(Diacyloxyiodo)benzenes-Driven Palladium-Catalyzed Cyclizations of Unsaturated N-Sulfonylamides: Opportunities of Path Selection

Article abstract of DOI:10.1002/adsc.201600813

A study of the palladium(II)-catalyzed cyclization of unsaturated N-sulfonylamides was undertaken, using (diacyloxyiodo)benzenes as terminal oxidizing agents. Different reactivities were observed as a function of the nature of the unsaturation (terminal vs. internal), or of the hypervalent iodine compound used (diacetoxyiodobenzene vs. bistrifluoroacetoxyiodobenzene). Proper parameter selection allows the direction of the cyclization to be chosen towards either a global aminoacetoxylation, an allylic amination via aminopalladation, or an allylic amination via allylic C–H activation. (Figure presented.).

Full text of DOI:10.1002/adsc.201600813

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DOI: 10.1002/adsc.201600813
(Diacyloxyiodo)benzenes-Driven Palladium-Catalyzed
Cyclizations of Unsaturated N-Sulfonylamides: Opportunities of
Path Selection
Tea Borelli,a,b Stefano Brenna,a Gianluigi Broggini,a,* Julie Oble,b
and Giovanni Polib,*
a
Dipartimento di Scienza e Alta Tecnologia, Universitꢀ dell’Insubria, via Valleggio 11, 22100 Como, Italy
Fax : (+39)-031-238-6449; phone: (+39)-031-238-6444; e-mail: gianluigi.broggini@uninsubria.it
Sorbonne Universitꢁs, UPMC Univ Paris 06, Institut Parisien de Chimie Molꢁculaire, UMR CNRS 8232, Case 229, 4
b
Place Jussieu, 75252 Paris Cedex 05, France
E-mail: giovanni.poli@upmc.fr
Received: July 25, 2016; Revised: December 6, 2016; Published online: && &&, 0000
Supporting information for this article can be found under: http://dx.doi.org/10.1002/adsc.201600813.
Abstract: A study of the palladium(II)-catalyzed
cyclization of unsaturated N-sulfonylamides was un-
dertaken, using (diacyloxyiodo)benzenes as termi-
nal oxidizing agents. Different reactivities were ob-
served as a function of the nature of the unsatura-
tion (terminal vs. internal), or of the hypervalent
iodine compound used (diacetoxyiodobenzene vs.
bistrifluoroacetoxyiodobenzene). Proper parameter
selection allows the direction of the cyclization to
be chosen towards either a global aminoacetoxyla-
tion, an allylic amination via aminopalladation, or
an allylic amination via allylic C–H activation.
stant interest in the mechanisms of Pd-catalyzed nu-
cleophilic additions to alkenes,[5,6] we envisioned an
extension of the above initial study to nitrogen-based
substrates bearing terminal as well as internal unsatu-
rations, and to the testing of new reaction conditions.
Our new study started with N-tosylglycine N’-crotyl-
N’-benzylamide 1b as the model substrate, using the
reaction conditions optimized in our previous study
[Pd(OAc)2 5 mol%, PhI(O2CCH3)2 (2.0 equiv.),
AcONa (1.0 equiv.) and Bu4NHSO4 (1.0 equiv.)].
No reaction occurred when working with CH2Cl2 as
solvent, either at room temperature or at reflux.
However, on changing to DCE at reflux (conditions
1), we obtained the 5-vinylpiperazinone 3b in 50%
yield (Scheme 2, and Table 1, entry 1), instead of the
anticipated corresponding aminoacetoxylated prod-
uct.[4] Performing the cyclization in MeCN at room
Keywords: allylic compounds; amination; C–H acti-
vation; homogeneous catalysis; palladium
The literature devoted to the oxidative Pd(II)-cata-
lyzed addition of nucleophiles to olefins is very exten-
sive and the method allows the construction of
a number of synthetically useful compounds starting
from simple unsaturated substrates.[1] Although differ-
ent terminal oxidants have been used for this purpose,
the attention was recently directed toward hyperva-
lent iodine reagents.[2,3] In particular, PhI(O2CCH3)2,
alias PIDA, has been efficiently used to promote 1,2-
aminoacetoxylations of unsaturated amine derivatives.
