Gold(I)-Catalyzed Intramolecular Dehydrative Amination of Sulfamate Esters Tethered to Allylic Alcohols: A Strategy for the Synthesis of Cyclic Sulfamidates

Article abstract of DOI:10.1002/adsc.202001330

An efficient synthesis protocol for cyclic sulfamidates has been developed via catalytic intramolecular cyclizations of sulfamate esters tethered to allylic alcohols. The reactions proceed smoothly at room temperature in the presence of (IPr)AuCl (5 mol%) and AgBF₄ (5 mol%). This protocol features good to excellent yields, high selectivity, broad substrate scope, and mild reaction conditions. This method is also applicable to the synthesis of a seven-membered sulfamidate. (Figure presented.).

Full text of DOI:10.1002/adsc.202001330

UPDATES
DOI: 10.1002/adsc.202001330
Gold(I)-Catalyzed Intramolecular Dehydrative Amination of
Sulfamate Esters Tethered to Allylic Alcohols: A Strategy for the
Synthesis of Cyclic Sulfamidates
Yunjeong Park,a Ji Sun Lee,a and Jae-Sang Ryua,*
a
College of Pharmacy & Graduate School of Pharmaceutical Sciences, Ewha Womans University, 52 Ewhayeodae-gil,
Seodaemun-gu, Seoul 03760, Republic of Korea
E-mail: ryuj@ewha.ac.kr
Manuscript received: October 28, 2020; Revised manuscript received: February 13, 2021;
Version of record online: March 3, 2021
Supporting information for this article is available on the WWW under https://doi.org/10.1002/adsc.202001330
oxidants and the preparation of complex allene
substrates remain critical issues associated with these
Abstract: An efficient synthesis protocol for cyclic
sulfamidates has been developed via catalytic intra-
strategies. Despite the aforementioned elegant works,
molecular cyclizations of sulfamate esters tethered
there is still an increasing demand to develop a general
to allylic alcohols. The reactions proceed smoothly
and mild method to synthesize various cyclic sulfami-
at room temperature in the presence of (IPr)AuCl
dates, which must be devoid of oxidant and harsh
(5 mol%) and AgBF4 (5 mol%). This protocol
reaction conditions. To meet such a demanding goal,
features good to excellent yields, high selectivity,
we have addressed this issue by using cyclization of
broad substrate scope, and mild reaction conditions.
sulfamate esters tethered to allylic alcohols
This method is also applicable to the synthesis of a
(Scheme 2d).
seven-membered sulfamidate.
We selected the Au/Ag catalyst combination system
for the development of new catalytic methods to
synthesize cyclic sulfamidates. Over the past decades,
Keywords: Homogeneous catalysis; Gold; Silver;
homogeneous gold and silver catalysis has proved to
Amination; Cyclic sulfamidate
be a versatile tool for the construction of complex
Cyclic sulfamidates[1] are flexible synthetic intermedi-
ates widely used for the synthesis of various function-
alized amines. Notably, the reactivity of 1,2- and 1,3-
cyclic sulfamidates is comparable to that of activated
aziridines and azetidines, respectively.[2] Thus, various
nucleophiles readily attack exclusively at the O-
bearing carbon center in a stereospecific (SN2) manner
to deliver an N-sulfate intermediate[3] further hydro-
lyzed under acidic conditions to the final functional-
À
ized amine (NuÀ =CNÀ , FÀ , N3 , RSÀ , ROÀ ),[4]
functionalized lactam (NuÀ =EtO2CHCÀ FG),[2] or
functionalized
piperazine/thiomorpholine
(NuÀ =
EtO2CCH2XÀ )[5] (Scheme 1).
Conventionally, cyclic sulfamidates are prepared
from the thionylation of amino alcohol followed by
oxidation (Scheme 2a).[6] Alternatively, transition metal
(Rh, Ru, Mn, or Ag)-catalyzed intramolecular oxida-
tive nitrene insertion into the C(sp3)À H bond has been
extensively studied (Scheme 2b),[7] and gold(I)-cata-
lyzed allene hydroamination has also been recently
reported (Scheme 2c).[8] However, the use of strong
Scheme 1. Cyclic sulfamidate as a synthetic intermediate.
