Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl α-diazoacetates

Article abstract of DOI:10.1016/j.tet.2017.01.048

The [1,2]- and [2,3]-rearrangements of iodonium ylides are synthetically useful reactions for the generation of functionalized α-iodoesters. Allylic iodides are coupled with α-diazoesters in the presence of a copper catalyst and a ligand to generate iodonium ylides, which undergo metal-mediated rearrangements. By fine-tuning the structure of the ligand, we have reversed the regioselectivity of copper-catalyzed reactions of iodonium ylides from [2,3]- to [1,2]-rearrangements with the use of alternate bipyridine ligands. The preference for [1,2]-rearrangements was further improved by using bulky aryl α-diazoester substrates. Several α-iodoesters with a diverse range of functional groups were generated in good yields (up to 88% yield) and high regioselectivities (up to >95:5 regioisomeric ratio). A deuterium-labeled substrate was utilized to gain insight into the mechanism of the reaction.

Full text of DOI:10.1016/j.tet.2017.01.048

Tetrahedron xxx (2017) 1e10
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Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl
diazoacetates
a-
Bin Xu, Jackson A. Gartman, Uttam K. Tambar*
Department of Biochemistry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390-9038, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
The [1,2]- and [2,3]-rearrangements of iodonium ylides are synthetically useful reactions for the gen-
eration of functionalized a-iodoesters. Allylic iodides are coupled with a-diazoesters in the presence of a
copper catalyst and a ligand to generate iodonium ylides, which undergo metal-mediated rearrange-
ments. By fine-tuning the structure of the ligand, we have reversed the regioselectivity of copper-
catalyzed reactions of iodonium ylides from [2,3]- to [1,2]-rearrangements with the use of alternate
Received 10 October 2016
Received in revised form
10 January 2017
Accepted 20 January 2017
Available online xxx
bipyridine ligands. The preference for [1,2]-rearrangements was further improved by using bulky aryl
a-
diazoester substrates. Several -iodoesters with a diverse range of functional groups were generated in
a
Keywords:
good yields (up to 88% yield) and high regioselectivities (up to >95:5 regioisomeric ratio). A deuterium-
labeled substrate was utilized to gain insight into the mechanism of the reaction.
© 2017 Elsevier Ltd. All rights reserved.
Rearrangement
Iodonium ylide
Copper catalysis
Ligand control
Iodine
Deuterium labeling
1. Introduction
we hypothesized that we could selectively form the [1,2]-
rearrangement product 4 by fine-tuning the steric and electronic
Sigmatropic rearrangements are a broad class of reactions that
have revolutionized the synthesis of functionalized molecules.1
Recent advances in metal catalysis have enhanced the synthetic
utility of these rearrangements. Ligands have been designed to
fine-tune the reactivity of metal complexes, converting unselective
sigmatropic rearrangements into highly selective catalytic
processes.
properties within the bipyridine class of ligands.4 Herein, we
describe the discovery and application of an alternate bipyridine
ligand that favors copper-catalyzed [1,2]-iodonium ylide rear-
rangements (Scheme 1c). We also present mechanistic data for this
switch in regioselectivity.
2. Results and discussion
We were intrigued by the [1,2]- and [2,3]-rearrangements of
iodonium ylides as efficient methods for generating functionalized
2.1. Ligand synthesis
a
-iodoesters.2 Despite the potential utility of these reactions,
metal-catalyzed regioselective methods have only recently been
reported in the literature.3 In the course of our studies on these
rearrangements, we discovered that copper-catalyzed reactions of
diazoesters and allylic iodides furnish a mixture of [2,3]- and [1,2]-
rearrangement products (Scheme 1a). However, a 6,60-dibromo-
2,20-bipyridine ligand L5 can tune the reactivity of the copper
catalyst and facilitate the selective formation of the [2,3]-
rearrangement product 3 in high yield and diastereoselectivity
(Scheme 1b).3 Based on our observation that other bipyridine li-
gands yielded different ratios of the two rearrangement products,
To build up a collection of bipyridine ligands with comprehen-
sive electronic and steric properties, we synthesized ligands L3, L4
and L6 via a homo-coupling of 6-substituted 2-chloropyridines
with catalytic amounts of Ni(PPh3)Br2, zinc powder, and tetrabu-
tylammonium bromide (Scheme 2b).5 Ligand L13 was generated
from 5-methoxy-2-chloropyridine under slightly modified condi-
tions (Scheme 2c).6 Ligands L1, L2, L5 and L7-L12 were purchased
from Sigma-Aldrich (Scheme 2a).
2.2. Substrate synthesis
We generated a series of
a-diazoesters 2a-2f to assay the effect
* Corresponding author.
E-mail address: uttam.tambar@utsouthwestern.edu (U.K. Tambar).
of the ester functionality on the outcome of the iodonium ylide
http://dx.doi.org/10.1016/j.tet.2017.01.048
0040-4020/© 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Xu B, et al., Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl
(2017), http://dx.doi.org/10.1016/j.tet.2017.01.048
a-diazoacetates, Tetrahedron

2
B. Xu et al. / Tetrahedron xxx (2017) 1e10
rearrangements (Scheme 3). Benzyl
a-diazoester 2a was generated
in two steps from a-
b
-ketoester 7 (Scheme 3a).7 Alternatively, aryl
diazoesters 2b-2f were synthesized from bromoacetyl bromide 8
via an esterification with various phenol derivatives followed by a
diazotization (Scheme 3b).8
We devised a convergent assembly of aryl-substituted allylic
iodides that commenced with a Sonogashira coupling of various
aryl iodides 10 and propargyl alcohol (Scheme 4).9 The resulting
internal alkynes 11 were subjected to directed reduction with
LiAlH4 to selectively yield (E)-cinnamyl alcohols 12.10 A subsequent
Appel reaction converted these allylic alcohols to the desired (E)-
allylic iodides 1a-i.11
To access other classes of allylic iodides, we took advantage of
the accessibility of the corresponding E-allylic alcohols and the ease
of iodination (Scheme 5). For example, commercially available
prenol 13 and geraniol 14 were directly converted to allylic iodides
1k and 1m, respectively. Trisubstituted allylic iodides 1j and 1l
were synthesized in three steps from acetophenone and cyclo-
hexanone. Horner-Wadsworth-Emmons olefination12 with triethyl
Scheme 1. Regiodivergent [2,3]- and [1,2]-rearrangement of iodonium ylides gener-
ated by diazo compounds.
phosphonoacetate furnished a,b-unsaturated esters 16, which were
reduced with DIBAL-H to allylic alcohols 17. Subsequent iodination
resulted in the formation of the desired allylic iodides 1j and 1l.
2.3. Reaction optimization
With the substrates and bipyridine ligands in hand, we
commenced the optimization of the copper-catalyzed [1,2]-rear-
rangement of iodonium ylides (Table 1). In the absence of an
external ligand, cinnamyl iodide 1a and
a-diazoester 2a reacted
with catalytic [Cu(MeCN)4]PF6 to furnish a 61:39 mixture of [2,3]-
and [1,2]-rearrangement products (entry 1). A survey of bipyridines
L1-L13 revealed a broad range of regioselectivities within this
structural class of ligands (entries 2e14). Whereas ligands L2-L6
favored the formation of the [2,3]-rearrangement product 3 (en-
tries 3e7), bipyridine ligands L1 and L7-L13 preferentially formed
the [1,2]-rearrangement product 4a (entries 2 and 8e14). Most
notably, ligand L11 facilitated the formation of the [1,2]-
rearrangement product in a regioisomeric ratio of 94:6 (entry 12).
Scheme 2. Synthesis of substituted bipyridines.
Next, we examined the effect of a-diazoester structure on the
regioselectivity of the rearrangement (entries 15e18). Sterically
Scheme 3. Synthesis of
a-diazoesters.
Scheme 4. Synthesis of aryl allylic iodides.
Please cite this article in press as: Xu B, et al., Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl
(2017), http://dx.doi.org/10.1016/j.tet.2017.01.048
a-diazoacetates, Tetrahedron

B. Xu et al. / Tetrahedron xxx (2017) 1e10
3
rearrangement product (entry 18).
A screen of alternative copper(I) and copper(II) sources was
conducted to identify the best catalyst precursor for the [1,2]-
iodonium ylide rearrangement (entries 19e21). Cu(OTf)2 was
most effective for yield while maintaining a high preference for the
[1,2]-rearrangement product 4a (entry 21). After conducting the
reaction at several temperatures (entries 21e23), we established
the optimal reaction conditions for the copper-catalyzed [1,2]-
rearrangement. In the presence of 5 mol% Cu(OTf)2 and 6 mol%
dimethoxy-bipyridine ligand L11, cinnamyl iodide 1a and 2,6-
dimethyl-phenyl
a
-diazoester 2e reacted at 40 ꢀC to furnish the
desired product 4a in 86% yield and >95:5 regioisomeric ratio
(entry 22).
