Direct catalytic cross-coupling of alkenyllithium compounds

Article abstract of DOI:10.1039/c4sc03117b

A catalytic method for the direct cross-coupling of alkenyllithium reagents with aryl and alkenyl halides is described. The use of a catalyst comprising Pd₂(dba)₃/XPhos allows for the stereoselective preparation of a wide variety of substituted alkenes in high yields under mild conditions. In addition (1-ethoxyvinyl)lithium can be efficiently converted into substituted vinyl ethers which, after hydrolysis, give readily access to the corresponding methyl ketones in a one pot procedure.

Full text of DOI:10.1039/c4sc03117b

Chemical
Science
View Article Online
View Journal
EDGE ARTICLE
Direct catalytic cross-coupling of alkenyllithium
compounds†
Cite this: DOI: 10.1039/c4sc03117b
Valentın Hornillos, Massimo Giannerini, Carlos Vila, Martın Fananas-Mastral
´
´
˜
´
*
and Ben L. Feringa
A catalytic method for the direct cross-coupling of alkenyllithium reagents with aryl and alkenyl halides is
described. The use of a catalyst comprising Pd2(dba)3/XPhos allows for the stereoselective preparation of
a wide variety of substituted alkenes in high yields under mild conditions. In addition (1-ethoxyvinyl)
lithium can be efficiently converted into substituted vinyl ethers which, after hydrolysis, give readily
access to the corresponding methyl ketones in a one pot procedure.
Received 10th October 2014
Accepted 26th November 2014
DOI: 10.1039/c4sc03117b
www.rsc.org/chemicalscience
knowledge, not been reported in Pd-catalysed cross-coupling
reactions. Alkenyllithium reagents are easily accessible by
Introduction
lithium–halogen exchange or via direct metallation of the
corresponding olens without requiring purication prior to
use.11 Their high reactivity has largely prohibited the use of
these reagents in cross-coupling reactions due to the lack of
selectivity. Pioneering studies by Murahashi and co-workers
on the use of aryl and alkyllithium reagents in catalytic cross-
coupling reactions revealed the limitations associated with
their high reactivity.12,13 However, if controlled, this reactivity
might be advantageous in facilitating the transmetallation
with Pd allowing for milder reaction conditions which are
benecial to preserve the geometry of the alkene. In addition,
their use would also drastically reduce the amount of
byproducts generated with the light and non-toxic lithium
halide being the only stoichiometric waste. Therefore, the
development of a general method for the use of alke-
nyllithium reagents in catalytic cross-coupling reactions is
highly desirable.
Recently, our group reported the direct palladium cata-
lysed cross-coupling of alkyl and (hetero)aryl lithium
reagents with aryl and alkenyl (pseudo)halides, providing
high yields and selectivity.14,15 The choice of the proper
combination of catalyst and reaction conditions allows for
efficient transmetallation, prevents the notorious lithium
halogen exchange and homocoupling reactions and gives rise
to the corresponding cross-coupled products in high yields.
However, the use of alkenyllithium reagents in this trans-
formation remains elusive.
Palladium-catalysed cross-coupling of organometallic
reagents with organic halides represents one of the most
powerful methods for the construction of carbon–carbon
bonds.1 Among these, reactions employing alkenylmetal
reagents remain indispensable tools to access a broad range
of highly substituted olens and polyenes.2 With a variety of
structurally diverse, functionalized organic halides available,
the challenge of this transformation oen remains the choice
of the alkenyl nucleophile. Tin3 and boron4 reagents are
frequently used for these coupling reactions. However, the
high toxicity of organostannanes makes the Stille cross-
coupling oen less desirable. On the other hand, alkenyl
boronic acids are prone to rapid protodeboronation or poly-
merization so requiring large excess of the coupling partner.
