 ppm) are also observed,
assigned to the Fortho atoms of the Pf groups in 9 and
10, respectively. The spectra of 8 and 10 in the mixture
can be fully analyzed. Due to overlapping of signals the
1H NMR spectrum of 9 could not be analyzed, but the
genesis and evolution of this complex support the
structure assigned in Scheme 1. When the temperature
is increased to -10 °C, the simultaneous isomerization
of 8 to the (η3-allyl)palladium derivatives 10-12 and,
in a lesser amount, to complex 9 was evident (13% 9
was found after 8 had disappeared; Scheme 1, T1 ) T3
) 263 K). The rate of isomerization of 8 was measured
36% (Scheme 1, n ) 3, T1 ) T3 ) 243 K). If the mixture
is warmed to -10 °C, isomerization of 21 occurs, and a
derivative which seems to be the 5.5-membered η1-η2-
enyl complex 22 is observed. After 1 h at this temper-
ature 22 was formed as the major product (50%)
(Scheme 1, n ) 3, T2 ) T4 ) 263 K). Complexes 20-
22, detected by 19F NMR, correspond to the number of
η1-η2-enyl)palladium derivatives expected for a diene
such as 1,7-octadiene. However, the structure of these
(η1-η2-enyl)palladium intermediates could not be un-
1
equivocally supported by H NMR due to their broad
signals which overlap with each other or with the
signals of other compounds. Finally, extensive forma-
tion of η3-allyl complexes is observed when the temper-
ature is raised to 20 °C (Scheme 1, n ) 3, T5 ) 293 K).
After 3 h the processes of isomerization and decomposi-
tion are complete, and the final product distribution is
23 (39%), 24 (25%), 25 (17%), and 26 (8%), plus
unknown organic (5%) and organometallic (6%) com-
pounds (each one less than 2%).
by 19F NMR spectroscopy; it shows a first-order depen-
263K
dence on 8 (kobs
) 2.87 × 10-4 ( 0.08 × 10-4 s-1).
Complete isomerization of 9 takes 10 h at room
temperature (Scheme 1, n ) 2, T4 ) 293 K). This rate
is similar to that observed for the analogous 5.5-
membered η1-η2-enyl complex 1. Three η3-allyl com-
plexes, 10 (57%), 11 (3%), and 12 (19%), are the final
products of isomerization, plus the organic isomeric
products 1-methyl-5-((pentafluorophenyl)methyl)-1-cy-
clopentene (13, 9%), and 2-methyl-1-((pentafluorophe-
nyl)methyl)-1-cyclopentene (14, 5%). A small amount
of PfH (3%) is also found. The major derivative 10 could
be isolated as yellow crystals in cyclohexane (9%, yield).
Rea ction s w ith Excess Dien e. If the reactions are
carried out using excess diene (5-fold), a noticeable
decrease in the percentage of η3-allyl derivatives formed
is observed, as well as the production of additional (η3-
allyl)palladium complexes lacking pentafluorophenyl.
The amount of Pf-η3-palladium allyls is similar to that
of the Pf-free derivatives. Also, pentafluorophenyl
diolefins are released. The products obtained for each
diene are shown in Scheme 2, and the relative ratios
found are collected in Table 1. Besides the products
depicted in Scheme 2, two isomeric pentafluorophenyl
dienes are also observed in the reaction with excess 1,7-
octadiene (n ) 3), namely, 8-(pentafluorophenyl)-2,5-
octadiene (32) and 1-(pentafluorophenyl)-2,6-octadiene
(33). They arise from double-bond isomerization of 29
and 30, presumably promoted by Pd-H species.
Rea ction w ith 1,7-Octa d ien e. [PdPfBr(NCMe)2]
and 1,7-octadiene react in CDCl3 at -40 °C, as shown
by the appearance of two new 19F NMR signals (ca.
-143 and -144.5 ppm) in an approximately 2:1 ratio.
When the temperature is raised to -30 °C, a clear
transformation of the former 19F NMR signal (-143
ppm) to the latter one (-144.5 ppm) is observed. Thus,
it is reasonable that the former corresponds to the 7.5-
membered η1-η2-enyl palladacycle (20, Scheme 1, n )
3), and the latter to the 6.5-membered metallacycle (21).
The starting material is consumed after 2 h at 243 K
and yields 21 as the major product (64%). Other
complexes, 22-25 (see below), account for the remaining

Palladium Migration along Linear Carbon Chains
Organometallics, Vol. 16, No. 19, 1997 4141
bond.3,12,16 Cis addition of Pd-R bonds with opposite
regiochemistry has been found, although always as a
minor pathway.4,7,19-21
Ta ble 1. P r od u cts Obta in ed in th e Rea ction s of
[P d P fBr (NCMe)2] w ith Excess Dien e (5-fold )a
Pd-allyls
Intramolecular Heck reaction is observed in every
case as a minor pathway, and cyclic organic products
4, 13, 14, and 26 bearing Pf groups are generated. All
of them are substituted cyclopentenes, indicating that
cyclization occurs significantly only in 6.5-membered η1-
η2-enyl palladacycles: 21 for 1,7-octadiene, 8 for 1,6-
heptadiene, and an undetected η1-η2-enyl for 1,5-
hexadiene (J , eq 1) which would be formed by one-step
Pd migration away from the unattacked double bond.