2.4. Substrate scope
The copper-catalyzed [1,2]-rearrangement of iodonium ylides in
the presence of bipyridine ligand L11 exhibits a wide substrate
scope and functional group tolerance (Table 2). A broad range of
aryl-substituted allylic iodides reacted with
a-diazoester 2e to
furnish the [1,2]-rearrangement product in high yield and regio-
selectivity. For example, allylic iodides substituted with aromatic
hydrocarbons yielded the rearrangement products in 72e86% yield
with >95:5 preference for the [1,2]-rearrangement product (4a-c).
The reaction is tolerant of phenyl rings with electron-withdrawing
groups, such as fluorine (4d and 4f), nitrile (4e), chlorine (4g), and
bromine (4h). Substitution at the ortho and para positions is
compatible with the conditions. Gratifyingly, an allylic iodide with
an electron-rich aromatic ring was also a suitable substrate for the
copper-catalyzed process (4i).
Scheme 5. Synthesis of more complex allylic iodides.
Table 1
Optimization of copper-catalyzed [1,2]-rearrangement of iodonium ylide.a
We extended the scope of the [1,2]-rearrangement to include
trisubstituted allylic iodides (4j-m). Products with multiple
aliphatic substituents (4k-4m) and a mixture of aliphatic and aro-
matic substituents (4j) were generated in high yields and regioi-
someric ratios. Interestingly, the configuration of the double bond
in the starting material allylic iodide was conserved in the product
Entry Ligand [Cu]
2
T (ꢀC) Time (h) Yield (%) 3/4
for all examples except for
a
-iodoester 4m, which was obtained as
1
2
3
4
5
6
7
8
None
L1
L2
L3
L4
L5
L6
L7
L8
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2a 25
[Cu(MeCN)4]PF6 2b 25
[Cu(MeCN)4]PF6 2c 25
[Cu(MeCN)4]PF6 2d 25
[Cu(MeCN)4]PF6 2e 25
0.5
2
2
8
2
0.5
0.5
2
2
2
2
2
2
2
2
2
2
2
13
60
70
32
64
68
42
70
73
73
68
70
68
71
74
70
33
76
24
50
81
86
NDb
61: 39
14: 86
85: 15
65: 35
62: 38
>95: 5
91: 9
10: 90
9: 91
10: 90
33: 67
6: 94
33: 67
17: 83
20: 80
6: 94
<5: 95
<5: 95
<5: 95
<5: 95
<5: 95
<5: 95
e
2:1 mixture of E:Z olefins.
We also investigated the scope of aryl
a
-diazoesters (Table 3).
Using various ester groups with different steric (2c and 2d) and
electronic (2f) properties, the desired products were obtained with
exceptional regioselectivities (>95:5) and moderate yields.
2.5. Mechanistic studies
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
L9
L10
L11
L12
L13
L11
L11
L11
L11
L11
L11
L11
L11
L11
We conducted a deuterium-labeled experiment to gain more
insight into the mechanism of the copper-catalyzed [1,2]-rear-
rangement (Scheme 6). Deuterated allylic iodide 18 reacted with
2,6-dimethyl-phenyl
a-diazoester 2e in the presence of catalytic
Cu(OTf)2 and dimethoxy-bipyridine ligand L11 to yield a mixture of
deuterated rearrangement products 19 and 20. Terminal allylic io-
dide 18 was utilized in this experiment to avoid any steric bias that
may exist for a substituted allylic iodide. The formation of almost
equal amounts of isomers 19 and 20 is consistent with a stepwise
mechanism that proceeds through an oxidative addition/reductive
CuBr
CuOTf
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
2e 25
2e 25
2e 25
2e 40
24
2
8
2
48
2e
5
elimination pathway. We propose that the
a-diazoester initially
a
reacts with the copper catalyst to form copper carbenoid I, which
then engages with the allylic iodide to yield a copper-coordinated
iodonium ylide that can exist as two copper enolate tautomers (II
and III).13 This intermediate can undergo an oxidative addition to
generate a copper(III) complex such as IV, V, or VI.14,15 Reductive
elimination of the copper allyl complex would furnish the observed
[1,2]-rearrangement product 4 and regenerate the copper catalyst.
We hypothesize that this remarkable switch in regioselectivity
by the two bipyridine ligands L5 and L11 can be rationalized by
Reaction conditions: allylic iodide 1a (0.4 mmol), a-diazoester 2 (1.2 equiv),
copper catalyst (5 mol%), ligand (6 mol%), CH2Cl2 (0.1 M).
b
ND: No product was detected, and a-diazoester substrate remained.
bulky aryl
high preference for the [1,2]-rearrangement product 4a (entries
16e18). We selected 2,6-dimethyl-phenyl -diazoester 2e as the
optimal substrate for both yield and regioselectivity of the [1,2]-
a-diazoesters 2c-2e were most effective in facilitating a
a
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a-diazoacetates, Tetrahedron

4
B. Xu et al. / Tetrahedron xxx (2017) 1e10
Table 2
Substrate scope of copper-catalyzed [1,2]-rearrangement of iodonium ylides.
Table 3
Aryl a-diazoesters scope of copper-catalyzed [1,2]-rearrangement of iodonium ylides.
examining the steric and electronic properties of these structurally
similar yet unique ligands. In the presence of dibromo-bipyridine
ligand L5, we propose the selective formation of [2,3]-
rearrangement product 3 via a concerted rearrangement mecha-
nism. We hypothesize that this reaction pathway is preferred for
II-III toward oxidative addition,16 thus favoring the formation of the
[2,3]-rearrangement product through a concerted mechanism. On
the other hand, an electron-rich ligand such as dimethoxy-
bipyridine L11 would facilitate oxidative addition of copper-
coordinated iodonium ylide II-III to form a copper(III) complex
such as IV-VI. In addition, the sterically unhindered dimethoxy-
bipyridine ligand L11 may favor oxidative addition more than the
ligands such as L5 that are poor
s-donors. Electron-deficient li-
gands decrease the reactivity of copper-coordinated iodonium ylide
Please cite this article in press as: Xu B, et al., Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl
(2017), http://dx.doi.org/10.1016/j.tet.2017.01.048
a-diazoacetates, Tetrahedron

B. Xu et al. / Tetrahedron xxx (2017) 1e10
5
structure represents a powerful approach to control other classes of
sigmatropic rearrangements. In addition, the combination of
copper-catalyzed diazo decomposition and copper(I)-(III) chemis-
try may represent a new direction in copper catalysis that could
lead to the discovery of many new transformations.
4. Experimental section
4.1. General information
All reactions were carried out in capped reaction vials or flasks
with magnetic stirring unless otherwise indicated. Commercially
obtained reagents were used as received. Solvents were dried by
passage through an activated alumina column under argon. Liquids
and solutions were transferred via syringe. All reactions were
monitored by thin-layer chromatography with E. Merck silica gel 60
F254 pre-coated plates (0.25 mm). Silica gel (particle size
0.032e0.063 mm) purchased from SiliCycle was used for flash
chromatography. 1H NMR spectra were recorded on Varian Inova-
400 or Varian Inova-500 spectrometers. 13C NMR spectra were
recorded on Varian Inova-400 spectrometers. Data for 1H NMR
spectra are reported relative to chloroform as an internal standard
(7.26 ppm) and are reported as follows: chemical shift (d ppm),
multiplicity, coupling constant (Hz), and integration. Data for 13C
NMR spectra are reported relative to chloroform as an internal
standard (77.0 ppm) and are reported in terms of chemical shift (
d
ppm). Melting points were measured on a Fisher ScientificTM
melting point apparatus (12e144). APCI-LRMS data were measured
using an AB Sciex QTRAP-4500 LC/MS.
4.2. Synthesis of substituted bipyridines
Scheme 6. Mechanistic studies.
