Electrophilic Phosphonium Cation-Mediated Phosphane Oxide Reduction Using Oxalyl Chloride and Hydrogen

Article abstract of DOI:10.1002/anie.201809275

The metal-free reduction of phosphane oxides with molecular hydrogen (H₂) using oxalyl chloride as activating agent was achieved. Quantum-mechanical investigations support the heterolytic splitting of H₂ by the in situ formed electrophilic phosphonium cation (EPC) and phosphane oxide and subsequent barrierless conversion to the phosphane and HCl. The reaction can also be catalyzed by the frustrated Lewis pair (FLP) consisting of B(2,6-F₂C₆H₃)₃ and 2,6-lutidine or phosphane oxide as Lewis base. This novel reduction was demonstrated for triaryl and diaryl phosphane oxides providing access to phosphanes in good to excellent yields (51–93 %).

Full text of DOI:10.1002/anie.201809275

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Electrophilic phosphonium cation-mediated phosphane oxide
reduction using oxalyl chloride and hydrogen
Authors: Arne Jan Stepen, Markus Bursch, Stefan Grimme, Douglas
W. Stephan, and Jan Henry Hakan Paradies
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201809275
Angew. Chem. 10.1002/ange.201809275
Link to VoR: http://dx.doi.org/10.1002/anie.201809275
http://dx.doi.org/10.1002/ange.201809275

10.1002/anie.201809275
Angewandte Chemie International Edition
COMMUNICATION
Electrophilic phosphonium cation-mediated phosphane oxide
reduction using oxalyl chloride and hydrogen
Arne J. Stepen,[a][b] Markus Bursch,[c] Stefan Grimme,*[c] Douglas W. Stephan,*[b] and Jan Paradies*[a]
Abstract: The metal-free reduction of phosphane oxides with
molecular hydrogen (H2) using oxalyl chloride as activating agent was
achieved. Quantum-mechanical investigations support the heterolytic
splitting of H2 by the in situ formed electrophilic phosphonium cation
(EPC) and phosphane oxide and subsequent barrierless conversion
to the phosphane and HCl. The reaction can also be catalyzed by the
frustrated Lewis pair (FLP) consisting of B(2,6-F2C6H3)3 and 2,6-
lutidine or phosphane oxide as Lewis base. This novel reduction was
demonstrated for triaryl and diaryl phosphane oxides providing access
to phosphanes in good to excellent yields (51-93%).
been explored.[7]Boron-derived Lewis acids show outstanding
reactivity in small molecule activation providing an unique
catalytic access to hydride species directly from H2.[8] Similarly,
electrophilic phosphonium cations (EPCs) act as active Lewis
acids and demonstrate high reactivity in bond activation[9] and in
hydrogenations.[10] Both classes of main group-derived Lewis
acids found wide application in hydrosilane reductions, reductive
defluorinations[9a] and deoxygenations.[11] The reduction of
phosphane oxides or derived chlorophosphoranes using H2 as
final reductant and main-group Lewis acid catalysts have so far
not been precedented.
We initiated our investigations by pressurizing a mixture of 1a
and 1.5 equiv. oxalyl chloride in CDCl3 with H2 (4 bar). The typical
31P NMR resonances of the phosphane oxide (38.3 ppm)
vanished over a period of 30 min. with concomitant appearance
of two new resonances, which were assigned to the dichlorotri-
phenylphosphorane (–46.2 ppm) and to the chlorophosphonium
chloride (65.5 ppm) (lit. ref. –47.0 ppm; 65.5 ppm).[12][13] However,
the reduction of these phosphorus species was not observed,
potentially due to the absence of a suitable Lewis acid and/or
Lewis base for H2-activation (Scheme 1).
The reduction of phosphane oxides, in particular triphenyl-
phosphane oxide (O=PPh3, 1a), is of great interest since it is
produced on ton-scale in the industrial Wittig-reaction for the
synthesis of vitamins.[1] Typical processes to recycle the
phosphine oxides rely on the reductive deoxygenation with
hydrosilanes at elevated temperatures in the presence of
amines.[2] Only recently, a metal-free reduction of phosphane
oxides using phosphites as reduction equivalent has been
reported.[3] Alternative oxygen trapping reagents are phosgene
derivatives and oxalyl chloride[4] which convert the phosphane
oxides to the corresponding dichlorophosphoranes,[5] which are in
equilibrium with the corresponding ionic chlorophosphonium
chlorides (eq. 1).
