Air-stable nickel precatalysts for fast and quantitative cross-coupling of aryl sulfamates with aryl neopentylglycolboronates at room temperature

Article abstract of DOI:10.1021/ol503061c

A library containing 10 air-stable Ni^IIX(Aryl)(PCy₃)₂ complexes as precatalysts (X = Cl, Br, OTs, OMs, aryl = 1-naphthyl, 2-naphthyl; X = Cl, 1-acenaphthenyl, 1-(2-methoxynaphthyl), 9-phenanthrenyl, 9-anthracyl) was synthesized and demonstrated to quantitatively cross-couple 2-methoxyphenyl dimethylsulfamate with methyl 4-(5,5-dimethyl-1,3,2-dioxaborinane-2-yl)benzoate at 23 °C in dry THF in the presence of K₃PO₄(H₂O)_3.2 in less than 60 min. Lower or higher amounts of H₂O in K₃PO₄ and as received THF mediate the same transformation in a maximum three times longer reaction time.

Full text of DOI:10.1021/ol503061c

Letter
pubs.acs.org/OrgLett
Air-Stable Nickel Precatalysts for Fast and Quantitative Cross-
Coupling of Aryl Sulfamates with Aryl Neopentylglycolboronates at
Room Temperature
Ryan L. Jezorek, Na Zhang, Pawaret Leowanawat, Matthew H. Bunner, Nicholas Gutsche,
Aleksander K. R. Pesti, James T. Olsen, and Virgil Percec*
Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323,
United States
S
* Supporting Information
ABSTRACT: A library containing 10 air-stable NiIIX(Aryl)-
(PCy3)2 σ-complexes as precatalysts (X = Cl, Br, OTs, OMs,
aryl = 1-naphthyl, 2-naphthyl; X = Cl, 1-acenaphthenyl, 1-(2-
methoxynaphthyl), 9-phenanthrenyl, 9-anthracyl) was synthe-
sized and demonstrated to quantitatively cross-couple 2-
methoxyphenyl dimethylsulfamate with methyl 4-(5,5-dimeth-
yl-1,3,2-dioxaborinane-2-yl)benzoate at 23 °C in dry THF in
the presence of K3PO4(H2O)3.2 in less than 60 min. Lower or higher amounts of H2O in K3PO4 and as received THF mediate
the same transformation in a maximum three times longer reaction time.
ince its discovery in 1995,1 the Ni-catalyzed Suzuki−
to be used to estimate the reactivity of these precatalysts in
SMiyaura reaction has evolved into an attractive synthetic cross-couplings of other electrophiles4a and nucleophiles.4l
2
method for borylation,3 cross-coupling of a variety of unreactive
electrophiles based on carbon−oxygen bonds,4 and even aryl
fluorides.5 Therefore, Ni catalysis provides both a less expensive
and a more reactive variant than Pd catalysis. The mixed-
NiIICl(1-naphthyl)(PPh3)2 was synthesized by the left-hand
route depicted in Scheme 1,10 while NiIICl(1-naphthyl)(PCy3)2
was obtained both by the top and right routes. All other
precatalysts were synthesized by the right-hand route.
Cross-coupling with Ni(COD)2/mixed-ligand, 4/mixed-
ligand, 5/mixed-ligand, and 6/mixed-ligand indicated that
PCy3 may exchange for COD or PPh3 to create precatalyst 6
in situ (Scheme 2).
The synthesis of 6 demonstrated that indeed in the absence
of the mixed ligands PPh3 and COD, this precatalyst is more
reactive than Ni(COD)2, 4 and 5 with PCy3 as mixed ligand.
Water is known to be involved in the cross-coupling catalytic
process.4e,12 Therefore, a series of samples of K3PO4 with
various amounts of water of hydration were used to perform
Ni-catalyzed cross-coupling experiments with both dry and as-
received wet and inhibited THF (Scheme 3).