4.2.1. 6,6'-di-tert-Butyl-2,2'-bipyridine (L3)18
A 100 mL oven-dried flask was charged with Ni(PPh3)2Br2
(520 mg, 0.7 mmol), zinc dust (137 mg, 2.1 mmol), tetrabuty-
lammonium bromide (676 mg, 2.1 mmol) and 6-tert-butyl-2-
chloro-pyridine (5a, 1.2 g, 7 mmol). After the flask was evacuated
and refilled with argon, dry DMF (20 mL) was added and the sus-
pension was stirred at 55 ꢀC. After the reaction was complete
(monitored by TLC), the mixture was filtered through Celite and
washed with Et2O (200 mL). The combined solution was then
washed with water (100 mL x 3) and brine (100 mL), dried over
anhydrous Na2SO4, concentrated and purified by column chroma-
tography on silica gel (Hexane/EtOAc ¼ 30:1, v/v) to afford desired
6,6'-di-tert-Butyl-2,2'-bipyridine as a white solid, 488 mg, 52%
electronically similar yet sterically more bulky dimethoxy-
bipyridine ligands L4 and L13, due to a more congested coordina-
tion sphere of the oxidative addition product.15 The ligand's steric
bulk can therefore impact the relative rates of oxidative addition,
which accounts for the lower regioisomeric ratio observed with the
less bulky ligands L4 and L13 (Table 1, entries 5 and 14).
The ester functionality of a-diazoesters 2a-2e also impacts the
regioselectivity of the copper-catalyzed rearrangement. Although
the structures of these esters most likely do not have a drastic effect
on the preference for a concerted rearrangement or a stepwise
oxidative addition/reductive elimination mechanism, we surmise
that the steric bulk of the ester group can effect the stability of the
yield. 1H NMR (500 MHz, CDCl3):
d
8.32 (d, J ¼ 7.5 Hz, 2H, ArH), 7.72
competing isomers of copper(III) complexes such as IV-VI.17
A
(t, J ¼ 7.5 Hz, 2H, ArH), 7.32 (d, J ¼ 7.5 Hz, 2H, ArH), 1.42 (s, 18H,
2tBu).
sterically bulky ester such as 2,6-dimethyl-phenyl
a
-diazoester 2e
may favor -complex V over the more congested
which would lead to the formation of [1,2]-rearrangement product
s
s-complex VI,
4.2.2. 6,60-Dimethoxy-2,2'-bipyridine (L4)4
Following the same procedure for the synthesis of L3, 6,6'-
dimethoxy-2,2'-bipyridine was obtained as a white solid, 550 mg
(starting from 10 mmol 5b), 51% yield. 1H NMR (500 MHz, CDCl3):
4 after reductive elimination.
3. Conclusion
d
8.02 (d, J ¼ 7.5 Hz, 2H, ArH), 7.69 (t, J ¼ 8.0 Hz, 2H, ArH), 6.76 (d,
J ¼ 8.0 Hz, 2H, ArH), 4.04 (s, 6H, 2OCH3).
We have developed a highly selective copper-catalyzed [1,2]-
rearrangement of iodonium ylides, in which the regioselectivity is
dictated by the steric and electronic properties of the bipyridine
4.2.3. 6,60-Bis(trifluoromethyl)-2,2'-bipyridine (L6)19
Following the same procedure for the synthesis of L3, 6,60-
Bis(trifluoromethyl)-2,2'-bipyridine was obtained as a white solid,
360 mg (starting from 3 mmol 5c), 82% yield. 1H NMR (500 MHz,
ligand and the steric properties of the a-diazoester. Remarkably, we
have been able to reverse the regioselectivity of iodonium ylide
rearrangements with the use of alternate bipyridine ligands. Orig-
inally selective for a [2,3]-rearrangement with L5, the outcome of
the reaction can be altered to selectively form the [1,2]-
rearrangement product with the use of bipyridine L11. This
drastic change in product distribution upon fine-tuning of ligand
CDCl3):
7.74 (d, J ¼ 7.5 Hz, 2H, ArH).
d
8.73 (d, J ¼ 8.0 Hz, 2H, ArH), 8.03 (t, J ¼ 8.0 Hz, 2H, ArH),
4.2.4. 5,50-Dimethoxy-2,2'-bipyridine (L13)5
A 100 mL round-bottom flask was charged with NiCl2$6H2O
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a-diazoacetates, Tetrahedron

6
B. Xu et al. / Tetrahedron xxx (2017) 1e10
(40 mg, 0.15 mmol) and DMF (10 mL). The resulting solution was
stirred and heated to 40 ꢀC. Then, 2-chloro-5-methoxypyridine (6,
3 mmol), anhydrous LiCl (130 mg, 3 mmol), and zinc dust (230 mg,
3.6 mmol) were added. When the temperature rose to 50 ꢀC, a grain
of iodine crystal and two drops of acetic acid were added to the
mixture. The mixture was stirred at 55e60 ꢀC until complete con-
version of 2-halopyridine (monitored by TLC). To the cooled reac-
tion mixture was added 1 N HCl aqueous solution (5 mL) to
consume the remaining zinc dust. The resulting mixture was made
alkaline with aqueous ammonia (25%) and diluted with CH2Cl2. The
organic layers were collected, dried over anhydrous Na2SO4,
concentrated, and purified by column chromatography on silica gel
(Hexane/EtOAc ¼ 10:1, v/v) to afford desired 5,5'-dimethoxy-2,2'-
bipyridine as a light yellow solid, 130 mg, 40% yield. 1H NMR
(d, J ¼ 7.2 Hz, 1H, ArH), 5.15 (brs, 1H, CHN2); 13C NMR (100 MHz,
CDCl3):
d 146.2, 134.6, 128.0, 127.0, 126.5, 126.4, 126.1, 125.3, 121.1,
118.2, 46.8. IR (neat, cmꢁ1): 3122, 2127, 1684, 1336, 1210, 1080, 924,
783. APCI-MS calcd for [C12H9N2O2, M þ H]þ: 213.07, Found 213.11.
4.3.4. Naphthalen-2-yl 2-diazoacetate (2d)
Following the same procedure for the synthesis of 2b, 2d was
obtained as a yellow solid, mp: 55e56 ꢀC, 1.1 g, 52% yield. 1H NMR
(400 MHz, CDCl3):
ArH), 7.53e7.44 (m, 2H, ArH), 7.28 (dd, J1 ¼ 8.8 Hz and J1 ¼ 2.0 Hz,
1H, ArH), 5.03 (brs, 1H, CHN2); 13C NMR (100 MHz, CDCl3):
148.0,
d
7.89e7.79 (m, 3H, ArH), 7.62 (d, J ¼ 2.0 Hz, 1H,
d
133.7, 131.4, 129.4, 127.7, 127.6, 126.6, 125.7, 121.1, 118.6, 46.9. IR
(neat, cmꢁ1): 3114, 2112, 1697, 1362, 1207, 1145, 970, 724.
[C12H9N2O2, M þ H]þ: 213.07, Found 213.12.
(500 MHz, CDCl3):
2H, ArH), 7.30 (dd, J1 ¼ 9.0 Hz and J2 ¼ 3.0 Hz, 2H, ArH), 3.91 (s, 6H,
d
8.33 (d, J ¼ 3.0 Hz, 2H, ArH), 8.24 (d, J ¼ 9.0 Hz,
4.3.5. 2,6-Dimethylphenyl 2-diazoacetate (2e)
2OCH3).
Following the same procedure for the synthesis of 2b, 2e was
obtained as a yellow solid, mp: 80e81 ꢀC, 684 mg, 36% yield. 1H
4.3. Synthesis of
a
-diazoesters
NMR (400 MHz, CDCl3):
d
7.08e7.05 (m, 3H, ArH), 5.02 (brs, 1H,
147.8, 130.6,
CHN2), 2.20 (s, 6H, 2CH3); 13C NMR (100 MHz, CDCl3):
d
NB: For safety considerations, during the synthesis of a-diazo-
compounds, TsN3 or NaN3 should not be in contact with metals.
Special precautions should also be taken when diazo- or azide-
compounds are subjected to heat or high pressure.
128.5, 126.0, 46.2, 16.3. IR (neat, cmꢁ1): 3124, 2133, 1693, 1371, 1182,
1148, 970, 729. APCI-MS calcd for [C10H11N2O2, M þ H]þ: 191.08,
Found 191.13.
