Fluorine-containing allenylpalladium complexes. Synthesis of optically active fluoroalkylated allenes and furan derivatives

Article abstract of DOI:10.1135/cccc20021421

The reaction of fluoroalkylated propargyl mesylates with various nucleophiles, such as zinc reagents and enolates derived from 1,3-dicarbonyl compounds, in the presence of a palladium catalyst was investigated in detail. Various zinc reagents participated

Full text of DOI:10.1135/cccc20021421

Fluorine-Containing Allenylpalladium Complexes
1421
FLUORINE-CONTAINING ALLENYLPALLADIUM COMPLEXES.
SYNTHESIS OF OPTICALLY ACTIVE FLUOROALKYLATED ALLENES
AND FURAN DERIVATIVES
1,
2
Tsutomu KONNO *, Mitsuru TANIKAWA, Takashi ISHIHARA and
3
Hiroki YAMANAKA
Department of Chemistry and Materials Technology, Kyoto Institute of Technology,
1
Sakyo-ku, Matsugasaki, Kyoto 606-8585, Japan; e-mail: konno@chem.kit.ac.jp,
2
3
ishihara@ipc.kit.ac.jp, yamanaka@ipc.kit.ac.jp
Received April 4, 2002
Accepted Septem ber 11, 2002
Dedicated to the memory of Professor Miloš Hudlický.
Th e reaction of fluoroalkylated propargyl m esylates with various n ucleoph iles, such as zin c
reagen ts an d en olates derived from 1,3-dicarbon yl com poun ds, in th e presen ce of a palla-
dium catalyst was in vestigated in detail. Various zin c reagen ts participated in th e couplin g
reaction to give th e correspon din g fluoroalkylated allen es in good yields. Wh en ch iral
m esylates were em ployed, th e correspon din g optically active allen es were obtain ed with out
an y loss of en an tiom eric purity in th e reaction . On th e oth er h an d, treatm en t of trifluoro-
m eth ylated propargyl m esylate with stabilized carban ion s derived from m eth yl acetoacetate,
acetylaceton e, an d dieth yl m alon ate afforded fluorin e-con tain in g furan derivatives in m od-
erate to h igh yields.
Keyw ord s: Fluorin e-con tain in g allen ylpalladium com plexes; Allen es; Alkyn es; Propargyl
esters; Furan es; Fluorin ated com poun ds; Palladium catalysis; En an tioselective syn th esis;
Cross-couplin g reaction s.
Tran sition m etals are able to catalyze a wide ran ge of syn th etically useful
organ ic reaction s, very often with h igh levels of ch em o- an d stereo-
selectivity1. In particular, palladium -catalyzed reaction s h ave been em -
ployed with success in a n um ber of im portan t ch em ical processes, such as
Stille couplin g2, Suzuki couplin g3, Negish i couplin g4, Heck reaction s5, an d
allylic substitution 6.
Palladium -catalyzed reaction s of propargylic com poun ds h ave also been
in vestigated in con siderable detail over th e last twen ty years, an d are con -
sidered as som e of th e m ost valuable syn th etic reaction s7. In sh arp con trast
to th ese in vestigation s, palladium -catalyzed tran sform ation s of fluorin e-
Collect. Czech. Chem. Commun. (Vol. 67) (2002)
doi:10.1135/cccc20021421

1422
Konno et al.:
con tain in g propargylic com poun ds h ave n ever been reported th us far, de-
spite th eir poten tially h igh syn th etic value. Herein , we wish to describe th e
first exam ples of th e palladium -catalyzed reaction s of fluoroalkylated
propargylic m esylates with various n ucleoph iles leadin g to optically active
fluorin e-con tain in g allen es as well as furan derivatives.
RESULTS AND DISCUSSION
The Reaction of Fluoroalkylated Mesylates 1 with Various Zinc Reagents
in the Presence of Pd(0) Catalyst
Th e fluoroalkylated m esylates 1, used as th e startin g m aterials in th is study,
were readily prepared from eth yl polyfluoroalkan oate an d lith ium acetyl-
ides in th ree steps (Sch em e 1).
1) R1C≡CLi
OMs
2)
NaBH4
RfCO2Et
Rf
3)
MsCl, Et3N
R1
1
R1 = n-C6H13
1a: R =
CF3
CF3
CF3
CF3
CF3
f
R1 = CH2OTBS
R1 = CH2OBn
R1 = t-Bu
1b: R =
f
1c: R =
f
1d: R =
f
R1 = TMS
1e: R =
f
R1 = n-C6H13
R1 = n-C6H13
1f: R =
CF2H
CF3CF2
f
1g: R =
f
SCHEME 1
In itially, ester 1a was treated with 5 m ole % of [Pd(PPh 3)4] at room tem -
perature for 10 m in , followed by th e addition of 2 equivalen ts of Ph MgBr
an d stirrin g at th at tem perature for 24 h , but m an y un iden tified products
were produced an d th e startin g ester was recovered in 37% yield (Table I;
en try 1). Even th e use of 3 equivalen ts of Ph MgBr provided on ly a trace
am oun t of product 2a (7%), alon g with a lower recovery of th e startin g es-
ter (8%) (en try 2). On th e oth er h an d, organ ozin c reagen ts were foun d to
participate m ore efficien tly in th e reaction th an th e Grign ard reagen ts did.
Two equivalen ts of a zin c reagen t, prepared from Ph MgBr an d Zn Cl2, were
allowed to react with 1a un der th e in fluen ce of th e Pd(0) catalyst to pro-
duce 2a in 47% yield, even th ough a part of th e startin g ester 1a (17%) re-
m ain ed un ch an ged (en try 3). Th ree equivalen ts of th e zin c reagen t were
sufficien t for th e com pletion of th e reaction , in wh ich 2a was obtain ed
in 63% yield (en try 4). Zn Cl2·TMEDA com plex was th en em ployed in place
of Zn Cl2 for th e preparation of th e organ ozin c reagen t, in view of its very
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

Fluorine-Containing Allenylpalladium Complexes
1423
easy h an dlin g due to a low m oisture-sen sitivity. On treatin g 1a with
Ph Zn Cl prepared from Ph MgBr an d Zn Cl2·TMEDA com plex in th e presen ce
of th e Pd(0) catalyst, th e reaction proceeded sm ooth ly to afford 2a in good
yields (en tries 5–8). Even tually, th e use of 2 equivalen ts of th e zin c reagen t
led to th e best result (77% yield), as sh own in en try 7. Sim ilarly, th e reac-
tion s of propargyl esters 1 h avin g various fluoroalkyl groups with a variety
of organ ozin c reagen ts were carried out an d th e results are sum m arized in
Table II.