Adv. Synth. Catal. 2021, 363, 2183–2188
2183
© 2021 Wiley-VCH GmbH

UPDATES
asc.wiley-vch.de
We envisaged a process in which a π-acidic cationic
gold/silver species would react with the alkene moiety
of allylic alcohol, and subsequent elimination of water
molecule would drive the cyclization to completion
(eq. 1). To validate our hypothesis, we began our study
by examining the cyclization of allylic alcohol-tethered
sulfamate ester 1 using a variety of gold and silver
salts as catalysts (Table 1). At the outset of this project,
various gold chloride salts including AuCl3,
NaAuCl4·2H2O, AuCl, (IPr)AuCl, (PMe3)AuCl, (PCy3)
AuCl, and (PPh3)AuCl were tested for cyclization at
room temperature in CH2Cl2 solvent (entries 1–7).
Gold(III) and gold(I) salts having Cl– ion were not
effective, and only a trace amount of cyclized product
2a was observed even after 48 h. However, (PPh3)Au-
–
catalyst carrying NTf2 increased the yield up to 35%
(entry 8). To our delight, treatment of 1a with the
catalyst combination (PPh3)AuCl/AgOTf gave the
cyclic sulfamidate 2a in much improved yields after
22 h (91%, entry 9).
Scheme 2. Strategies for the synthesis of cyclic sulfamidates.
molecular architecture.[9] Gold and silver act as soft
and carbophilic Lewis acids,[10] and hence can make
the CÀ C π bond more susceptible to a nucleophilic
attack. However, despite much success in alkyne,
allene, and terminal alkene activation, the activation of
internal olefins by gold and silver catalysts has been
elusive and remained relatively unexplored.
Table 1. Catalyst screening and optimization of reaction con-
ditions.[a]
Related to this topic, allylic alcohols have been
used as important substrates. Especially, the gold-
catalyzed intramolecular dehydrative functionalizations entry catalyst
of allylic alcohols have been widely studied and well
documented for a range of nucleophiles. Bandini and
time solvent yield (%) [b]
(h)
(cis:trans) [c]
1
2
3
4
5
6
7
8
AuCl3
NaAuCl4·2H2O
AuCl
(IPr)AuCl
(PMe3)AuCl
(PCy3)AuCl
(PPh3)AuCl
(PPh3)AuNTf2
48
48
48
48
48
48
48
48
CH2Cl2 trace[d]
co-workers reported gold-catalyzed cyclization of
indoles tethered to allylic alcohols.[11] In addition,
Aponick, Bandini, and Widenhoefer independently
developed gold-catalyzed intramolecular functionaliza-
tion of allylic alcohols using O-nucleophiles[12] and N-
nucleophiles.[13] In these reactions, allylic alcohols
served as valuable synthetic equivalents of non-
activated alkenes and/or allenes. As part of a program
to develop new catalytic synthetic methods for cyclic
sulfamidates, we herein report gold/silver-catalyzed
intramolecular dehydrative amination of sulfamate
esters tethered to more easily accessible allylic alco-
hols.
CH2Cl2 trace[d]
CH2Cl2 trace[d]
CH2Cl2 0[d]
CH2Cl2 0[d]
CH2Cl2 trace[d]
CH2Cl2 0[d]
CH2Cl2 35 (3.7:1)
CH2Cl2 91 (4.1:1)
toluene 38 (2.5:1)[e]
9
(PPh3)AuCl/AgOTf 22
10
11
12
13
(PPh3)AuCl/AgOTf[e] 26
(PPh3)AuCl/AgOTf
(PPh3)AuCl/AgOTf
(PPh3)AuCl/AgOTf
48
24
48
THF
trace[d]
dioxane 16 (2.9:1)[d]
CH3CN trace[d]
[a] Reaction conditions: 1 a (300 μmol), gold catalyst
(15.0 μmol), silver catalyst (15.0 μmol), solvent (3.0 mL).