1.5 equiv.
(COCl)2
additive
additive:
yield
0%
no additive, 4 bar
O
P
P
B(2,6-F2C6H3)3 (20 mol%)
2,6-lutidine (20 mol%), 4 bar
Ph
Ph
Ph
+ 2 HCl
Ph
Ph
1a
93%
Ph
H2 (4 bar)
CDCl3
130°C,
48h
Cl
Cl
2a
B(2,6-F2C6H3)3 (20 mol%), 4 bar 98%
no additive, 80 bar
93%
R
P
P
R
eq. 1
Cl
R
R
R
Cl
R
Treatment of these electrophiles with elemental main-group
metals (Si or Al) or sodium borohydride produces the
corresponding phosphanes accompanied with stoichiometric
amounts of aluminum/silicon chlorides or boron species.[4a, 6] The
use of molecular hydrogen (H2) as stoichiometric reductant would
be highly desirable since only hydrochloric acid is produced. To
date, no catalyst has been reported for such application. Only one
Scheme 1. FLP-catalyzed reduction of triphenylphosphine oxide (1a) by
(COCl)2/H2. Yields were determined after column chromatography.
This prompted us to use a FLP-catalyst consisting of the weak
Lewis-acid B(2,6-F2-C6H3)3[14] (3) and 2,6-lutidine (4) to generate
hydroborate species in situ. Indeed, the presence of 20 mol% of
3/4 and 4 bar H2 resulted in 93% yield triphenylphosphine (2a).
This result is remarkable, since 2 equiv. HCl are produced in the
the reaction, which protonates 2,6-lutidine and should shut-down
the hydrogenation. The control experiment with 3 (20 mol%) alone
provided the product in almost quantitative yield of 98%. We
identified triphenylphosphine oxide 1a as the active Lewis base in
the activation of H2 (Scheme 2).
patent
details
the
reduction
of
phosgene-generate
chlorotricyclohexylphosphane chloride with 150 bar H2 at 160 °C.
Neither further examples were presented nor the mechanism has
[a]
[b]
[c]
Arne J. Stepen, Prof. Dr. Jan Paradies
Department of Chemistry, University of Paderborn
Warburger Strasse 100, D-33098 Paderborn (Germany)
E-mail: jan.paradies@uni-paderborn.de
Prof. Dr. Douglas W. Stephan
Department of Chemistry, University of Toronto
80 St. George St, Toronto Ontario M5S3H6 (Canada)
E-mail: dstephan@chem.utoronto.ca
Markus Bursch, Prof. Dr. Stefan Grimme
Mulliken Center for Theoretical Chemistry, University of Bonn,
Beringstr. 4, D-53115 Bonn (Germany)
E-mail: grimme@thch.uni-bonn.de
Supporting information for this article is given via a link at the end of
the document.
Scheme 2. Isotope exchange experiment with the FLP consisting of B(2,6-
F2C6H3)3 (3) and Ph3PO (1a) as Lewis base.
This article is protected by copyright. All rights reserved.

10.1002/anie.201809275
Angewandte Chemie International Edition
COMMUNICATION
The reaction of a 1:1 mixture of 3 and 1a with H2/D2 (4 bar) at
80 °C resulted within 5d in the isotope scrambling to HD/H2/D2.
These observations clearly indicate the ability of 3/1a to act as
hydrogenation catalyst.
(Angles / °: O-H-H = 176.1, P-H-H = 142.7; distances / Å: O-H =
1.337, P-H = 1.864) with a significantly elongated H-H bond
distance of 0.904 Å. Some short intermolecular C-C interligand
distances of approx. 3.5 Å in the structure of the transition state
indicate the significance of attractive intermolecular interligand
interactions, including π-π stacking for the stabilization of the
transition state.[17] The subsequent conversion of the triphenyl-
hydrochlorophosphorane (6a) into the protonated phosphane
([2a–H]) by chloride-loss is exergonic by –5.7 kcal∙mol−1 leading
to an overall exergonic process of –30.8 kcal∙mol−1 after deproto-
nation of the protonated phosphane oxide intermediate (1a-H)
and 2a-H re-yielding 1a and 2a, respectively. According to this
mechanistic model, the competence of the phosphine oxide/phos-
phonium Lewis pair to activate H2 is strongly influenced by their
electronic and steric properties.