diene
1,5-hexadiene 2 (30), 3 (2)
1,6-heptadiene 10 (15), 11 (1), 15 (22),
Pf-substituted
Pf-free
Pf dienes
other
5 (30)
6 (19), 7 (7)
4 (10)
17 (18), 18 (13), 13 (4)
16 (13) 19 (3)
12 (8)
1,7-octadiene
23 (15), 24 (9), 27 (9),
29 (9), 30 (7),
31 (2), 32 (3),
33 (4)
26 (4)
25 (7)
28 (25)
a
Percentages are given in parentheses. A small amount of
unknown products (between 2% and 7%, each one less than 2%)
is formed in each case.
Discu ssion
The mechanism of formation of all of the Pf-containing
derivatives detected is shown in Scheme 3. Arylation
of 1,5-, 1,6-, or 1,7-dienes leads to the generation of a
(η1-η2-enyl)palladium intermediate A, by simple coor-
dination of the unattacked double bond (Scheme 3, Br
bridges are omitted for simplicity). A is an (n+4.5)-
membered metallacycle (n ) 1, 2, 3 for 1, 8, and 20,
respectively), and its stability depends mostly on the
ring size. The following order of stability is found: 5.5-
> 6.5- > 7.5-membered, as shown by the temperatures
at which they show comparable rates of isomerization:
293 K (5.5-membered cycle, 1), 263 K (6.5-membered
cycle, 8), 243 K (7.5-membered cycle, 20).
After cyclization, Pd migration follows to generate an
endocyclic double bond. Combination of the “PdHBr”
moiety generated in the final Pd-H elimination with
the starting “PdPfBr” produces the small amount of PfH
observed (eq 2).22 Oxidative cyclization of a variety of
1,5-dienes in the presence of a Pd(II)-catalyst system
has been reported,23 and five-membered rings are com-
mon in recently developed Pd-mediated syntheses of
cyclic and polycyclic systems.5,6,8
The isomerization of A to B (9, 21), and that of B to
C (22) occurs via 1,2-hydrogen shift (one-step Pd migra-
tion), which leads eventually to the final η3-allyl deriva-
tives. It is worth noting that 4.5-membered-ring de-
rivatives are not detected, even though (η1-η2-
enyl)palladium complexes of this type have been observed
in the arylation of 1,4-pentadienes at low temperature.7
Pd migration to give a terminal (η3-allyl)palladium
complex at the initial position of the unattacked double
bond (2, 10, 23) is the main mechanism for the dienes
tested. Thus, rather efficient remote palladium migra-
tion is again observed here.3 Also, internal (η3-allyl)-
palladium complexes 3, 11, 12, 24, and 25 are obtained
as competitive products. The origin of these derivatives
must be an intramolecular hydride transfer to the
terminal double bond in the putative diene intermedi-
ates D, E, and F that could be formed in the course of
Pd migration from the corresponding η1-η2 palladium
complexes A, B, and C (Scheme 3). Once insertion has
taken place (G, H, and I), Pd migration develops and
brings about the formation of internal (η3-allyl)palla-
dium complexes. None of the intermediates D-I were
detected. However, not every possible internal allyl
derivative is formed, but only those which derive from
intermediates D and E corresponding to a 1,5 or 1,6
diene (3 for n ) 1; 11 and 12 for n ) 2; 24 and 25 for n
) 3). This suggests that, regardless the η2- or η4-
coordination mode of the diolefin when insertion of the
terminal double bond occurs, an η4-diene palladium
intermediate is formed at some point. Only from the
relatively stable six- or seven-membered diene palla-
dacycles is the switch of double bonds possible in the
Pd-migration process.
“PdHBr” + “PdPfBr” f PfH + Pd + PdBr2 (2)
Besides the above mentioned (η3-allyl)palladium com-
plexes bearing the Pf group, use of excess diolefins leads
to the production of additional (η3-allyl)palladium de-
rivatives not containing the Pf group. Pf-substituted
dienes are also formed. Thus, the presence of an excess
of starting diene promotes the displacement of the Pf-
substituted dienes in the intermediate diene-palladium-
hydride D-F (Scheme 3). Insertion into the Pd-H bond
and subsequent Pd migration gives the η3-allyl deriva-
tives (5, 15, and 27). The number and structures of
these η3-allyl species are governed by the same factors
observed for the Pf allyls, i.e., not only terminal but also
internal allyls (complexes 16 and 28) are formed. This
effect of the addition of excess diene had been observed
previously,3,12 and the exchange of monoolefins in an
η2-alkene-hydride palladium intermediate has also
been reported.24
Exp er im en ta l Section
Gen er a l Da ta . C, H, and N elemental analyses were
performed on a Perkin-Elmer 240 microanalyzer. 1H and 19F
NMR spectra were recorded on Bruker AC-300 and ARX-300
spectrometers. Chemical shifts (in δ units, ppm) were refer-
1
enced to TMS for H and 13C and to CFCl3 for 19F. The spectral
data were recorded at 293 K unless noted otherwise. Integra-
1
tion of 19F or H NMR signals was used to determine the ratios
(19) Bender, D. D.; Stakem, F. G.; Heck, R. F. J . Org. Chem. 1982,
47, 1278-1284.