[b] Isolated yields after column chromatography.
1
[c] Diastereomeric ratio is based on H NMR.
[d] Starting material was recovered.
[e]
°
Carried out at 60 C.
Adv. Synth. Catal. 2021, 363, 2183–2188
2184
© 2021 Wiley-VCH GmbH

UPDATES
asc.wiley-vch.de
At this stage, we investigated the solvent effect on although the reaction was slower than the AgBF4
the yield of gold(I)-catalyzed intramolecular dehydra- reaction.
tive amination of sulfamate ester 1a in the presence of
The addition of silver salt significantly enhanced
silver salt to choose the best solvent condition for the reactivity of the gold catalyst, which encouraged us
further catalyst screening. The yields were varied to further investigate the effect of counterion and silver
based on the used solvents. The reaction was only on the cyclization reaction. As shown in entry 7 in
effective in CH2Cl2, and a small amount of the product Table 2, AgOTf alone was not an effective catalyst.
was observed or isolated in the other solvents, such as When used as a sole catalyst, only a trace of the
toluene, THF, dioxane, and CH3CN (Table 1, en- product was observed after 48 h. However, the (PPh3)
tries 10–13). Considering the yield of the product, AuCl/AgOTf combination showed a better activity
CH2Cl2 was the best solvent for the reaction (Table 1, over (PPh3)AuCl or AgOTf alone (Table 1, entry 9, vs.
entry 9), and thus chosen for further study.
Table 1, entry 7, and Table 2, entry 7). Likewise, the
Interestingly, changing the PPh3 ligand to IPr (IPr)AuCl/AgBF4 combination demonstrated a better
dramatically accelerated the reaction: the reaction activity over (IPr)AuCl or AgBF4 alone (Table 2,
using (IPr)AuCl/AgOTf combination rapidly com- entry 6, vs. Table 1, entry 4, and Table 2, entry 8),
pleted in 3 hours, and afforded the desired product 2a which could originate from the silver[14] or/and
in a better yield and selectivity compared with the counterion[15] effect. To assess the silver and counterion
reaction of (PPh3)AuCl/AgOTf (3 h, 97%, Table 2, effect, we performed the control reaction catalyzed by
entry 1, vs. 22 h, 91%, Table 1, entry 9). Since IPr (IPr)AuOTs, prepared by premixing (IPr)AuCH3 and
turned out to be the best ligand for gold catalysts, we TsOH in the absence of silver salts, which gave 2a in
decided to screen a variety of silver salts combined 80% yield after 48 h (Table 2, entry 9). The reaction
with (IPr)AuCl (Table 2, entries 1–6). The reactions was clean and comparable to the reaction of (IPr)-
were efficiently catalyzed by a 1:1 mixture of (IPr) AuCl/AgOTs. Compared with the poor reactivity of
AuCl and a range of silver salts. Among the silver salts (IPr)AuCl (Table 1, entry 4) or AgOTs alone (Table 2,
screened, AgBF4 was particularly rapid and effective, entry 10), the improved reactivity of the (IPr)AuCl/
and provided 2a in the best yield (99%) in 2 h AgOTs combination might derive from the counterion
(Table 2, entry 6). However, the best selectivity was and the intrinsic activity of the gold(I) catalyst rather
obtained with AgOTs (dr=24:1, Table 2, entry 2), than from the silver(I) catalyst. Meanwhile, TsOH did
not catalyze the cyclization (Table 2, entry 11). Ac-
cording to our observation, the counterion effect[15] is
unambiguously more significant than silver effect.[14]
Therefore, it cannot be excluded that the apparent
Table 2. Silver salt and counterion effect on the cyclization of
silver salt effect may originate from the counterion
effect. Our observation is well consistent with recent
report about counterion effect: weakly coordinating
anions generate more-electrophilic gold centers with
consequent stronger metal-π system interactions.[15]
Currently, further investigation of the silver and
counterion effect on the yield and selectivity of
cyclization reaction is in progress.