Scheme 4 compares the role of X (Cl, OTs, OMs) and excess
PCy3 in cross-coupling reactions as monitored by GC to
quantitative conversion. It was observed that precatalysts 6−11
yield quantitative conversions in 50−60 min regardless of the
nature of X when no excess of PCy3 was used or even in 30−50
min when excess PCy3 was used.
Additional recrystallization of precatalyst 7, isolated by
precipitation in hexane when prepared by left or right route
from Scheme 1, does not change its activity (Scheme 4).
Exchange of Cl from 6 and 7 for tosylate in 8 and 9 and
mesylate in 10 and 11 maintains the same catalytic activity.
7
ligand4h,6 Ni(COD)2/PCy3 and the precatalyst8−10 based on
the σ-complex trans-chloro(1-naphthyl) bis(triphenylphos-
phine)NiII 9,10 (precatalyst 4) together with PCy3 mixed-ligand,
[NiIICl(1-naphthyl)(PPh3)2]/PCy3,10 facilitated entries into
room temperature cross-coupling reactions of carbon−oxygen
based electrophiles4a,10 with a diversity of boron-based
nucleophiles.4e,10 Since Ni0 catalysts including Ni(COD)2 are
air sensitive, σ-complexes obtained by oxidative addition of aryl
electrophiles to Ni0 species generated an attractive approach to
reactive and air stable nickel precatalysts. Inspired by the
NiIICl(1-naphthyl)(PPh3)2/PCy3 precatalyst/mixed-ligand sys-
tem,10 we report here the discovery of a library of air stable
NiIIX(Aryl)(PCy3)2 (X = Cl, Br, OTs, OMs, aryl = 1-naphthyl,
2-napththyl; X = Cl, aryl = 1-acenaphthenyl, 1-(2-methox-
ynaphthyl), 9-phenanthrenyl, 9-anthracenyl) precatalysts that
mediate the quantitative cross-coupling of ortho-substituted aryl
sulfamates with aryl neopentylglycolboronates in less than 1 h
at room temperature (23 °C) in dry THF. The ortho-
substituted aryl sulfamate electrophile was selected because of
its synthetic versatility4c and lower reactivity compared with
aryl mesylates4a,l and aryl halides.4l The aryl neopentylglycol-
boronate nucleophile, synthesized from the in situ prepared
neopentylglycolborane by a method inspired by the procedure
reported for pinacolborane,11 was used due to its lower
reactivity when compared with other arylboron nucleophiles.4l
This selection will allow the preliminary results reported here
Received: October 19, 2014
© XXXX American Chemical Society
A
dx.doi.org/10.1021/ol503061c | Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 1. Synthesis of trans-NiIIX(1-naphthyl)(PR3)2 σ-Complexes (X = Br, Cl, OMs, OTs) and the Proposed Mechanism of
Nickel-Catalyzed Suzuki−Miyaura Cross-Coupling
Scheme 2. Cross-Coupling of 2-Methoxyphenyl
Scheme 3. Effect of Water on Ni-Catalyzed Cross-Coupling
of 2-Methoxyphenyl Dimethylsulfamate with Methyl 4-(5,5-
Dimethyl-1,3,2-dioxaborinan-2-yl)benzoate at 23 °C in
Dimethylsulfamate with Methyl 4-(5,5-Dimethyl-1,3,2-
dioxaborinan-2-yl)benzoate at 23 °C in THF Catalyzed by
a
a
Ni Precatalysts and Mixed-Ligand Systems
THF
a
Reaction conditions: aryl sulfamates (0.30 mmol), aryl neo-
a
Reaction conditions: aryl sulfamates (0.30 mmol), aryl neo-
pentylglycolboronates (0.32 mmol), Ni precatalyst (0.015 mmol),
mixed ligand (10 to 20 mol %) vs aryl sulfamate, K3PO4(H2O)3.2 (191
mg), THF (1.0 mL). Conversion by GC, isolated yield in parentheses.
pentylglycolboronates (0.32 mmol), Ni precatalyst (0.015 mmol),
K3PO4(H2O)n (191 mg), THF (1.0 mL). Conversion by GC.
