Visible Light-Induced Room-Temperature Heck Reaction of Functionalized Alkyl Halides with Vinyl Arenes/Heteroarenes

Article abstract of DOI:10.1002/anie.201706554

The first visible light-induced Pd-catalyzed Heck reaction of α-heteroatom substituted alkyl iodides and -bromides with vinyl arenes/heteroarenes has been developed. This transformation efficiently proceeds at room temperature and enables synthesis of valuable functionalized allylic systems, such as allylic silanes, boronates, germanes, stannanes, pivalates, phosphonates, phthalimides, and tosylates from the corresponding α-substituted methyl iodides. Notably, synthesis of the latter substrates failed under existing thermally induced Pd-catalyzed conditions, which highlights the importance of visible light for this transformation.

Full text of DOI:10.1002/anie.201706554

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Accepted Article
Title: Visible Light-Induced Room Temperature Heck Reaction of
Functionalized Alkyl Halides with Vinyl Arenes/Heteroarenes
Authors: Vladimir Gevorgyan, Daria Kurandina, and Marvin Parasram
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10.1002/anie.201706554
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Visible Light-Induced Room Temperature Heck Reaction of
Functionalized Alkyl Halides with Vinyl Arenes/Heteroarenes
Daria Kurandina, Marvin Parasram, and Vladimir Gevorgyan*
Abstract: The first visible light-induced Pd-catalyzed Heck reaction
of α-heteroatom substituted alkyl iodides and -bromides with vinyl
arenes/heteroarenes has been developed. This transformation
efficiently proceeds at room temperature and enables synthesis of
valuable functionalized allylic systems, such as allylic silanes, -
boronates, -germanes, -stannanes, -pivalates, -phosphonates, -
phthalimides, and -tosylates from the corresponding α-substituted
methyl iodides. Notably, synthesis of the latter substrates failed
under existing thermally induced Pd-catalyzed conditions, which
highlights the importance of visible light for this transformation.
Scheme 1. Palladium-catalyzed alkyl-Heck reactions.
a. Intramolecular alkyl-Heck reaction
b. Intermolecular alkyl-Heck reaction
Pd-cat.
100oC
Alk
Alk
X
Pd-cat.
R
R
X
R
R
65-110 o
C
X = I: Alexanian, 2014
X = I, Br, Cl: Zhou, 2014
X = I, Br, Cl
Fu, 2007
Alexanian, 2011
This work
c. Visible light-induced room temperature Heck reaction of heteroatom-substituted alkyl halides
Pd-cat.
G
Hal
G
C-
Ar/Het
G
Ar/Het
rt, blue LED
N-, O-, P-, S-
B-, Si-, Ge-, Sn-
• ambient temperature
The Mizoroki-Heck reaction is
a
fundamental synthetic
• broad scope of functionalizable allylic synthons
• exogenous photosensitizer free
transformation that enables coupling of aryl and vinyl
halides/pseudohalides with alkenes.[1] Recently, unactivated
alkyl halides were found to be competent substrates for both
intra- (Scheme 1, a) and intermolecular (Scheme 1, b) versions
of this reaction. In his seminal work, Fu reported that
employment of bulky NHC ligands promotes the intramolecular
reaction of unactivated alkyl bromides and chlorides operating
via classical Heck mechanism.[2] Later, in 2012, Alexanian
introduced the first intramolecular alkyl Heck reaction of
unactivated alkyl iodides, which occurred via formation of alkyl
hybrid Pd-radical intermediates.[3,4] Very recently, Alexianan and
Table 1: Optimization of the reaction conditions.[a]
catalyst (10 mol%)
ligand (20 mol%)
PPh2
Me Me
TMS
I
Fe
TMS
1a
2a
3 equiv Cs2CO3
O
3aa
P(R)2
conditions, PhH, 12 h
PPh2
PPh2
R = t-Bu : L
R = Ph : dppf
Xantphos
yield,[b]
%
(E:Z)
traces
35(5:1)
#
catalyst
ligand
base
cond.