Finally, we investigated the reaction at 80 bar H2 in the absence
of borane or amine. Surprisingly, under these conditions the
product 2a was obtained in 93% yield. The reduction proceeds
presumably through the activation of H2 by a Lewis pair consisting
of Ph3PO (1a) and of the electrophilic phosphonium cation
[Ph3PCl]+. Careful consultation of the 31P NMR spectra of the
reaction revealed small quantities of phosphane oxide, most
probably arising from water traces in the H2 atmosphere. As
control experiment, a sample of Ph3PCl2 was reacted with purified
H2 (4 bar) for 24 h at 130 °C in CDCl3, but the formation of PPh3
was not observed. After addition of phosphane oxide 1a (20
mol%) to the sample, re-pressurization with purified H2 (4 bar) and
heating to 130 °C for 24 h, 2a was produced in 25% yield. The
reduced reaction rate must be attributed to the drastic pressure
decrease. Nevertheless, these experiments strongly support the
role of phosphine oxide as active Lewis base.
Table 1. Reduction of phosphane oxides with oxalyl chloride/hydrogen.
1.5 equiv. (COCl)2
no additive
H2 (80 bar)
O
P
P
+ 2 HCl
Ar
R
Quantum mechanical investigations at the double-hybrid
PWPB95-D3(BJ, ATM)+COSMO-RS(CHCl3)/def2-QZVPP//
PBEh-3c (COSMO(CHCl3))[15] level of theory with structure pre-
optimizations applying GFN-xTB[16] revealed the ability of
[Ph3PCl]+ to act as Lewis acid in combination with Ph3PO as Lewis
base (Figure 1).
Ar
R
chloroform
130°C
– CO
Ar
Ar
1
2
– CO2
Products
Me
Me
Me
Ph2P
2c
(
)
3
Ph2P
2a
P
P (
)
P (
Me )3
3
2b
2d
2e
83% (80%)
91% (93%) 48% (51%)
93% (88%) 94% (93%)
Me
(
)
3
P
Ph2P Bn Ph2P Cy
PCy3
O
PPh2
PPh2
Me
2g
2h
48%[b]
2f
56%[b]
2i
2j
35% (29%), 64% (45%)[b]
88% (85%) 0%
(
)
3
Ph2P
COtBu Ph2P
CO2H Ph2P
Br
P
F
2k
96% (98%)[b]
2l
2m
90% (93%)
2n
86% (86%)
89% (90%)
F
(
)
3
P
CF3
(
)
3
P
2o
57%[b]
2p
81% (86%)
[a] yields were determined by NMR spectroscopy, values in parentheses
correspond to isolated yields after column chromatography; [b] reactions were
performed in the presence of 20 mol% B(2,6-F2C6H3)3 (3) and 20 mol% 2,6-
dimethylpyridine (4) at 4 bar H2-pressure;
Figure 1. Relative Gibbs free energy diagram of the phosphane oxide reduction
in CHCl3. All energy values in kcal∙mol−1 relative to 1a. T = 130 °C.
We investigated the reduction of a series of phosphane oxides
(Table 1) at 80 bar H2 (the results of the FLP-catalyzed low-
pressure variant are summarized in Table S1 in the SI). Generally,
triaryl and diaryl phosphane oxides were efficiently reduced. The
diminished Lewis-acidity of more electron-rich chlorophos-
phonium ions is apparently counterbalanced by the increased
Lewis-basicity of the corresponding phosphane oxides in the H2-
activation step. In detail, triphenylphosphane-oxide (1a) was
reduced in excellent yield. Increase of steric bulk resulted in
decrease of yields, as observed for P(oTol)3 (1b, 51%) and
Ph2P(oTol) (1c, 88%). Methyl groups in meta or para position in
1d-f were well tolerated and yields of 56% to 98% were obtained.