Elegant solutions have been found via the conversion into
more stable derivates such as boronic esters, MIDA boro-
nates5 and triuoroborates.6 Organosilicon compounds
feature high stability and low toxicity although the use of
uoride anion for the activation is generally needed.7 None-
theless, non-uoride activators have recently been intro-
duced to enhance the utility of these compounds.8,2d Alkenyl
reagents for the Negishi cross-coupling (Zn, Al and Zr), have
also been used in Pd-catalysed alkenylation reactions with a
broad scope for the synthesis of dienes and polyenes.9 These
alkenyl intermediates are routinely prepared by ele-
mentometalation9 from alkynes or transmetallation from the
corresponding organolithium reagents, as is the case for
boron, tin and silicon reagents. In contrast, the direct use of
alkenyllithium compounds10 have, to the best of our
Herein, we report a palladium-based method for the direct
catalytic cross-coupling of alkenyllithium reagents and
organic halides to afford substituted alkenes in high yield
and isomeric purity under mild conditions in short reaction
times (Scheme 1).
Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG
Groningen, The Netherlands. E-mail: b.l.feringa@rug.nl; Fax: +31 50 363 4278; Tel:
+31 50 3634296
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c4sc03117b
This journal is © The Royal Society of Chemistry 2015
Chem. Sci.

View Article Online
Chemical Science
Edge Article
side product 4 (entries 2 and 3). To our delight, the use of XPhos
L3 led to the cross-coupled product 2a, in 1 h at r.t., with
excellent selectivity (>99%), avoiding dehalogenation and
inhibiting the formation of the homocoupling product (entry 4).
We also found that the air stable Pd-PEPPSI-IPent catalyst,
introduced by Organ,19 displayed good selectivity although the
presence of 4% of homocoupling was observed (entry 5).
With Pd2(dba)3/Xphos as a highly efficient catalytic system,
we set out to investigate the scope of this new reaction (Table
2)‡. A wide variety of alkenes were readily lithiated via direct
metallation or by halogen–lithium exchange as shown in
Scheme 2 (see ESI† for details).
Scheme
reagents.
1 Palladium catalysed cross-coupling of alkenyllithium
Results and discussion
The catalytic system proved to be also highly efficient in the
reaction of (3-methylbut-2-en-2-yl)lithium with 1-chlorona-
phthalene 1b at r.t. (see also ESI, Table S1†). The corresponding
Our investigation started with the reaction between (3-methyl-
but-2-en-2-yl)lithium, readily prepared from the corresponding
bromide, and 4-methoxy-bromobenzene 1a, a reluctant aryl-
bromide in many coupling reactions,16 in the presence of
various Pd-based catalytic systems using toluene as solvent
(Table 1).
Table 2 Pd-catalysed cross-coupling of alkenyllithium reagents with
aryl and alkenyl halidesa
17
The use of Pd[P(t-Bu)3]2 (Table 1, entry 1), a catalyst we
previously disclosed to be highly successful for the cross-
coupling of alkyllithium reagents with aryl bromides14a,d led to
the desired product 2a but in the presence of a large amount of
dehalogenated side product 3. We then examined the use of
Buchwald biaryl phosphine ligands18 in combination with
Pd2(dba)3 (2.5 mol%). When ligands L1 and L2 were used,
incomplete conversion was observed, along with homocoupling
Table 1 Screening of different Ligands
Entrya
[Pd]
Ligand
Conv. (%)
2a : 3 : 4b
1
2
3
4
5
Pd[P(t-Bu)3]2
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd-PEPPSI-IPent
Full
46
38
Full
Full
44 : 56 : 0
83 : 0 : 17
87 : 0 : 13
>99 : 0 : 0
96 : 0 : 4
L1, SPhos
L2, CPhos
L3, XPhos
a
Conditions: RLi (1.3 equiv.) was added to a solution of organic
bromide (0.3 mmol) and catalyst in toluene, 1 h addition time unless
otherwise noted. Selectivity 2 : 3,4 > 90%. Isolated yields aer column
chromatography. For limitations of the method see Table S3, Schemes
a
b
c
d
Conditions: (3-methylbut-2-en-2-yl)lithium (0.40 mmol, 0.6 M in THF) S2 and S3. X ¼ Cl. The reaction was performed at 40 ꢀC. 3.5 h
e
f
was added to a solution of 1a (0.3 mmol) and catalyst in toluene (1 mL), addition time. The reaction was performed at 35 ꢀC. Aer workup,
b
1 h addition time. 2a : 3 : 4 ratios determined by GC analysis. dba ¼ product mixture was treated with TBAF to remove the silyl group prior
dibenzylideneacetone.
