Highly (≥98a%) selective trisubstituted alkene synthesis of wide applicability via fluoride-promoted Pd-catalyzed cross-coupling of alkenylboranes

Article abstract of DOI:10.1002/ijch.201000051

(Z)-β-bromo-1-propenyl(pinacol)borane (4), recently made available in 85a% yield as a ≥98a% isomerically pure compound via bromoboration of 1-propyne, has been converted to β-alkyl-, aryl-, and alkenyl-substituted (Z)-2-methyl-1-alkenyl(pinacol)boranes (2

Full text of DOI:10.1002/ijch.201000051

Full Paper
E. Negishi et al.
DOI: 10.1002/ijch.201000051
Highly (ꢀ98%) Selective Trisubstituted Alkene Synthesis
of Wide Applicability via Fluoride-Promoted Pd-Catalyzed
Cross-Coupling of Alkenylboranes
Ei-ichi Negishi,*[a] Tomas Tobrman,[a] Honghua Rao,[a] Shiqing Xu,[a] and Ching-Tien Lee[a]
Dedicated to Prof. Morris Srebnik in recognition and appreciation of his pioneering contributions in organometallic
chemistry.
Abstract: (Z)-b-bromo-1-propenyl(pinacol)borane (4), re-
cently made available in 85% yield as a ꢀ98% isomerically
pure compound via bromoboration of 1-propyne, has been
converted to b-alkyl-, aryl-, and alkenyl-substituted (Z)-2-
methyl-1-alkenyl(pinacol)boranes (2a) in ca. 75% yield
based on propyne via Pd-catalyzed Negishi alkenylation with
suitable organozinc bromide. The previously sluggish and
modest-yielding Suzuki alkenylation of b,b-disubstituted al-
kenylboranes has been significantly promoted by fluorides,
especially nBu4NF(TBAF) or CsF, to give trisubstituted al-
kenes, i.e., (Z)-b-Me-substituted 3-i–3-xi and (E)-b-Ph-sub-
stituted 2b–i and 2b–ii. In all cases, each alkene product
was formed in a ꢀ98% stereoselectivity. The propyne-based
protocol nicely complements the widely used Zr-catalyzed
alkyne methylalumination–Pd-catalyzed alkenylation by pro-
viding a highly stereoselective(ꢀ98%) route to (Z)-Me-sub-
stituted alkenes.
Keywords: alkene synthesis · bromoboration · cross-coupling · F-promoted alkenylation · (Z)-b-bromo-1-alkenyl(pinacol)borane
1. Introduction
Haloboration of alkynes with haloboranes, reported first
by Lappert in 1964[1] (Scheme 1), is a rare alkyne halome-
It should be noted here that, despite very high synthet-
ic utilities of the Zr-catalyzed carboalumination, especial-
ly methylalumination (ZMA) discovered and developed
by us,[3] and Normantꢀs prototypical carbocupration[4] of
alkynes, their scopes are largely limited to syn-alkylmeta-
lation of alkynes. Since both halogen (X) and boryl
groups (BY2) of 1 can, in principle, be substituted with a
wide variety of carbon groups by Pd-catalyzed Negishi
and/or Suzuki alkenylation,[5] the protocol shown in
Scheme 2 promised to provide an unprecedentedly broad-
scoped and highly (ꢀ98%) selective route to trisubstitut-
ed alkenes (3) via 2. In reality, however, some critical lim-
itations including the following have been reported: (i)
The arguably single most important case of propyne halo-
boration was reported to be ꢁ90% stereoselective.[2b] (ii)
Although haloboration of terminal alkynes containing
aryl and other unsaturated carbon groups proceeds satis-
factorily, subsequent Pd-catalyzed substitution of the b-
Scheme 1.
talation which must be rendered thermodynamically fa-
vorable, in part, by virtue of boronꢀs high electronegativi-
ty for a metal. Its kinetic facility and high stereoselectiv-
ity, often nearly 100% syn, make it an attractive and po-
tentially useful tool for selective synthesis of trisubstitut-
ed alkenes.