(20) Heck, R. F. Acc. Chem. Res. 1979, 12, 146-151.
(21) Cabri, W.; Candlani, I. Acc. Chem. Res. 1995, 28, 2-7 and
references therein.
(22) Albe´niz, A. C.; Espinet, P.; Lin, Y.-S. Organometallics, in press.
(23) Moberg, C.; Sutin, L.; Cso¨regh, I.; Heumann, A. Organometallics
1990, 9, 974 and references therein.
(24) Reger, D. L.; Garza, D. G.; Lebioda, L. Organometallics 1992,
11, 4285.
The insertion step is fully regioselective: the Pf group
always binding the less substituted carbon. The results
follow the usual trend in Pd-mediated substitution of
olefins by cis-addition and coincide with the previous
investigation on the insertion of dienes into the Pd-Pf

4142 Organometallics, Vol. 16, No. 19, 1997
Albe´niz et al.
Sch em e 3
of products formed; a relaxation delay of at least 5T1 was
ensured in every recording. Organic products were analyzed
using a HP-5890 gas chromatograph connected to a HP-5988
mass spectrometer at an ionizing voltage of 70 eV and a
quadrupole analyzer. All diolefins were purchased from
Aldrich, J anssen, and Fluka Chemical Co. and used without
further purification. [PdPfBr(NCMe)2] was prepared as de-
scribed elsewhere.16
g, 0.0574 mmol), 1,5-hexadiene (0.069 mL, 0.0574 mmol), and
CDCl3 (0.6 mL) were mixed at room temperature. The
1
analysis of 19F and H NMR spectra showed that the reaction
was complete after 32 h and 2 (70%), 3 (14%), 4 (8%), and PfH
(3%) were formed; the yields (in parentheses) are based on the
integration of 19F NMR signals.
The reaction with excess 1,5-hexadiene (5-fold) was also
1
tried. It was monitored by 19F and H NMR, which indicated
Rea ction s w ith 1,5-Hexa d ien e. To a solution of [PdPfBr-
(NCMe)2] (0.400 g, 0.918 mmol) in CH2Cl2 (20 mL) was added
1,5-hexadiene (0.110 mL, 0.918 mmol) at 0 °C. After 5 min
activated carbon was added to the solution, the resulting
mixture was filtered, and the filtrate was evaporated to
dryness. The residue was triturated with ether, and the
suspension was cooled. A white solid, 1, was obtained (61%
yield). The mother liquors were maintained at room temper-
ature for 32 h. After eliminating Pd metal traces by filtration
through Celite, the mixture was chromatographed through a
silica gel column using n-hexane and then ether as eluents.
Evaporation of the n-hexane solvent of the first batch gave a
colorless oily residue, which contained 4 as the major compo-
nent. Elution with Et2O yielded a mixture of 2 and 3.
In order to measure the ratio of all products, the reaction
was also carried out in an NMR tube. [PdPfBr(NCMe)2] (0.025
that the reaction had finished after 15 h. The following
products were formed: 2 (30%, mixture of syn and anti isomers
in the ratio 13:1), 3 (2%), 5 (30%, mixture of anti and syn
isomers in the ratio 14:1), 4 (10%), 6 (19%), and 7 (7%). The
organic derivatives could be separated from the mixture by
column chromatography eluting with hexane, and they were
checked by GC-MS. The separation of the two major com-
plexes 2-syn and 5-syn was performed by preparative TLC
using hexane/EtOAc (10:1) as eluent (Rf ) 0.24, 2-syn ; Rf )
0.38, 5-syn ).
1: 19F NMR (CDCl3, δ, 283 K, 282 MHz) -163.0 (m, Fmeta),
-157.7 (t, Fpara), -142.3 (m, Fortho); 1H NMR (CDCl3, δ, 283 K,
300 MHz), 6.20 (m, 1H, H2), 4.65 (d, J ) 8.0 Hz, 1H, H1), 4.51
(d, J ) 14.0 Hz, 1H, H1′), 3.52 (m, 1H, H5), 3.28 (m, 1H, H6),
2.86 (m, 1H, H6′), 2.38 (m, 1H, H3), 2.0 (m, 1H, H3′), 1.55 (m,
1H, H4), 0.53 (m, 1H, H4′).13

Palladium Migration along Linear Carbon Chains
Organometallics, Vol. 16, No. 19, 1997 4143
2-syn : 19F NMR (CDCl3, δ, 282 MHz), -163.2 (m, Fmeta),
-158.1 (t, Fpara), -144.5 (m, Fortho); 1H NMR (CDCl3, δ, 300
MHz), 5.27 (m, J ) 6.8, 11.9 Hz, 1H, H2), 3.97 (d, J ) 6.8 Hz,
1H, H1syn), 3.90 (m, 1H, H3), 2.86 (d, J ) 11.9 Hz, 1H, H1anti),
2.75 (bt, J ) 7.2 Hz, 2H, PfCH2), 1.7-1.95 (m, 4H, H4, H5).13
2-a n ti: 19F NMR (CDCl3, δ, 282 MHz), -163.0 (m, Fmeta),
-157.9 (t, Fpara), -144.4 (m, Fortho); 1H NMR (CDCl3, δ, 300
MHz), 5.25 (m, 1H, H2), 4.82 (q, J ) 7.5 Hz, 1H, H3), 4.19 (d,
J ) 7.4 Hz, 1H, H1syn), 3.34 (d, J ) 13.0 Hz, 1H, H1anti), 2.69
(t, J ) 6.4 Hz, 2H, H6), 1.6-2.0 (m, 4H, H4, H5).