to purication. g 0.9 mmol scale. Reaction performed at 60 ꢀC.
Chem. Sci.
This journal is © The Royal Society of Chemistry 2015

View Article Online
Edge Article
Chemical Science
such as 2-bromo-1,10-biphenyl 1p could be coupled in high yield
and without loss of selectivity. Remarkably, alkenyllithium
reagents bearing a protected alcohol functionality could also be
used, providing the corresponding allylic TBS-protected alcohol
2q, allylic alcohol 2r and homoallylic alcohol 2s in fair to good
yields with retention of the (E)-conguration. Interestingly,
compound 2q is an intermediate in the synthesis of (ꢁ)-cytox-
azone, a Novel Cytokine Modulator Isolated from Streptomyces
sp.23
We envisioned extension of this coupling to allenyllithium24
compounds, providing a synthesis of substituted allenes.25
Under the optimized reaction conditions the coupling between
(3-methylbuta-1,2-dienyl)lithium, readily available by direct
metallation of the corresponding allene, and both 4-methoxy-
bromobenzene and 2-chloronaphthalene proceeded in good
yields and high regioselectivity and with less than 5% of
regioisomeric alkyne arising from 1,3-lithium shi of the
organolithium reagent.26
Next the use of functionalized (a-alkoxyvinyl)lithium
reagents in this new cross-coupling transformation was inves-
tigated. An illustrative example is the reaction of (3,4-dihydro-
2H-pyran-6-yl)lithium, obtained by direct metallation of
commercially available dihydropyran with tBuLi.27a To our
delight, reaction with p-methyl- and p- and m-methoxy-
substituted bromoarenes provided compounds 2v, 2w and 2x in
high yields and excellent selectivity (Table 2). Due to the
reduced reactivity of this organometallic reagent, a slightly
higher temperature was required (60 ꢀC, 1 h). Nonetheless,
established methods for the cross-coupling of glycal metal
reagents require severe reaction conditions, long reaction times
or they only were examined with the corresponding aryl
iodides.27b,c
Encouraged by these results, we studied other a-alkoxyvinyl
precursor such as the cheap and simple ethyl vinyl ether (Table
3). The use of the corresponding lithium reagent, readily
obtained by direct lithiation, in the Pd-catalysed cross-coupling
reaction could be used as a masked acetylating agent giving,
aer hydrolysis, the corresponding aryl methyl ketones.27b,28
This class of carbonyl derivates serves as versatile synthetic
building blocks and are intermediates in the synthesis of drug
candidates, fragrances and heterocycles.29 We performed this
one pot transformation on larger scale (6 mmol), employing 2.5
mol% of catalyst to illustrate the synthetic utility of the method.
As shown in Table 3, the method tolerates a variety of functional
groups including acetals, ethers, amines alcohols and phenols.
Electron rich substrates bearing amine, methyl and methoxy
substituents underwent the expected coupling reaction at 40 ꢀC
in 2.5 h to give the corresponding ketones 6a–6c in good yields.