Indeed, this was realized by Suzuki[2] in the late 1980s
through development of an alkyne haloboration–Pd-cata-
lyzed Negishi–Suzuki tandem alkenylation (Scheme 2).
[a] E.-i. Negishi, T. Tobrman, H. Rao, S. Xu, C.-T. Lee
Herbert C. Brown Laboratories of Chemistry,
Purdue University, 560 Oval Drive,
West Lafayette, IN 47907-2084, USA
phone: +1 (0)765 494-5301
fax: +1 (0)765 494-0239
e-mail: negishi@purdue.edu
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/ijch.201000051
Scheme 2.
696
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Highly (ꢀ98%) Selective Trisubstituted Alkene Synthesis of Wide Applicability via Fluoride-Promoted Pd-Catalyzed
halogen atom was plagued with unwanted dehaloboration
to regenerate the original 1-alkynes.[6] (iii) As reported by
Suzuki,[2a] the Suzuki alkenylation with b,b-disubstituted
alkenylboranes for producing the desired trisubstituted al-
kenes not only required a large excess, up to 75 equiva-
lents, of a base, such as LiOH and LiOMe, but led to
modest product yields of mostly 50–70%. To cope with
these difficulties and inconveniences, Wang[7] and the au-
thorsꢀ group[8] opted for a circuitous route via borane-to-
iodide conversion followed by the second Negishi alkeny-
lation, but a more direct and satisfactory procedure was
clearly desirable.
reported,[9a,10] despite an early pioneering work of Srebni-
k[10a] reporting a CsF-promoted selective Suzuki alkenyla-
tion with a b,b-disubstituted alkenylboranes in preference
to a (Z)-a,b-disubstituted alkenylborane present in the
same compound.
We herein report the development of highly (ꢀ98%)
selective and satisfactory procedure for Pd-catalyzed
cross-coupling of b,b-disubstituted alkenylboranes(2) to
give a wide range of trisubstituted alkenes (3) that is pro-
moted by fluorides, such as nBu4NF(TBAF) and CsF.
Gratifyingly, recent efforts in the authorsꢀ group have
led to an excellent procedure for one-pot conversion of
propyne into 4 of 98% Z in 85% yield and its subsequent
conversion to a wide variety of 5 in good yield via Negishi
alkenylation followed by iodinolysis (Scheme 3) and the
corresponding procedure with arylethynes[6] (Scheme 4).
2. Results and Discussion
Preparation of (Z)-2-bromo-1-alkenyl(pinacol)boranes(1) and
b,b-disubstituted -1-alkenyl(pinacol)boranes (2)
Preparation of (Z)-2-bromo-1-propenyl(pinacol)borane
(4) was carried out by bromoboration of propyne with
BBr3 (1.1 equiv.) in CH2Cl2 at –78 to 238C followed by
addition of pinacol (1.2 equiv., –78 to 238C) to give 4 as a
ꢀ98% isomerically pure compound in 85% isolated yield
(Scheme 3).[8b] Since 4 was to be used for the preparation
of ten to a dozen trisubstituted alkenes, we opted for pre-
paring isolated and pure 4 and using it for subsequent
transformations. For the syntheses of arylethyne-derived
trisubstituted alkenes, we opted for generating in situ (Z)-
2-bromo-2-aryl-1-ethenyl(pinacol)boranes (7) and con-
verting them into 2b without isolation of 7 in the more
limited part of this study. In both cases, those results re-
ported earlier were closely reproduced, and those that
are pertinent to this study are summarized in Table 1.