ln[signal integral] versus time gave the first-order rate con-
stant. The reported uncertainty in the isomerization rate
corresponds to 1 standard deviation in the slope of the best fit
line multiplied by Student’s factor t1-R(f).25
The reaction of [PdPfBr(NCMe)2] (0.025 g, 0.0574 mmol)
with excess 1,6-heptadiene (0.039 mL, 0.287 mmol) was also
studied. After 5 h the reaction was complete, and the final
product mixture contained 10 (15%), 11 (1%), 12 (8%), 15
(22%), 16 (13%), 13 (4%), 17 (18%), 18 (13%), and 19 (3%).
Silica gel column chromatography was employed to separate
the organic compounds and the palladium complexes by using
hexane and ether as eluents, respectively. The 1H NMR
spectra of the mixture of (η3-allyl)palladium complexes were
3: 19F NMR (CDCl3, δ, 282 MHz), -162.4 (m, Fmeta), -153.9
(t, Fpara), -140.5 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.97
(t, J ) 11.2 Hz, 1H, H2), 4.34 (d, J ) 11.2 Hz, 1H, H1), 4.07
(m, 1H, H3), 1.60-1.95 (m, 4H, H4, H5), 0.99 (t, J ) 7.2 Hz,
3H, H6).
1
assigned with the help of H-1H COSY. The Pf-substituted
1
1
diolefins were identified by H, 19F NMR, H-1H COSY, and
GC-MS. 10 could be separated out from the organometallic
mixture by preparative TLC in hexane/EtOAc (20:1). Rf ) 0.18
for 10 and 0.25 for the rest of the palladium complexes.
4: 19F NMR (CDCl3, δ, 282 MHz), -163.9 (m, Fmeta), -159.1
(t, Fpara), -144.3 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.21
(m, 1H, H2), 4.25 (m, 1H, H5), 2.35-2.58 (m, 3H, H3, H3′, H4),
1.95 (m, 1H, H4′), 1.78 (dd, J ) 1.2, 0.8 Hz, 3H, Me); MS (EI)
m/z (relative intensity) 248 (M+, 33), 233 (100), 181 (35), 79
(9), 51 (9), 41 (14).
5-syn : 1H NMR (CDCl3, δ, 300 MHz), 5.26 (td, J ) 12.1,
6.6 Hz, 1H, H2), 3.94 (d, J ) 6.6 Hz, 1H, H1syn), 3.9 (m, 1H,
H3), 2.85 (d, J ) 12.1 Hz, 1H, H1anti), 1.85 (m, 1H, H4), 1.42-
1.74 (m, 3H, H4′, H5, H5′), 0.95 (t, J ) 7.3 Hz, 3H, H6).3b
5-a n ti: 1H NMR (CDCl3, δ, 300 MHz), 5.25 (m, 1H, H2),
4.86 (q, J ) 7.5 Hz, 1H, H3), 4.15 (d, J ) 7.4 Hz, 1H, H1syn),
3.34 (d, J ) 13.0 Hz, 1H, H1anti), 1.42-1.85 (m, 4H, H4, H5,
overlapped with signals of other compounds), 0.88 (t, J ) 7.3
Hz, 3H, H6).
6: 19F NMR (CDCl3, δ, 282 MHz), -163.2 (m, Fmeta), -158.2
(t, Fpara), -144.7 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.78
(m, 1H, H2), 5.52 (m, 2H, H4, H5), 5.0 (m, 2H, H1), 3.39 (d, J )
5.0 Hz, 2H, H6), 2.74 (m, 2H, H3); MS (EI) m/z (relative
intensity) 248 (M+, 6), 233 (6), 181 (18), 69 (14), 67 (100), 65
(12), 41 (33).
7: 19F NMR (CDCl3, δ, 282 MHz), -163.8 (m, Fmeta), -158.2
(t, Fpara), -144.2 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 6.55
(dt, J ) 16.8, 6.6 Hz, 1H, H2), 6.28 (d, J ) 16.8 Hz, 1H, H1),
5.80 (m, 1H, H5), 5.0 (m, 2H, H6), 2.32-2.45 (m, 4H, H3, H4);
MS (EI) m/z (relative intensity) 248 (M+, 21), 233 (11), 207
(100), 187 (82), 181 (68), 138 (11), 67 (20), 41 (15).