Remarkably, bromouorene was successfully employed, despite
the acidity of the benzylic protons (pKa ¼ 22). Although the
formation of 6e demonstrates that hindered substrates are
tolerated, we further validated this by coupling 9-bromoan-
thracene to give 5f in 78% yield. Facile multiple coupling is
illustrated with the two fold acetylation of 4,40-bis-bromobi-
phenyl, providing 6g in 76% yield. b-Bromo-styrene was coupled
in moderate yield, with retention of the conguration. Acetal-
protected p-bromobenzaldehyde was also tolerated in the
Scheme 2 Synthesis of alkenyllithium reagents.
tetrasubstituted alkene 2b was obtained in good yield with no
trace of the 2-substituted regioisomer, indicating that benzyne
intermediates via 1,2-elimination are not formed. To further
explore the effectiveness of this catalytic systems we studied the
more reluctant coupling partner 4-methoxy-chlorobenzene.14b
Unfortunately, low conversion was found in the reaction at
room temperature. However, the use of slightly higher
ꢀ
temperatures (40 C) and longer addition times (3.5 h) of the
organolithium reagent allowed full conversion with high
selectivity (see ESI, Table S2†). Substrate 1c, bearing an unpro-
tected hydroxyl group, could also be coupled with this organo-
lithium reagent (2.2 equiv.). The use of acetal-protected
aldehyde 1d was also tolerated without cleavage of the pro-
tecting group. The cross-coupling of (cyclohexylidenemethyl)-
lithium and 1-chloronaphthalene proceeds efficiently giving
alkene 2e in good yield. It is important to note that (E) and (Z)
alkenyl bromides 1f and 1g reacted under the optimized
conditions to give conjugated dienes 2f and 2g in good yield and
with no presence of Fritsh–Butlenberg–Wiechell type rear-
rangement side products.20 In addition, both (E) and (Z)-olens
were coupled to form dienes 2f–2h with retention of stereo-
chemistry. Illustrative is the use of (Z)-propenyllithium,
obtained by treatment of (Z)-1-bromopropene with elemental
lithium, which was smoothly coupled with retention of the
(Z)-conguration, with a variety of alkenyl and aryl bromides
providing the corresponding dienes 2h, 2i and alkenes 2j, 2k
and 2l in good yields. Synthesis of diene 2h illustrates that both
the alkenyl nucleophile and electrophile retain their geomet-
rical conguration as conrmed by 1H NMR.21 In addition, vinyl
bromide 1i reacted chemoselectively, leaving the chloride intact
and available for further functionalization. It is interesting to
note that (Z)-propenyllithium compared with the more
hindered (3-methylbut-2-en-2-yl)lithium, required higher
temperature in the coupling with 1-chloronaphthalene. This
result could be due to a faster reductive elimination taking place
from the more strained Pd(II) intermediates.22 This result is in
accordance with similar observation using less hindered
2-chloronaphthalene. (see ESI, Scheme S1†).
2-Propenyllithium underwent cross-coupling reaction with 4-
methoxy-bromobenzene and the more electron rich 4-bromo-
N,N-dimethylaniline providing styrenes 2m and 2n in good yield
without the need to increase temperature or reaction time.
Retention of the olen conguration was also observed in the
reaction of this organolithium reagent with (E)-bromostyrene 2o.
Moreover, a sterically hindered ortho-substituted arylbromide
This journal is © The Royal Society of Chemistry 2015
Chem. Sci.

View Article Online
Chemical Science
Edge Article
Table 3 Pd-catalysed cross-coupling of (1-ethoxyvinyl)lithiuma
Notes and references
‡ Representative procedure: In a dry Schlenk ask Pd2(dba)3 (2.5 mol%) and
XPhos (10 mol%) were dissolved in toluene (2 mL/0.3 mmol of substrate) and the
solution was stirred under nitrogen atmosphere at room temperature for 5 min.
The substrate (1 equiv.) was added and the solution stirred at the indicated
temperature. The corresponding lithium reagent solution (1.3 equiv., 0.6 or 0.68
M, see ESI† for details) was slowly added over 1 h by the use of a syringe pump.
Aer the addition was completed a saturated solution of aqueous NH4Cl was
added and the mixture was extracted with Et2O or AcOEt. The organic phases were
combined and dried with anhydrous Na2SO4. Evaporation of the solvent under
reduced pressure afforded the crude product that was then puried by column
chromatography.