4.3.6. 2,6-Dichlorophenyl 2-diazoacetate (2f)
4.3.1. Benzyl 2-diazoacetate (2a)6
Following the same procedure for the synthesis of 2b, 2f was
A 250 mL oven-dried flask was charged with benzyl 3-
oxobutanoate (7, 5.8 g, 30 mmol), triethylamine (4.5 g, 45 mmol)
and dry acetonitrile (80 mL), followed by slow addition of 4-
methylbenzenesulfonyl azide (7.7 g, 39 mmol). The mixture was
stirred at room temperature until the reaction was complete
(monitored by TLC). An aqueous solution of LiOH (100 mmol in
60 mL H2O) was slowly added. The suspension was stirred at room
temperature for 6 h and extracted by Et2O (100 mL x 3). The organic
layers were combined, washed with brine, dried over anhydrous
Na2SO4, concentrated and purified by column chromatography on
silica gel (Hexane/EtOAc ¼ 15:1, v/v) to afford 2a as an orange oil,
obtained as a light yellow oil, 808 mg, 35% yield. 1H NMR (400 MHz,
CDCl3):
d
7.36 (d, J ¼ 8.0 Hz, 2H, ArH), 7.15 (t, J ¼ 8.0 Hz, 2H, ArH),
5.12 (brs, 1H, CHN2); 13C NMR (100 MHz, CDCl3):
d 143.6, 129.4,
128.6, 127.3, 46.8. IR (neat, cmꢁ1): 3123, 2115, 1700, 1443, 1361,
1338, 1196, 1127, 768. APCI-MS calcd for [C8H5Cl2N2O2, M þ H]þ:
230.97, Found 230.99.
4.4. Synthesis of allylic iodides
4.4.1. (E)-(3-Iodoprop-1-en-1-yl)benzene (1a)3
A 100 mL flask was charged with Pd(PPh3)Cl2 (70 mg, 0.1 mmol)
and CuI (38 mg, 0.2 mmol). After the flask was evacuated and
refilled with argon, NEt3 (20 mL) was added and the suspension
was stirred at room temperature. A solution of iodobenzene (10a,
2.04 g, 10 mmol) and propargyl alcohol (616 mg, 11 mmol) in NEt3
(10 mL) was added to the suspension. After the reaction was
complete (monitored by TLC), the mixture was filtered through a
plug of Celite and washed with EtOAc (20 mL x 3). The combined
solution was concentrated and purified by column chromatography
on silica gel (Hexane/EtOAc ¼ 3:1, v/v) to afford 3-phenylprop-2-
yn-1-ol (11a, 1.24 g, 94% yield) as a yellow oil.
4.3 g, 82% yield. 1H NMR (400 MHz, CDCl3):
ArH), 5.21 (s, 2H, CH2), 4.80 (brs, 1H, CHN2).
d 7.42e7.30 (m, 5H,
4.3.2. Phenyl 2-diazoacetate (2b)7
Phenol (940 mg, 10 mmol) and pyridine (1.58 g, 20 mmol) were
dissolved in acetonitrile (20 mL) and bromoacetyl bromide (3.03 g,
15 mmol) was slowly added at 0 ꢀC. After stirring for 10 min at this
temperature, the reaction was quenched with H2O. The solution
was extracted with CH2Cl2 (50 mL x 3). The organic layers were
combined, washed with brine, dried over anhydrous Na2SO4 and
concentrated to afford a residue, which was dissolved with N,N'-
ditosylhydrazine (6.8 g, 20 mmol) in THF (50 mL). The mixture was
cooled to 0 ꢀC, followed by a slow addition of DBU (7.6 g, 50 mmol).
The mixture was stirred at 0 ꢀC until the reaction was complete
(monitored by TLC). The reaction was quenched by saturated
NaHCO3 solution, and extracted with Et2O (100 mL x 3). The organic
layers were combined, washed with brine, dried over anhydrous
Na2SO4, concentrated and purified by flash column chromatog-
raphy on silica gel (Hexane/EtOAc ¼ 15:1, v/v) to afford 2b as a
yellow semi-oil, 0.9 g, 56% yield. 1H NMR (500 MHz, CDCl3):
A 50 mL oven-dried flask was charged with LiAlH4 (190 mg,
5 mmol) and dry THF (15 mL). The mixture was cooled to 0 ꢀC,
followed by a slow addition of 11a (660 mg, 5 mmol, in 5 mL THF).
The mixture was stirred at room temperature until the reaction was
complete (monitored by 1H NMR). The mixture was then cooled to
0
ꢀC and carefully quenched by H2O (1.2 mL), 15% NaOH (1.2 mL)
and H2O (1.2 mL) to afford a suspension, which was filtered through
Celite and washed with EtOAc (30 mL x 3). The combined solution
was concentrated and purified by column chromatography on silica
gel (Hexane/EtOAc ¼ 3:1, v/v) to afford (E)-3-phenylprop-2-en-1-ol
(12a, 636 mg, 95% yield) as a colorless oil.
d
7.42e7.35 (m, 2H, ArH), 7.26e7.21 (m, 1H, ArH), 7.16e7.11 (m, 2H,
ArH), 4.97 (brs, 1H, CHN2).
A 50 mL flask was charged with PPh3 (786 mg, 3 mmol), imid-
azole (224 mg, 3.3 mmol) and CH2Cl2 (10 mL). To the stirring so-
lution was added iodine (750 g, 3 mmol) in portions. After 30 min,
the flask was wrapped with aluminum foil and cooled by ice bath,
followed by slow addition of 12a (402 mg, 3 mmol, in 5 mL CH2Cl2).
After the reaction was complete (monitored by 1H NMR), the
mixture was filtered through a plug of silica gel, which was then
4.3.3. Naphthalen-1-yl 2-diazoacetate (2c)
Following the same procedure for the synthesis of 2b, 2c was
obtained as a yellow solid, mp: 76e77 ꢀC, 975 mg, 46% yield. 1H
NMR (400 MHz, CDCl3):
1H, ArH), 7.58e7.51 (m, 2H, ArH), 7.49 (t, J ¼ 8.0 Hz, 1H, ArH), 7.33
d
7.95e7.86 (m, 2H, ArH), 7.77 (d, J ¼ 8.4 Hz,
Please cite this article in press as: Xu B, et al., Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl
(2017), http://dx.doi.org/10.1016/j.tet.2017.01.048
a-diazoacetates, Tetrahedron

B. Xu et al. / Tetrahedron xxx (2017) 1e10
7
washed with Hexane/EtOAc (v/v ¼ 10:1, 20 mL x 2). The combined
solution was concentrated and purified by flash column chroma-
tography on silica gel (Hexane/EtOAc ¼ 30:1, v/v) to afford 1a as a
bright yellow solid, 622 mg, 85% yield. 1H NMR (500 MHz, CDCl3):
1464, 1435, 1145, 1021, 957, 747. APCI-MS calcd for [C9H9BrI,
M þ H]þ: 322.89, Found 322.90.
4.4.9. (E)-5-(3-Iodoprop-1-en-1-yl)benzo[d][1,3]dioxole (1i)
Following the same procedure for the synthesis of 1a, 1i was
obtained as a yellow solid, mp: 49e50 ꢀC, 622 mg, 72% yield. 1H
d
7.39e7.35 (m, 2H, ArH), 7.34e7.30 (m, 2H, ArH), 7.28e7.23 (m, 1H,
ArH), 6.60 (d, J ¼ 15.5 Hz, 1H, ArCH ¼ ), 6.44 (dt, J1 ¼ 15.5 Hz and
J2 ¼ 8.5 Hz, 1H, ¼CHCH2), 4.12 (d, J ¼ 8.5 Hz, 2H, CH2I).
NMR (400 MHz, CDCl3):
d
6.91 (d, J ¼ 2.0 Hz, 1H, ArH), 6.80 (dd,
J1 ¼ 8.0 Hz and J2 ¼ 1.6 Hz, 1H, ArH), 6.75 (d, J ¼ 8.0 Hz, 1H, ArH),
6.52 (d, J ¼ 15.6 Hz, 1H, ArCH ¼ ), 6.26 (dt, J1 ¼ 15.6 Hz and
J2 ¼ 8.0 Hz, 1H, ¼CHCH2), 5.96 (s, 2H, OCH2O), 4.10 (dd, J1 ¼ 8.0 Hz
4.4.2. (E)-2-(3-Iodoprop-1-en-1-yl)naphthalene (1b)3
Following the same procedure for the synthesis of 1a, 1b was
obtained as a yellow solid, 723 mg, 82% yield. 1H NMR (500 MHz,
and J2 ¼ 1.5 Hz, 2H, CH2I); 13C NMR (100 MHz, CDCl3):
d 148.1, 147.7,
132.9, 130.3, 125.1, 121.6, 108.3, 105.7, 101.2, 7.4. IR (neat, cmꢁ1):
2893, 1500, 1486, 1443, 1248, 1038, 928. APCI-MS calcd for
[C10H10IO2, M þ H]þ: 288.97, Found 288.97.
CDCl3): d 7.82e7.76 (m, 3H, ArH), 7.73 (s,1H, ArH), 7.59e7.55 (m,1H,
ArH), 7.50e7.42 (m, 2H, ArH), 6.76 (d, J ¼ 15.5 Hz, 1H, ArCH ¼ ), 6.57
(dt, J1 ¼15.5 Hz and J2 ¼ 8.0 Hz, 1H, ¼CHCH2), 4.18 (d, J ¼ 8.0 Hz, 2H,
CH2I).