Rea ction s w ith 1,6-Hep ta d ien e. [PdPfBr(NCMe)2] (0.200
g, 0.459 mmol) was mixed with 1,6-heptadiene (0.062 mL,
0.459 mmol) in CH2Cl2 (20 mL). After 10 h the dark yellow
solution was treated with activated carbon, the resulting
mixture filtered, and the filtrate evaporated to dryness. Yellow
10 was obtained by adding cyclohexane to the residue and
cooling (9% yield). The mother liquors were evaporated to
dryness, and the residue was separated into two batches by
column chromatography, using silica gel and eluting with
n-hexane first and then diethyl ether. The first batch con-
tained 13 and 14 as major components; the second one
included 10, 11, 12, and 16. Both batches were analyzed by
1H and 19F NMR with the help of 1H-1H COSY. 13C NMR
and 1H-13C COSY were also used to identify the organic
derivatives.
8: 19F NMR (CDCl3, 243 K, δ, 282 MHz), -162.6 (b, Fmeta),
-157.6 (b, Fpara), -142.8 (b, Fortho); 1H NMR (CDCl3, 243 K, δ,
300 MHz), 6.11 (b, 1H, H2), 5.08 (bd, J ) 8.4 Hz, 1H, H1), 4.42
(bd, J ) 15.0 Hz, 1H, H1′), 3.69 (b, 1H, H6), 3.06 (dd, J ) 13.4,
7.3 Hz, 1H, H7), 2.42 (b, 1H, H7′), 2.10 (b, 2H, H3), 1.72 (b, 2H,
H4), 1.20 (b, 1H, H5), 0.44 (bd, J ) 14.1 Hz, 1H, H5′).
9: 19F NMR (CDCl3, 243 K, δ, 282 MHz), -162.6 (b, Fmeta),
-157.6 (b, Fpara), -143.2 (b, Fortho).
10: Anal. Calcd for C26H24F10Br2Pd2: C, 34.71; H, 2.69.
Found: C, 34.76; H, 2.71. 19F NMR (CDCl3, δ, 282 MHz):
-163.3 (m, Fmeta), -158.4 (t, Fpara), -144.7 (m, Fortho). 1H NMR
(CDCl3, δ, 300 MHz): 5.27 (td, J ) 11.8, 6.8 Hz, 1H, H2), 3.96
(d, J ) 6.6 Hz, 1H, H1syn), 3.89 (m, J ) 11.8, 7.4, 4.4 Hz, 1H,
H3), 2.85 (d, J ) 11.8 Hz, 1H, H1anti), 2.70 (t, J ) 6.5 Hz, 2H,
H7), 1.90 (m, J ) 4.4 Hz, 1H, H4), 1.76 (m, J ) 7.4 Hz, 1H,
H4′), 1.48-1.70 (m, 4H, H5, H6).
11: 19F NMR (CDCl3, δ, 282 MHz), -162.9 (m, Fmeta), -153.9
(t, Fpara), -140.5 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.96
(t, J ) 11.3 Hz, 1H, H2), 4.33 (d, J ) 11.3 Hz, 1H, H1), 4.08
(m, J ) 11.3 Hz, 1H, H3), 1.3-1.9 (m, 6H, H4, H5, H6), 0.92 (t,
J ) 7.3 Hz, 3H, H7).
12: 19F NMR (CDCl3, δ, 282 MHz), -162.3 (m, Fmeta), -156.6
(t, Fpara), -143.4 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.29
(t, J ) 10.6 Hz, 1H, H3), 3.89 (m, J ) 10.6 Hz, 1H, H4), 3.65
(m, J ) 10.6, 7.0, 6.9 Hz, 1H, H2, ABX system), 3.31 (dd, J )
14.6, 6.9 Hz, 1H, H1, ABX system), 3.04 (dd, J ) 14.6, 7.0 Hz,
1H, H1′, ABX system), 1.45-1.95 (m, 4H, H5, H6), 0.93 (t, J )
7.3 Hz, 3H, H7).
13: 19F NMR (CDCl3, δ, 282 MHz), -163.4 (m, Fmeta), -158.4
(t, Fpara), -143.6 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.42
(b, 1H, H2), 2.94 (bd, J ) 13.7 Hz, 1H, PfCH H′), 2.68 (m, 1H,
H5), 2.50 (dd, J ) 13.7, 12.1 Hz, 1H, PfCHH′), 2.1-2.35 (m,
2H, H3)*, 1.86 (m, 1H, H4), 1.76 (m, 3H, Me)*, 1.54 (m, 1H,
H4′); 13C NMR (CDCl3, δ, 74.5 MHz), 126.1 (C2), 31.9 (C3), 29.7
(C4), 26.3 (PfCH2), 21.8 (C5), 14.7 (Me); MS (EI) m/z (relative
intensity) 262 (M+, 2), 181 (12), 81 (100), 79 (26), 77 (6), 53
(8), 41 (6); (*) overlapped with signals of other compounds.