In this context, some of us recently described the
intra-intermolecular conversion of glycine allylamides
into
acetoxymethyl-substituted
piperazinones
[Scheme 1, Eq. (1)].[4] In this contribution, we show
that slight modifications of the substrate and/or the
oxidizing system can trigger alternative mechanisms
Scheme 1. Previous and present studies on Pd(II)-catalyzed
[Scheme 1, Eqs. (2) and (3)]. In the frame of our con- cyclizations using PhI(O2CR)2.
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Table 1. Pd(II)-catalyzed cyclization of allyl and crotyl N-
sulfonyl derivatives with PhI(O2CCH3)2 under Conditions
1.[a]
Scheme 2. Pd(OAc)2-catalyzed cyclization of 1b with
PhI(O2CCH3)2, Conditions 1.
temperature for 24 h also furnished the product, al-
though in lower yield.
These new conditions were then tested on other dif-
ferently substituted N-sulfonyl-N’-allyl or N’-crotyl-
ACHTUNGTRENNUNG
gave the vinyl piperazinone 3c in 47% yield (entry 2),
while the 4-tert-butylphenylsulfonyl derivative 1d af-
forded the corresponding 5-vinylpiperazinone 3d in
35% yield (entry 3). The different behavior between
the allyl and the crotyl derivatives was confirmed in
the next tests. Indeed, N-tosyl-anthranilic acid N’-
crotyl-N’-benzylamide 1e provided the corresponding
vinyl-substituted benzodiazepinone 3e in 72% yield
(entry 4), while the corresponding N-allyl-N-methyl
derivative 1f gave the 2-acetoxymethyl-benzodiazepi-
none 2f in 92% yield (entry 5). Carbamate substrates
showed the same behavior. In fact, N-tosyl crotyl car-
bamate 1g led to the 4-vinyloxazolidinone 3g in 55%
yield (entry 6), while the corresponding allyl deriva-
tive 1h gave the 4-acetoxymethyloxazolidone 2h, al-
though in this case the b-H elimination product 4 was
prevailing (entry 7). Worthy of note, the reaction con-
ditions to convert 1g into 3g (Table 1, entry 6) turned
out to be more effective than the acidic conditions
previously reported by some of us,[7] which led to
total degradation of the substrate.
The two different outcomes of the above described
reactions can be understood in terms of an initial
common aminopalladation step, to afford a transient
aminopalladated intermediate I (step 1), from which
two
alternative
paths
are
possible:
a)
a PhI(O2CCH3)2-promoted oxidative cleavage via the
high valent species II, if a distocyclic b-H elimination
is unavailable (clockwise steps 2+3); or b) a distocy-
clic b-H elimination followed by palladium hydride
reoxidation (anticlockwise steps 4+5), if the former
step is possible (Scheme 3).[8] Thus, when a distocyclic
hydrogen is available (I, R2 =CH3), the b-H elimina-
tion path turns out to be faster than the oxidative
cleavage. On the other hand, the difficulty of b-H
elimination of intermediates I and II (R2 =H), having
only a proxicyclic b-hydrogen available has been al-
ready noticed by us.[6d,7]
[a]
Reaction conditions: Pd(OAc)2 (5 mol%), PhI(O2CCH3)2
(2.0 equiv.), AcONa (1.0 equiv.), Bu4NHSO4 (1.0 equiv.)
in DCE at reflux, 5 h.