4.4.10. (E)-(4-Iodobut-2-en-2-yl)benzene (1j)20
4.4.3. (E)-4-(3-Iodoprop-1-en-1-yl)-1,1'-biphenyl (1c)3
Neat triethyl phosphonoacetate (2.24 g, 10 mmol) was added to
a suspension of NaH (60%, 400 mg, 10 mmol) in dry THF (50 mL).
After 30 min, a solution of acetophenone (960 mg, 8 mmol) in dry
THF (10 mL) was added, and the resulting mixture was stirred
overnight. The reaction was quenched by the addition of water
(50 mL). The organic layer was separated, and the aqueous layer
was extracted with Et2O (3 ꢂ 50 mL). The combined organic solu-
tions were dried over anhydrous Na2SO4, concentrated and purified
by column chromatography on silica gel (Hexane/EtOAc ¼ 10:1, v/v)
to afford ethyl (E)-3-phenylbut-2-enoate (16a) as a colorless oil,
Following the same procedure for the synthesis of 1a, 1c was
obtained as a yellow solid, 816 mg, 85% yield. 1H NMR (500 MHz,
CDCl3): d 7.62e7.54 (m, 4H, ArH), 7.47e7.41 (m, 4H, ArH), 7.37e7.32
(m, 1H, ArH), 6.64 (d, J ¼ 15.5 Hz, 1H, ArCH ¼ ), 6.49 (dt, J1 ¼15.5 Hz
and J2 ¼ 8.0 Hz, 1H, ¼CHCH2), 4.15 (dd, J1 ¼ 8.5 Hz and J2 ¼ 1.0 Hz,
2H, CH2I).
4.4.4. (E)-1-Fluoro-4-(3-iodoprop-1-en-1-yl)benzene (1d)3
Following the same procedure for the synthesis of 1a, 1d was
obtained as a yellow solid, 676 mg, 86% yield. 1H NMR (500 MHz,
1.25 g, 82% yield. 1H NMR (500 MHz, CDCl3):
d 7.50e7.45 (m, 2H,
CDCl3):
d 7.37e7.30 (m, 2H, ArH), 7.05e6.97 (m, 2H, ArH), 6.56 (d,
ArH), 7.40e7.33 (m, 3H, ArH), 6.15e6.11 (m, 1H, CH ¼ ), 4.22 (q,
J ¼ 7.0 Hz, 2H, OCH2), 2.58 (d, J ¼ 1.0 Hz, 3H, CH3), 1.32 (t, J ¼ 7.0 Hz,
3H, CH2CH3).
J ¼ 15.5 Hz, 1H, ArCH ¼ ), 6.36 (dt, J1 ¼ 15.5 Hz and J2 ¼ 8.0 Hz,
1H, ¼CHCH2), 4.10 (dd, J1 ¼ 8.0 Hz and J2 ¼ 1.0 Hz, 2H, CH2I).
To a cooled (ꢁ78 ꢀC) solution of 16a (950 mg, 5 mmol) in CH2Cl2
(30 mL) was added DIBAL-H (1.2 M in toluene, 9 mL, 11 mmol).
When the reduction was complete, the reaction was quenched by
Na2SO4$10H2O (4.8 g, 15 mmol). When a precipitate appeared, the
mixture was diluted with Et2O (50 mL) and stirred for 1 h. Solids
were filtered off and washed with Et2O (50 mL x 3). After drying
over anhydrous Na2SO4, the solution was concentrated to afford
(E)-3-phenylbut-2-en-1-ol (17a) as a crude oil, which underwent
an iodination to afford desired 1j as a yellow oil, 460 mg (2 mmol
4.4.5. (E)-4-(3-Iodoprop-1-en-1-yl)benzonitrile (1e)3
Following the same procedure for the synthesis of 1a, 1e was
obtained as a yellow solid, 726 mg, 90% yield. 1H NMR (500 MHz,
CDCl3):
d
7.60 (d, J ¼ 8.5 Hz, 2H, ArH), 7.44 (d, J ¼ 8.5 Hz, 2H, ArH),
6.62e6.51 (m, 2H, CH]CH), 4.09 (d, J ¼ 7.0 Hz, 2H, CH2I).
4.4.6. (E)-1-Fluoro-3-(3-iodoprop-1-en-1-yl)benzene (1f)3
Following the same procedure for the synthesis of 1a, 1f was
obtained as a yellow solid, 652 mg, 83% yield. 1H NMR (500 MHz,
scale), 89% yield. 1H NMR (500 MHz, CDCl3):
d 7.50e7.30 (m, 5H,
CDCl3): d 7.30e7.23 (m, 1H, ArH), 7.15e7.09 (m, 1H, ArH), 7.08e7.01
ArH), 6.17 (t, J ¼ 9.0 Hz, 1H, CH), 4.19 (d, J ¼ 9.0 Hz, 2H, CH2I), 2.12 (s,
(m, 1H, ArH), 6.97e6.90 (m, 1H, ArH), 6.55 (d, J ¼ 15.5 Hz, 1H,
ArCH ¼ ), 6.43 (dt, J1 ¼15.5 Hz and J2 ¼ 8.0 Hz,1H, ¼CHCH2), 4.08 (d,
J ¼ 8.0 Hz, 2H, CH2I).
3H, CH3).
4.4.11. 1-Iodo-3-methylbut-2-ene (1k)3
Following the same iodination procedure for the synthesis of 1a,
1k was obtained from commercially available 3-methylbut-2-en-1-
ol (13) as a light yellow oil, 764 mg (5 mmol scale), 78% yield. 1H
4.4.7. (E)-1-Chloro-2-(3-iodoprop-1-en-1-yl)benzene (1g)
Following the same procedure for the synthesis of 1a, 1g was
obtained as a yellow solid, mp: 28e29 ꢀC, 734 mg, 88% yield. 1H
NMR (500 MHz, CDCl3):
1H, ArH), 1.73 (s, 3H, CH3), 1.65 (s, 3H, CH3).
d
5.56e5.49 (m, 1H, CH), 3.93 (d, J ¼ 9.0 Hz,
NMR (400 MHz, CDCl3):
d
7.53 (dd, J1 ¼ 7.6 Hz and J2 ¼ 2.0 Hz, 1H,
ArH), 7.35 (dd, J1 ¼ 7.6 Hz and J2 ¼ 2.0 Hz, 1H, ArH), 7.25e7.17 (m,
2H, ArH), 6.99 (d, J ¼ 15.6 Hz, 1H, ArCH ¼ ), 6.44 (dt, J1 ¼15.6 Hz and
J2 ¼ 8.0 Hz, 1H, ¼CHCH2), 4.13 (dd, J1 ¼ 8.0 Hz and J2 ¼ 1.5 Hz, 2H,
4.4.12. (2-Iodoethylidene)cyclohexane (1l)3
CH2I); 13C NMR (100 MHz, CDCl3):
d 133.9, 133.1, 129.7, 129.5, 129.1,
Following the same procedure for the synthesis of 1j, 1l was
obtained as light yellow oil, 448 mg (2 mmol scale), 95% yield. 1H
128.8,126.9,126.8, 6.1. IR (neat, cmꢁ1): 3040,1468,1440,1146, 1035,
959, 749. APCI-MS calcd for [C9H9ClI, M þ H]þ: 278.94, Found
278.96.
NMR (500 MHz, CDCl3):
d
5.48 (t, J ¼ 8.5 Hz, 1H, CH ¼ ), 3.95 (d,
J ¼ 8.0 Hz, 2H, CH2I), 2.19e2.14 (m, 2H, CH2), 2.10e2.06 (m, 2H,
CH2), 1.58e1.50 (m, 6H, 3CH2).