In th e case of arylzin c reagen ts (en tries 1–4), th e desired allen es 2a–2d
were obtain ed in excellen t yields. With (E)-styrylzin c ch loride, h owever,
th e yield of 2e decreased due to th e in stability of th e product (en try 5). Th e
reaction of a 1-alkyn ylzin c reagen t, prepared from th e correspon din g lith -
ium acetylide an d Zn Cl2·TMEDA, gave th e desired allen e in less th an 10%
yield. Even th e use of 3 equivalen ts of th e zin c reagen t did n ot lead to a sig-
n ifican t im provem en t. However, 3 equivalen ts of th e zin c reagen t prepared
TABLE I
In vestigation of th e reaction con dition s
OMs
F3C
H
5 mole % [Pd(PPh3)4]
R1
Ph
F3C
R1
PhMX, THF
R1 = n-C6H13
1a
2a
Recovery of 1a,
En trya Ph MX (equivalen ts)
Tim e, h
Yield of 2a, %b
c
%
1
Ph MgBr (2.0)
24
24
24
24
6
0
7
37
8
2
Ph MgBr (3.0)
3
Ph MgBr/Zn Cl2 (2.0)
47
63
67
70
77
76
17
0
4
Ph MgBr/Zn Cl2 (3.0)
5
Ph MgBr/Zn Cl2·TMEDA (1.5)
Ph MgBr/Zn Cl2·TMEDA (1.5)
Ph MgBr/Zn Cl2·TMEDA (2.0)
Ph MgBr/Zn Cl2·TMEDA (3.0)
0
6d
7d
8d
6
0
2
0
1
0
a
b
All reaction s were carried out at room tem perature, un less oth erwise n oted.
Isolated
yields. Determ in ed by 19F NMR. Zin c reagen t was added to th e reaction m ixture at 0 °C,
c
d
an d th e resultan t m ixture was stirred at room tem perature.
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

1424
Konno et al.:
from lith ium acetylide an d an h ydrous Zn Cl2 allowed a sm ooth reaction of
1a, givin g th e desired allen e 2f in 78% yield, wh en th e reaction tim e was
prolon ged to 24 h (en try 6). As sh own in en tries 1, 7, an d 8, propargyl
m esylates 1 carryin g a lin ear side ch ain R1 participated readily in th e reac-
tion , wh ile th ose h avin g a bulky side ch ain such as a t-Bu or TMS group did
n ot (en tries 9 an d 10).
Very in terestin gly, it was foun d th at th e pen tafluoroeth yl m esylate 1g
un derwen t th e reaction as effectively as th e trifluorom eth yl m esylate 1a
(en tries 13 an d 14), wh ile th e difluorom eth yl m esylate 1f did n ot react at
all; n o trace of th e desired product could be observed an d th e startin g m ate-
rial was recovered alm ost quan titatively (en tries 11 an d 12).
TABLE II
Palladium -catalyzed reaction of various types of m esylates 1 with organ ozin c reagen ts
OMs
Rf
R1
R
5 mole % Pd(PPh3)4
Rf
RZnCl, THF, 0 oC-r.t., 2 h
R1
H
1
2
En try
Rf
R1
RZn Cl
Product
Yield of 2, %a
1
2
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF2H
CF2H
n -C6H13
n -C6H13
n -C6H13
n -C6H13
n -C6H13
n -C6H13
CH2OTBS
CH2OBn
t-Bu
Ph Zn Cl
2a
2b
2c
2d
2e
2f
2g
2h
–
83 (77)
4-MeC6H4Zn Cl
4-MeOC6H4Zn Cl
1-C10H7Zn Cl
Ph CH=CHZn Cl
n -C6H13C≡CZn Cl
Ph Zn Cl
89 (81)
3
86
80
4
5b
6c
7
50 (50)
78
(86)
73
8
Ph Zn Cl
9
Ph Zn Cl
tr
10
11
12
13
14
TMS
Ph Zn Cl
–
tr
n -C6H13
n -C6H13
n -C6H13
n -C6H13
Ph Zn Cl
–
0
4-MeC6H4Zn Cl
Ph Zn Cl
–
0
CF3CF2
CF3CF2
2i
2j
(70)
(79)
4-MeC6H4Zn Cl
a
c
b
Determ in ed by 19F NMR. Isolated yields are sh own in paren th eses. Carried out for 4 h .
Th e reaction was perform ed at room tem perature for 24 h by usin g 3 equivalen ts of a zin c
reagen t wh ich was prepared from th e correspon din g lith ium acetylide an d an h ydrous Zn Cl2.
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

Fluorine-Containing Allenylpalladium Complexes
1425
Synthesis of Optically Active Fluorine-Containing Allenes
Our atten tion was th en directed to th e preparation of optically active
fluorin e-con tain in g allen es, as described in Sch em e 2.
5 mole% [Pd(PPh3)4]
OMs
Rf
n-C6H13
Ph
PhZnCl
THF, 0 oC-r.t., 2 h
Rf
H
n-C6H13
(S)-1a :
(S)-2a :
Rf = CF3 (96% ee)
Rf = CF3 (77%; 96% ee)
(S)-1g :
(S)-2i :
Rf = CF3CF2 (94% ee)
Rf = CF3CF2 (70%; 96% ee)
SCHEME 2
Th e startin g optically active m esylate esters (S)-1a an d (S)-1g were easily
prepared accordin g to a literature m eth od8. Th eir en an tiom eric purities
were determ in ed to be 96 an d 94% ee, respectively, by gas ch rom atograph y
after th e con version to MTPA esters9. Wh en th ese n on racem ic m esylates
(S)-1a an d (S)-1g were allowed to react with Ph Zn Cl in th e presen ce of
5 m ole % of [Pd(PPh 3)4], th e correspon din g allen es (S)-2a an d (S)-2i were
obtain ed in 77 an d 70% yields, respectively, with h igh en an tiom eric excess
(96% ee), as determ in ed by HPLC usin g a ch iral colum n (DAICEL,
CHIRAL-CEL OD)10. It is of great syn th etic value th at n o loss of en an tio-
m eric purity was observed. Th is in dicates th at th e reaction proceeds in a
h igh ly stereoselective m an n er.
The Reaction of Fluorine-Containing Mesylates with Various Carbanions
Derived from Dicarbonyl Compounds in the Presence of Pd(0) Catalyst
Next we exam in ed th e reaction of 1a with various stabilized carban ion s de-
rived from 1,3-dicarbon yl com poun ds, as sh own in Table III.