allylic alcohol-tethered sulfamate ester.[a]
entry
catalyst
time
(h)
yield (%) [b]
(cis:trans) [c]
After establishing the optimal conditions, we
demonstrated the scope of gold(I)-catalyzed intra-
molecular dehydrative amination of allylic alcohol-
tethered sulfamate esters 1b–p using (IPr)AuCl and
silver salts including AgBF4, AgOTs, AgSbF6, or
AgOTf (Scheme 3). In most cases, AgBF4 showed the
best performance in terms of yield and reaction times,
whereas in cases of 2g and 2l, AgOTf and AgSbF6
provided respective desired cyclized products in better
yields than AgBF4. Notably, improved dr’s were
observed with AgOTs (except in cases of 2o and 2p),
although the reaction time was prolonged, and the
yield decreased.
1
2
3
4
5
6
7
8
(IPr)AuCl/AgOTf
(IPr)AuCl/AgOTs
(IPr)AuCl/AgNO3
(IPr)AuCl/AgSbF6
(IPr)AuCl/AgNTf2
(IPr)AuCl/AgBF4
AgOTf
AgBF4
(IPr)AuCH3/TsOH
AgOTs
3
97 (7.0:1)
93 (24:1)
84 (19:1)
97 (3.5:1)
73 (22:1)
99 (11:1)
trace[d]
48
48
3
48
2
48
48
48
48
48
trace[d]
9
10
11
80 (16:1)
0[d]
TsOH
trace[d]
[a] Reaction conditions: 1 a (300 μmol), gold catalyst
(15.0 μmol), silver catalyst (15.0 μmol), CH2Cl2 (3.0 mL).
[b] Isolated yields after column chromatography.
When AgBF4 was used, the substrates containing
aliphatic substituents such as n-pentyl, c-hexyl, and t-
butyl groups smoothly provided the cyclized products
2b–d in 3 h in excellent yields (89–90%). The
[c] Diastereomeric ratio is based on H NMR.
1
[d] Starting material was recovered.
Adv. Synth. Catal. 2021, 363, 2183–2188
2185
© 2021 Wiley-VCH GmbH

UPDATES
asc.wiley-vch.de
methyl substituent on the sulfamidate ring significantly
affected the dr (cis/trans 4.8:1 for 2g vs. cis/trans
1:1.8 for 2h) due to the large energy difference
between the transition states during cyclization, while
the methyl substituent on the side chain showed a
negligible effect on the dr (cis/trans 7.2:1 for 2i vs.
cis/trans 8.7:1 for 2j). The reaction was also effective
for the synthesis of benzo-fused cyclic sulfamidate[16]
heterocycle: 2l was obtained in 86% yield at room
temperature after 41 h in the presence of AgSbF6 under
standard conditions.
The power of this method was well-demonstrated
by the synthesis of cyclic sulfamidates variously
substituted on alkene residue. The reaction was tolerant
of various types of substituents on allylic moiety:
treatment of 1m, 1n, and 1o with (IPr)AuCl/AgBF4
led to the clean formation of gem-dimethyl, c-hexyl,
and methyl-substituted products 2m, 2n, and 2o.
Another feature of note is a seven-membered ring
formation. Even though transition metal-catalyzed
intramolecular hydroaminations show remarkable effi-
ciency, unfortunately, seven-membered ring cyclization
is hampered by both unfavorable enthalpic and
entropic factors.[17] Despite extensive studies on the
gold-catalyzed intramolecular hydroamination of al-
kene, allene, and alkyne, seven-membered ring for-
mation is rare and limited to the alkyne substrate
preorganized for cyclization.[18] Surprisingly, our meth-
od was well applicable to the synthesis of seven-
membered sulfamidate 2p, which was obtained in 75%
yield in the presence of (IPr)AuCl/AgBF4 at room
temperature rapidly in 2 h.