Selection of the reaction conditions was mostly based
on our recent studies.[6,8] Thus, for conversion of b-
bromo-1-propenyl(pinacol)boranes (4) to b,b-disubstitut-
ed-1- alkenyl(pinacol)boranes (2a), organozincs were uni-
formly satisfactory reagents. For alkenylation, alkenylin-
dium and alkenylzirconium derivatives were also reasona-
bly satisfactory.[8b] For Pd-catalyzed Negishi coupling of
alkyl-substituted b-bromo-1-alkenylboranes, such as 4,
various conventional Pd catalysts, such as Pd(PPh3)4,
PdCl2(PPh3)2, and PdCl2(DPEphos), were arbitrarily and
successfully used. On the other hand, b-aryl-containing b-
bromo-1-alkenylboranes, such as 7, are much more readi-
ly prone to competitive b-debromoboration. To cope with
this difficulty, the use of highly active catalysts, such as
Pd(tBu3P)2 and PEPPSITM-IPr (8) (Figure 1), where
PEPPSI stands for [1,3-bis(2,6-diisopropylphenyl)imida-
zol-2-ylidene](3-chloropyridyl)palladium(II) dichloride,[11]
proved to be essential.[6] Each of the products 2a and 2b
was formed and isolated as a ꢀ98% isomerically pure
Scheme 3.
Scheme 4.
Although these procedures are highly selective and sat-
isfactory, especially in those cases where the use of orga-
nozincs rather than the corresponding halides is distinctly
more favorable, as in alkylation with alkylzincs, it was
nevertheless desirable to avoid the intermediacy of alken-
yl iodides 5 and 6 for the synthesis of 3. To this end, the
use of fluorides as promotors of Suzuki alkenylation of
b,b-disubstituted alkenylboranes (2) was considered.
Survey of the literature has indicated that the use of fluo-
rides in Suzuki arylation[9] has been extensively studied,
but their use in Suzuki alkenylation has been much less
1
compound. Neither H nor 13C NMR spectrum at the S/N
ratio of ꢀ50–100 revealed any signals for isomeric prod-
ucts. The assigned stereochemistry is fully supported by
NMR spectroscopy including NOE measurements.
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E. Negishi et al.
Table 1. Preparation of (Z)-2-methyl-1-alkenyl(pinacol)boranes (2a)
and 2-aryl-1-alkenyl(pinacol)boranes (2b).
lyzed cross-coupling of potassium alkenyltrifluoroborates
reported by Molander.[10b,d–f] Our own brief screening of
various fluorides and some oxy bases for the reaction of
b,b-disubstituted alkenylborane (2a–ii) with p-nitroiodo-
benzene in the presence of 1 mol% of PdCl2(DPEphos)
indicated that (a) TBAF (95%), Et4NF (87%), and CsF
(90%) were among the most effective, the numbers in pa-
rentheses indicating isolated yields. On the other hand,
nBu4NI (0%), LiF (0%), and K2CO3 (5%) were almost
totally ineffective, while some others, including NaF
(83%), and Cs2CO3 (70%), also were of considerable ef-
ficiency. Based on these findings, TBAF was chosen be-
cause of its superior efficiency. In view of its considerably
high cost, however, CsF was also chosen as the best com-
promise. As summarized in Table 2, both TBAF and CsF
have proved to be highly effective promoters. Both the
product yields and isomeric purities were generally excel-
lent. The only notable difficulty recorded in Table 2 was
observed in the reaction of 2a–ii with 1-iodophenylacety-
lene, where the low product yield was attributable to the
competitive homodimerization of 1-iodophenylacetylene.
Fortunately, this problem was fully suppressed by using 1-
bromophenylacetylene in place of 1-iodophenylacetylene.
All trisubstituted alkenes (3) shown in Table 2 were
formed and isolated as ꢀ98% isomerically pure com-
pounds, and their stereochemical assignments were made
on the basis of their NOE measurements.