1[c]
2[c]
3[d]
4[e]
5
Pd(OAc)2
Pd(dppf)Cl2
Pd(PPh3)2Cl2
(5 mol%)
Pd(PPh3)4
(35 mol%)
L
-
iPr2NEt
Cy2NMe
120 oC
100 oC
100 oC
Zhou independently reported an intermolecular version of this
[3b, 5]
reaction.
Although these methods are highly innovative,
Xantphos
(10 mol%)
Cs2CO3
K2CO3
0
challenges still remain. Currently, alkyl Heck reaction has been
established for unactivated,[3,5] activated (possessing carbonyl
group and equivalents at the β-position),[6] and perfluorinated[7]
alkyl halide coupling partners. However, employment of α-
heteroatom-substituted alkyl electrophiles toward synthesis of
valuable allylic systems (vide infra) is unknown. Moreover, most
alkyl Heck methods proceed at high temperatures, which often
results in coupling products with low stereoselectivity.[5] Evidently,
development of an alkyl Heck reaction that would feature milder
reaction conditions and broader substrate scope are highly
warranted. Herein, we report the first example of a visible light-
induced, exogenous photosensitizer free[8] room temperature
intermolecular Pd-catalyzed Heck reaction of α-heteroatom
substituted electrophiles, such as silyl-, germyl-, tosyl-,
phosphonyl-, phthalimidyl-, pinacolboronyl-, stannyl-, and
pivaloyl methyl halides, with vinyl arenes/heteroarenes. This
protocol allows for a facile and efficient formation of valuable
diversely functionalized allylic synthons with high stereocontrol
(Scheme 1, c).
-
-
100 oC
10 (1:0)
35(56[f])
(30:1)
traces
traces
traces
Pd(PPh3)4
Cs2CO3
rt, blue LED
6
7
8
Pd(dppf)Cl2
Pd(OAc)2
Pd(OAc)2
-
dppf
L
Cy2NMe
iPr2NEt
iPr2NEt
rt, blue LED
rt, blue LED
rt, blue LED
85
9
Pd(OAc)2
Xantphos
Cs2CO3
rt, blue LED
(49:1)
10
11
12
Pd(OAc)2
Pd(OAc)2
-
Xantphos
Xantphos
Xantphos
Cs2CO3
Cs2CO3
Cs2CO3
Up to 110 oC
rt, dark
traces
traces
0
rt, blue LED
[a] Standard conditions: 1a 0.1 mmol scale, PhH 0.25 M, 120 °C or 34W blue
LED; [b] GC-MS yield and ratio; [c] PhCF3 as solvent; [d] DCE as solvent; [e]
PhMe as solvent; [f] THF as solvent.
Development of an intermolecular version of this reaction would
be of synthetic interest, as it would provide facile access to
valuable
cinnamyl
silanes.[10]
Thus,
reaction
of
iodomethyltrimethyl silane 1a and styrene 2a was tested (Table
1). However, employment of our previously developed reaction
conditions provided only traces of allylic silane 3aa (entry 1).
Next, various reaction conditions, reported for the Pd-catalyzed
alkyl Heck reactions by Alexanian[3](entry 2), Zhang[7a](entry 3),
and Reutrakul[7c](entry 4), were tested, however, low yields and
poor stereoselectivity of 3aa were obtained. Apparently, other
means of activation were required to promote this transformation.
Our recent work[11] and reports from other groups[12] have
illustrated the beneficial effect of visible light on TM-catalyzed
transformations. Indeed, we were pleased to find that 35% yield
of coupling adduct 3aa was obtained under visible light
irradiation (blue LED) at room temperature in the presence of
Aiming at the development of α-heteroatom substituted alkyl
Heck reaction, we commenced our studies with iodomethyl silyl
electrophiles. We have previously reported the Pd-catalyzed
endo-selective alkyl Heck reaction featuring this moiety.[9]
[*]
D. Kurandina, M. Parasram, and V. Gevorgyan
Department of Chemistry, University of Illinois at Chicago, 845 West
Taylor Street, Chicago, Illinois 60607-7061, United States
E-mail: vlad@uic.edu.