Ester 1a was treated with sodium en olate derived from m eth yl aceto-
acetate in th e presen ce of 5 m ole % of [Pd(PPh 3)4] (en try 1). After stirrin g
th e reaction m ixture for 24 h , dih ydrofuran 3a was obtain ed in 80% yield
as a sole product. In th is case, n o isom erization product, like 4 or 5, was de-
tected. Wh en 1,2-bis(diph en ylph osph in o)eth an e (dppe) was used as a
ligan d on Pd(0), th e startin g m aterial was com pletely con sum ed in on ly
3 h , an d 3a was obtain ed in 84% isolated yield (en try 2). Sim ilarly, th ese re-
action con dition s were also used for th e reaction of 1a with th e sodium
en olate of acetylaceton e (en tries 3 an d 4). 19F NMR an alysis of th e reaction
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

1426
Konno et al.:
m ixture in dicated th at th e correspon din g com poun d 3 was produced in
good yield as a sin gle isom er, but subsequen t purification by silica gel
colum n ch rom atograph y caused easy isom erization to afford 4a in 61%
isolated yield. Wh en th e reaction m ixture was h eated at reflux for 2 h , th e
yield of 4a was im proved (71%). As listed in en tries 5 an d 6, dppe was n ot a
suitable ligan d for th e reaction with dieth yl m alon ate. Th e em ploym en t of
PPh 3 as a ligan d led to a m ore satisfactory result (43% yield), as sh own in
en try 7.
Mechanism for the Formation of Allenes
To clarify th e m ech an ism , th e reaction of m esylate 1a with Ph Zn Cl in th e
presen ce of an equim olar am oun t of [Pd(PPh 3)4] was m on itored by 19F NMR
(Fig. 1). Th us, 1a was added to a solution of an equim olar am oun t of
[Pd(PPh 3)4] in THF at 0 °C, an d th e m ixture was stirred at th is tem perature
for 10 m in . 19F NMR an alysis of th e reaction m ixture in dicated th at th e
startin g ester (19F NMR δ 86.5 (d), referred C6F6) was com pletely con sum ed
TABLE III
Syn th esis of furan derivatives
O
O
(1.2 eq.)
R2
R3
R2CO
R3
CF3
R2CO
R3
CF3
R1
OMs
H+
5 mole % Pd(0), NaH (1.2 eq)
F3C
isomerization
R1
R1
Temp., Time, THF
R1 = n-C6H13
O
O
1a
3
4 or 5
Yield of
Yield of
Recovery
En try Pd(0)
R2
R3
Tem p.
Tim e
3
4 or 5
of 1a
b
b
b
%
%
%
1
2
3
4
5
6
7
Pd(PPh 3)4
OMe Me
r.t.
24
3
80 (3a)
0
0
0
0.5[Pd2(dba)3]/2dppe OMe Me
r.t
84 (3a)
0
c
0.5[Pd2(dba)3]/2dppe Me
0.5[Pd2(dba)3]/2dppe Me
Me
Me
r.t
24
2
61a (4a)
71a (4a)
8 (5a)
25 (5a)
43 (5a)
27
0
c
c
c
c
reflux
0.5[Pd2(dba)3]/2dppe OEt OEt r.t.
0.5[Pd2(dba)3]/2dppe OEt OEt reflux
24
6
27
0
[Pd(PPh 3)4]
OEt OEt r.t.
24
0
a
b
c
Isolated yields. Determ in ed by 19F NMR, un less oth erwise n oted. Not determ in ed.
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

Fluorine-Containing Allenylpalladium Complexes
1427
an d in term ediate 6a was produced (19F NMR δ 105 (d), Fig. 1b). Ph Zn Cl
(2 equivalen ts) was added to th e reaction m ixture at 0 °C, an d th e resultan t
solution was allowed to warm to room tem perature. After stirrin g th e reac-
tion m ixture for 3 h , th e above peak in 19F NMR disappeared com pletely
an d th e fluorin ated allen e 2a was form ed (19F NMR δ 103 (d), Fig. 1c). Th e
ch em ical sh ift of 6a is apparen tly very close to th at of th e allen e an d very
differen t from th at of th e startin g ester 1a. Th is observation stron gly sug-
gests th at th e reaction proceeds via an allen ylpalladium in term ediate.
Alth ough th e absolute con figuration s of th e above-obtain ed ch iral allen es
were n ot establish ed con clusively, th e origin of th e anti-substitution prod-
ucts (S)-2a an d (S)-2i is con ceivable by assum in g th e reaction sequen ce de-
picted in Sch em e 3 11. Th us, th e oxidative in sertion of th e Pd(0) catalyst
in to m esylate 1 gives rise to th e allen ylpalladium in term ediate 6 (in ver-
sion ), wh ich is in turn tran sform ed in to 7 (reten tion ) via n ucleoph ilic dis-
placem en t of th e m esylate ligan d by th e organ ozin c reagen t. Th e resultin g
in term ediate 7 un dergoes reductive elim in ation to produce th e allen ic com -
poun d 2 (reten tion ), alon g with th e regen eration of th e Pd(0) species. For
th e n on fluorin ated series, it is proposed th at depen din g on th e startin g
propargyl ester used, an in term ediate allen ylpalladium com plex 6, is in
equilibrium with a propargyl palladium in term ediate 8 12. Th e latter in ter-
m ediate m ay be displaced directly by a n ucleoph ile to afford th e syn-substi-
tution product, wh ich results in a decrease of th e stereoselectivity of th e
reaction , i.e., en an tiom eric purity of th e product. Th e extrem ely h igh
OMs
F3C
a
n-C6H13
1a
F3C
H
n-C6H13
Pd-OMs
b
c
6a
F3C
H
n-C6H13
Ph
2a
105
100
95
90
85
ppm
FIG. 1
19F NMR m on itorin g
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

1428
Konno et al.:
stereoselectivity observed in th is study en ables us to con clude th at n o
isom erization of 6 to 8 occurs in th e reaction of 1a an d 1g. Th e difficulty in
th is isom erization can be ascribed prim arily to a large steric bulk of th e
perfluoroalkyl group13. It is also possible th at th e allen ylpalladium com plex
6f gen erated in itially from th e difluorom eth yl ester 1f isom erizes m ore
readily to th e propargylpalladium in term ediate 8f th an com plexes 1a an d
1g, because th e CF2H group is n ot so bulky as th e CF3 an d C2F5 groups. Th e
resultin g propargylpalladium in term ediate 8f seem s to be stabilized by th e
electron egative CF2H group14 so th at th e catalytic cycle is en tirely proh ib-
ited leavin g th e startin g ester 1f in tact.