The results shown in Table 2 clearly indicate that the
propyne bromoboration–Pd-catalyzed Negishi–Suzuki
tandem alkenylation route to methyl-branched (Z)-trisub-
stituted alkenes of high (ꢀ98%) isomeric purity and
wide applicability has finally been developed as a high-
yielding and efficient method for their head-to-tail (H-to-
T) construction (Scheme 5), nicely complementing the
widely used Zr-catalyzed alkyne carboalumination–Pd-
catalyzed Negishi alkenylation tandem route to methyl-
branched (E)-trisubstituted alkenes.[3]
It should also be recalled that another widely applica-
ble tail-to-head (T-to-H) construction (Scheme 5) route
to either E or Z trisubstituted alkenes via Pd-catalyzed
double substitution of 1,1-dibromo-1-alkenes developed
several years ago by us[12] is also highly selective and com-
plementary with the method developed herein.
Figure 1. The structure of PEPPSITM-IPr (8).
Noting that the N- or O-centered base-promoted Pd-
catalyzed alkenylation with preformed potassium b,b-dis-
ubstituted alkenyltrifluoroborates does not appear to
have been reported, 2a–ii was treated with 2–4 equiva-
lents of KHF2 as described in the literature[10b] to gener-
ate in situ the corresponding potassium (Z)-2-methyl-1-
octenyltrifluoroborate (9), which was in situ subjected to
Pd-catalyzed cross-coupling with PhI. However, the de-
sired 3-ii was obtained only in low yields (ꢁ30–40%). As
indicated in Tables 1 and 2, 2a–ii was obtained in 85%
yield from propyne and converted into 3-ii in 83% yield
(71% yield from propyne). The corresponding reaction of
(E)-1-octenyltrifluoroborate (8) produced the desired
Pd-Catalyzed Cross-Coupling Reactions of b,b-disubstituted-1-
alkenyl(pinacol)boranes (2) Promoted by nBu4NF(TBAF) or CsF
For overcoming the reported difficulties and inconvenien-
ces observed in the oxy base-promoted Pd-catalyzed
cross-coupling of alkenylboranes,[2a] the use of fluoride
salts[9,10] was investigated. Although the number of studies
on fluoride-promoted Pd-catalyzed cross-coupling with al-
kenylboranes was limited,[10] an investigation by Srebni-
k[10a] on CsF-promoted Pd-catalyzed cross-coupling of
b,b- and a,b-disubstituted alkenylboranes proved to be of
crucial importance. Also to be noted here is the possible
usefulness of N- or O-centered base-promoted Pd-cata-
698
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Isr. J. Chem. 2010, 50, 696 – 701

Highly (ꢀ98%) Selective Trisubstituted Alkene Synthesis of Wide Applicability via Fluoride-Promoted Pd-Catalyzed
Table 2. Coversion of b,b-disubstituted-1-alkenyl(pinacol)boranes
(2) into trisubstitued alkenes (3) via fluoride-promoted Pd-catalyzed
alkenylation with 2.
Scheme 5.
product 10-i in 67% yield (Scheme 6), which is roughly
comparable with the results reported for a similar
case.[10b] Although further investigation is clearly desira-
ble, it is our tentative view that the two seemingly very
similar protocols may be significantly different. In partic-
ular, it would appear desirable to clarify the role of F vis-
ꢁ-vis an added base, i.e., tBuNH2, in Molanderꢀs protocol.
Scheme 6.
3. Conclusions
(1) In search for previously elusive widely applicable and
highly (ꢀ98%) selective head-to-tail construction routes
to trisubstituted alkenes, especially those that are readily
applicable to the synthesis of (Z)-b-methyl trisubstituted
alkenes, fluoride-promoted Pd-catalyzed alkenylation
with (Z)-b-methyl-1-alkenyl(pinacol)boranes(2a) was ex-
amined and found to be excellent, producing the desired
trisubstituted alkenes (3i–3xi) in 74–98% yields in ꢀ98%
stereoselectivity. The requisite (Z)-b,b-disubstituted-1-
alkenyl(pinacol)boranes (2a) can now be prepared from
propyne via propyne bomoboration–Pd-catalyzed Negishi
alkenylation either in one pot or in two steps in good
overall yields (73–77% observed). This protocol is nicely
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E. Negishi et al.