Intriguingly, preliminary cyclization tests on allyl
and crotyl amides of N-tosyl and Ns-glycine 1a, b, i, j
We then turned our attention to PhI(O2CCF3)2, furnished neither type 3 products (deriving from ami-
alias PIFA, as alternative oxidizing agent (Conditions nopalladation/dehydropalladation), nor type 2 ones
2) (Scheme 4).[9–11]
(deriving from aminopalladation/trifluoroacetoxyla-
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Table 2. Optimization of the Pd(II)-catalyzed cyclization of
N-tosylamide 1b with Conditions 2.
Entry Pd(OAc)2
(mol%)
Oxidant
(equiv.)
Bu4NHSO4
(equiv.)
T
Yield
[8C] [%]
1
2
3
4
5
6
7
5
–
5
5
5
5
5
4.0
4.0
4.0
1.0
2.0
4.0
2.0
1.0
1.0
–
1.0
0.2
0.2
1.0
25
25
25
25
80
25
80
78
s.m.
<5
40
18
45
85
Scheme 3. Proposed mechanism for the cyclization of N-allyl
and N-crotyl derivatives with Conditions 1, depicted on
amide 1b.
(Table 3). The reaction was effective on glycine N-
crotyl-N-benzylamides protected at the nucleophilic
nitrogen with sulfonyl groups other than tosyl or
nosyl groups, such as 1c and 1d, to give the corre-
sponding imidazolidinones 5c and 5d in 31% and
35% yield (entries 2 and 3). N-Tosyl-anthranilic acid
N’-crotyl-N’-benzylamide 1e and N’-allyl-N’-methyl 1f
afforded the corresponding dihydroquinazolinones 5e
and 5f in 40% and 26% yield (entries 4 and 5). Anal-
ogously, N-tosylglycine N’-cyclohexenyl-N’-benzyla-
mide 1k provided the spiranic compound 5k in 37%
yield (entry 6), while N-tosylglycine N’-benzyl-N’-cin-
namylamide 1l afforded the corresponding imidazoli-
dinone in 44% yield (entry 7).
Scheme 4. Preliminary experiments on the cyclization of
allyl and crotyl N-sulfonylamides using Conditions 2.
tion). Instead, the corresponding 2-vinyl- or 2-prope-
Several spectroscopic experiments (1H NMR,
nylimidazolidinones 5a, b, i, j were unexpectedly ob- 13C NMR, IR, and UV, see the Supporting Informa-
tained (Scheme 4). On the basis of this general behav- tion) were conducted to detect the putative genera-
ior, optimization of this reaction on N-tosylglycine N’- tion of Pd(O2CCF3)4 from oxidation of Pd(O2CCH3)2
crotyl-N’-benzylamide 1b was next undertaken or Pd(O2CCF3)2 by PhI(O2CCF3)2. However, no ex-
(Table 2). Use of Pd(OAc)2 (5 mol%), PhI(O2CCF3)2 periment revealed conclusive findings. Although more
(2.0 equiv.), NaOAc (1.0 equiv.), and Bu4NHSO4 work will be required to clarify this point, we believe
(1.0 equiv.) in DCE at room temperature for 3 h gave that oxidation of the metal by the hypervalent reagent
the 2-vinylimidazolidinone 5b in 78% yield (entry 1). is more likely to take place on a more electron-rich
No reaction occurred in the absence of either the pal- organometallic Pd(II) intermediate, or on Pd(0). Ac-
ladium catalyst (entry 2),[12] or of Bu4NHSO4 cordingly, we propose that under the reaction condi-
(entry 3). Reduction of the amount of PhI(O2CCF3)2 tions 2, an initial, rapid, although reversible, amino-
from 4.0 to 1.0 equivalents, or of the molar ratio palladation/Pd(II)-to-Pd(IV)
oxidation
sequence
PhI(O2CCF3)2/Bu4NHSO4 from 4.0/1.0 to 2.0/0.2 (at might still be possible (Scheme 5), (step 1). However,
reflux of the solvent), or to 4.0/0.2 brought about con- in this case, and in contrast to what was observed
siderable yield erosions, too (entries 4, 5, and 6). Fi- with PhI(O2CCH3)2, neither dehydropalladation (R2 =
nally,
by
employing
Pd(OAc)2
(5 mol%), CH3) nor reductive elimination from the Pd(IV) inter-
PhI(O2CCF3)2 (2.0 equiv.), NaOAc (1.0 equiv.), and mediate (R2 =H) are permitted from the resulting
Bu4NHSO4 (1.0 equiv.) in DCE at reflux, we were aminopalladated intermediate II. In particular, the re-
able to increase the yield to 85% (entry 7).