The efficient activation of precatalyst 6 is depicted in Scheme
5. Upon mixing with dioxaborinane 2, precatalyst 6 generates
quantitatively the active species Ni0(PCy3)2 in less than 5 min
(Scheme 5). This coordinatively unsaturated Ni0 species, in
contrast with the coordinatively saturated Ni0(PCy3)3,13 may
act as the active catalyst in the subsequent cross-coupling
reaction (Scheme 1). Additional mechanistic investigations are
required to support this hypothesis.
In order to elucidate the role of substitution of the naphthyl
groups of these precatalysts, several electron-rich substituents
and extra fused aromatic rings were incorporated in the
structure of 6. Therefore, precatalysts 12−15 were prepared
and tested in the same cross-coupling reaction (Scheme 6).
Additional ortho-substitution on the 1-naphthyl group of
precatalyst 13 leads to slightly lower reactivity, while para-
substitution (precatalyst 12) has no effect. An additional fused
aromatic ring as in precatalysts 14 and 15 does not significantly
change reactivity but does decrease the atom economy of the
catalytic system (Scheme 6).
In summary, a library of 10 Ni precatalysts which mediate
quantitative cross-coupling of ortho-substituted aryl sulfamates
with aryl neopentylglycolboronates in the presence of
K3PO4(H2O)3.2 in less than 60 min at room temperature was
reported. Precatalyst 6 was prepared by both the left and right
B
dx.doi.org/10.1021/ol503061c | Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 4. Activity of NiIIX(naphthyl)(PCy3)2 Precatalysts in
Cross-Coupling of 2-Methoxyphenyl Dimethylsulfamate
with Methyl 4-(5,5-Dimethyl-1,3,2-dioxaborinane-2-
Scheme 6. Activity of NiIIX(R-naphthyl)(PCy3)2 Precatalysts
in Cross-Coupling of 2-Methoxyphenyl Dimethylsulfamate
with Methyl 4-(5,5-Dimethyl-1,3,2-dioxaborinan-2-
a
a
yl)benzoate at 23 °C in THF
yl)benzoate at 23 °C in THF
a
Reaction conditions: aryl sulfamates (0.30 mmol), aryl neo-
pentylglycolboronates (0.32 mmol), Ni precatalyst (0.015 mmol),
K3PO4(H2O)3.2 (191 mg), THF (1.0 mL). Conversion by GC.
probably make them valuable for cross-coupling reactions in
medicinal, materials, supramolecular, and macromolecular
synthesis. Additional Ni precatalysts and electrophilic and
nucleophilic substrates are under investigation.
a
Reaction conditions: aryl sulfamates (0.30 mmol), aryl neo-
pentylglycolboronates (0.32 mmol), Ni precatalyst (0.015 mmol),
K3PO4(H2O)3.2 (191 mg), THF (1.0 mL). Conversion by GC, isolated
yield in parentheses. Precatalyst was recrystallized from toluene/
hexanes (1:10).
ASSOCIATED CONTENT
* Supporting Information
b
■
S
Synthesis of precatalysts, conversions monitored in time,
supporting data for Scheme 2, and experimental procedures
and spectral data for all new compounds (1H NMR, 13C NMR,
HRMS, elemental analysis). This material is available free of
charge via the Internet at http://pubs.acs.org.
a
Scheme 5. Activation of Precatalyst 6
AUTHOR INFORMATION
Corresponding Author
■
*E-mail: percec@sas.upenn.edu.
Notes
a
Conditions 1: 6 (0.10 mmol), 2 (0.20 mmol), K3PO4(H2O)3.2 (0.30
mmol), dry THF (1.0 mL). 16 was isolated in 0.088 mmol in 12 h.