Representative Procedure for Fluoride-Promoted Pd-Catalyzed
Alkenylation of b,b-disubstituted-1-alkenyl(pinacol)boranes
complementary with the (E)-selective Zr-catalyzed
alkyne carboalumination–Pd-catalyzed alkenylation. It is
also complementary with the tail-to-head protocol via Pd-
catalyzed stepwise and highly selective tandem alkenyla-
tion of 1,1-dibromo-1-alkenes.
A flame-dried, 25-mL, round-bottomed flask, equipped with a
magnetic stirring bar, a rubber septum, and an argon inlet, was
charged with PdCl2(DPEphos) (0.01 mmol), 2 (1.2 mmol), an or-
ganic iodide or bromide (1.0 mmol), and THF (4 mL) under an
atmosphere of argon. TBAF or CsF (1.5–2.0 mmol) was as
added. The mixture was heated to 60oC and monitored by TLC.
The reaction mixture was then quenched with aqueous NH4Cl.
The aqueous layer was separated and extracted with ethyl ace-
tate. The combined organic phase was washed with brine, dried
over anhydrous magnesium sulfate, filtered, and concentrated by
rotary evaporator (408C, 20 mmHg) to give the crude product.
The product was purified by flash chromatography.
(2) Although not encountered in this study, it should
be clearly kept in mind that the alkyne haloboration–Pd-
catalyzed alkenylation protocols have, in the past, posed
and will continue to pose at least two potential limitations
to cope with and overcome. One is debromoboration of
b-bromoalkenylboron derivatives, and the other is an as-
sortment of complications due to intermediary formation
of fundamentally capricious allyl-, propargyl-, and even
benzylpalladium derivatives. Although we speculate that
two examples of conversion of phenylacetylene to 2b-i
and 2b-ii, which required highly active catalysts, such as
Pd(tBu3P)2 and PEPPSITM-IPr (8), may have displayed a
difficulty pertaining to both of the two mentioned above,
it was luckily overcome in these cases.
1
3-i. H NMR (CDCl3, 300 MHz) d=0.8–0.9 (m, 6H), 1.3–1.5 (m,
12H), 1.72 (s, 3H), 2.28 (q, J=7.2 Hz, 4H), 5.27 (s, 1H);
13C NMR (CDCl3, 75 MHz) d=13.8, 13.9, 19.4, 22.1, 22.4, 22.5,
28.5, 28.9, 29.7, 31.3, 34.0, 78.2, 91.9, 105.5, 150.5. HRMS(ESI)
calcd for C15H26: 206.2035; found: 206.2038 [M]+.
1
3-ii. H NMR (CDCl3, 300 MHz) d=0.8–0.9 (m, 3H), 1.2–1.3 (m,
(3) The relationship between the fluoride-promoted
Pd-catalyzed alkenylation with alkenyl(pinacol)boranes
reported herein and the recently developed N- or O-cen-
tered base-promoted Pd-catalyzed alkenylation with pre-
formed potassium alkenyltrifluoroborates remains un-
clear. Comparison of their synthetic merits, and efforts to
gain mechanistic insights, appear to be very desirable.
(4) Finally, our own efforts to further improve Pd-cata-
lyzed cross-coupling of various types continue. Even
though Pd-catalyzed cross-coupling with organometals
containing Zn appears to be generally the fastest and
most highly selective (with that involving Zr, Al, and per-
haps In as well, closely trailing the organozinc cross-cou-
pling), it is gratifying to learn that the significantly slower
Pd-catalyzed organoboron cross-coupling, generally re-
quiring heating to 50–100oC, can be and has been contin-
uously improved, as indicated by recent results, including
those reported herein. Many further improvements of Pd-
catalyzed cross-coupling involving all of the metals men-
tioned above, as well as those not mentioned here, may
be predicted, and such efforts are very much encouraged.