R1
Rf
MsO
Rf
R1
Pd(0)
R
H
2
1
anti substitution
product
R1
Rf
R1
Pd
Rf
Pd OMs
R
H
H
6
7
MsO Pd
Rf
a
f
g
: Rf = CF3
: Rf = CF2H
: Rf = CF3CF2
R1
8
RZnCl
MsOZnCl
syn substitution
product
SCHEME 3
Th e m ech an ism for th e form ation of furan s 4 or 5 is as follows
(Sch em e 4)15. Th e stabilized carban ion can attack th e sp-h ybridized carbon
of allen ylpalladium in term ediate 6a (vide supra) to furn ish in term ediate 9a.
In tram olecular proton abstraction th en results in th e form ation of both
en olate an d σ-allylpalladium parts, leadin g to in term ediates 10a an d 11a.
In th e in term ediate 11a, th e Pd m oiety m igh t be closer to th e CF3 group
th an to R1 due to th e electron -with drawin g effect of CF3. Th erefore, oxygen
attacks preferen tially th e less h in dered γ-carbon of 11a to give furan deriva-
tives followin g th e reductive elim in ation of Pd. In th e case of acetylaceton e
an d dieth yl m alon ate, treatm en t of 3 with aqueous HCl caused isom er-
ization to give furan derivatives 4 an d 5.
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

Fluorine-Containing Allenylpalladium Complexes
1429
R2CO
R3
CF3
R1
O
4 or 5
isomerization
CF3
R2CO
R3
MsO
F3C
R1
Pd(0)
R1
O
1a
3
OMs
R1
Pd OMs
6a
F3C
H
Pd
g
α
F3C
R2
R1
O
β
O
O
O
R3
R2
R3
π-allylpalladium complex (11a)
OMs
Pd
OMs
Pd
R1
R3
F3C
R2
R1
O
F3C
R2
H
O
R3
σ-allylpalladium complex (10a)
O
O
9a
SCHEME 4
Conclusion
In sum m ary, we h ave developed th e palladium (0)-catalyzed couplin g reac-
tion of fluoroalkyl propargyl m esylates 1 with organ ozin c reagen ts an d sta-
bilized carban ion s derived from 1,3-dicarbon yl com poun ds, leadin g to th e
fluorin ated allen ic com poun ds 2 an d furan derivatives 3a, 4a, an d 5a in
h igh yields. More sign ifican tly, it h as also been dem on strated th at utiliza-
tion of ch iral startin g m esylates 1 leads to th e form ation of ch iral fluori-
n ated allen es with an excellen t level of stereoselectivity.
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

1430
Konno et al.:
EXPERIMENTAL
Gen eral Meth ods
In frared spectra (waven um bers in cm –1) were taken on a Sh im adzu FTIR-8200(PC) spectrom -
eter as film on a NaCl plate. 1H NMR spectra were m easured on a Gen eral Electric QE-300
an d/or Bruker DRX-500 NMR spectrom eter in a CDCl3 solution with tetram eth ylsilan e as an
in tern al referen ce. 13C NMR spectra were recorded on a Bruker DRX-500 (125.75 MHz) NMR
spectrom eter in a CDCl3 solution with Me4Si as an in tern al stan dard. A JEOL JNM-EX90A
(84.21 MHz) FT-NMR spectrom eter was used for recordin g 19F NMR spectra in a CDCl3 solu-
tion with th e in tern al stan dard of trich lorofluorom eth an e. Ch em ical sh ifts (δ) are given in
ppm , couplin g con stan ts (J) in Hz. High -resolution m ass spectra (HRMS) were taken on a
Hitach i M-80B m ass spectrom eter by electron im pact (EI) or ch em ical ion ization (CI)
m eth od. Elem en tal an alyses were perform ed on a Yan aco CHN recorder MT-5 in strum en t.
Gas-liquid ch rom atograph y (GLC) was perform ed on a Sh im adzu GC-7AG ch rom atograph
equipped with a flam e ion ization detector, usin g n itrogen as th e carrier gas an d a Sh im adzu
capillary colum n HiCap CBP-5-M25-025 (25 m × 0.2 m m ). Th in -layer ch rom atograph y was
perform ed on alum in ium sh eets coated with silica gel (Merck 60 F254), an d colum n ch rom a-
tograph y was carried out usin g silica gel (Wacogel C-200) as an adsorben t. Optical rotation s
were taken on a HORIBA SEPA-200 in strum en t; [α]D values are given in 10–1 deg cm 2 g–1
.
Tetrah ydrofuran (THF) an d dieth yl eth er were fresh ly distilled from sodium /ben zoph e-
n on e ketyl un der argon . Oth er solven ts were dried by con ven tion al m eth ods before use.
Butyllith ium (1.6 M h exan e solution ) was com m ercially available from Kan to Ch em ical Co.
Am in es were distilled over calcium h ydride an d stored un der argon . All ch em icals were of
reagen t grade an d, if n ecessary, th ey were purified in a usual m an n er prior to use.
Typical Procedure for th e Preparation of Fluorin e-Con tain in g Propargyl Mesylates
BuLi (1.6 M h exan e solution , 7.5 m l, 12 m m ol) was added to a solution of oct-1-yn e (1.5 m l,
10 m m ol) in THF (20 m l) at –78 °C, an d th e reaction m ixture was stirred at th at tem perature
for 0.5 h . A solution of eth yl trifluoroacetate (1.8 m l, 15 m m ol) in THF (10 m l) was added to
th is m ixture at –78 °C. After stirrin g th e reaction m ixture for 1 h , sodium boroh ydride
(0.253 g, 0.75 m m ol) was added to th e reaction m ixture, an d th e m ixture was warm ed to
room tem perature after stirrin g for 0.5 h . After stirrin g th e solution for 24 h , th e reaction
was quen ch ed with saturated aqueous am m on ium ch loride, th en extracted with eth yl ace-
tate, wash ed with brin e, dried over an h ydrous sodium sulfate, an d con cen trated in vacuo.
Th e residue was purified by silica gel colum n ch rom atograph y to give th e correspon din g
propargyl alcoh ol (1.47 g, 7.1 m m ol).
Meth an esulfon yl ch loride (0.66 m l, 8.5 m m ol) an d trieth ylam in e (1.18 m l, 8.5 m m ol)
were added to a solution of th is propargyl alcoh ol (1.47 g, 7.1 m m ol) in CH2Cl2 (35 m l) at
–50 °C, an d th e m ixture was stirred for 1 h . Th e reaction was quen ch ed with saturated aque-
ous sodium h ydrogen carbon ate. Th e m ixture was warm ed to room tem perature an d ex-
tracted with CH2Cl2 (3 ×). Th e com bin ed organ ic layers were wash ed with brin e, dried over
an h ydrous Na2SO4, an d con cen trated in vacuo. Th e crude m aterial was purified by silica gel
colum n ch rom atograph y to give th e desired propargyl m esylate.