The steric impact on the reactivity is also observed for
bisphosphane derivatives. Although the dioxide derivatives of
BINAP, xantphos and DPEphos (1g) were cleanly converted into
The triphenylchlorophosphonium cation 5a is obtained in a
strongly exergonic reaction from the triphenylphosphane oxide
(1a) and (COCl)2. 5a is in an almost barrierless equilibrium with
the energetically slightly favoured triphenyldichlorophosphorane
1
(5a-Cl) (∆∆G = 1.2 kcal∙mol− ). An O-P coordinated, π-stacked
adduct 1a/5a (see Figure S1 in SI) of 1a and 5a is disfavoured by
4.2 kcal∙mol−1 with respect to its isolated fragments in solution
while the gas-phase association free energy amounts to
1
−3.0 kcal∙mol− . The heterolytic activation of H2 by 5a and the
1
phosphane oxide 1a requires 35.8 kcal∙mol− with an overall
reaction barrier of 37.0 kcal∙mol−1 with respect to 5a-Cl, which is
in agreement with the required drastic reaction conditions. The
transition state TS1 has an asymmetric, non-linear O-H-H-P unit
This article is protected by copyright. All rights reserved.

10.1002/anie.201809275
Angewandte Chemie International Edition
COMMUNICATION
Tellez, Z. S. Nixon, L. J. Kang, A. L. Carter, S. R. Kunkel, K. C.
Przeworski, G. A. Chass, Angew. Chem. Int. Ed. 2009, 48, 6836-6839.
P. Li, R. Wischert, P. Métivier, Angew. Chem. Int. Ed. 2017, 56, 15989-
15992; Angew. Chem. 2017, 129, 16205–16208.
the corresponding bis(chlorophosphonium chlorides, only the
latter could be reduced in moderate yield of 45%. Next, we
investigated the reactivity of alkyl-substituted phosphane oxides.
Both, the benzyl and cyclohexyl derivatives 2h and 2i were
reduced in 48% and 85% yield respectively, although differing
methods were required. The low yield of 2h may arise from a
nucleophilic substitution on the chlorophosphonium intermediate
by chloride. Steric hindrance in 1i provides some kinetic
stabilization and leads to significantly enhanced yield. Higher
steric congestion in the tricyclohexyl derivative 1j did not result in
the formation of 2j although quantitative formation of the
corresponding chlorophosphonium chloride was observed. This is
in agreement with a higher computed reaction barrier of 39.7
kcal∙mol− and an endergonic reaction free energy of 6 kcal∙mol−
from 5j to 2j (For details see the Supporting Information). Finally,
we investigated the impact of electron-withdrawing groups on the
arene ring. Substituents in the 4-position of the arene ring in 1k-
m were well tolerated and the functionalized phoshanes were
obtained in 90-98 % yield. Also, fluorinated triphenylphosphane
derivatives 1n-p were reactive. Whereas the 4-fluoro derivative
1n was reduced in 86% yield, the corresponding CF3-substituted
derivative 1o was only reactive in the presence of 20 mol% of the
FLP. However, the 2-fluorophenyl derivative 1p was obtained in
high yield of 86%.
[3]
[4]
a) K. V. Rajendran, D. G. Gilheany, Chem. Commun. 2012, 48, 817-819;
b) K. V. Rajendran, D. G. Gilheany, Chem. Commun. 2012, 48, 10040-
10042.
[5]
[6]
H. Babad, A. G. Zeiler, Chem. Rev. 1973, 73, 75-91.
a) L. Horner, H. Hoffmann, P. Beck, Chem. Ber. 1958, 91, 1583-1588; b)
R. Salmon, John Wiley & Sons, Ltd., 2001, p. No pp. given; c) T. Yano,
M. Hoshino, M. Kuroboshi, H. Tanaka, Synlett 2010, 801-803; d) T. Yano,
M. Kuroboshi, H. Tanaka, Tetrahedron Lett. 2010, 51, 698-701.
Method for synthesizing cyclohexyl-substituted phosphines, A. Tishkov,
K. Massonne, D. Mirk, J. Henkelmann, M. Maase, T. Wettling, US
2010/0137643 A1, 03.06.2010, BASF SE, Ludwigshafen.