ORCID: orcid.org/0000-0002-7836-7596
Supporting information for this article is given via a link at the end of
the document.
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10.1002/anie.201706554
Angewandte Chemie International Edition
COMMUNICATION
Pd(PPh3)4 catalyst (entry 5). Testing other catalyst/ligand
combinations, such as Pd(dppf)Cl2, and Pd(OAc)2 with dppf or L
under photoirradiation were less efficient (entries 6-8).
Delightfully, employment of Pd(OAc)2 and Xantphos catalytic
system delivered 85% of 3aa with excellent stereoselectivity
(entry 9). It should be mentioned that attempts on promoting the
reaction by thermal means were ineffective (entry 10). Also,
control experiments indicated that both light and the Pd-catalyst
are essential for this transformation (entries 11,12).
order to determine if visible light can provide any beneficial
effects for established thermally induced alkyl Heck reactions,[3,5]
known alkyl electrophiles 1m-o possessing β-hydrogens were
Table 2: Scope of alkenes.[a]
10 mol% Pd(OAc)2
20 mol% XantPhos
R
R
3 equiv Cs2CO3
I(Br)
Si
Ar/Het
2a-n
Si
Ar/Het
PhH, rt, Blue LED, 12 h
1a
3a-n
OMe
TMS
TMS
TMS
With the optimized reaction conditions in hand, the generality
of this transformation with respect to the alkene component was
investigated (Table 2). Reactions of 1a with styrene derivatives
(2),[13] possessing both electron-withdrawing and electron-
donating groups at the para-position were found to be highly
efficient (3aa-3af). Remarkably, this transformation is not only
limited to alkyl iodides, as bromo-analogue of 1a (X=Br) also
participated in this reaction. It was also found that not only
halomethyltrimethylsilanes (1a), but also its synthetically more
N
R
3ag, 83%
Me
3ak, 59%
R = H, 3aa, X = I, 88%
X = Br, 55%
TMS
N
R = OMe, 3ab, 82%
R = F, 3ac, 73%
TMS
TMS
3al, 71%
3ah, 72%
Ph
R = CN, 3ad, 80%
R = CO2Me, 3ae, 89%[b]
R = Br, 3af, 59%
TMS
N
OMe
Ph
3ai, 80%[b]
3am, 84%
Si
O
appealing analogs, such as trialkoxysilyl-[14] (1b) and
–
silatranyl[15] (1c) derivatives, reacted well producing allylic
silanes (3ba, 3ca) in reasonable yields. Styrenes containing
substituents at either the meta- or ortho-positions reacted well,
affording products 3ag and 3ah in 83% and 72% yield,
Si = Si(OEt)3, 3ba, 65%
H
TMS
O
O
S
H
H
, 3ca, 62%
Si =
Si
N
3aj, 58%[b]
TMS
O
3an, 81%
respectively. Notably, 1,1-diphenylethylene,
a
challenging
[a] Standard Conditions I: 1a 0.75 mmol, 2 0.5 mmol, Pd(OAc)2 0.05 mmol,
Xantphos 0.1 mmol, Cs2CO3 1.5 mmol, PhH 0.25 M, 34W blue LED, rt. [b]
Pd(OAc)2 (2 mol%) and Xantphos (4 mol%) was added to the reaction mixture
after 12 h, and the reaction was stirred for additional 6 h.
coupling partner for a related silyl-Heck reaction,[10] reacted
smoothly with 1a to produce 3ai in high yield. Next, this
methodology toward reaction of vinyl heteroarenes was
examined. Coupling 1a with 3-vinylbenzothiophene 3j, and p-
and m-vinyl pyridines (3ak, 3al) proceeded uneventfully,
producing the corresponding products in good yields (3ak-3al).