1,1,1-Trifluorodec-3-yn-2-yl methanesulfonate (1a). 1H NMR (CDCl3): 5.45–5.49 m , 1 H
(H-2′); 3.17 s, 3 H (CH3SO3); 2.30 td, 2 H, J(5′,6′ an d 2′,5′) = 7.3, 2.0 (H-4′); 1.56 tt, 2 H,
J(6′,5′ an d 6′,7′) = 7.3, 7.3 (H-6′), 1.26–1.42 m , 6 H (H-7′, 8′, 9′); 0.89 t, 3 H, J(9′,10′) = 6.5
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Fluorine-Containing Allenylpalladium Complexes
1431
(H-10′). 13C NMR (CDCl3): 120.95 q, J = 280.8 (CF3); 93.44; 67.99 d, J = 2.1 (CF3CHC);
67.64 q, J = 38.8 (CF3CH); 39.52; 31.11; 28.33; 27.66; 22.43; 18.62; 13.93. 19F NMR (CDCl3):
–77.54 d, 3 F, J = 6.6 (CF3). IR (n eat): 2 936, 2 862, 2 245, 1 466, 1 377. For C11H17F3O3S
(286.3) calculated: 46.14% C, 5.98% H; foun d: 45.75% C, 5.77% H.
(2S)-1,1,1-Trifluorodec-3-yn-2-yl methanesulfonate (1a). [α ]2D1 +71.5 (c 0.815, CHCl3, 96% ee).
All oth er data were iden tical with th ose of racem ic 1a.
1-tert-Butyldimethylsilyloxy-5,5,5-trifluoropent-2-yn-4-yl methanesulfonate (1b ). 1H NMR
(CDCl3): 5.52 q, 1 H, J(4′,F) = 5.0 (H-4′); 4.40 s, 2 H (H-1′); 3.18 s, 3 H (CH3SO3); 0.90 s, 9 H
(t-Bu); 0.11 s, 6 H (t-Bu(CH3)2Si). 13C NMR (CDCl3): 120.81 q, J = 281.0 (CF3); 90.51; 72.19;
67.13 q, J = 38.8 (CF3CH); 51.32; 39.55; 25.60; 18.14; 5.37. 19F NMR (CDCl3): –77.07 d, 3 F,
J = 6.6 (CF3). IR (n eat): 2 955, 2 936, 2 862, 2 361, 2 241, 1 474, 1 377, 1 273.
1-Benzyloxy-5,5,5-trifluoropent-2-yn-4-yl methanesulfonate (1c). 1H NMR (CDCl3): 7.30–7.38 m ,
5 H (Ph ); 5.56 tq, 1 H, J(1′,4′ an d 4′,F) = 5.5, 1.5 (H-4′); 4.59 s, 2 H (Ph CH2O); 4.25 d, 2 H,
J(1′,4′) = 1.5 (H-1′); 3.16 s, 3 H (CH3SO3). 13C NMR (CDCl3): 136.59; 128.54; 128.16; 128.14;
120.80 q, J = 281.1 (CF3); 74.02 d, J = 2.0 (CF3CHC); 72.02; 66.86 q, J = 38.8 (CF3CH); 56.70;
39.47. 19F NMR (CDCl3): –77.20 d, 3 F, J = 4.4 (CF3). IR (n eat): 3 032, 2 943, 2 866, 2 237,
1 377, 1 273. For C13H13F3O4S (322.3) calculated: 48.45% C, 4.07% H; foun d: 48.18% C,
4.02% H.
1,1,1-Trifluoro-5,5-dimethylhex-3-yn-2-yl methanesulfonate (1d ). 1H NMR (CDCl3): 6.17 d,
1 H, J(4′,5′) = 15.50 (H-4′); 5.45 dd, 1 H, J(2′,3′ an d 3′,4′) = 8.00, 15.50 (H-3′); 5.24 dq, 1 H,
J(2′,3′ an d 2′,F) = 8.00, 6.00 (H-2′); 3.07 s, 3 H (CH3SO3); 1.07 s, 9 H (t-Bu). 13C NMR
(CDCl3): 154.28; 122.35 q, J = 280.73 (CF3); 113.31; 78.21 q, J = 34.19 (CF3CH); 39.55;
33.70; 28.72.
1,1,1-Trifluoro-4-trimethylsilyl-but-3-yn-2-yl methanesulfonate (1e). 1H NMR (CDCl3): 5.47 q,
1 H, J(2′,F) = 5.0 (H-2′); 3.20 s, 3 H (CH3SO3); 0.24 s, 9 H (TMS). 13C NMR (CDCl3):
116.21 q, J = 281.1 (CF3); 98.63; 91.21; 67.41 q, J = 38.8 (CF3CH); 39.58; –0.84. 19F NMR
(CDCl3): –77.05 d, 3 F, J = 4.4 (CF3). IR (n eat): 3 036, 2 963, 1 736, 1 371.
1,1-Difluorodec-3-yn-2-yl methanesulfonate (1f). 1H NMR (CDCl3): 5.83 td, 1 H, J(1′,F an d
1′,2′) = 55.0, 2.0 (H-1′); 5.26–5.31 m , 1 H (H-2′); 3.15 s, 3 H (CH3SO3); 2.29 td, 2 H, J(5′,6′
an d 2′,5′) = 7.0, 2.0 (H-5′); 1.55 tt, 2 H, J(5′,6′ an d 6′,7′) = 7.5, 7.5 (H-6′); 1.24–1.41 m , 6 H
(H-7′, 8′, 9′); 0.89 t, J(9′,10′) = 6.5, 3 H (H-10′). 13C NMR (CDCl3): 111.56 t, J = 248.5 (CF2H);
93.34; 69.28; 69.22 t, J = 29.6 (CF2HCH); 39.34; 31.10; 28.34; 27.79; 22.40; 18.62; 13.90.
19F NMR (CDCl3): –128.43 ddd, 1 F, J = 286.2, 55.1, 8.8 (CF2H); –125.67 ddd, 1 F, J = 286.2,
55.1, 8.8 (CF2H). IR (n eat): 2 936, 2 862, 2 241, 1 466, 1 373. For C11H18F2O3S (268.3) calcu-
lated: 49.24% C, 6.76% H; foun d: 49.09% C, 6.62% H.