ductive elimination may be forbidden by the highly
With the optimal conditions in hand, we proceeded withdrawing power of the trifluoroacetyl ligand,[13]
to explore the scope of this cyclization on different N- while the absence of available vacant sites on the
sulfonylated amino acid allylamide substrates metal in II(n=1) may account for the blockage of dehy-
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Table 3. Pd(II)-catalyzed cyclization of allyl and crotyl N-
sulfonyl derivatives with PhI(O2CCF3)2 with Conditions 1.[a]
Scheme 5. Proposed mechanism for the cyclization of N-allyl
and N-crotyl amides with Conditions 2.
the h3-allyl system generates the cyclic product 5 and
colloidal Pd(0) (step 4),[17] which can be reoxidized to
Pd(O2CCF3)2 by PhI(O2CCF3)2 (step 5). However, an
alternative or competitive oxidation of IV(n=1) to
IV(n=3), by PhI(O2CCF3)2, (step 6) before the cycliza-
tion (step 7) cannot be ruled out. Thus, the competi-
tion between the former [Pd(0)/Pd(II)] and the latter
[Pd(II)/Pd(IV)] mechanism will depend on the rela-
tive rates between oxidation and cyclization of inter-
mediate IV(n=1)
.
Worthy of note, with these substrates the cycliza-
tion step is favored over the alternative trifluoroace-
toxylating reductive elimination step, observed by
Szabꢃ and co-workers.[10a]
In conclusion, in the framework of our continuing
research project devoted to the study of Pd-catalyzed
cyclizations, we have shown that N-sulfonylamides ex-
hibit different reactivity patterns, when using (diacyl-
[a]
Reaction conditions: Pd(OAc)2 (5 mol%), PhI(O2CCF3)2
(2.0 equiv.), AcONa (1.0 equiv.), Bu4NHSO4 (1.0 equiv.)
in DCE at reflux, 3–7 h.
AHCTUNGTREGoNNUN xyiodo)benzenes as the terminal oxidizing agents.
Indeed, as a function of the position of the unsatura-
tion, or of the nature of the hypervalent iodine com-
pound used, as well as of the judicious selection of
the reaction conditions, a global aminoacetoxylation,
dropalladation step.[14] As a result, a slower, but irre- an allylic amination via aminopalladation, or an allylic
versible allylic C–H activation (steps 2+3)[15,16] gener- amination via allylic C–H activation, can be predicta-
ates the h3-allylcomplex IV(n=1), via III. Subsequent in- bly obtained at will.
tramolecular addition of the sodium salt of the N-sul-
fonylated nitrogen atom onto the proximal position of
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(E)-3-Benzyl-2-(prop-1-en-1-yl)-1-tosyl-2,3-dihydroquina-
Experimental Section
zolin-4-one (5e): Reaction time: 5 h; eluent: (1/1 AcOEt/pe-
1
troleum ether); yield: 40%; orange oil; H NMR (400 MHz,
General Procedure for the Palladium-Catalyzed
CDCl3): d=1.54 (d, J=6.5 Hz, 3H), 2.28 (s, 3H), 4.04 (d,
J=14.2 Hz, 1H), 4.86 (d, J=14.2 Hz, 1H), 5.30 (ddd, J=
15.2, 5.8, 1.6 Hz, 1H), 5.57–5.66 (m, 1H), 6.07 (d, J=5.8 Hz,
1H), 7.22–7.39 (m, 10H), 7.50–7.55 (m, 1H), 7.78 (dd, J=
8.1, 1.0 Hz, 1H), 7.94 (dd, J=7.7, 1.6 Hz, 1H); 13C NMR
(100 MHz, CDCl3): d=17.3 (q), 21.5 (q), 48.8 (t), 71.1 (d),
124.2 (s), 125.0 (d), 125.4 (d), 126.7 (d), 126.9 (d), 128.0 (d),
128,3 (d), 128.7 (d), 129.4 (d), 129.8 (d), 131.2 (d), 132.9 (d),
134.4 (s), 135.9 (s), 136.0 (s), 144.1 (s), 160.9 (s); anal. calcd.