The effect of the double-bond configuration of the
substrate on this gold(I)-catalyzed dehydrative amina-
tion was also evaluated employing Z-allylic alcohol
substrate (Z)-1a, which can be considered as an
alternative substrate (Scheme 4). When Z-allylic alco-
hol substrate (Z)-1a was subjected to the standard
catalytic conditions, (�)-2a was isolated in a some-
what decreased yield with improved selectivity (88%,
cis/trans=26:1), compared to the reaction of (E)-1a
(Table 2, entry 6).
A plausible brief mechanistic pathway is proposed
in Scheme 5, based on previous studies[12c,13,19] and our
observation. The initial coordination of π-acidic cati-
onic gold(I) species[20] to the olefin of 1 would form
Scheme 3. Synthesis of cyclic sulfamidates via gold(I)-cata-
lyzed intramolecular cyclization reaction.[a]
substrates containing aromatic substituents such as p-
trifluoromethylphenyl and p-nitrophenyl groups also
afforded the corresponding cyclized product 2e and 2f
in 38% and 70% yield, respectively. Benzyl and TBS
protecting groups for the hydroxyl group were compat-
ible with the (IPr)AuCl/AgBF4 conditions (2g–k). The
Scheme 4. The cyclization of Z-allylic alcohol-tethered sulfa-
mate ester.
Adv. Synth. Catal. 2021, 363, 2183–2188
2186
© 2021 Wiley-VCH GmbH

UPDATES
asc.wiley-vch.de
conformation B’ (Scheme 5). The structure of
(+)-(R,R,E)-2o and dr of the reaction were unambigu-
ously confirmed by NMR experiments (Supporting
Information).
In summary, we have successfully developed an
efficient gold/silver-catalyzed intramolecular dehydra-
tive amination of sulfamate esters tethered to allylic
alcohols to furnish cyclic sulfamidates under mild
conditions. This is the first report on the construction
of synthetically valuable cyclic sulfamidates using
sulfamate esters tethered to allylic alcohols, which are
easily accessible. This methodology is useful in
medicinal chemistry, and its application to the syn-
thesis of bioactive natural products is currently under-
way in our laboratory.
Experimental Section
Synthesis of Cyclic Sulfamidates 2a; Typical Proce-
dure
To a 5 mL oven-dried round-bottom flask with a side arm were
added (IPr)AuCl (9.3 mg, 15.0 μmol, 5 mol%.) and AgBF4
(2.9 mg, 15.0 μmol, 5 mol%). A solution of (E)-7-hydroxy-1-
phenylhept-5-en-3-yl sulfamate (1a, 85.6 mg, 300 μmol) in
anhydrous CH2Cl2 (3 mL) was added. The reaction mixture was
stirred at room temperature for 2 h. Upon completion of the
reaction, the reaction mixture was filtered through a plug of
Celite® and rinsed with EtOAc (30 mL). The filtrate was
concentrated in vacuo and purified by column chromatography
hexanes/EtOAc, (4:1!2:1) to afford cis and trans sulfamidates
2a.
Scheme 5. Plausible mechanism.
metal-π-alkene complex A, the intramolecular cycliza-
tion of which would proceed via an anti-addition and
lead to the hydrogen-bonded metal-alkyl complex B.
Proton transfer to the hydroxyl group would generate
intermediate C, and the subsequent anti-elimination of
water would yield the cyclic sulfamidate 2 through the
metal-π-alkene complex D. This proposed mechanism
is well-supported by previous studies[12c,13,19] for an
anti-addition/anti-elimination sequence for the gold(I)-
catalyzed intramolecular functionalization of allylic
alcohols. However, a detailed mechanism and the
participation of silver is still unclear.