1,1,1,2,2-Pentafluoroundec-4-yn-3-yl methanesulfonate (1g). 1H NMR (CDCl3): 5.58 t, 1 H,
J(3′,F) = 9.0 (H-3′); 3.17 s, 3 H (CH3SO3); 2.31 td, 2 H, J(3′,6′ an d 6′,7′) = 7.0, 2.0 (H-6′);
1.55 tt, 2 H, J(6′,7′ an d 7′,8′) = 7.5, 7.5 (H-7′); 1.27–1.42 m , 6 H (H-8′, 9′, 10′); 0.89 t, 3 H,
J(10′,11′) = 7.0 (H-11′). 13C NMR (CDCl3): 118.17 qt, J = 287.1, 34.2 (CF3); 110.52 tq, J =
261.6, 37.4 (CF3CF2); 94.56; 67.50 t, J = 2.9 (CF3CF2CH); 67.25; 39.56; 31.10; 28.29; 27.63;
22.41; 18.62; 13.87. 19F NMR (CDCl3): –122.95 dd, 2 F, J = 26.4, 8.8 (CF3CF2); –81.40 s, 3 F
(CF3). IR (n eat): 2 936, 2 862, 2 245, 1 466, 1 377, 1 335. For C12H17F5O3S (336.3) calcu-
lated: 42.86% C, 5.09% H; foun d: 42.93% C, 4.96% H.
(3S)-1,1,1,2,2-Pentafluoroundec-4-yn-3-yl methanesulfonate (1g). [α ]2D1 +61.9 (c 0.825, CHCl3,
94% ee). All oth er data were iden tical with th ose of racem ic 1g.
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Typical Procedure for th e Syn th esis of Allen es
Propargyl m esylate 1a (100 m g, 0.350 m m ol) was added to a solution of [Pd(PPh 3)4] (20 m g,
5 m ole %) in THF (2 m l) at room tem perature, an d th e m ixture was stirred for 10 m in . After
th e reaction m ixture was cooled to 0 °C, ph en ylzin c ch loride (0.696 m m ol, prepared from
Ph MgBr an d Zn Cl2·TMEDA) was added, an d th e m ixture was allowed to warm to room tem -
perature. After stirrin g th e reaction m ixture for 2 h , th e reaction was quen ch ed with satu-
rated aqueous am m on ium ch loride, an d th e resultan t m ixture was extracted with eth yl
acetate (3 ×). Th e com bin ed organ ic layers were wash ed with brin e, dried over an h ydrous
Na2SO4, an d con cen trated in vacuo. Th e residue was purified by silica gel colum n ch rom ato-
graph y to give th e title com poun d.
1,1,1-Trifluoro-4-(phenyl)deca-2,3-diene (2a). 1H NMR (CDCl3): 7.27–7.39 m , 5 H (Ph );
5.75–5.79 m , 1 H (H-2′); 2.50–2.54 m , 2 H (H-5′); 1.26–1.57 m , 8 H (H-6′, 7′, 8′, 9′); 0.89 t,
3 H, J(9′,10′) = 7.0 (H-10′). 13C NMR (CDCl3): 205.62 q, J = 6.0 (CF3CH=C=C); 133.88;
128.69; 128.15; 126.45; 122.79 q, J = 271.1 (CF3); 113.76; 88.55 q, J = 38.8 (CF3CH=C=C);
31.57; 29.80; 28.84; 27.39; 22.59; 14.03. 19F NMR (CDCl3): –60.61 d, 3 F, J = 6.6 (CF3). IR
(n eat): 2 932, 2 858, 1 963, 1 454, 1 412. HRMS (EI): calculated for C16H19F3 268.1439;
foun d: 268.1445.
(3S)-1,1,1-Trifluoro-4-(phenyl)deca-2,3-diene (2a). [α ]2D1 +19.0 (c 0.915, CHCl3, 96% ee). All
oth er data were iden tical with th ose of racem ic 2a.
1,1,1-Trifluoro-4-(4′-methylphenyl)deca-2,3-diene (2b). 1H NMR (CDCl3): 7.26 d, 2 H, J = 7.5
(4-CH3C6H4); 7.16 d, 2 H, J = 8.0 (4-CH3C6H4); 5.73–5.75 m , 1 H (H-2′); 2.47–2.51 m , 2 H
(H-5′), 2.34 s, 3 H (4-CH3C6H4); 1.30–1.56 m , 8 H (H-6′, 7′, 8′, 9′); 0.89 t, 3 H, J(9′,10′) = 5.5
(H-10′). 13C NMR (CDCl3): 205.55 q, J = 5.9 (CF3CH=C=C); 138.10; 130.84; 129.41; 126.34;
122.83 q, J = 270.6 (CF3CH=C=C); 113.60; 88.38 q, J = 38.8 (CF3CH=C=C); 31.59; 29.82;
28.86; 27.42; 22.61; 21.12; 14.02. 19F NMR (CDCl3): –60.64 d, 3 F, J = 6.6 (CF3). IR (n eat):
2 932, 2 858, 1 959, 1 512, 1 423. HRMS (EI): calculated for C17H21F3 282.1595; foun d:
282.1589.
1,1,1-Trifluoro-4-(4′-methoxyphenyl)deca-2,3-diene (2c). 1H NMR (CDCl3): 7.30 d, 2 H, J =
9.0 (4-CH3OC6H4); 6.89 d, 2 H, J = 9.0 (4-CH3OC6H4); 5.73–5.76 m , 1 H (H-2′); 3.81 s, 3 H
(4-CH3OC6H4); 2.46–2.50 m , 2 H (H-5′); 1.26–1.56 m , 8 H (H-6′, 7′, 8′, 9′); 0.89 t, 3 H,
J(9′,10′) = 6.5 (H-10′). 13C NMR (CDCl3): 205.43 q, J = 5.3 (CF3CH=C=C); 159.56; 127.63;
125.87; 122.80 q, J = 271.0 (CF3); 114.12; 113.27; 88.38 q, J = 38.6 (CF3CH=C=C); 55.29;
31.57; 29.87; 28.84; 27.39; 22.59; 14.02. 19F NMR (CDCl3): –60.65 d, 3 F, J = 4.5 (CF3). IR
(n eat): 2 932, 2 858, 1 960, 1 609, 1 512. HRMS (EI): calculated for C17H21F3O 298.1544;
foun d: 298.1527.