Finally, reaction of 1a with vinyl derivative of estrone 2n
generated product 3an in 81% yield, highlighting the applicability
of this visible light-induced Heck reaction protocol in complex
settings.
Table 3: Scope of alkyl iodides.[a,b]
10 mol%
Xantphos Pd G3
2 equiv iPr2NEt
10 mol% Pd(OAc)2
20 mol% Xantphos
3 equiv Cs2CO3
or
conditions I [a]
conditions II [b]
G
Ar/Het
I(Br)
1b-k
Ar/Het
G
PhH, rt, Blue LED, 12 h
3
2
G
(EtO)2(O)P
N
(EtO)3Si
Naturally, after developing this silyl methyl Heck reaction, we
were eager to verify if this novel visible light-induced protocol is
efficient for other α-heteroatom substituted methyl iodides, which,
if successful, would provide expeditious access to valuable
diversely functionalized allylic systems (Table 3). Accordingly,
reactions of pinacolboronyl- (1d), trialkylstannyl- (1e),
phthalimidyl- (1f), pivaloyl- (1g), phosphonyl- (1h), tosyl- (1i),
and germyl- (1j) methyl iodides with 2a were tested. To our
delight, all of these systems reacted efficiently, leading to
privileged cinnamyl derivatives in good yields (3da-3ja).
Moreover, bromo-analogues of 1d, 1f, and 1i (PhSO2CH2Br)
were found to be competent coupling partners for this
transformation. Coupling of electronically different vinyl arenes
and heteroarenes, with selected α-heteroatom substituted
methyl iodides all proceeded in a highly efficient manner (3fc,
3dd, 3ig, 3bb, 3hm, 3ho). Excitingly, reaction of 2a with α,α-
disubstituted methyl iodides possessing two trimethylsilyl groups
(1j), as well as unsymmetrically disubstituted substrate
possessing pinacolboronyl and dimethylphenyl silyl moieties (1k),
proceeded well, producing dually functionalizable allylic systems
3ja and 3ka in 97% and 90% yields, respectively.
N
Me
OMe
G = BPin, 3da, X = I, 70%[b,c]
X = Br, 80%[b,c]
G = SnBu3, 3ea, 71%[d]
G = NPhthl, 3fa, X = I, 72%[b]
X = Br, 59%[b,c]
G = OPiv, 3ga, 76%[d,e]
G = P(O)(OEt)2, 3ha, 58%[a]
G = Ts, 3ia, 61%[a] X = Br, 39%[b,c,f]
G = GeMe3, 3ja, 68%[a]
3ho, 53%[a]
3bb, 64%[a]
PhthlN
t-Bu
F
3fc, 56%[b]
3ma, 87%[a]
(74%, 6:1)[5]
OMe
Ts
n-Oct
3ig, 80%[a]
TMS
3na, 79%[a]
(74%, 8:1)[5]
TMS
(EtO)2(O)P
3hm, 77%[a]
3ka, 97%
(E:Z = 10:1)
N
OMe
BPin
BPin
3dd, 78%[b,c]
3oa, 76%[a]
(84%)[3b], (78%)[5]
Me2PhSi
3la, 90%[a]
CN
[a] Standard Conditions I: 1a 0.75 mmol, 2 0.5 mmol, Pd(OAc)2 0.05 mmol,
XantPhos 0.1 mmol, Cs2CO3 1.5 mmol, PhH 0.25 M, 34W blue LED, rt,
isolated yields; [b] Standard Conditions II: 1a 0.75 mmol,
2 0.5 mmol,
Xantphos Pd G3 0.05 mmol, iPr2NEt 1 mmol, PhH 0.25 M, 34W blue LED, rt,
isolated yields; [c] NMR yield; [d] 0.25 mmol scale, 1a 1 equiv, 2a 4 equiv,
Cs2CO3 6 equiv and PhH 0.0625 M, isolated yields; [e] The reaction requires 2
h for completion. [f] PhSO2CH2Br was used.