14: 19F NMR (CDCl3, δ, 282 MHz), -163.4 (m, Fmeta), -158.7
(t, Fpara), -143.8 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 3.43
(b, 2H, PfCH2), 2.2-2.3 (m, 4H, H3, H5)*, 1.76 (m, 3H, Me)*,
1.73 (m, 2H, H4); 13C NMR (CDCl3, δ, 74.5 MHz), 38.4, 35.2
(C3, C5), 21.5 (PfCH2), 21.2 (C4), 13.8 (Me); MS (EI) m/z (relative
intensity) 262 (M+, 21), 247 (5), 181 (39), 81 (100), 79 (24), 53
(9), 41 (7); (*) overlapped with signals of other compounds.
15: 1H NMR (CDCl3, δ, 300 MHz), 5.27 (m, 1H, H2)*, 3.95
(d, J ) 6.4 Hz, 1H, H1syn), 3.90 (m, 1H, H3)*, 2.83 (d, J ) 11.4
Hz, 1H, H1anti), 1.45-1.95 (m, 6H, H4, H5, H6)*, 0.94 (t, J )
7.3 Hz, 3H, H7);3b (*) overlapped with signals of other com-
pounds.
The reaction was monitored by NMR at low temperature.
An NMR tube was charged with [PdPfBr(NCMe)2] (0.025 g,
0.0574 mmol) and CDCl3 (0.6 mL) and cooled to -30 °C. 1,6-
Heptadiene (0.008 mL, 0.0574 mmol) was added. After 1 h at
this temperature 8, 9, and 10 had formed in the ratio 40:5:1,
based on integration of 19F resonances. The temperature was
increased to -10 °C, and isomerization of 8 occurred. Finally,
the reaction mixture was warmed to room temperature. After
1
10 h, analysis of H and 19F NMR spectra indicated that the
final products were 10 (57%), 11 (3%), 12 (19%), 13 (9%), 14
(5%), and C6F5H (3%). The yields in parentheses are based
1
on the integration of H and 19F NMR signals.
The rate constant for the isomerization of 8 was measured
by recording 19F NMR spectra every 10 min at 263 K
(relaxation delays of at least 5T1s were used). A plot of
(25) (a) Spiridonov, V. P.; Lopatkin, A. A. Tratamiento Matema´tico
de Datos Fisico-Quı´micos; Mir: Madrid, 1983. (b) Graham, R. C. Data
Analysis for the Chemical Sciences; VCH: New York, 1993.

4144 Organometallics, Vol. 16, No. 19, 1997
Albe´niz et al.
16: 1H NMR (CDCl3, δ, 300 MHz), 5.17 (t, J ) 11.1 Hz, 1H,
H3), 3.77 (m, J ) 11.1 Hz, 2H, H2, H4), 1.45-1.95 (m, 4H, H5,
H6), 1.40 (d, J ) 6.4 Hz, 3H, H1), 0.89 (t, J ) 7.3 Hz, 3H, H7).
17: 19F NMR (CDCl3, δ, 282 MHz), -163.3 (m, Fmeta), -158.3
(t, Fpara), -144.8 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.8
(m, 1H, H2)*, 5.46-5.53 (m, 2H, H5, H6), 4.9-5.05 (m, 2H, H1)*,
3.38 (d, J ) 5.3 Hz, 2H, H7), 2.1 (m, 4H, H3, H4); MS (EI) m/z
(relative intensity) 262 (M+, 2), 181 (13), 81 (100), 79 (64), 67
(18), 54 (23), 53 (44), 51 (12), 41 (62); (*) overlapped with
signals of other compounds.
18: 19F NMR (CDCl3, δ, 282 MHz), -163.5 (m, Fmeta), -158.4
(t, Fpara), -144.5 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.8
(m, 1H, H2)*, 5.4-5.45 (m, 2H, H4, H5), 4.9-5.05 (m, 2H, H1)*,
2.76 (t, J ) 7.2 Hz, 2H, H7), 2.71 (m, J ) 5.0, 2.0 Hz, 2H, H3),
2.28 (td, J ) 7.2, 5.9 Hz, 2H, H6); MS (EI) m/z (relative
intensity) 262 (M+, 1), 221 (6), 181 (39), 151 (7), 81 (100), 79
(14), 53 (14), 51 (9), 41 (33); (*) overlapped with signals of other
compounds.
19: 19F NMR (CDCl3, δ, 282 MHz), -163.9 (m, Fmeta), -158.3
(t, Fpara), -144.3 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 6.54
(dt, J ) 16.2, 7.0 Hz, 1H, H2), 6.27 (d, J ) 16.2 Hz, 1H, H1),
5.8 (m, 1H, H6)*, 4.9-5.05 (m, 2H, H7)*, 2.33 (m, 2H, H3), 2.14
(m, 2H, H5), 1.68 (qi, J ) 7.4 Hz, 2H, H4); MS (EI) m/z (relative
intensity) 262 (M+, 4), 181 (23), 81 (63), 79 (66), 77 (17), 67
(59), 65 (24), 54 (50), 53 (44), 51 (22), 41 (100); (*) overlapped
with signals of other compounds.