1 (a) Metal-Catalysed Cross-Coupling Reactions, ed. A. de
Meijere and F. Diederich, Wiley-VCH, Weinheim, 2nd edn,
2004; (b) Transition Metals for Organic Synthesis, ed. M.
Beller and C. Bolm, Wiley-VCH, Weinheim, 2nd edn, 2004;
(c) Handbook of Organopalladium Chemistry for Organic
Synthesis, ed. E.-I. Negishi, Wiley-Interscience, New York,
2002; (d) Topics in Organometallic Chemistry: Palladium in
Organic Synthesis, ed. J. Tsuji, Springer, New York, 2005; (e)
C. C. C. Johansson Seechurn, M. O. Kitching, T. J. Colacot
and V. Snieckus, Angew. Chem., Int. Ed., 2012, 51, 5062; (f)
X.-F. Wu, P. Anbarasan, H. Neumann and M. Beller, Angew.
Chem., Int. Ed., 2010, 49, 9047.
a
Conditions: 3.0–6.0 mmol scale reaction. Aryl bromide (1 equiv.), (1-
ethoxyvinyl)lithium (1.5 equiv., 0.60 M in THF). 2.5 h addition time.
Toluene at 40 ꢀC. Selectivity >90%. Yield values refer to isolated yields
b
c
d
aer purication. 70% conversion. 80% selectivity. iPrMgCl (1.0
equiv., 2 M in Et2O) was added over 5 min prior to the organolithium.
2 (a) Science of synthesis, ed. G. Molander, J. P. Wolfe and M.
Larhed, Thieme, 2013; (b) S. E. Kelly,in Comprehensive
Organic Synthesis, ed. B. M. Trost and I. Fleming,
Pergamon, Oxford, 1991, pp. 729–817; (c) Preparation of
Alkenes, ed. J. M. J. Williams, Oxford University, Oxford,
1996; (d) S. E. Denmark and C. R. Butler, Chem. Commun.,
2009, 20.
3 (a) A. Suzuki, Angew. Chem., Int. Ed., 2011, 50, 6723; (b) L. Yin
and J. Liebscher, Chem. Rev., 2007, 107, 133; (c) J. P. Corbet
and G. Mignani, Chem. Rev., 2006, 106, 2651; (d) Boronic
Acids, ed. D. G. Hall, Wiley-VCH, Weinheim, 2005; (e)
N. E. Leadbeater, Chem. Commun., 2005, 2881.
4 (a) P. Espinet and A. M. Echavarren, Angew. Chem., Int. Ed.,
2004, 43, 4704; (b) A. F. Littke, L. Schwartz and G. C. Fu, J.
Am. Chem. Soc., 2002, 124, 6343; (c) J. K. Stille, Angew.
Chem., Int. Ed., 1986, 25, 508.
5 (a) E. P. Gillis and M. D. Burke, J. Am. Chem. Soc., 2007, 129,
6716; (b) E. P. Gillis and M. D. Burke, Aldrichimica Acta, 2009,
42, 17; (c) E. M. Woerly, J. Roy and M. D. Burke, Nat. Chem.,
2014, 6, 484.
reaction affording, aer subsequent hydrolysis, 4-acetyl-
benzaldehyde 6i in excellent yield. Alcohols and phenols as Mg
alkoxides are tolerated in this method to afford 6j and 6k. It
should be noted that same of the compounds obtained such as
6a, 6d, 6e, 6i, or 6j would be challenging to synthesize through
standard Friedel–Cras acylation chemistry.30
Conclusions
In summary, a fast and selective method has been developed for
the Pd-catalysed alkenylation of aryl and alkenylhalides using
organolithium reagents. This transformation leads to highly
substituted alkenes under mild conditions and shows tolerance
to various functional groups. Moreover, we describe the one pot
synthesis of aryl methyl ketones involving coupling of lithiated
alkenyl ethers.