It deserves mentioning that α-heteroatom-substituted alkyl
iodides, due to the lack of β-hydrogens, are seemingly “easy”
substrates for an alkyl-Heck reaction. However, they showed
much lower efficiency under reported thermal conditions.[16] In
tested under our reaction conditions (Table 3). Remarkably, it
was found that coupling of 1m-o and styrene 2a provided Heck
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10.1002/anie.201706554
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products 3ma-3oa in yields comparable to these obtained under
the previously reported thermal conditions,[3,5] however with
superior stereocontrol (3ma-3na)! The observed phenomenon
can be attributed to the milder reaction conditions of our method
(room temperature), where a thermally-induced isomerization of
the reaction products did not occur.[1,3,5]
The obtained diverse cinnamyl products (3) are useful
synthetic intermediates,[17-23] widely used as reactive substrates
toward further functionalization. However, depending on the
nature of the cinnamyl products (possessing nucleophilic or
electrophilic group G), methods toward these synthons involve
different synthetic routes and starting materials. Conversely, our
approach offers an attractive general method toward accessing
these important fragments. Thus, after establishing the reaction
scope, the synthetic applications of selected cinnamyl products
2 produces radical intermediate C. A subsequent β –H-
elimination from the latter delivers allylic product 3 and closes
the catalytic cycle. The radical nature of this transformation was
confirmed by employment of radical traps[24] and radical clock[25]
studies (Scheme 4). Thus, subjecting TEMPO to the reaction of
1a and 2a resulted in 42% NMR yield of TEMPO-trapped adduct
12 (Scheme 4, a). Next, reaction 1a with a radical clock 13
resulted in regioselective radical-ring opening of the cyclopropyl
unit 14 in 59% as a mixture of stereoisomers. Formation of a
product of Pd-β-C elimination[26] of the cyclopropane component
(15), or the coupling adduct possessing an intact cyclopropane
unit (16), was not detected (Scheme 4, b).
Scheme 3. Plausible reaction mechanism.
Pd(0)Ln
were tested (Scheme 2).
A
sequential one-pot Heck
hν (450 nm)
reaction/oxidation procedure of 1g with 2i generated allylic
alcohol 4 in good overall yield. Similarly, a one-pot reaction of 1g
with 2a, followed by allylation of 4-nitrobenzenaldehyde
I
G
B HI
*
Pd(0)Ln
1
A
B
SET
Scheme 2. Performed and reported transformations of obtained products.
HPd(II)I
Pd(I)I
G
B
D
OH
Ar
Me
Ar
O
G
Ar
2
Ph
Ph
3
Pd(I)I
Ar
BPin
Ar = p-NO2C6H4
5, 51%
Ph
Me
HO
G
Ph
C
6, 55%
4, 60%
At this stage, the origins of the visible light induction of this
transformation are not fully understood. In 2009, Köhler studied
an accelerating effect of visible light on classical thermal Heck
reaction of aryl halides. In his studies,[27] the observed visible
light acceleration effect was solely attributed to the facilitation of
the initial off-cycle reduction step of the pre-catalyst Pd(II) into
a
b
c
Ph
G = B
G=B
3da
G=SiCH(B)
3la
3di
Ts
N
G=N
3fc
R
ref 22b
SO2Ar
G
Ph
G = S,
ref 23a
3
3ia
11
7
G=Sn,
3ea
G = P, 3ha
ref 21a
F
G=O,
3ga
ref 20a
the active Pd(0) species. To test this possibility, Pd(II)OAc2 was
[16]
ref 19a
O
replaced with Pd(0) pre-catalyst, such as Pd2dba3
This
Br
Me
N
P(OEt)2
Ph
resulted in comparable efficiency of the reaction compared to
that in the presence of Pd(II)OAc2, thus, disfavoring this
scenario[27] for our visible light-induced Pd-catalyzed alkyl Heck
reaction. Therefore, it is likely that visible light promotes photo
excitation of the formed Pd(0) catalyst (Scheme 3, complex
F
8
BnO2C
10
HO Me
Ph
Ph
9
Conditions: a) One-pot reaction: 1) Xantphos Pd G3 (10 mol%), N(i-Pr)2Et (2.2
equiv), 1g (1.5 equiv), 2i (1 equiv), PhH, blue LED, rt, 12 h. 2) 30% H2O2, THF,
rt; b) One-pot reaction: 1) Xantphos Pd G3 (10 mol%), N(i-Pr)2Et (2.2 equiv),
1g (1.5 equiv), 2a (1 equiv), PhH, blue LED, rt, 12 h. 2) 4-Nitrobenzaldehyde
(2 equiv), diphenyl phosphate (2 equiv), PhH, rt, 12 h; c) 3ka (1 equiv), 1,1-
dimethoxyethane (1.03 equiv), TiCl4 (1.2 equiv), DCM, -78 °C, 15 min.