Reaction s with 1,7-Octadien e. An NMR tube was charged
with [PdPfBr(NCMe)2] (0.025 g, 0.0574 mmol) and CDCl3 (0.5
mL) and then cooled to -40 °C. 1,7-Octadiene (0.0085 mL,
0.0574 mmol) was added, and the reaction was monitored by
19F NMR. The temperature was increased in 10 °C steps, and
the different isomerization processes were observed. The
spectra showed that the reaction was complete after 3 h at
293 K, and the final mixture was analyzed by 1H and 19F NMR
and found to contain 23 (39%), 24 (25%), 25 (17%), and 26
(8%), plus unknown organic (5%) and organometallic (6%)
compounds (each one less than 2%). The yields in parentheses
are based on the integration of 19F NMR signals.
H7)*, 0.88 (t, J ) 6.8 Hz, 3H, H8); (*) overlapped with signals
of other compounds.
25: 19F NMR (CDCl3, δ, 282 MHz), -162.9 (m, Fmeta), -157.5
(t, Fpara), -143.9 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.07
(t, J ) 11.0 Hz, 1H, H4), 3.8 (m, J ) 11.0 Hz, 1H, H5)*, 3.64
(m, J ) 11.0 Hz, 1H, H3)*, 2.98-2.83 (m, 2H, H1)*, 2.16 (m,
1H, H2), 1.90 (m, 1H, H2′)*, 1.78-1.28 (m, 4H, H6, H7)*, 0.91
(t, J ) 6.7 Hz, 3H, H8); (*) overlapped with signals of other
compounds.
26: 19F NMR (CDCl3, δ, 282 MHz), -163.5 (m, Fmeta), -158.8
(t, Fpara), -145.2 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.37
(bs, 1H, H2), 2.68 (t, J ) 7.3 Hz, 2H, PfCH2), 2.2-2.4 (m, 3H,
H3, H5), 2.14 (m, 1H, H4), 1.85 (m, 1H, PfCH2CH H′), 1.66 (m,
3H, Me), 1.60 (m, 1H, H4′), 1.38 (m, 1H, PfCH2CHH′); MS (EI)
m/z (relative intensity) 276 (M+, 2), 95 (23), 81 (100), 79 (22),
67 (10), 53 (10), 41 (9).
27: 1H NMR (CDCl3, δ, 300 MHz), 5.25 (m, 1H, H2)*, 3.93
(d, J ) 7.2 Hz, 1H, H1syn), 3.90 (m, 1H, H3)*, 2.83 (d, J ) 11.9
Hz, 1H, H1anti)*, 1.96-1.28 (m, 8H, H4, H5, H6, H7)*, 1.11 (t, J
) 7.5 Hz, 3H, H8);3b (*) overlapped with signals of other
compounds.
28: 1H NMR (CDCl3, δ, 300 MHz), 5.17 (t, J ) 10.5 Hz, 1H,
H3), 3.8 (m, J ) 10.5 Hz, 2H, H2, H4)*, 1.96-1.28 (m, 6H, H5,
H6, H7)*, 1.40 (d, J ) 6.0 Hz, 3H, H1), 0.88 (t, J ) 6.8 Hz, 3H,
H8)*;3b (*) overlapped with signals of other compounds.
29: 19F NMR (CDCl3, δ, 282 MHz), -163.2-163.7 (m, Fmeta),
-158.6 (t, Fpara), -144.8 (m, Fortho); 1H NMR (CDCl3, δ, 300
MHz), 5.78 (m, 1H, H2)*, 5.35-5.55 (m, 2H, H5, H6)*, 4.95 (m,
2H, H1)*, 2.75 (t, J ) 7.3 Hz, 2H, H8), 2.3 (m, 2H, H7)*, 1.95-
2.1 (m, 4H, H3, H4)*; MS (EI) m/z (relative intensity) 276 (M+,
0.2), 181 (100), 95 (91), 67 (40), 54 (12), 41 (33); (*) overlapped
with signals of other compounds.
30: 19F NMR (CDCl3, δ, 282 MHz), -163.2-163.7 (m, Fmeta),
-158.4 (t, Fpara), -144.4 (m, Fortho); 1H NMR (CDCl3, δ, 300
MHz), 5.78 (m, 1H, H2)*, 5.35-5.55 (m, J ) 5.4 Hz, 2H, H6,
H7)*, 4.95 (m, 2H, H1)*, 3.37 (d, J ) 5.4 Hz, 2H, H8), 1.95-2.1
(m, J ) 7.2 Hz, 4H, H3, H5)*, 1.44 (qi, J ) 7.2 Hz, 2H, H4); MS
(EI) m/z (relative intensity) 276 (M+, 2), 234 (19), 219 (20),
181 (83), 95 (100), 82 (22), 67 (47), 55 (93), 54 (44), 53 (21), 41
(37); (*) overlapped with signals of other compounds.