4.4.8. (E)-1-Bromo-2-(3-iodoprop-1-en-1-yl)benzene (1h)
Following the same procedure for the synthesis of 1a, 1h was
obtained as a yellow solid, mp: 31e32 ꢀC, 833 mg, 86% yield. 1H
4.4.13. (E)-1-Iodo-3,7-dimethylocta-2,6-diene (1m)10
Following the same iodination procedure for the synthesis of 1a,
1m was obtained from commercially available geraniol (14) as a
light yellow oil, 502 mg (5 mmol scale), 38% yield. 1H NMR
NMR (400 MHz, CDCl3): d 7.57e7.49 (m, 2H, ArH), 7.30e7.24 (m, 1H,
ArH), 7.14e7.08 (m, 1H, ArH), 6.94 (d, J ¼ 15.2 Hz, 1H, ArCH ¼ ), 6.40
(dt, J1 ¼ 15.6 Hz and J2 ¼ 8.0 Hz, 1H, ¼CHCH2), 4.13 (dd, J1 ¼ 8.0 Hz
(500 MHz, CDCl3):
d
5.51 (t, J ¼ 8.4 Hz, 1H, CH ¼ ), 5.04 (t, J ¼ 6.8 Hz,
and J2 ¼ 1.5 Hz, 2H, CH2I); 13C NMR (100 MHz, CDCl3):
d
135.6,133.0,
1H, CH ¼ ), 3.91 (d, J ¼ 8.8 Hz, 2H, CH2I), 2.12e1.94 (m, 4H, 2CH2),
131.4, 129.6, 129.3, 127.5, 127.0, 123.7, 5.9. IR (neat, cmꢁ1): 3038,
1.66 (s, 3H, CH3), 1.62 (s, 3H, CH3), 1.58 (s, 3H, CH3).
Please cite this article in press as: Xu B, et al., Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl
(2017), http://dx.doi.org/10.1016/j.tet.2017.01.048
a-diazoacetates, Tetrahedron

8
B. Xu et al. / Tetrahedron xxx (2017) 1e10
4.5. Copper-catalyzed [1,2]-rearrangement of iodonium ylide
4.5.5. 2,6-Dimethylphenyl (E)-5-(4-cyanophenyl)-2-iodopent-4-
enoate (4e)
Typical procedure: A 8 mL reaction vial was charged with
Cu(OTf)2 (7.2 mg, 0.02 mmol) and 4,4'-dimethoxy-2,2'-bipyridine
(5.2 mg, 0.024 mmol). The vial was degassed and refilled with
argon. After CH2Cl2 (4 mL) was added, the mixture was stirred at
Colorless semi-oil, 66% yield, >95:5 rr. 1H NMR (400 MHz,
CDCl3):
d
7.61 (d, J ¼ 8.4 Hz, 2H, ArH), 7.44 (d, J ¼ 8.4 Hz, 2H, ArH),
7.07e7.01 (m, 3H, ArH), 6.60 (d, J ¼ 16.0 Hz, 1H, ArCH ¼ ), 6.33 (dt,
J1 ¼ 16.0 Hz and J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 4.70 (dd, J1 ¼ 8.8 Hz and
J2 ¼ 6.8 Hz, 1H, CHI), 3.25e2.98 (m, 2H, CH2), 2.15 (brs, 6H, 2CH3);
room temperature for 2 h. Then the mixture was stirred in a 40 ꢀ
C
-
oil bath, followed by addition of allylic iodides 1 (0.4 mmol) and
a
13C NMR (100 MHz, CDCl3):
d 168.5, 147.5, 141.0, 132.7, 132.5, 130.2,
diazoester 2 (0.48 mmol) in sequence. The mixture was stirred at
40 ꢀC until the reaction was complete (monitored by TLC). The
mixture was then concentrated and purified by flash column
chromatography on silica gel (PE/EtOAc ¼ 30:1) to afford [1,2]-
rearrangement products 4.
130.0, 128.8, 126.7, 126.3, 118.8, 111.0, 39.4, 16.6, 16.5. IR (neat,
cmꢁ1): 3036, 2922, 2224, 1746, 1604, 1473, 1161, 1110, 969, 772, 731.
APCI-MS calcd for [C20H19INO2, M þ H]þ: 432.05, Found 432.06.
4.5.6. 2,6-Dimethylphenyl (E)-5-(3-fluorophenyl)-2-iodopent-4-
enoate (4f)
Colorless semi-oil, 78% yield, 93:7 rr. 1H NMR (400 MHz, CDCl3):
4.5.1. 2,6-Dimethylphenyl (E)-2-iodo-5-phenylpent-4-enoate (4a)
White solid, mp: 58e59 ꢀC, 86% yield, >95:5 rr. 1H NMR
(400 MHz, CDCl3): d 7.38e7.29 (m, 4H, ArH), 7.28e7.23 (m,1H, ArH),
d
7.31e7.24 (m, 1H, ArH), 7.12 (d, J ¼ 7.6 Hz, 1H, ArH), 7.09e7.01 (m,
4H, ArH), 6.96 (td, J1 ¼ 8.4 Hz and J2 ¼ 2.0 Hz, 1H, ArH), 6.56 (d,
J ¼ 16.0 Hz, 1H, ArCH ¼ ), 6.20 (dt, J1 ¼ 16.0 Hz and J2 ¼ 7.2 Hz,
1H, ¼CHCH2), 4.68 (dd, J1 ¼ 8.8 Hz and J2 ¼ 6.4 Hz, 1H, CHI),
3.23e295 (m, 2H, CH2), 2.16 (brs, 6H, 2CH3); 13C NMR (100 MHz,
7.09e7.00 (m, 3H, ArH), 6.59 (d, J ¼ 16.0 Hz, 1H, ArCH ¼ ), 6.19 (dt,
J1 ¼ 16.0 Hz and J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 4.68 (dd, J1 ¼ 9.2 Hz and
J2 ¼ 6.4 Hz, 1H, CHI), 3.24e2.94 (m, 2H, CH2), 2.17 (brs, 6H, 2CH3);
13C NMR (100 MHz, CDCl3):
d 168.7, 147.6, 136.6, 134.4, 130.4, 128.8,
CDCl3):
d
168.6, 163.1 (d, J ¼ 244.2 Hz), 147.5, 138.9 (d, J ¼ 7.7 Hz),
128.6, 127.8, 126.3, 126.2, 125.8, 39.6, 17.5, 16.5. IR (neat, cmꢁ1):
3026, 2923, 1747, 1162, 1108, 965, 769, 744, 691. APCI-MS calcd for
[C19H20IO2, M þ H]þ: 407.05, Found 407.05.
133.3 (d, J ¼ 2.6 Hz), 130.3, 130.1 (d, J ¼ 8.4 Hz), 128.8, 127.3, 126.2,
122.2 (d, J ¼ 2.7 Hz), 114.7 (d, J ¼ 21.2 Hz), 112.6 (d, J ¼ 21.5 Hz), 39.4,
17.1, 16.5. IR (neat, cmꢁ1): 2923, 1747, 1609, 1582, 1473, 1446, 1248,
1162, 1109, 967, 770. APCI-MS calcd for [C19H19FIO2, M þ H]þ:
425.04, Found 425.04.
4.5.2. 2,6-Dimethylphenyl (E)-2-iodo-5-(naphthalen-2-yl)pent-4-
enoate (4b)
4.5.7. 2,6-Dimethylphenyl (E)-5-(2-chlorophenyl)-2-iodopent-4-
enoate (4g)
White solid, mp: 110e112 ꢀC, 82% yield, >95:5 rr. 1H NMR
(400 MHz, CDCl3):
d 7.83e7.76 (m, 3H, ArH), 7.72 (s, 1H, ArH), 7.57
Colorless semi-oil, 88% yield, >95:5 rr. 1H NMR (400 MHz,
(dd, J1 ¼ 8.8 Hz and J2 ¼ 1.6 Hz, 1H, ArH), 7.50e7.42 (m, 2H, ArH),
7.07e7.00 (m, 3H, ArH), 6.75 (d, J ¼ 16.0 Hz, 1H, ArCH ¼ ), 6.32 (dt,
J1 ¼ 16.0 Hz and J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 4.71 (dd, J1 ¼ 9.2 Hz and
J2 ¼ 6.4 Hz, 1H, CHI), 3.29e3.00 (m, 2H, CH2), 2.16 (brs, 6H, 2CH3);
CDCl3): d 7.52e7.48 (m, 1H, ArH), 7.38e7.33 (m, 1H, ArH), 7.25e7.17
(m, 2H, ArH), 7.07e7.03 (m, 3H, ArH), 6.98 (d, J ¼ 16.0 Hz, 1H,
ArCH ¼ ), 6.20 (dt, J1 ¼ 16.0 Hz and J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 4.70
(dd, J1 ¼ 8.4 Hz and J2 ¼ 6.8 Hz, 1H, CHI), 3.25e3.01 (m, 2H, CH2),
13C NMR (100 MHz, CDCl3):
d 168.8, 147.6, 134.5, 134.0, 133.5, 133.0,
2.18 (brs, 6H, 2CH3); 13C NMR (100 MHz, CDCl3):
d 168.6, 147.6,
130.4, 128.8, 128.3, 128.0, 127.7, 126.4, 126.3, 126.2, 126.1, 126.0,
123.2, 39.8, 17.4, 16.5. IR (neat, cmꢁ1): 3053, 2922, 1747, 1472, 1161,
1108, 964, 809, 770, 744. APCI-MS calcd for [C23H22IO2, M þ H]þ:
457.07, Found 457.06.