Scheme 4. Initial mechanistic studies
TEMPO
1 equiv
N
3aa
TMS
I
(a)
TMS
O
12
Conditions I
PhH, rt
blue LED, 12h
1a
2a
0%
42% (NMR yield)
Ph
furnished 5 in good yield and high diastereoselectivity. Finally,
Hosomi-Sakurai reaction of dually functionalizable 3ka with 1,1’-
dimethoxyethane resulted in the selective formation of vinyl
boronic ester 6 in respectable yield. Other nucleophilic synthons
such as 3fa and 3ha-ia, as well as electrophilic allylic systems
3da-ea, have been extensively featured in numerous reported
synthetic transformations[17-23] (Scheme 2, 3→7-11).
Ph
radical path
TMS
59%
Ph
14
Ph
Me
Conditions I
PhH, rt
blue LED, 12h
Ph
Pd-β-carbon
elimination
path
TMS
I
1a
(b)
TMS
13
Ph
not observed 15
Ph
classical
Heck
Ph
TMS
not observed 16
Based on the literature precedents on Heck reactions of alkyl
iodides, a hybrid-Pd radical mechanism is proposed for this
transformation (Scheme 3).[3,4,5,9] First, the active Pd(0) complex
A is formed via an in situ reduction of Pd(II)OAc2. Then, complex
A undergoes an SET with alkyl halide 1 to generate the putative
Pd(I) species and alkyl radical B. Addition of the latter to alkene
A),[29] which consequently undergoes SET with 1 and thus
triggers the catalytic cycle. The control experiments including
reactions performed in dark (Table 1, entry 11), light on/off
tests,[28] UV/vis analysis of Pd(0) species,[29] as well as Stern-
Volmer studies,[30] are in agreement with this mechanistic
scenario.[16]
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10.1002/anie.201706554
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COMMUNICATION
N. Primer, M. Jouffroy, N. R. Patel, G. A. Molander, Acc. Chem. Res.
2016, 49, 1429; m) K. L. Skubi, T. R. Blum, T. P. Yoon, Chem. Rev.
2016, 116, 10035.
In conclusion, we developed the first visible light-induced Pd-
catalyzed room temperature Heck reaction of α-functionalized
alkyl halides with vinyl arenes and heteroarenes leading to
synthetically valuable allylic systems. Importantly, synthesis of
these privileged synthons by reported thermal Heck protocols
was ineffective, thus highlighting the benefits of employing
visible light for this transformation. In addition, for unactivated
alkyl halides, the obtained products were formed with higher
stereoselectivity compared to the established thermally-induced
methods.
[9] M. Parasram, V. O. Iaroshenko, V. Gevorgyan, J. Am. Chem. Soc. 2014,
136, 17926.
[10] For Watson’s pioneering work on the silyl Heck reactions toward allylic
silanes, see: a) J. R. McAtee, S. E. S. Martin, D. T. Ahneman, K. A.
Johnson, D. A. Watson, Angew. Chem. Int. Ed. 2012, 51, 3663; Angew.
Chem. 2012, 124, 3723; b) J. R. McAtee, G. P. A. Yap, D. A. Watson, J.
Am. Chem. Soc. 2014, 136, 10166.