1,1,1-Trifluoro-4-(1′-naphthyl)deca-2,3-diene (2d ). 1H NMR (CDCl3): 7.79–7.86 m , 3 H
(n aph th yl); 7.43–7.53 m , 4 H (n aph th yl); 5.52–5.57 m , 1 H (H-2′); 2.51–2.55 m , 2 H (H-5′);
1.24–1.56 m , 8 H (H-6′, 7′, 8′, 9′); 0.87 t, 3 H, J(9′,10′) = 6.5 (H-10′). 13C NMR (CDCl3):
203.41 q, J = 6.0 (CF3CH=C=C); 133.83; 128.46; 128.37; 126.36; 126.04; 125.60; 125.34;
124.99; 123.04 q, J = 270.5 (CF3); 112.29; 85.71 q, J = 38.7 (CF3CH=C=C); 34.44; 31.56;
28.74; 27.45; 22.57; 14.02. 19F NMR (CDCl3): –60.50 d, 3 F, J = 6.6 (CF3). IR (n eat): 2 932,
2 858, 1 975, 1 416. HRMS (EI): calculated for C20H21F3 318.1595; foun d: 318.1598.
(1E)-6,6,6-Trifluoro-3-hexyl-1-(phenyl)hepta-1,3,4-triene (2e). 1H NMR (CDCl3): 7.11–7.42 m ,
5 H (Ph ); 6.64 d, 1 H, J = 16.0 (H-2′); 6.60 d, 1 H, J = 16.0 (H-1′); 5.66–5.68 m , 1 H (H-5′);
2.26–2.40 m , 2 H (CH2(CH2)4)CH3); 1.26–1.57 m , 8 H (CH2(CH2)4)CH3); 0.90 t, 3 H, J = 6.5
(CH2(CH2)4)CH3). 13C NMR (CDCl3): 208.45 q, J = 6.3 (CF3CH=C=C); 136.6; 130.6; 128.7;
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Fluorine-Containing Allenylpalladium Complexes
1433
128.5; 128.0; 127.6; 126.5; 126.1; 123.2; 122.5 q, J = 276.7 (CF3); 87.10 q, J = 39.0
(CF3CH=C=C); 31.60; 28.91; 28.32; 27.26; 22.60; 14.04. 19F NMR (CDCl3): –60.77 d, 3 F, J =
6.6 (CF3). IR (n eat): 2 932, 2 858, 1 956, 1 416. HRMS (EI): calculated for C18H21F3 294.1595;
foun d: 294.1595.
1,1,1-Trifluoro-4-hexyldodeca-2,3-dien-5-yne (2f). 1H NMR (CDCl3): 5.55–5.56 m , 1 H (H-2′);
2.33 t, 2 H, J(7′,8′) = 7.0 (H-7′); 2.18 dq, 2 H, J = 7.5, 2.5 (CH2(CH2)4CH3); 1.26–1.57 m ,
16 H (H-8′, 9′, 10′, 11′, CH2(CH2)4CH3); 0.87–0.91 m , 6 H (H-12′, CH2(CH2)4CH3). 13C NMR
(CDCl3): 210.67 q, J = 5.5 (CF3CH=C=C); 122.09 q, J = 270.6 (CF3CH=C=C); 98.64; 96.65;
86.38 q, J = 39.0 (CF3CH=C=C); 72.64; 33.67; 31.50; 31.29; 28.52; 28.43; 28.33; 27.23; 22.53;
22.52; 19.59; 14.00; 13.99. 19F NMR (CDCl3): –61.03 d, 3 F, J = 6.6. IR (n eat): 2 932, 2 858,
2 226, 1 963, 1 416, 1 265. HRMS (EI): calculated for C18H27F3 300.2065; foun d: 300.2075.
1-tert-Butyldimethylsilyloxy-5,5,5-trifluoro-2-(phenyl)penta-2,3-diene (2g). 1H NMR (CDCl3):
7.31–7.48 m , 5 H (Ph ); 5.88–5.91 m , 1 H (H-4′); 4.68 s, 2 H (H-1′); 0.92 s, 9 H (t-Bu); 0.11 s,
6 H (Si(CH3)2). 13C NMR (CDCl3): 205.23 q, J = 5.5; 141.24; 128.70; 128.41; 127.16; 126.71;
122.60 q, J = 271.3; 114.29; 89.87 q, J = 39.2; 61.51; 25.71; 18.23; –5.44. 19F NMR (CDCl3):
–60.49 d, 3 F, J = 4.5. IR (n eat): 2 955, 2 932, 2 858, 1 963, 1 720, 1 454. HRMS (EI): calcu-
lated for C17H23F3OSi 328.1470; foun d: 328.1458.
5-(Benzyloxy)-1,1,1-trifluoro-4-phenylpenta-2,3-diene (2h ). 1H NMR (CDCl3): 7.26–7.47 m ,
10 H (Ph ); 5.85–5.88 m , 1 H (H-2′); 4.49–4.59 m , 4 H (Ph CH2OCH2). 13C NMR (CDCl3):
206.02 q, J = 5.2 (CF3CH=C=C); 141.21; 137.50; 131.56; 128.79; 128.41; 127.87; 127.22;
127.13; 122.48 q, J = 271.3 (CF3); 110.33, 88.88 q, J = 38.9 (CF3CH=C=C); 71.77; 57.63.
19F NMR (CDCl3): –59.87 d, 3 F, J = 6.6 (CF3). IR (n eat): 3 032, 2 928, 2 862, 1 963, 1 720.
HRMS (EI): calculated for C18H15F3O 304.1075; foun d: 304.1071.
1,1,1,2,2-Pentafluoro-5-(phenyl)undeca-3,4-diene (2i). 1H NMR (CDCl3): 7.27–7.39 m , 5 H
(Ph ); 5.71 tt, 1 H, J = 10.0, 3.0 (H-3′); 2.47–2.57 m , 2 H (H-6′); 1.26–1.57 m , 8 H (H-7′, 8′, 9′,
10′); 0.89 t, 3 H, J = 7.0 (H-11′). 13C NMR (CDCl3): 207.11 t, J = 7.8 (CF3CF2CH=C=C);
133.63; 128.70; 128.19; 126.41; 120.17 qt, J = 285.8, 38.6 (CF3CF2); 113.76; 111.62 tq, J =
251.0, 37.8 (CF3CF2); 86.57 t, J = 28.2 (CF3CF2CH=C=C); 31.56; 29.81; 28.92; 27.36; 22.57;
14.00. 19F NMR (CDCl3): –111.65 d, 2 F, J = 11.0 (CF3CF2); –85.53 s, 3 F (CF3CF2). IR (n eat):
2 932, 2 862, 1 960, 1 454. HRMS (EI): calculated for C17H19F5 318.1407; foun d: 318.1412.