for C25H24N2O3S: C 69.42, H 5.59, N 6.48; found: C 69.23, H
5.84, N 6.75.
Amination Reactions with PhI(OAc)2 (Conditions 1)
A
mixture of Pd(OAc)2 (5 mol%, 0.02 mmol, 5.0 mg),
PhI(O2CCH3)2 (2 equiv., 0.6 mmol, 0.193 g), AcONa
(1.0 equiv., 0.3 mmol, 25 mg), Bu4N+HSO4
(1 equiv.,
ꢀ
0.3 mmol, 0.102 g) and substrate 1b–h (1 equiv., 0.3 mmol)
in DCE (0.02M, 15 mL) was heated at reflux for 5 h. The
solvent was evaporated and the mixture was taken up with
5 mL of CH2Cl2 and aqueous Na2S2O3 was added (5 mL).
The two phases were separated, the organic extract was
washed with brine (5 mL), and the brine layer was extracted
with CH2Cl2 (5 mL). The combined organic phases were
dried over Na2SO4 and the solvent was evaporated under re-
duced pressure. The crude product was purified by silica gel
column chromatography.
1-Benzyl-4-tosyl-1,4-diazaspiro[4.5]dec-6-en-2-one
(5k):
Reaction time: 7 h; eluent: (6/4 AcOEt/petroleum ether,
1
then 9/1 CH2Cl2/MeOH); yield: 37%; orange oil; H NMR
(400 MHz, CDCl3): d=1.75–2.22 (m, 4H), 2.35–2.40 (m,
2H), 2.43 (s, 3H), 4.08 (s, 2H), 4.27 (d, J=15.8 Hz, 1H),
4.47 (d, J=15.8 Hz, 1H), 5.15 (d, J=10.1 Hz, 1H), 6.25 (d,
J=10.1 Hz, 1H), 7.09–7.11 (m, 2H), 7.21–7.32 (m, 3H), 7.71
(d, J=8.3 Hz, 2H), 7.81 (d, J=8.3 Hz, 2H); 13C NMR
(100 MHz, CDCl3): d=18.9 (t), 21.6 (q), 23.8 (t), 34.8 (t),
43.9 (t), 49.1 (t), 80.9 (s), 124,6 (d), 127.1 (d), 127.8 (d),
128.5 (d), 129.7 (d), 132.9 (d), 136.9 (s), 137.0 (s), 138.3 (d),
144.0 (s), 167.5 (s): anal. calcd. for C22H24N2O3S: C 66.64, H
6.10, N 7.07; found: C 66.53, H 6.34, N 6.81.