[11] M. Parasram, P. Chuentragool, D. Sarkar, V. Gevorgyan, J. Am. Chem.
Soc. 2016, 138, 6340.
[12] For a review on visible light-induced TM-catalyzed transformations, see:
M. Parasram, V. Gevorgyan, Chem. Soc. Rev. 2017, DOI:
10.1039/C7CS00226B.
Acknowledgements
[13] Employment of electron rich alkenes, such as aliphatic alkenes and vinyl
ethers, were not compatible with our transformation.
We thank National Institutes of Health (GM120281) and National
Science Foundation (CHE-1663779) for financial support of this
work. We also thank Ms. Yana McAuliff and Dr. Yang Wang for
technical help and assistance during the preparation of this
manuscript, and Mr. Stefan Ilic and Professor Ksenija Glusac for
their guidance and assistance with photophysical studies.
[14] For synthetic usefulness of trialkoxysilyl systems, see a) K. Tamao, K.
Kobayashi, Y. Ito, Tetrahedron Lett. 1989, 30, 6051; b) S. E. Denmark, J.
H. C. Liu, Angew. Chem. Int. Ed. 2010, 49, 2978; Angew. Chem. 2010,
122, 3040; c) C. J. Handy, A. S. Manoso, W. T. McElroy, W. M.
Seganish, P. DeShong, Tetrahedron 2005, 61, 12201; d) T. Komiyama,
Y. Minami, T. Hiyama, ACS Catal. 2017, 7, 631. For a review, see: e) H.
F. Sore, W. R. J. D. Galloway, D. R. Spring, Chem. Soc. Rev. 2012, 41,
1845;
Keywords: Heck reaction • Visible light • Alkyl Radical •
[15] For a review on the chemistry of silatranes, see: J. K. Puri, R. Singh, V.
K. Chahal, Chem. Soc. Rev. 2011, 40, 1791.
Palladium
[16] See Supporting Information for details.
[1] M. Oestreich. The Mizoroki-Heck Reaction; John Wiley & Sons: West
Sussex, U.K., 2009.
[17] For selected examples of reactions using cinnamyl silanes, see: a) H.
Sakurai, Synlett 1989, 1989, 1; b) J. W. J. Kennedy, D. G. Hall, Angew.
Chem. Int. Ed. 2003, 42, 4732; Angew. Chem. 2003, 115, 4880; c) M.
Yasuda, T. Saito, M. Ueba, A. Baba, Angew. Chem. Int. Ed. 2004, 43,
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Entry for the Table of Contents
COMMUNICATION
The first room temperature visible
light-induced Pd-catalyzed Heck
reaction of α-heteroatom substituted
alkyl halides with vinyl
Daria Kurandina, Marvin Parasram, and
Vladimir Gevorgyan*
Pd-cat.
G
Ar/Het
Hal
G
Ar/Het
Page No. – Page No.
rt, blue LED
G
arenes/heteroarenes is reported. This
transformation enables synthesis of
valuable functionalized allylic systems,
such as allylic silanes, -boronates,
-germanes, stannanes, -pivalates,
-phosphonates, -phthalimides, and
-tosylates, from the corresponding
α−substituted methyl halides in good
yields.
Visible
Temperature
Light-Induced
Room
Reaction of
5
6
7
8
B
C
N
O
10.81
12.011
14.007
15
15.999
• ambient temperature
13
14
16
Heck
Al Si
P
S
• broad scope of functionalizable
allylic synthons
26.982
31
28.085
32
30.974
32.06
33
34
Functionalized Alkyl Halides with
Vinyl Arenes/Heteroarenes
Ga Ge As Se
69.723
49
72.630
50
74.922
51
78.97
52
• exogenous photosensitizer free
In Sn Sb Te
127.60
114.82
118.71
121.76
BPin
PhthlN
72%
Ph
Me2PhSi
Ph
90%
OEt
P
EtO
O
77%
N
OMe
This article is protected by copyright. All rights reserved.