6H), 1.4–1.5 (m, 2H), 1.91 (s, 3H), 2.25 (t, J=7.5 Hz, 2H), 6.30
(s, 1H), 7.2–7.3 (m, 5H); 13C NMR (CDCl3, 75 MHz) d=14.1,
22.6, 24.1, 28.1, 29.3, 31.7, 32.5, 125.2, 125.7, 128.0, 128.5, 138.6,
139.8. HRMS(ESI) calcd for C15H22: 202.1722; found: 202.1719
[M]+.
3-iii. 1H NMR (CDCl3, 300 MHz) d=0.87 (t, J=6.8 Hz, 3H),
1.1–1.3 (m, 6H), 1.4–1.5 (m, 2H), 1.92 (s, 3H), 2.1–2.2 (m, 2H),
6.29 (s, 1H), 7.31 (d, J=8.4 Hz, 2H), 8.76 (d, J=8.8 Hz, 2H);
13C NMR (CDCl3, 75 MHz) d=14.0, 22.5, 24.4, 27.9, 29.2, 31.5,
32.7, 123.4, 123.7, 129.0, 144.3, 145.4, 145.6. HRMS(ESI) calcd
for C15H21NO2: 247.1572; found: 247.1581 [M]+.
1
3-iv. H NMR (CDCl3, 300 MHz) d=0.7–0.9 (m, 3H), 1.2–1.5 (m,
8H), 1.89 (s, 3H), 2.1–2.2 (m, 2H), 6.23 (s, 1H), 7.12 (d, J=
8.1 Hz, 2H), 7.29 (d, J=8.1 Hz, 1H); 13C NMR (CDCl3,
75 MHz) d=14.0, 22.6, 24.0, 27.9, 29.3, 31.6, 32.4, 124.1, 128.1,
129.8, 131.4, 137.0, 140.6. HRMS(ESI) calcd for C15H21Cl:
236.1332; found: 236.1338 [M]+.
1
3-v. H NMR (CDCl3, 300MHz) d=0.96 (t, J=7.2 Hz, 3H), 1.2–
1.4 (m, 6H), 1.4–1.6 (m, 2H), 1.92 (s, 3H), 2.2–2.3 (m, 2H), 3.84
(s, 3H), 6.28 (s, 1H), 6.91 (d, J=8.8 Hz, 2H), 7.13 (d, J=8.4 Hz,
2H); 13C NMR (CDCl3, 75 MHz) d=14.0, 22.6, 24.1, 28.0, 29.3,
31.7, 32.4, 55.0, 113.3, 124.6, 129.5, 131.1, 138.3, 157.6. HRMS-
(ESI) calcd for C16H24O: 232.1827; found: 232.1835 [M]+.
3-vi. 1H NMR (CDCl3, 300 MHz) d=0.8–0.9 (m, 3H), 1.3–1.6
(m, 8H), 1.92 (s, 3H), 2.3–2.4 (m, 2H), 6.40 (s, 1H), 6.90 (d, J=
3.3 Hz, 1H), 7.00 (dd, J=5.1, 3.6 Hz, 1H), 7.19 (d, J=5.1 Hz,
1H); 13C NMR (CDCl3, 75 MHz) d=14.0, 22.6, 24.7, 27.6, 29.5,
31.7, 33.6, 118.2, 123.5, 125.7, 126.5, 139.3, 141.1. HRMS(ESI)
calcd for C13H20S: 208.1286; found: 208.1288 [M]+.
Experimental Section
General
All reactions were run under a dry Ar atmosphere. Reactions
were monitored by thin layer chromatography (TLC) carried out
on 0.25-mm Merck silica gel plates (60F-254) or by GC analysis
of reaction aliquots. GC analysis was performed on an HP 6890
Gas Chromatograph using an HP-5 capillary column (30 m ꢂ
0.32 mm, 0.5 mM film) packed with SE-30 on Chromosorb W.
Column chromatography was carried out on 230–400 mesh silica
gel. 1H and 13C NMR spectra were recorded on Varian-Inova-
300. Commercially available solvents and reagents were of re-
agent grade and used without further purification, unless other-
wise indicated. THF was dried by distillation under Ar from
sodium/benzophenone. CH2Cl2 was dried by distillation under Ar
from CaH2. ZnBr2 was flame-dried in vacuo.