[7]
[8]
1
1
a) D. W. Stephan, Org. Biomol. Chem. 2008, 6, 1535-1539; b) D. W.
Stephan, Dalton Trans. 2009, 3129-3136; c) D. W. Stephan, G. Erker,
Angew. Chem. Int. Ed. 2010, 49, 46-76; Angew. Chem. 2010, 122, 50-
81; d) J. Paradies, Synlett 2013, 777-780; e) D. Stephan, G. Erker, Isr. J.
Chem. 2015, 55, 133-133; f) D. W. Stephan, J. Am. Chem. Soc. 2015,
137, 10018-10032; g) D. W. Stephan, G. Erker, Angew. Chem. Int. Ed.
2015, 54, 6400-6441; Angew. Chem. 2015, 127, 6498-6541.
a) C. B. Caputo, L. J. Hounjet, R. Dobrovetsky, D. W. Stephan, Science
2013, 341, 1374-1377; b) L. J. Hounjet, C. B. Caputo, D. W. Stephan,
Dalton Trans. 2013, 42, 2629-2635; c) M. Perez, C. B. Caputo, R.
Dobrovetsky, D. W. Stephan, Proc. Natl. Acad. Sci. U. S. A. 2014, 111,
10917-10921; d) M. H. Holthausen, M. Mehta, D. W. Stephan, Angew.
Chem. Int. Ed. 2014, 53, 6538-6541; Angew. Chem. 2014, 126, 6656-
6659; e) S. A. Weicker, D. W. Stephan, Bull. Chem. Soc. Jpn. 2015, 88,
1003-1016; f) M. H. Holthausen, R. R. Hiranandani, D. W. Stephan,
Chem. Sci. 2015, 6, 2016-2021.
[9]
In summary, we have developed the metal-free reduction of
phosphane oxides using oxalyl chloride and H2. Quantum-
mechanical calculations support the EPC-mediated heterolytic
splitting of H2 by the in situ generated chlorophosphonium ion
followed by barrierless conversion to the phosphane and HCl. The
applicability of the reduction was demonstrated for electron-
donating and electron-withdrawing group substituted triaryl
phosphane oxides providing the products in 51-98% yield.
[10] T. vom Stein, M. Perez, R. Dobrovetsky, D. Winkelhaus, C. B. Caputo,
D. W. Stephan, Angew. Chem. Int. Ed. 2015, 54, 10178-10182.
[11] a) J. M. Blackwell, E. R. Sonmor, T. Scoccitti, W. E. Piers, Org. Lett. 2000,
2, 3921-3923; b) M. Rubin, T. Schwier, V. Gevorgyan, J. Org. Chem.
2002, 67, 1936-1940; c) J. Hermeke, M. Mewald, M. Oestreich, J. Am.
Chem. Soc. 2013, 135, 17537-17546; d) A. Simonneau, M. Oestreich,
Angew. Chem. Int. Ed. 2013, 52, 11905-11907; Angew. Chem. 2013, 125,
12121–12124; e) L. Greb, S. Tamke, J. Paradies, Chem. Commun. 2014,
50, 2318-2320; f) M. Oestreich, J. Hermeke, J. Mohr, Chem. Soc. Rev.
2015, 44, 2202-2220; g) M. H. Holthausen, J. M. Bayne, I. Mallov, R.
Dobrovetsky, D. W. Stephan, J. Am. Chem. Soc. 2015, 137, 7298-7301;
h) M. H. Holthausen, R. R. Hiranandani, D. W. Stephan, Chem. Sci. 2015,
6, 2016-2021; i) P. Manuel, Q. Zheng-Wang, C. C. B., P. Vitali, H. L. J.,
H. Andreas, D. Roman, G. Stefan, S. D. W., Chem. Eur. J. 2015, 21,
6491-6500; j) M. Mehta, M. H. Holthausen, I. Mallov, M. Perez, Z. W. Qu,
S. Grimme, D. W. Stephan, Angew. Chem. Int. Ed. 2015, 54, 8250-8254;
k) M. Mehta, I. G. de la Arada, M. Perez, D. Porwal, M. Oestreich, D. W.