1-Benzyl-4-tosyl-5-vinylpiperazin-2-one (3b): Eluent: (6/4
AcOEt/ petroleum ether); yield: 50%; white solid; mp
1
1008C; H NMR (400 MHz, CDCl3): d=2.44 (s, 3H), 3.13
(dd, J=12.5 Hz, J=2.1 Hz, 1H), 3.45 (dd, J=12.5 Hz, J=
4.7 Hz, 1H), 3.78 (d, J=17.4, 1H), 4.26 (d, J=17.4 Hz, 1H),
4.34 (d, J=14.4 Hz, 1H), 4.63 (m, 1H), 4.68 (d, J=14.4 Hz,
1H), 5.02 (dd, J=17.3 Hz, J=1.4 Hz, 1H), 5.14 (dd, J=
10.6 Hz, J=1.4 Hz, 1H), 5.45–5.49 (m, 1H), 7.14–7.16 (m,
2H), 7.27–7.31 (m, 5H), 7.69 (d, J=8.3 Hz, 2H); 13C NMR
(100 MHz, CDCl3): d=21.5 (q), 45.1 (t), 48.7 (t), 49.9 (t),
52.7 (d), 119.4 (t), 127.4 (d), 127.9 (d), 128.4 (d), 128.7 (d),
129.8 (d), 131.9 (d), 135.5 (s), 135.6 (s), 144.1 (s), 164.1 (s);
anal. calcd. for C20H22N2O3S: C 64.84, H 5.99, N 7.56; found:
C 65.01, H 5.87, N 7.39.
Acknowledgements
4-Benzyl-1-tosyl-2-vinyl-1,2,3,4-tetrahydrobenzo[e][1,4]di-
azepin-5-one (3e): Eluent: (6/4 AcOEt/ etroleum ether);
yield: 72%; yellow oil; H NMR (400 MHz, CDCl3): d=2.42
We thank Omar Khaled (UPMC) for HR-MS analyses. The
Universitꢀ degli Studi dell’Insubria, CNRS, UPMC, and
Labex Michem are acknowledged for financial support. Sup-
port through CMST COST Action, CM1205 (CARISMA)
and CMST COST Action, CA15106 (CHAOS) is also grate-
fully acknowledged.
1
(s, 3H), 3.02–3.12 (m, 2H), 3.62 (d, J=14.8 Hz, 1H), 4.74
(d, J=14.8 Hz, 1H), 4.92–4.99 (m, 1H), 5.25 (d, J=10.4 Hz,
1H), 5.44 (d, J=17.2 Hz, 1H), 5.65–5.74 (m, 1H), 7.27–7.73
(m, 13H); 13C NMR (100 MHz, CDCl3): d=21.6 (q), 46.1
(t), 49.1 (t), 63.2 (d), 118.1 (t), 127.3 (d), 127.8 (d), 128.6 (d),
128.7 (d), 129.2 (d), 129.8 (d), 130.3 (d), 131.9 (d), 132.3 (d),
132.6 (d), 132.8 (s), 135.0 (s), 136.2 (s), 136.6 (s), 143.8 (s),
167.9 (s); anal. calcd. for C25H24N2O3S: C 69.42, H 5.59, N
6.48; found: C 69.55, H 5.37, N 6.66.
References
[1] For books and reviews see: a) J. Tsuji, Palladium Re-
agents and Catalysts, Wiley, 2nd edn., New York, 2004;
b) R. I. McDonald, G. Liu, S. S. Stahl, Chem. Rev. 2011,
111, 2981; c) T. Hoosokawa, Aminopalladation and Re-
lated Reactions Involving Other Group 15 Atom Nucle-
ophiles: Aminopalladation-Dehydropalladation and Re-
lated Reactions, in: Handbook of Organopalladium
Chemistry for Organic Synthesis, (Ed.: E.-i. Negishi),
John Wiley & Sons, Inc., New York, 2003; d) A. Minat-
ti, K. MuÇiz, Chem. Soc. Rev. 2007, 36, 1142.
General Procedure for Palladium-Catalyzed
Amination Reactions with PhI(OCOCF3)2
(Conditions 2)
A
mixture of Pd(OAc)2 (5 mol%, 0.02 mmol, 5.0 mg),
PhI(O2CCF3)2 (2 equiv., 0.6 mmol, 0.260 g), AcONa
ꢀ
(1 equiv., 0.3 mmol, 25 mg), Bu4N+HSO4
(1 equiv.,
0.3 mmol, 0.102 g) and substrate 1b–f, l (1 equiv., 0.3 mmol)
in DCE (0.02M, 15 mL) was heated at reflux for 3–7 h. The
solvent was evaporated and the mixture was taken up with
5 mL of CH2Cl2 and aqueous Na2S2O3 was added (5 mL).