Scheme 3 shows the formation of cis-cyclic sulfa-
midate (+)-(R,R,E)-2o as a major product in good
yields with good diastereoselectivity from configura-
tionally defined and enantiomerically enriched allylic
alcohol substrate (+)-(R,E,S)-1o. The effect of a chiral
secondary allylic alcohol moiety on the efficiency and
stereoselectivity of gold-catalyzed allylic amination/
alkoxylation was well-documented by Aponick[12c] and
Widenhoefer.[13c] In our case, the similar net syn
addition of À NH2 relative to À OH was also observed.
Regarding the stereoselective intramolecular dehydra-
tive amination of chiral secondary allylic alcohols,
Widenhoefer and co-workers proposed hydrogen-
bonded decalin-type conformation.[13c] Likewise, the
selective formation of (+)-(R,R,E)-2o can be rational-
ized by the potential trans-decalin-type chair-like
Acknowledgements
This research was supported by National Research Foundation
of Korea (NRF) grant funded by the Korea government (MSIT)
(NRF-2018R1A5A2025286) and (NRF-2020R1F1A1052496).
References
[1] R. E. Meléndez, W. D. Lubell, Tetrahedron 2003, 59,
2581–2616.
[2] J. F. Bower, J. Švenda, A. J. Williams, J. P. H. Charmant,
R. M. Lawrence, P. Szeto, T. Gallagher, Org. Lett. 2004,
6, 4727–4730.
[3] A. Avenoza, J. H. Busto, F. Corzana, G. Jiménez-Osés,
J. M. Peregrina, Chem. Commun. 2004, 980–981.
[4] C. Venkateswarlu, B. Datta, S. Chandrasekaran, RSC
Adv. 2014, 4, 42952–42956.
[5] A. J. Williams, S. Chakthong, D. Gray, R. M. Lawrence,
T. Gallagher, Org. Lett. 2003, 5, 811–814.
[6] For examples, see: M. Atfani, L. Wei, W. D. Lubell, Org.
Lett. 2001, 3, 2965–2968.
[7] J. F. Bower, J. Rujirawanich, T. Gallagher, Org. Biomol.
Chem. 2010, 8, 1505–1519.
Adv. Synth. Catal. 2021, 363, 2183–2188
2187
© 2021 Wiley-VCH GmbH

UPDATES
asc.wiley-vch.de
[8] a) M. C. M. Higginbotham, M. W. P. Bebbington, Chem.
Commun. 2012, 7565–7567; b) M. C. M. Higginbotham,
L. Kennedy, A. G. Lindsay, A. Troester, M. W. P.
Bebbington, Tetrahedron 2015, 71, 727–737.
[9] a) P. Y. Toullec, V. Michelet, Isr. J. Chem. 2018, 58,
578–585; b) Y. Zhang, T. Luo, Z. Yang, Nat. Prod. Rep.
2014, 31, 489–503; c) M. Naodovic, H. Yamamoto,
Chem. Rev. 2008, 108, 3132–3148; d) Y. Wang, P.
2012, 51, 1405–1407; Angew. Chem. 2012, 124, 1434–
1436; c) P. Mukherjee, R. A. Widenhoefer, Org. Lett.
2011, 13, 1334–1337.
[14] a) A. Zhdanko, M. E. Maier, ACS Catal. 2015, 5, 5994–
6004; b) D. Wang, R. Cai, S. Sharma, J. Jirak, S. K.
Thummanapelli, N. G. Akhmedov, H. Zhang, X. Liu,
J. L. Petersen, X. Shi, J. Am. Chem. Soc. 2012, 134,
9012–9019.
Zhang, X. Di, Q. Dai, Z.-M. Zhang, J. Zhang, Angew. [15] a) M. Jia, M. Bandini, ACS Catal. 2015, 5, 1638–1652;
Chem. Int. Ed. 2017, 56, 15905–15909; Angew. Chem.
2017, 129, 16121–16125.
b) A. Homs, C. Obradors, D. Leboeuf, A. M. Echavar-
ren, Adv. Synth. Catal. 2014, 356, 221–228.