(4S)-1,1,1,2,2-Pentafluoro-5-(phenyl)undeca-3,4-diene (2i). [α ]2D1 +43.9 (c 0.835, CHCl3, 96% ee).
All oth er data were iden tical with th ose of racem ic 2i.
1,1,1,2,2-Pentafluoro-5-(4′-methylphenyl)dodeca-3,4-diene (2j). 1H NMR (CDCl3): 7.26 d, 2 H,
J = 8.0 (Ar); 7.16 d, 2 H, J = 8.0 (Ar); 5.69 tt, 1 H, J(3′,F an d 3′,6′) = 10.0, 2.5 (H-3′);
2.44–2.55 m , 2 H (H-6′); 2.34 s, 3 H (4-CH3C6H4); 1.26–1.56 m , 8 H (H-7′, 8′, 9′, 10′); 0.89 t,
3 H, J = 7.0 (H-11′). 13C NMR (CDCl3): 207.07 t, J = 7.6 (CF3CF2CH=C=C); 138.14; 130.57;
129.42; 120.19 qt, J = 285.7, 38.0 (CF3CF2); 113.59; 126.29; 111.64 tq, J = 250.9, 37.9
(CF3CF2); 86.40 t, J = 28.1 (CF3CF2CH=C=C); 31.57; 29.82; 28.9; 27.38; 22.58; 21.12; 14.01.
19F NMR (CDCl3): –85.50 s, 3 F (CF3CF2); –111.62 d, 2 F, J = 8.8 (CF3CF2). IR (n eat): 2 932,
2 862, 1 960, 1 512, 1 458. HRMS (EI): calculated for C18H21F5 332.1563; foun d: 332.1554.
Typical Procedure for th e Syn th esis of Furan Derivatives
A solution of [Pd2(dba)3·CHCl3] (5 m g, 2.5 m ole %) an d 1,2-bis(diph en ylph osph in o)eth an e
(60 m g, 10 m ole %) in THF (2 m l) was stirred at room tem perature for 10 m in . Propargyl
m esylate 1a (51 m g, 0.178 m m ol), m eth yl acetoacetate (61 m g, 0.526 m m ol), an d sodium
h ydride (14 m g, 0.588 m m ol) were added to th e solution in th is order. After stirrin g th e re-
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Konno et al.:
action m ixture at room tem perature for 3 h , th e reaction was quen ch ed with water, an d th e
resultan t m ixture was extracted with eth yl acetate (3 ×). Th e com bin ed organ ic layers were
wash ed with saturated aqueous am m on ium ch loride, dried over an h ydrous Na2SO4, an d
con cen trated in vacuo. Th e residue was purified by silica gel colum n ch rom atograph y to give
th e correspon din g furan derivatives.
In th e case of acetylaceton e an d dieth yl m alon ate, th e organ ic layer was treated with 3
aqueous HCl in th e extraction step.
M
Methyl 2-hexyl-5-methyl-3-(2,2,2-trifluoroethylidene)-2,3-dihydrofuran-4-carboxylate (3a ).
1H NMR (CDCl3): 5.04–5.07 m , 1 H (CH3(CH2)4CH2CHO); 4.98 qd, 1 H, J = 9.5, 2.5
(CF3CH); 3.76 s, 3 H (CH3OCO); 2.25 s, 3 H (CH3); 1.26–1.87 m , 10 H (CH2(CH2)4CH3);
0.89 t, 3 H, J = 6.5 (CH2(CH2)4CH3). 13C NMR (CDCl3): 177.71; 164.98; 150.32 q, J = 5.4
(CF3CH=C); 123.54 q, J = 268.0 (CF3); 106.98; 99.5 q, J = 37.5 (CF3CH=C); 87.80; 51.25;
36.01; 31.56; 29.69; 28.95; 25.60; 24.04; 22.54; 14.81; 14.01. 19F NMR (CDCl3): –57.56 d,
3 F, J = 8.8 (CF3). IR (n eat): 2 959 (m ), 2 932, 2 858, 1 720, 1 659, 1 605, 1 443, 1 416.
HRMS (EI): calculated for C15H21F3O3 306.1443; foun d: 306.1425.
3-Acetyl-5-hexyl-2-methyl-4-(2,2,2-trifluoroethyl)furan (4a). 1H NMR (CDCl3): 3.55 q, 2 H, J =
10.5 (CH2CF3); 2.56 s, 3 H (CH3); 2.43 s, 3 H (CH3CO); 1.60 q, 2 H, J = 7.5 (CH2(CH2)4CH3);
1.26–1.35 m , 8 H (CH2(CH2)4CH3); 0.89 t, 3 H, J = 6.5 ((CH2)4CH2CH3). 19F NMR (CDCl3):
–66.61 t, 3 F, J = 11.0 (CF3). IR (n eat): 2 932, 2 858, 1 670, 1 570, 1 420, 1 354. HRMS (EI):
calculated for C15H21F3O2 290.1494; foun d: 290.1502.
Ethyl 2-ethoxy-5-hexyl-4-(2,2,2-trifluoroethyl)furan-3-carboxylate (5a ). 1H NMR (CDCl3):
4.40 q, 2 H, J = 7.0 (CH3CH2O); 4.26 q, 2 H, J = 7.0 (CH3CH2OCO); 3.47 q, 2 H, J = 11.0
(CF3CH2); 2.50 t, 2 H, J = 7.3 (CH3(CH2)4CH2); 1.27–1.35 m , 12
H (CH3(CH2)3CH2,
CH3CH2O); 1.55–1.59 m , 2 H (CH3(CH2)3CH2); 0.89 t, 3 H, J = 6.5 (CH3CH2OCO). 19F NMR
(CD2Cl2, stan dard TFA): 9.89 t, 3 F, J = 10.9 (CF3CH2). IR (n eat): 2 959, 2 932, 2 862, 1 709,
1 605. HRMS (EI): calculated for C17H25F3O4 350.1705; foun d: 350.1686.
REFERENCES AND NOTES
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f) Snieckus V.: Chem. Rev. (Washington, D. C.) 1990, 90, 879; g) Matterson D. S.:
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compound 2a: R isomer, 6.1 min, S isomer, 7.1 min; compound 2c: R isomer, 5.9 min,
S isomer, 6.5 min.
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10 min, and 19F and 1H NMR analysis of the reaction mixture was carried out. The
formation of a single product was detected by 19F NMR. Furthermore, only two peaks
were observed (δ 4.0 (br s, 1 H, CF2HCH); 4.78 (dt, J = 6.7, 57.1, 1 H, CF2H)) in the range
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