Stephan, Organometallics 2016, 35, 1030-1035; l) V. Fasano, J. H. W.
LaFortune, J. M. Bayne, M. J. Ingleson, D. W. Stephan, Chem. Commun.
2018, 54, 662-665; m) A. Augurusa, M. Mehta, M. Perez, J. T. Zhu, D.
W. Stephan, Chem. Commun. 2016, 52, 12195-12198.
Acknowledgements
The German science foundation (DFG) and the Fonds der
Chemischen Industrie (FCI) are gratefully acknowledged for
financial support (PA 1562/6-1, PA 1562/16-1 and Gottfried
Wilhelm Leibnitz prize to SG). DWS acknowledges the support of
NSERC of Canada and is grateful for the award of a Canada
Research Chair and a Einstein Visiting Professorship in Berlin.
Keywords: hydrogenation • phosphane oxide • phosphane •
frustrated Lewis pair • electrophilic phosphonium cation
[12] a) S. M. Godfrey, C. A. McAuliffe, R. G. Pritchard, J. M. Sheffield, Chem.
Commun. 1996, 2521-2522; b) N. Bricklebank, S. M. Godfrey, C. A.
McAuliffe, P. Deplano, M. L. Mercuri, J. M. Sheffield, Dalton Trans. 1998,
2379-2382; c) S. M. Godfrey, C. A. McAuliffe, I. Mushtaq, R. G. Pritchard,
J. M. Sheffield, Dalton Trans. 1998, 3815-3818; d) S. M. Godfrey, C. A.
McAuliffe, R. G. Pritchard, J. M. Sheffield, Chem. Commun. 1998, 921-
922.
[1]
[2]
M. Eggersdorfer, D. Laudert, U. Letinois, T. McClymont, J. Medlock, T.
Netscher, W. Bonrath, Angew. Chem. Int. Ed. 2012, 51, 12960-12990;
Angew. Chem. 2012, 124, 13134–13165
a) L. Horner, W. D. Balzer, Tetrahedron Lett. 1965, 6, 1157-1162; b) N.
L. Bauld, F. Farr, J. Am. Chem. Soc. 1969, 91, 2788-&; c) R. Tang, K.
Mislow, J. Am. Chem. Soc. 1969, 91, 5644-&; d) K. Naumann, G. Zon, K.
Mislow, J. Am. Chem. Soc. 1969, 91, 7012-&; e) K. L. Marsi, J. Org.
Chem. 1974, 39, 265-267; f) T. Coumbe, N. J. Lawrence, F. Muhammad,
Tetrahedron Lett. 1994, 35, 625-628; g) H. C. Wu, J. Q. Yu, J. B. Spencer,
Org. Lett. 2004, 6, 4675-4678; h) M. Berthod, A. Favre-Reguillon, J.
Mohamad, G. Mignani, G. Docherty, M. Lemaire, Synlett 2007, 1545-
1548; i) C. Petit, A. Favre-Reguillon, B. Albela, L. Bonneviot, G. Mignani,
M. Lemaire, Organometallics 2009, 28, 6379-6382; j) C. J. O'Brien, J. L.
[13] In chloroform the equilibrium was shifted to the chlorophosphonium
species, wheras in toluene the dichlorophosphorane was the dominant
species.
[14] a) D. Naumann, H. Butler, R. Gnann, Z. Anorg. Allg. Chem. 1992, 618,
74-76; b) L. Greb, C. G. Daniliuc, K. Bergander, J. Paradies, Angew.
Chem. Int. Ed. 2013, 52, 5876-5879; Angew. Chem. 2013, 125, 5989-
5992; c) J. A. Nicasio, S. Steinberg, B. Ines, M. Alcarazo, Chem. Eur. J.
This article is protected by copyright. All rights reserved.