3-vii. 1H NMR (CDCl3, 300 MHz) d=0.8–0.9 (m, 6H), 1.3–1.5
(m, 12H), 1.74 (s, 3H), 1.80 (s, 3H), 2.08 (t, J=7.6 Hz, 2H), 2.16
(t, J=7.6 Hz, 2H) 6.01 (s, 2H); 13C NMR (CDCl3, 75 MHz) d=
13.9, 14.0, 16.2, 22.3, 22.6, 24,1, 28.1, 29.2, 30.2, 31.8, 32.0, 40.0,
120.5, 121.4, 136.0, 136,7. HRMS(ESI) calcd for C16H30:
222.2348; found: 222.2352 [M]+.
3-viii. 1H NMR (CDCl3, 300MHz) d=0.8–0.9 (m, 3H), 1.3–1.5
(m, 8H), 1.86 (s, 3H), 2.43 (t, J=5.7 Hz, 2H), 5.51 (s, 1H), 7.3–
7.4 (m, 3H), 7.45 (d, J=6.0 Hz, 2H); 13C NMR (CDCl3, 75 MHz)
d=14.0, 22.6, 27.5, 28.9,31.6, 34.7, 87.6, 91.3, 105.7, 124.1, 127.5,
700
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Highly (ꢀ98%) Selective Trisubstituted Alkene Synthesis of Wide Applicability via Fluoride-Promoted Pd-Catalyzed
128.1, 131.1, 153.1. HRMS(ESI) calcd for C17H22: 226.1722;
References
found: 226.1723 [M]+.
[1] M. F. Lappert, B. J. Prokai, J. Organomet. Chem. 1964, 1,
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6.63 (s, 1H), 6.73 (d, J=3.0 Hz, 1H), 6.81 (dd, J=5.1, 3.9 Hz,
1H), 6.95 (d, J=5.1 Hz, 1H), 7.2–7.2 (m, 2H), 7.3–7.4 (m, 3H);
13C NMR (CDCl3, 75 MHz) d=27.2, 120.3, 124.5, 125.8, 126.6,
127.4, 128.0, 128.8, 137.6, 140.8, 141.8. HRMS(ESI) calcd for
C13H12S: 200.0660; found: 200.0665 [M]+.
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1
3-x. H NMR (CDCl3, 300 MHz) d=0.90 (t, J=6.9 Hz, 3H), 1.3–
1.4 (m, 8H), 2.00 (d, J=1.5 Hz, 3H), 2.12 (dd, J=6.9, 6.3 Hz,
2H), 5.86 (dt, J=15.6, 6.9 Hz, 1H), 6.35 (s, 1H), 6.50 (d, J=
15.9 Hz, 1H), 7.2–7.4 (m, 5H); 13C NMR (CDCl3, 75 MHz) d=
14.3, 21.5, 22.8, 29.1, 29.6, 31.9, 33.4, 126.3, 127.5, 128.2, 128.4,
129.5, 133.4, 135.0, 138.1. HRMS(ESI) calcd for C17H24:
228.1878; found: 228.1875 [M]+.
3-xi. 1H NMR (CDCl3, 300 MHz) d=0.8–0.9 (m, 6H), 1.3–1.4
(m, 12H), 1.84 (s, 3H), 2.1–2.2 (m, 4H), 5.6–5.7 (m, 1H), 5.69 (d,
J=15.3 Hz, 1H), 5.84 (d, J=11.7 Hz, 1H), 6.50 (dd, J=14.7,
11.7 Hz, 1H), 6.60 (d, J=15.3 Hz, 1H); 13C NMR (CDCl3,
75 MHz) d=14.1, 14.3, 20.8, 22.4, 22.8, 29.1, 29.8, 31.9, 32.0, 32.9,
33.6, 125.8, 127.1, 127.9, 131.5, 131.9, 134.2. HRMS(ESI) calcd
for C17H30: 234.2348; found: 234.2347 [M]+.