6 (a) G. A. Molander, T. Barcellos and K. M. Traister, Org. Lett.,
´
2013, 15, 3342; (b) E. Alacid and C. Najera, J. Org. Chem.,
2009, 74, 8191; (c) G. A. Molander and L. A. Felix, J. Org.
Chem., 2005, 70, 3950; (d) G. A. Molander and
C. R. Bernardi, J. Org. Chem., 2002, 67, 8424; (e)
G. A. Molander and M. R. Rivero, Org. Lett., 2002, 4, 107.
7 (a) T. Hiyama and Y. Nakao, Chem. Soc. Rev., 2011, 40, 4893;
(b) S. Bracegirdle and E. A. Anderson, Chem. Soc. Rev., 2010,
39, 4114.
8 (a) S. E. Denmark and C. S. Regens, Acc. Chem. Res., 2008, 41,
1486; (b) S. E. Denmark and C. S. Regens, Acc. Chem. Res.,
2012, 45, 864.
Acknowledgements
The Netherlands Organization for Scientic Research
(NWO-CW), the National Research School Catalysis
(NRSC-C), the European Research Council (ERC advanced
grant 227897 to BLF), the Royal Netherland Academy of Arts
and Sciences (KNAW) and the Ministry of Education Culture
and Science (Gravitation program 024.601035) are acknowl-
edged for nancial support. C.V. was supported by Intra-
European Marie Curie fellowship (FP7-PEOPLE-2011-IEF-
300826).
Chem. Sci.
This journal is © The Royal Society of Chemistry 2015

View Article Online
Edge Article
Chemical Science
9 (a) G. Wang, S. Mohan and E.-I. Negishi, Proc. Natl. Acad. Sci. 15 For highlights of the use of organolithium reagents in cross-
U. S. A., 2011, 108, 11344; (b) E.-I. Negishi, Q. Hu, Z. Huang,
M. Qian and G. Wang, Aldrichimica Acta, 2005, 38, 71; (c)
coupling, see: (a) V. Pace and R. Luisi, ChemCatChem, 2014,
6, 1516; (b) V. Capriati, F. M. Perna and A. Salomone, Dalton
Trans., 2014, 43, 14204.
´
R. Alvarez, B. Vaz, H. Gronemeyer and A. R. de Lera, Chem.
Rev., 2014, 114, 1.
10 The use of organolithium and their subsequent
16 S. E. Denmark, R. C. Smith, W. T Tau and J. M. Muhuhi, J.
Am. Chem. Soc., 2009, 131, 3104.
transmetallation to soer organometallics to use in cross- 17 G. C. Fu, Acc. Chem. Res., 2008, 41, 1555.
coupling is well established: (a) E. J. Anctil and 18 R. Martin and S. L. Buchwald, Acc. Chem. Res., 2008, 41, 1461.
V. Snieckus, in Metal Catalysed Cross-Coupling Reactions, 19 C. Valente, S. Calimsiz, K. H. Hoi, D. Mallik, M. Sayah and
ed. A. de Meijere and F. Diederich, Wiley-VCH, Weinheim,
M. G. Organ, Angew. Chem., Int. Ed., 2012, 51, 3314.
2004, vol. 1, pp. 761–813; (b) J. Board, J. L. Cosman, 20 H. Rezaei, S. Yamanoi, F. Chemla and J. F. Normant, Org.
T. Rantanen, S. P. Singh and V. Snieckus, Platinum Met.
Rev., 2013, 57, 234.
Lett., 2010, 2, 419.
21 The E–Z geometry of both the alkenyllithium reagents and
alkenyl halides is fully preserved; the product geometry
11 (a) Lithium Compounds in Organic Synthesis, ed. R. Luisi and
V. Capriati, Wiley-VCH, Weinheim, 2014; (b) The Chemistry of
Organolithium Compounds, ed. Z. Rappoport and I. Marek,
Wiley-VCH, Weinheim, 2004; (c) V. Snieckus, Chem. Rev.,
1990, 90, 879.