Conditions 2: 6 (0.015 mmol), 2 (0.32 mmol) K3PO4(H2O)3.2 (191
mg), dry THF (1.0 mL). 100% conversion was obtained in 5 min as
The authors declare no competing financial interest.
1
determined by H NMR.
ACKNOWLEDGMENTS
■
Financial support by the National Science Foundation (DMR-
1066116, DMR-1120901, and OISE-1243313), the Humboldt
Foundation, and the P. Roy Vagelos Chair at Penn is gratefully
acknowledged.
routes from Scheme 1, while the other was prepared by the
right route that is recommended for aryl tosylates, aryl
mesylates, and more reactive aryl chlorides such as 9-
chloroanthracene. It is remarkable that precatalysts 6−15
maintain their reactivity after being stored for 1 year at room
temperature in air, despite the sensitivity of free PCy3 to
oxygen. Furthermore, precatalyst 4 has not changed reactivity
even after 4 years in air. Previously reported Ni precatalysts
were stable in air for at least 2 weeks at 0 °C.8c The simple
synthesis of the precatalysts reported here, their much higher
reactivity than that of the corresponding π-complex,4b,c,h their
air stability, and their ability to achieve complete conversion at
room temperature in dry and in as received THF will most
REFERENCES
■
(1) Percec, V.; Bae, J. Y.; Hill, D. H. J. Org. Chem. 1995, 60, 1060−
1065.
(2) Suzuki, A. Angew. Chem., Int. Ed. 2011, 50, 6722−6737.
(3) (a) Leowanawat, P.; Resmerita, A.-M.; Moldoveanu, C.; Liu, C.;
Zhang, N.; Wilson, D. A.; Hoang, L. M.; Rosen, B. M.; Percec, V. J.
Org. Chem. 2010, 75, 7822−7828. (b) Moldoveanu, C.; Wilson, D. A.;
Wilson, C. J.; Corcoran, P.; Rosen, B. M.; Percec, V. Org. Lett. 2009,
11, 4974−4977. (c) Rosen, B. M.; Huang, C.; Percec, V. Org. Lett.
2008, 10, 2597−2600. (d) Wilson, D. A.; Wilson, C. J.; Moldoveanu,
C
dx.doi.org/10.1021/ol503061c | Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
C.; Resmerita, A.-M.; Corcoran, P.; Hoang, L. M.; Rosen, B. M.;
Percec, V. J. Am. Chem. Soc. 2010, 132, 1800−1801.
(4) (a) Leowanawat, P.; Zhang, N.; Percec, V. J. Org. Chem. 2012, 77,
1018−1025. (b) Rosen, B. M.; Quasdorf, K. W.; Wilson, D. A.; Zhang,
N.; Resmerita, A.-M.; Garg, N. K.; Percec, V. Chem. Rev. 2011, 111,
1346−1416. (c) Quasdorf, K. W.; Antoft-Finch, A.; Liu, P.; Silberstein,
A. L.; Komaromi, A.; Blackburn, T.; Ramgren, S. D.; Houk, K. N.;
Snieckus, V.; Garg, N. K. J. Am. Chem. Soc. 2011, 133, 6352−6363.
(d) Quasdorf, K. W.; Tian, X.; Garg, N. K. J. Am. Chem. Soc. 2008,
130, 14422−14423. (e) Guan, B.-T.; Wang, Y.; Li, B.-J.; Yu, D.-G.; Shi,
Z.-J. J. Am. Chem. Soc. 2008, 130, 14468−14470. (f) Yu, D.-G.; Li, B.-
J.; Shi, Z.-J. Acc. Chem. Res. 2010, 43, 1486−1495. (g) Tasker, S. Z.;
Standley, E. A.; Jamison, T. F. Nature 2014, 509, 299−309. (h) Percec,
V.; Golding, G. M.; Smidrkal, J.; Weichold, O. J. Org. Chem. 2004, 69,
3447−3452. (i) Mesganaw, T.; Garg, N. K. Org. Process Res. Dev. 2013,
17, 29−39. (j) Han, F.-S. Chem. Soc. Rev. 2013, 42, 5270−5298.