1
3-xii. H NMR (CDCl3, 300 MHz) d=2.29 (s, 3H), 7.04 (s, 1H),
7.1–7.6 (m, 8H); 13C NMR (CDCl3, 75 MHz) d=18.3, 120.9,
125.0, 125.9, 126.9, 127.0, 127.5, 128.3, 135.6, 141.4, 144.0. HRMS-
(ESI) calcd for C13H12S: 200.0660; found: 200.0661 [M]+.
3-xiii. 1H NMR (CDCl3, 300 MHz) d=0.8–0.9 (m, 6H), 1.2–1.3
(m, 6H), 1.4–1.6 (m, 4H), 1.6–1.7 (m, 2H), 1.90 (s, 3H), 2.20 (t,
J=6.9 Hz, 2H), 2.53 (t, J=6.9 Hz, 2H), 6.58 (d, J=9.0 Hz, 1H),
7.11 (d, J=11.7 Hz, 1H), 7.1–7.3 (m, 1H), 7.6–7.7 (m, 2H);
13C NMR (CDCl3, 75 MHz) d=13.9, 14.0, 17.2, 19.7, 22.4, 22.6,
28.6, 28.8, 30.1, 31.3, 40.1, 78.1, 98.3, 121.0, 123.7, 125.9, 127.1,
128.2, 130.2, 139.1, 143.8. HRMS(ESI) calcd for C23H32:
308.2504; found: 308.2508 [M]+.
8. 1H NMR (d6-DMSO, 300MHz) d=0.8–0.9 (m, 3H), 1.2–1.3
(m, 8H), 1.8–1.9 (m, 2H), 5.1–5.3 (m, 1H), 5.4–5.5 (m, 1H);
13C NMR (d6-DMSO, 75 MHz) d=14.0, 22.1, 28.5, 29.2, 31.3,
35.4, 133.6, 133.7. HRMS(ESI) calcd for C8H15BF3K: 218.0856;
found: 179.1224 [M-K]À.
10-i. 1H NMR (CDCl3, 300 MHz) d=0.9–1.0 (m, 3H), 1.3–1.6
(m, 8H), 2.2–2.4 (m, 2H), 6.2–6.4 (m, 1H), 6.4–6.5 (m, 1H), 7.2–
7.4 (m, 5H); 13C NMR (CDCl3, 75 MHz) d=14.2, 22.8, 29.1,
29.5, 31.9, 33.2, 126.0, 126.8, 128.5, 129.8, 131.2, 138.0. HRMS-
(ESI) calcd for C14H20: 188.1565; found: 188.1573 [M]+.
10-ii. 1H NMR (CDCl3, 300 MHz) d=0.9–1.0 (m, 3H), 1.3–1.6
(m, 8H), 2.1–2.3 (m, 2H), 3.82 (s, 3H), 6.0–6.4 (m, 4H), 7.3–7.4
(m, 2H); 13C NMR (CDCl3, 75 MHz) d=14.1, 22.6, 29.0, 29.5,
31.8, 33.0, 55.1, 113.8, 126.9, 129.0, 130.8, 158.5. HRMS(ESI)
calcd for C15H22O: 218.1671; found: 218.1676 [M]+.
[12] a) X. Zeng, Q. Hu, M. Qian, E. Negishi, J. Am. Chem. Soc.
2003, 125, 13636–13637; b) X. Zeng, M. Qian, Q. Hu, E.
Negishi, Angew. Chem. 2004, 116, 2309–2313; Angew.
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Acknowledgments
This work was mainly supported by National Institutes of
Health (GM36792) and Purdue University. We also ac-
knowledge support of various forms by Aldrich Chemical
Co. and Johnson Matthey Catalysts Co.
Received: August 26, 2010
Accepted: October 6, 2010
Published online: November 29, 2010
Isr. J. Chem. 2010, 50, 696 – 701
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.ijc.wiley-vch.de
701