134.7, 133.0, 130.4, 130.3, 129.8, 128.9, 128.8, 128.7, 126.9, 126.7,
126.2, 39.5, 17.5, 16.6. IR (neat, cmꢁ1): 3041, 2921, 1746, 1470, 1162,
1107, 965, 768, 748. APCI-MS calcd for [C19H19ClIO2, M þ H]þ:
441.01, Found 441.01.
4.5.3. 2,6-Dimethylphenyl (E)-5-([1,1'-biphenyl]-4-yl)-2-iodopent-
4-enoate (4c)
4.5.8. 2,6-Dimethylphenyl (E)-5-(2-bromophenyl)-2-iodopent-4-
enoate (4h)
White solid, mp: 138e140 ꢀC, 78% yield, >95:5 rr. 1H NMR
White solid, mp: 52e53 ꢀC, 78% yield, >95:5 rr. 1H NMR
(400 MHz, CDCl3): d 7.63e7.54 (m, 4H, ArH), 7.47e7.41 (m, 4H, ArH),
(400 MHz, CDCl3):
d
7.55 (dd, J1 ¼ 8.0 Hz and J2 ¼ 0.8 Hz, 1H, ArH),
7.38e7.32 (m, 1H, ArH), 7.08e7.00 (m, 3H, ArH), 6.63 (d, J ¼ 16.0 Hz,
1H, ArCH ¼ ), 6.24 (dt, J1 ¼ 16.0 Hz and J2 ¼ 7.2 Hz, 1H, ¼CHCH2),
4.69 (dd, J1 ¼ 9.2 Hz and J2 ¼ 6.4 Hz, 1H, CHI), 3.25e2.96 (m, 2H,
7.49 (dd, J1 ¼ 8.0 Hz and J2 ¼ 1.6 Hz, 1H, ArH), 7.30e7.24 (m, 1H,
ArH), 7.16e7.10 (m, 1H, ArH), 7.08e7.01 (m, 3H, ArH), 6.94 (d,
J ¼ 16.0 Hz, 1H, ArCH ¼ ), 6.16 (dt, J1 ¼ 16.0 Hz and J2 ¼ 7.2 Hz,
1H, ¼CHCH2), 4.70 (dd, J1 ¼ 8.4 Hz and J2 ¼ 6.8 Hz, 1H, CHI),
3.25e3.01 (m, 2H, CH2), 2.19 (brs, 6H, 2CH3); 13C NMR (100 MHz,
CH2), 2.18 (brs, 6H, 2CH3); 13C NMR (100 MHz, CDCl3):
d 168.7, 147.6,
140.6, 140.5, 135.6, 133.9, 130.4, 128.8, 128.7, 127.4, 127.3, 126.9,
126.7, 126.2, 125.9, 39.7, 17.5, 16.6. IR (neat, cmꢁ1): 3027, 1747, 1484,
1161, 1109, 968, 758, 697. APCI-MS calcd for [C25H24IO2, M þ H]þ:
483.08, Found 483.08.
CDCl3):
d 168.6, 147.6, 136.5, 133.0, 130.3, 129.0, 128.9, 128.8, 127.5,
126.9, 126.2, 123.5, 110.0, 39.4, 17.5, 16.6. IR (neat, cmꢁ1): 3042,
2922, 1746, 1466, 1163, 1107, 1022, 964, 769, 749. APCI-MS calcd for
[C19H19BrIO2, M þ H]þ: 484.96, Found 484.97.
4.5.4. 2,6-Dimethylphenyl (E)-5-(4-fluorophenyl)-2-iodopent-4-
enoate (4d)
4.5.9. 2,6-Dimethylphenyl (E)-5-(benzo[d][1,3]dioxol-5-yl)-2-
iodopent-4-enoate (4i)
White solid, mp: 77e78 ꢀC, 84% yield, >95:5 rr. 1H NMR
(400 MHz, CDCl3):
d
7.35e7.29 (m, 2H, ArH), 7.08e6.97 (m, 5H,
White solid, mp: 94e96 ꢀC, 45% yield, >95:5 rr. 1H NMR
ArH), 6.55 (d, J ¼ 16.0 Hz, 1H, ArCH ¼ ), 6.10 (dt, J1 ¼ 16.0 Hz and
J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 4.66 (dd, J1 ¼ 9.2 Hz and J2 ¼ 6.4 Hz, 1H,
CHI), 3.21e293 (m, 2H, CH2), 2.15 (brs, 6H, 2CH3); 13C NMR
(400 MHz, CDCl3):
d
7.07e7.00 (m, 3H, ArH), 6.90 (d, J ¼ 1.2 Hz, 1H,
ArH), 6.79 (dd, J1 ¼ 8.0 Hz and J2 ¼ 1.2 Hz, 1H, ArH), 6.75 (d,
J ¼ 8.0 Hz, 1H, ArH), 6.49 (d, J ¼ 15.6 Hz, 1H, ArCH ¼ ), 6.01 (dt,
J1 ¼16.0 Hz and J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 5.96 (s, 2H, OCH2O), 4.64
(dd, J1 ¼ 8.8 Hz and J2 ¼ 6.4 Hz, 1H, CHI), 3.19e2.91 (m, 2H, CH2),
(100 MHz, CDCl3):
d
168.7, 162.4 (d, J ¼ 246.0 Hz), 147.6, 133.2, 132.8
(d, J ¼ 3.4 Hz), 130.3, 128.8, 127.8 (d, J ¼ 8.0 Hz), 126.2, 125.5 (d,
J ¼ 2.3 Hz), 115.5 (d, J ¼ 21.6 Hz), 39.5, 17.4, 16.5. IR (neat, cmꢁ1):
3039, 2922, 1747, 1600, 1508, 1473, 1229, 1159, 1109, 967, 771. APCI-
MS calcd for [C19H19FIO2, M þ H]þ: 425.04, Found 425.04.
2.16 (brs, 6H, 2CH3); 13C NMR (100 MHz, CDCl3):
d 168.7, 148.0,
147.6, 147.3, 134.0, 131.1, 130.4, 128.8, 126.2, 124.0, 121.1, 108.3, 105.4,
101.1, 39.5, 17.7, 16.5. IR (neat, cmꢁ1): 2920, 1746, 1503, 1488, 1445,
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(2017), http://dx.doi.org/10.1016/j.tet.2017.01.048
a-diazoacetates, Tetrahedron

B. Xu et al. / Tetrahedron xxx (2017) 1e10
9
1249, 1162, 1037, 963, 929, 770. APCI-MS calcd for [C20H20IO4,
7.37e7.31 (m, 2H, ArH), 7.30e7.26 (m, 1H, ArH), 7.23 (dd, J1 ¼ 8.8 Hz
and J2 ¼ 2.4 Hz, 1H, ArH), 6.62 (d, J ¼ 15.6 Hz, 1H, ArCH ¼ ), 6.22 (dt,
J1 ¼ 16.0 Hz and J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 4.66 (dd, J1 ¼ 8.8 Hz and
J2 ¼ 6.8 Hz, 1H, CHI), 3.22e2.96 (m, 2H, CH2); 13C NMR (100 MHz,
M þ H]þ: 451.04, Found 451.05.
4.5.10. 2,6-Dimethylphenyl (E)-2-iodo-5-phenylhex-4-enoate (4j)
Colorless semi-oil, 82% yield, >95:5 rr. 1H NMR (400 MHz,
CDCl3):
d 169.7, 148.1, 136.7, 134.2, 133.6, 131.6, 129.5, 128.7, 127.8,
CDCl3):
d
7.40e7.36 (m, 2H, ArH), 7.35e7.30 (m, 2H, ArH), 7.29e7.26
127.7,127.6,126.7,126.3,125.9,125.8,120.2,118.1, 39.4,18.7. IR (neat,
cmꢁ1): 3024, 1747, 1628, 1508, 1207, 1155, 1100, 964, 740. APCI-MS
calcd for [C21H18IO2, M þ H]þ: 429.03, Found 429.03.