31: 19F NMR (CDCl3, δ, 282 MHz), -164.0 (m, Fmeta), -158.4
(t, Fpara), -144.3 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 6.54
(dt, J ) 15.9, 6.6 Hz, 1H, H2), 6.26 (d, J ) 15.9 Hz, 1H, H1),
5.78 (m, 1H, H7)*, 4.95 (m, 2H, H8)*, 2.3 (m, J ) 6.6 Hz, 2H,
H3)*, 1.95-2.1 (m, 2H, H6)*, 1.6 (m, 4H, H4, H5); MS (EI) m/z
276 (M+); (*) overlapped with signals of other compounds.
32: 19F NMR (CDCl3, δ, 282 MHz), -163.2-163.7 (m, Fmeta),
-158.7 (t, Fpara), -144.8 (m, Fortho); 1H NMR (CDCl3, δ, 300
MHz), 5.35-5.55 (m, 4H, H2, H3, H5, H6)*, 2.71 (t, J ) 7.3 Hz,
2H, H8), 2.7 (m, 2H, H4), 2.3 (m, 2H, H7)*, 1.66 (m, 3H, H1)*;
MS (EI) m/z 276 (M+); (*) overlapped with signals of other
compounds.
When the reaction was carried out with a larger amount of
starting materials, column chromatography (silica gel) could
be used to separate the organic compounds obtained, eluting
with n-hexane. Further verification and assignment of spectra
for the palladium complexes and 26 were accomplished by 1H-
1H COSY experiments and (for 26) GC-MS. Attempts at
isolation as solids of the organometallic compounds failed due
to their high solubility.
Excess 1,7-octadiene (0.085 mL, 0.575 mmol) was added to
[PdPfBr(NCMe)2] (0.050 g, 0.115 mmol) in CDCl3 (0.6 mL). The
reaction was complete after 2 h at room temperature as shown
by 19F NMR. A mixture containing 23 (15%), 24 (9%), 25 (7%),
27 (9%), 28 (25%), 26 (4%), 29 (9%), 30 (7%), 31 (2%), 32 (3%),
33 (4%), and unknown organics (4%) and organometallics (2%)
was obtained. The organic compounds could be separated by
column chromatography. Assignment of 1H NMR spectra was
33: 19F NMR (CDCl3, δ, 282 MHz), -163.2-163.7 (m, Fmeta),
-158.5 (t, Fpara), -144.4 (m, Fortho); 1H NMR (CDCl3, δ, 300
MHz), 5.35-5.55 (m, 4H, H2, H3, H6, H7)*, 3.43 (d, J ) 6.2 Hz,
2H, H1), 1.95-2.1 (m, 4H, H4, H5)*, 1.66 (m, 3H, H8)*; MS (EI)
m/z (relative intensity) 276 (M+, 7), 194 (10), 181 (94), 95 (91),
82 (30), 81 (24), 67 (56), 55 (100), 54 (44), 53 (23), 41 (38); (*)
overlapped with signals of other compounds.
1
accomplished by using H-1H COSY.
20: 19F NMR (CDCl3, δ, 243 K, 282 MHz), -161.6 (m, Fmeta),
-156.7 (t, Fpara), -142.8 (m, Fortho).
21: 19F NMR (CDCl3, δ, 243 K, 282 MHz), -162.6 (m, Fmeta),
-157.8 (t, Fpara), -144.5 (m, Fortho).
22: 19F NMR (CDCl3, δ, 263 K, 282 MHz), -163.1 (m, Fmeta),
-158.4 (t, Fpara), -144.4 (m, Fortho).
23: 19F NMR (CDCl3, δ, 282 MHz), -163.4 (m, Fmeta), -158.6
(t, Fpara), -144.8 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.25
(m, 1H, H2), 3.94 (d, J ) 6.6 Hz, 1H, H1syn), 3.90 (m, 1H, H3),
2.83 (d, J ) 11.9 Hz, 1H, H1anti)*, 2.68 (t, J ) 7.5 Hz, 2H, H8),
1.96-1.50 (m, 8H, H4, H5, H6, H7)*; (*) overlapped with signals
of other compounds.
24: 19F NMR (CDCl3, δ, 282 MHz), -162.3 (m, Fmeta), -156.7
(t, Fpara), -143.4 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz), 5.27
(t, J ) 11.3 Hz, 1H, H3), 3.8 (m, J ) 11.3 Hz, 1H, H4)*, 3.64
(m, J ) 11.3 Hz, 1H, H2)*, 3.30 (dd, J ) 14.4, 4.4 Hz, 1H, H1),
3.03 (dd, J ) 14.4, 9.7 Hz, 1H, H1′), 1.96-1.28 (m, 6H, H5, H6,
Ack n ow led gm en t. This work was supported by the
Direccio´n General de Investigacio´n Cient´ıfica y Te´cnica
(Spain) (Project PB96-0363), the Commission of the
European Communities (Network “Selective Processes
and Catalysis Involving Small Molecules”, CHRX-CT93-
0147), and the J unta de Castilla y Leo´n (Project VA 40-
96). Y.-S.L. thanks the Spanish Ministerio de Educacio´n
y Ciencia and the AECI/ICDsUniversidad de Valladolid
for fellowships.
OM9703907