The two phases were separated, the organic extract was
washed with brine (5 mL), and the brine layer was extracted
with CH2Cl2 (5 mL). The combined organic phases were
dried over Na2SO4 and the solvent was evaporated under re-
duced pressure. The crude product was purified by silica gel
column chromatography.
[2] For reviews on hypervalent iodine compounds see: a)
Metal-Catalyzed Cross-Coupling Reactions and More,
(Eds.: A. de Meijere, S. Brꢄse, M. Oestreich), in: Oxi-
˜
dative Functionalization of Alkenes, (Eds.: K. Muniz, C.
Martꢅnez), Chapt 16, Wiley-VCH, p 1259, 2014;
b) M. S. Yusubov, A. V. Maskaev, V. V. Zhdankin, Arki-
voc 2011, 370.
[3] See for example: E. J. Alexanian, C. Lee, E. J. Soren-
sen, J. Am. Chem. Soc. 2005, 127, 7690.
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[4] G. Broggini, E. M. Beccalli, T. Borelli, F. Brusa, S. Gaz-
zola, A. Mazza, Eur. J. Org. Chem. 2015, 4261.
Soc. 2009, 131, 3452; c) X.-F. Hou, Y.-N. Wang, I.
Gçttker-Schnetmann, Organometallics 2011, 30, 6053.
[11] For examples of metal-free intramolecular amidations
of unsaturated substrates, see: a) S. Serna, I. Tellitu, E.
Domꢅnguez, I. Moreno, R. SanMartꢅn, Tetrahedron
Lett. 2003, 44, 3483; b) H. Shi, T. Guo, D. Zhang-Negr-
erie, Y. Du, K. Zhao, Tetrahedron 2014, 70, 2753;
c) L. M. Pardo, I. Tellitu, E. Domꢅnguez, Tetrahedron
2012, 68, 3692.
[12] This negative result is of particular relevance from
a mechanistic viewpoint (see below) as, under particu-
lar circumstances, PhI(O2CCF3)2 is known to oxidative-
ly activate alkenes and amines even in the absence of
palladium.
[5] a) E. M. Beccalli, G. Broggini, S. Gazzola, A. Mazza,
Org. Biomol. Chem. 2014, 12, 6767; b) G. Broggini, V.
Barbera, E. M. Beccalli, U. Chiacchio, A. Fasana, S.
Galli, S. Gazzola, Adv. Synth. Catal. 2013, 355, 1640;
c) G. Broggini, V. Barbera, E. M. Beccalli, E. Borsini,
S. Galli, G. Lanza, G. Zecchi, Adv. Synth. Catal. 2012,
354, 159; d) E. Borsini, G. Broggini, A. Fasana, S. Galli,
M. Khansaa, U. Piarulli, M. Rigamonti, Adv. Synth.
Catal. 2011, 353, 985; e) G. Broggini, E. M. Beccalli, E.
Borsini, A. Fasana, G. Zecchi, Synlett 2011, 227; f) G.
Abbiati, E. M. Beccalli, G. Broggini, M. Martinelli, G.
Paladino, Synlett 2006, 73.
[6] a) F. Nahra, F. Liron, G. Prestat, C. Mealli, A. Mes-
saoudi, G. Poli, Chem. Eur. J. 2009, 15, 11078; b) M. M.
Lorion, F. Nahra, V. L. Ly, C. Mealli, A. Mesaoudi, F.
Liron, J. Oble, G. Poli, Chem. Today 2014, 32, 30;
c) F. J. S. Duarte, G. Poli, M. J. Calhorda, ACS Catal.
2016, 6, 1772; d) M. M. Lorion, F. J. S. Duarte, M. J.
Calhorda, J. Oble, G. Poli, Org. Lett. 2016, 18, 1020;
e) M. M. Lorion, J. Oble, G. Poli, Pure Appl. Chem.