1
was unequivocally established by H NMR analysis and by
comparison of the geometrical isomers with known
compounds in the literature.
22 J. F. Hartwig, Inorg. Chem., 2007, 46, 1936.
12 (a) S. Murahashi, M. Yamamura, K. Yanagisawa, N. Mita and 23 M. Seki and K. Mori, Eur. J. Org. Chem., 1999, 2965.
K. Kondo, J. Org. Chem., 1979, 44, 2408; (b) S. Murahashi, J. 24 T. Jeffery-Luong and G. Linstrumelle, Synthesis, 1982, 738.
Organomet. Chem., 2002, 653, 27.
25 (a) Modern Allene Chemistry, ed. N. Krause and A. S. K.
Hashmi, Wiley-VCH, Weinheim, 2004, vol. 1 and 2; (b) For
the use of allenyl metal reagents in cross-coupling
13 For recent approaches to the indirect cross-coupling of
organolithium reagents see: (a) A. B. Smith III, A. T. Hoye,
D. Martinez-Solorio, W. Kim and R. Tong, J. Am. Chem.
Soc., 2012, 51, 4533; (b) D. Martinez-Solorio, A. T. Hoye,
¨
reactions see: K. Radkowski, G. Seidel and A. Furstner,
Chem. Lett., 2011, 40, 950 and references cited therein.
M. H. Nguyen and A. B. Smith III, Org. Lett., 2013, 15, 26 Unfortunately, mixtures of propargyl/1,2-allenyl species were
2454; (c) M. H. Nguyen and A. B. Smith III, Org. Lett., 2014,
16, 2070, For an use of ow-chemistry technology for the
observed when other allenyl lithium reagents or substrates
were used (see ESI, Scheme S3†).
Pd-catalysed cross-coupling with lithium reagents see: (d) 27 (a) J. A. Soderquist and G. J.-H. Hsu, Organometallics, 1982, 1,
A. Nagaki, A. Kenmoku, Y. Moriwaki, A. Hayashi and
J. Yoshida, Angew. Chem., Int. Ed., 2010, 49, 7543.
830; (b) U. Lehmann, S. Awasthi and T. Minehan, Org. Lett.,
2003, 5, 2405; (c) S. E. Denmark and L. Neuville, Org. Lett.,
2000, 2, 3221.
˜
´
14 (a) M. Giannerini, M. Fananas-Mastral and B. L. Feringa,
Nat. Chem., 2013, 5, 667; (b) V. Hornillos, M. Giannerini, 28 (a) M. Kosugi, T. Sumiya, Y. Obara, M. Suzuki, H. Sano and
˜
´
C. Vila, M. Fananas-Mastral and B. L. Feringa, Org. Lett.,
T. Migita, Bull. Chem. Soc. Jpn., 1987, 60, 767; (b)
H. B. Kwon, B. H. McKee and J. K. Stille, J. Org. Chem.,
1990, 55, 3114; (c) C. E. Russell and L. S. Hegedus, J. Am.
Chem. Soc., 1983, 105, 6943.
2013, 15, 5114; (c) M. Giannerini, V. Hornillos, C. Vila,
M. Fananas-Mastral and B. L. Feringa, Angew. Chem., Int.
Ed., 2013, 52, 13329; (d) C. Vila, M. Giannerini,
˜
´
˜
´
V. Hornillos, M. Fananas-Mastral and B. L. Feringa, Chem. 29 H. Siegel and M. Eggersdorf, Ketones, Ullmann's
Sci., 2014, 5, 1361; (e) C. Vila, V. Hornillos, M. Giannerini,
Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag
GmbH, Germany, 2000, pp. 187–207.
30 S. D. Ramgren and N. K. Garg, Org. Lett., 2014, 16, 824 and
references cited therein.
˜
´
M. Fananas-Mastral and B. L. Feringa, Chem.–Eur. J., 2014,
20, 13078.
This journal is © The Royal Society of Chemistry 2015
Chem. Sci.