10.1002/anie.201809275
Angewandte Chemie International Edition
COMMUNICATION
2013, 19, 11016-11020; d) S. Tussing, L. Greb, S. Tamke, B. Schirmer,
C. Muhle-Goll, B. Luy, J. Paradies, Chem. Eur. J. 2015, 21, 8056-8059;
e) S. Tussing, K. Kaupmees, J. Paradies, Chem. Eur. J. 2016, 22, 7422-
-7426.
J. Chem. Phys. 2015, 143, 54107; l) TURBOMOLE, V7.0.2 ed., 2015, pp.
a Development of University of Karlsruhe and Forschungszentrum
Karlsruhe GmbH, 1989-2007, TURBOMOLE GmbH, since 2007;
Available from http://www.turbomole.com; m) F. Neese, Wiley Interdiscip.
Rev. Comput. Mol. Sci. 2012, 2, 73–78; n) F. Neese, V. 4.0.0 ed., MPI
Für Chemische Energiekonversion, Mülheim A. D. Ruhr, Germany, 2017,
pp. ORCA: An Ab Initio, Density Functional and Semiempirical Program
Package.
[15] a) L. Goerigk, S. Grimme, J. Chem. Theory Comput. 2011, 7, 291–309;
b) B. M. Axilrod, E. Teller, J. Chem. Phys. 1943, 11, 299–300; c) Y. Muto,
Proc. Phys. Math. Soc. Jpn. 1943, 17, 629–631; d) A. Klamt, G.
Schüürmann, J. Chem. Soc., Perkin Trans. 2 1993, 0, 799–805; e) F.
Eckert, A. Klamt, AIChE 2002, 48, 369–385; f) F. Weigend, R. Ahlrichs,
Phys. Chem. Chem. Phys. 2005, 7, 3297; g) S. Grimme, J. Antony, S.
Ehrlich, H. A. Krieg, J. Chem. Phys. 2010, 132, 154104; h) S. Grimme,
S. Ehrlich, L. Goerigk, J. Comput. Chem. 2011, 32, 1456–1465; i) F.
Furche, R. Ahlrichs, C. Hättig, W. Klopper, M. Sierka, F. Weigend, Wiley
Interdiscip. Rev. Comput. Mol. Sci. 2014, 4, 91–100; j) S. Grimme, A.
Hansen, J. G. Brandenburg, C. Bannwarth, Chem. Rev. 2016, 116,
5105–5154; k) S. Grimme, J. G. Brandenburg, C. Bannwarth, A. Hansen,
[16] a) S. Grimme, C. Bannwarth, P. A. Shushkov, J. Chem. Theory Comput.
2017, 13, 1989–2009; b) S. Grimme, C. Bannwarth, S. Dohm, A. Hansen,
J. Pisarek, P. Pracht, J. Seibert, F. Neese, Angew. Chem. Int. Ed. 2017,
56, 14763–14769; Angew. Chem. 2017, 129, 14958–14964.
[17] S. Grimme, H. Kruse, L. Goerigk, G. Erker, Angew. Chem. Int. Ed. 2010,
49, 1402-1405; Angew. Chem. 2010, 122, 1444-1447.
This article is protected by copyright. All rights reserved.

10.1002/anie.201809275
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
Layout 1:
COMMUNICATION
The metal-free reduction of phosphane
oxides with H2 using oxalyl chloride as
Arne J. Stepen, Markus Bursch, Stefan
Grimme,* Douglas W. Stephan* and Jan
Paradies*
activating agent was achieved. H2 is
activated by the in situ formed
electrophilic phosphonium cation and
phosphane oxide. The reaction is also
be catalyzed by B(2,6-F2C6H3)3 and
2,6-lutidine or phosphane oxide as
Lewis base. This novel reduction was
demonstrated for triaryl and diaryl
phosphane oxides providing access to
phosphanes in good to excellent yields
(51-93%).
Electrophilic Phosphonium Cation (EPC)
mediated reduction
1.5 equiv. (COCl)2
no additive
H2 (80 bar)
Page No. – Page No.
O
P
Electrophilic phosphonium cation-
mediated phosphane oxide reduction
using oxalyl chloride and hydrogen
P
Ar
Ar
R
Ar
Ar
R
chloroform
130°C
48-98%
– CO, – CO2
– 2 HCl
This article is protected by copyright. All rights reserved.