2016, DOI: 10.1515/pac-2015-1102; f) F. Louafi, M. M.
Lorion, J. Oble, G. Poli, Synlett 2015, 26, 2237. See
also: g) G. Zanoni, A. Porta, A. Meriggi, M. Franzini,
G. Vidari, J. Org. Chem. 2002, 67, 6064.
[13] The difficulty of reductive elimination from RPdX
complexes carrying electron-withdrawing ligands is well
known. See for example: a) A. H. Roy, J. F. Hartwig, J.
Am. Chem. Soc. 2001, 123, 1232. See also: b) E. J. Cho,
T. D. Senecal, T. Kinzel, Y. Zhang, D. A. Watson, S. L.
Buchwald, Science 2010, 328, 1679.
[14] While with PhI(O2CCH3)2 dehydropalladation from I is
expected to be faster than metal oxidation (Scheme 3,
right hemicycle), with PhI(O2CCF3)2, Pd(II)-to-Pd(IV)
oxidation is likely to be the fastest step.
[15] For an analogous Pd-catalyzed mechanism passing
through allylic C–H activation, as a result of a reversible
aminopalladation step, see: ref.[7]
[16] For a recent review on direct allylic functionalization
through Pd-catalyzed C–H activation, see: F. Liron, J.
Oble, M. M. Lorion, G. Poli, Eur. J. Org. Chem. 2014,
5863.
[17] Tetraalkylammonium salts are known to favor forma-
tion of colloidal Pd(0). The stabilizing effect is due to
the electrostatic interaction of the anions as well as to
the steric repulsion of the massive tetraalkylammonium
cations nearby the nanoparticle core. See, for example:
P. Mastrorilli, A. Monopoli, M. A. Dell’Anna, M. La-
tronico, P. Cotugno, A. Nacci, Ionic Liquids (ILs) in
Organometallic Catalysis, in: Ionic Liquids in Palladi-
um-Catalyzed Cross-Coupling Reactions, in: Topics in
Organometallic Chemistry, (Eds.: J. Dupont, L. Kollar),
Vol. 51, Springer, p 237, Springer, 2015.
[7] J. Rajabi, M. M. Lorion, V. L. Ly, F. Liron, J. Oble, G.
Prestat, G. Poli, Chem. Eur. J. 2014, 20, 1539.
[8] An alternative path I!3, wherein oxidation precedes
the b-H elimination step, cannot be totally ruled out, as
this will depend on the relative rates of b-H elimination
vs. oxidation I!II. We thank a referee for having
pointed out this aspect.
[9] For selected reviews on polyvalent iodine compounds,
see: a) A. Yoshimura, V. V. Zhdankin, Chem. Rev.
2016, 116, 3328; b) ref.[2b] and ref.[1] quoted therein;
c) V. V. Zhdankin, J. Org. Chem. 2011, 76, 1185; d) Q.
Ding, Y. Ye, R. Fan, Synthesis 2013, 45, 1.
[10] For examples of use of PhI(O2CCF3)2 as oxidizing
agent in Pd(II)-catalyzed transformations, see: a) R.
Alam, L. T. Pilarski, E. Pershagen, K. J. Szabꢃ, J. Am.
Chem. Soc. 2012, 134, 8778; b) T. Tsujihara, K. Takena-
ka, K. Onitsuka, M. Hatanaka, H. Sasai, J. Am. Chem.
Adv. Synth. Catal. 0000, 000, 0 – 0
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ÞÞ
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COMMUNICATIONS
(Diacyloxyiodo)benzenes-Driven Palladium-Catalyzed
Cyclizations of Unsaturated N-Sulfonylamides:
Opportunities of Path Selection
7
Adv. Synth. Catal. 2017, 359, 1 – 7
Tea Borelli, Stefano Brenna, Gianluigi Broggini,*
Julie Oble, Giovanni Poli*
Adv. Synth. Catal. 0000, 000, 0 – 0
7
ꢂ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!