[10] a) A. Fürstner, P. W. Davies, Angew. Chem. Int. Ed. [16] Y.-Q. Wang, Y. Zhang, H. Dong, J. Zhang, J. Zhao, Eur.
2007, 46, 3410–3449; Angew. Chem. 2007, 119, 3478– J. Org. Chem. 2013, 3764–3770.
3519; b) E. Jiménez-Núnez, A. M. Echavarren, Chem. [17] For the details of enthalpic and entropic factors for ring
Commun. 2007, 333–346.
closure, see: a) F. C. Lightstone, T. C. Bruice, Bioorg.
Chem. 1998, 26, 193–199; b) M. A. Casadei, C. Galli, L.
Mandolini, J. Am. Chem. Soc. 1984, 106, 1051–1056;
c) C. Galli, G. Illuminati, L. Mandolini, P. Tamborra, J.
Am. Chem. Soc. 1977, 99, 2591–2597.
[11] a) M. Bandini, A. Bottoni, M. Chiarucci, G. Cera, G. P.
Miscione, J. Am. Chem. Soc. 2012, 134, 20690–20700;
b) M. Bandini, A. Gualandi, M. Monari, A. Romaniello,
D. Savoia, M. Tragni, J. Organomet. Chem. 2011, 696,
338–347.
[18] H. Ito, T. Harada, H. Ohmiya, M. Sawamura, J. Org.
Chem. 2011, 7, 951–959.
[12] a) J. Liu, R. J. Miotto, J. Segard, A. M. Erb, A. Aponick,
Org. Lett. 2018, 20, 3034–3038; b) J. A. Goodwin, C. F. [19] P. Mukherjee, R. A. Widenhoefer, Org. Lett. 2010, 12,
Ballesteros, A. Aponick, Org. Lett. 2015, 17, 5574–5577; 1184–1187.
c) T. Ghebreghiorgis, B. Biannic, B. H. Kirk, D. H. Ess, [20] For examples of cationic, two-coordinate gold(I) π-
A. Aponick, J. Am. Chem. Soc. 2012, 134, 16307–16318;
d) B. Biannic, T. Ghebreghiorgis, A. Aponick, Beilstein
J. Org. Chem. 2011, 7, 802–807; e) A. Aponick, B.
Biannic, M. R. Jong, Chem. Commun. 2010, 46, 6849–
6851; f) M. Bandini, M. Monari, A. Romaniello, M.
Tragni, Chem. Eur. J. 2010, 16, 14272–14277; g) A.
Aponick, C.-Y. Li, B. Biannic, Org. Lett. 2008, 10, 669–
671; h) A. Aponick, B. Biannic, Synthesis, 2008, 3356–
3359.
alkene complexes see: a) T. J. Brown, M. G. Dickens,
R. A. Widenhoefer, J. Am. Chem. Soc. 2009, 131, 6350–
6351; b) T. J. Brown, M. G. Dickens, R. A. Widenhoefer,
Chem. Commun. 2009, 6451–6453; c) T. N. Hooper, M.
Green, J. E. McGrady, J. R. Patel, C. A. Russell, Chem.
Commun. 2009, 3877–3879; d) D. Zuccaccia, L. Belpas-
si, F. Tarantelli, A. Macchioni, J. Am. Chem. Soc. 2009,
131, 3170–3171; e) P. de Frémont, N. Marion, S. P.
Nolan, J. Organomet. Chem. 2009, 694, 551–560;
f) N. D. Shapiro, F. D. Toste, Proc. Natl. Acad. Sci. USA
2008, 105, 2779–2782.
[13] a) J. M. Ketcham, F. S. P. Cardoso, B. Biannic, H. Piras,
A. Aponick, Isr. J. Chem. 2013, 53, 923–931; b) P.
Mukherjee, R. A. Widenhoefer, Angew. Chem. Int. Ed.
Adv. Synth. Catal. 2021, 363, 2183–2188
2188
© 2021 Wiley-VCH GmbH