(k) Hong, X.; Liang, Y.; Houk, K. N. J. Am. Chem. Soc. 2014, 136,
2017−2025. (l) Zhang, N.; Hoffman, D. J.; Gutsche, N.; Gupta, J.;
Percec, V. J. Org. Chem. 2012, 77, 5956−5964.
(5) (a) Tobisu, M.; Xu, T.; Shimasaki, T.; Chatani, N. J. Am. Chem.
Soc. 2011, 133, 19505−19511. (b) Ichitsuka, T.; Fujita, T.; Arita, T.;
Ichikawa, J. Angew. Chem., Int. Ed. 2014, 53, 7564−7568. (c) Yang, X.;
Sun, H.; Zhang, S.; Li, X. J. Organomet. Chem. 2013, 723, 36−42.
(6) Fan, Y.; Cong, M.; Peng, L. Chem.Eur. J. 2014, 20, 2698−2702.
(7) Leowanawat, P.; Zhang, N.; Resmerita, A.-M.; Rosen, B. M.;
Percec, V. J. Org. Chem. 2011, 76, 9946−9955.
(8) (a) Standley, E. A.; Smith, S. J.; Mueller, P.; Jamison, T. F.
Organometallics 2014, 33, 2012−2018. (b) Standley, E. A.; Jamison, T.
F. J. Am. Chem. Soc. 2013, 135, 1585−1592. (c) Ge, S.; Hartwig, J. F.
Angew. Chem., Int. Ed. 2012, 51, 12837−12841. (d) Christian, A. H.;
Muller, P.; Monfette, S. Organometallics 2014, 33, 2134−2137.
̈
(e) Park, N. H.; Teverovskiy, G.; Buchwald, S. L. Org. Lett. 2013,
16, 220−223. (f) Shields, J. D.; Ahneman, D. T.; Graham, T. J. A.;
Doyle, A. G. Org. Lett. 2014, 16, 142−145.
(9) (a) Fan, X.-H.; Yang, L.-M. Eur. J. Org. Chem. 2011, 1467−1471.
(b) Fan, X.-H.; Yang, L.-M. Eur. J. Org. Chem. 2010, 2457−2460.
(10) Leowanawat, P.; Zhang, N.; Safi, M.; Hoffman, D. J.; Fryberger,
M. C.; George, A.; Percec, V. J. Org. Chem. 2012, 77, 2885−2892.
(11) Tucker, C. E.; Davidson, J.; Knochel, P. J. Org. Chem. 1992, 57,
3482−3485.
(12) (a) Antoft-Finch, A.; Blackburn, T.; Snieckus, V. J. Am. Chem.
Soc. 2009, 131, 17750−17752. (b) Dallas, A. S.; Gothelf, K. V. J. Org.
Chem. 2005, 70, 3321−3323. (c) Lou, S.; Fu, G. C. Adv. Synth. Catal.
2010, 352, 2081−2084. (d) Quasdorf, K. W.; Antoft-Finch, A.; Liu, P.;
Silberstein, A. L.; Komaromi, A.; Blackburn, T.; Ramgren, S. D.; Houk,
K. N.; Snieckus, V.; Garg, N. K. J. Am. Chem. Soc. 2011, 133, 6352−
6363. (e) Xing, C.-H.; Lee, J.-R.; Tang, Z.-Y.; Zheng, J. R.; Hu, Q.-S.
Adv. Synth. Catal. 2011, 353, 2051−2059.
(13) Favero, G.; Morvillo, A.; Turco, A. Gazz. Chim. Ital. 1979, 109,
27−28.
D
dx.doi.org/10.1021/ol503061c | Org. Lett. XXXX, XXX, XXX−XXX