(m, 1H, ArH), 7.06e7.01 (m, 3H, ArH), 5.75 (td, J1 ¼ 7.2 Hz and
J2 ¼ 1.2 Hz, 1H, ¼CH), 4.67 (dd, J1 ¼ 8.8 Hz and J2 ¼ 6.8 Hz, 1H, CHI),
3.27e2.96 (m, 2H, CH2), 2.16 (brs, 6H, 2CH3), 2.10 (s, 3H, CH3); 13C
NMR (100 MHz, CDCl3):
d 168.9, 147.6, 143.0, 139.2, 130.4, 128.8,
4.5.16. 2,6-Dichlorophenyl (E)-2-iodo-5-phenylpent-4-enoate (4p)
128.3, 127.2, 126.2, 125.7, 124.1, 35.8, 17.7, 16.5, 16.4. IR (neat, cmꢁ1):
2920, 1747, 1473, 1157, 1108, 768, 756, 696. APCI-MS calcd for
[C20H22IO2, M þ H]þ: 421.07, Found 421.09.
Colorless oil, 61% yield, 95:5 rr. 1H NMR (400 MHz, CDCl3):
d
7.41e7.31 (m, 6H, ArH), 7.30e7.26 (m, 1H, ArH), 7.16 (t, J ¼ 8.0 Hz,
1H, ArH), 6.59 (d, J ¼ 15.6 Hz, 1H, ArCH ¼ ), 6.22 (dt, J1 ¼16.0 Hz and
J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 4.70 (dd, J1 ¼ 8.8 Hz and J2 ¼ 6.8 Hz, 1H,
CHI), 3.25e2.95 (m, 2H, CH2); 13C NMR (100 MHz, CDCl3):
d 167.5,
4.5.11. 2,6-Dimethylphenyl 2-iodo-5-methylhex-4-enoate (4k)
Colorless oil, 74% yield, >95:5 rr. 1H NMR (400 MHz, CDCl3):
143.3, 136.7, 134.4, 129.1, 128.8, 128.6, 127.7, 127.5, 126.3, 125.7, 39.5,
16.4. IR (neat, cmꢁ1): 3025, 2921, 1762, 1576, 1445, 1226, 1138, 1090,
964, 795, 770, 741, 692. APCI-MS calcd for [C17H14Cl2IO2, M þ H]þ:
446.94, Found 446.95.
d
7.08e7.02 (m, 3H, ArH), 5.20e5.12 (m, 1H, ¼CH), 4.53 (dd,
J1 ¼ 9.6 Hz and J2 ¼ 6.0 Hz, 1H, CHI), 3.06e2.73 (m, 2H, CH2), 2.19
(brs, 6H, 2CH3), 1.71 (s, 3H, CH3), 1.67 (s, 3H, CH3); 13C NMR
(100 MHz, CDCl3):
d 169.0, 147.6, 136.7, 130.4, 128.7, 126.1, 121.0,
35.4, 25.8, 18.2, 18.1, 16.4. IR (neat, cmꢁ1): 2967, 2923, 1750, 1473,
1342, 1164, 1139, 1107, 768. APCI-MS calcd for [C15H20IO2, M þ H]þ:
359.05, Found 359.05.
4.6. Deuterium study
A 8 mL reaction vial was charged with Cu(OTf)2 (7.2 mg,
0.02 mmol) and 4,4'-dimethoxy-2,2'-bipyridine (5.2 mg,
0.024 mmol). The vial was degassed and refilled with argon. After
CH2Cl2 (3 mL) was added, the mixture was stirred at room tem-
perature for 1 h. Then the mixture was stirred in a 40 ꢀC oil bath,
followed by addition of 183 (0.4 mmol) and 2e (0.48 mmol) as a
mixed solution in CH2Cl2 (1 mL). The mixture was stirred at 40 ꢀC
until the reaction was complete (monitored by TLC). The mixture
was then concentrated and purified by flash column chromatog-
raphy on silica gel (PE/EtOAc ¼ 30:1) to afford a colorless semi-oil as
a mixture of 19 and 20, 77% yield, 19: 20 ¼ 40%: 60% (monitored by
4.5.12. 2,6-Dimethylphenyl 4-cyclohexylidene-2-iodobutanoate
(4l)
Colorless oil, 42% yield, 94:6 rr. 1H NMR (400 MHz, CDCl3):
d
7.07e7.01 (m, 3H, ArH), 5.12 (t, J ¼ 7.2 Hz, 1H, ¼CH), 4.50 (dd,
J1 ¼ 9.2 Hz and J2 ¼ 6.4 Hz, 1H, CHI), 3.01e2.75 (m, 2H, CH2), 2.19
(brs, 6H, 2CH3), 2.26e2.00 (m, 4H, 2CH2), 1.60e1.48 (m, 6H, 3CH2);
13C NMR (100 MHz, CDCl3):
d 168.9, 147.6, 144.7, 130.4, 128.7, 126.1,
117.6, 37.1, 34.4, 29.1, 28.3, 27.6, 26.7, 18.7, 16.5. IR (neat, cmꢁ1):
2925, 2852, 1751, 1473, 1445, 1342, 1164, 1148, 1103, 768. APCI-MS
calcd for [C18H24IO2, M þ H]þ: 399.08, Found 399.08.
1H NMR). 1H NMR (400 MHz, CDCl3):
d 7.08e7.03 (m, 3H, ArH),
5.86e5.76 (m, 1H, CH ¼ ), 5.29e5.21 (m, 2(H/D), ¼C(H/D)2),
4.5.13. 2,6-Dimethylphenyl 2-iodo-5,9-dimethyldeca-4,8-dienoate
(4m, E/Z ¼ 2:1)
4.64e4.57 (m, 1H, CHI), 3.06e2.80 (m, 2(H/D), C(H/D)2), 2.20 (s, 6H,
2CH3); 13C NMR (100 MHz, CDCl3):
d 168.7, 147.6, 134.4 (134.5),
Colorless oil, 74% yield, >95:5 rr, E/Z ¼ 2:1. 1H NMR (400 MHz,
130.4, 128.8, 126.2, 119.3, 40.2, 17.4 (17.2), 16.6. APCI-MS calcd for
[C13H14D2IO2, M þ H]þ: 333.03, Found 333.03.
CDCl3):
d
7.08e7.03 (m, 3H, ArH), 5.18 (t, J ¼ 7.2 Hz, 1H, ¼CH),
5.14e5.06 (m, 1H, ¼CH), 4.56e4.48 (m, 1H, CHI), 3.05e2.75 (m, 2H,
CH2), 2.19 (brs, 6H, 2CH3), 2.14e1.97 (m, 4H, 2CH2), 1.72e1.66 (m,
6H, 2CH3), 1.63e1.59 (m, 3H, CH3); 13C NMR (100 MHz, CDCl3):
Acknowledgments
d
169.0, 147.6, 140.2, 131.7, 130.4, 128.7, 126.1, 123.8, 120.7, 39.7
Financial support was provided by W. W. Caruth, Jr. Endowed
Scholarship, Welch Foundation (I-1748), National Institutes of
Health (R01GM102604), National Science Foundation (1150875),
and Sloan Research Fellowship.
(35.0), 35.2 (32.2), 26.4 (26.2), 25.7 (23.4), 18.3 (18.4), 17.7 (17.6),
16.6 (16.4), 16.5. IR (neat, cmꢁ1): 2965, 2921, 1751, 1163, 1137, 1105,
768. APCI-MS calcd for [C20H28IO2, M þ H]þ: 427.11, Found 427.11.
4.5.14. Naphthalen-1-yl (E)-2-iodo-5-phenylpent-4-enoate (4n)
Colorless semi-oil, 76% yield, >95:5 rr. 1H NMR (400 MHz,
Appendix A. Supplementary data
CDCl3):
d
7.99 (d, J ¼ 8.4 Hz, 1H, ArH), 7.87 (d, J ¼ 8.0 Hz, 1H, ArH),
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2017.01.048.
7.76 (d, J ¼ 8.4 Hz, 1H, ArH), 7.52e7.45 (m, 2H, ArH), 7.44e7.40 (m,
2H, ArH), 7.39e7.32 (m, 3H, ArH), 7.32e7.27 (m, 1H, ArH), 7.23 (dd,
J1 ¼ 7.6 Hz and J2 ¼ 0.8 Hz, 1H, ArH), 6.65 (d, J ¼ 15.6 Hz, 1H,
ArCH ¼ ), 6.27 (dt, J1 ¼ 15.6 Hz and J2 ¼ 7.2 Hz, 1H, ¼CHCH2), 4.78
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(2017), http://dx.doi.org/10.1016/j.tet.2017.01.048
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Please cite this article in press as: Xu B, et al., Copper-catalyzed [1,2]-rearrangements of allylic iodides and aryl
(2017), http://dx.doi.org/10.1016/j.tet.2017.01.048
a-diazoacetates, Tetrahedron