Asymmetric Synthesis of Diarylmethyl Sulfones by Palladium-Catalyzed Enantioselective Benzylic Substitution: A Remarkable Effect of Water

Article abstract of DOI:10.1002/chem.201800744

A Pd/(R)-BINAP-catalyzed enantioselective benzylic sulfonation of diarylmethyl carbonates with sodium sulfinates proceeds to deliver the corresponding chiral diarylmethyl sulfones in good yields with high enantioselectivity. The reaction occurs in a dynamic kinetic asymmetric transformation (DYKAT) manner and thus provides convergent access to optically active benzylic sulfones from racemic secondary benzylic carbonates. Additionally, the addition of H₂O is found to be critical for high enantioselectivity.

Full text of DOI:10.1002/chem.201800744

A Journal of
Accepted Article
Title: Asymmetric Synthesis of Diarylmethyl Sulfones by Palladium-
Catalyzed Enantioselective Benzylic Substitution: A Remarkable
Effect of Water
Authors: Atifah Najib, Koji Hirano, and Masahiro Miura
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: Chem. Eur. J. 10.1002/chem.201800744
Link to VoR: http://dx.doi.org/10.1002/chem.201800744
Supported by

10.1002/chem.201800744
Chemistry - A European Journal
COMMUNICATION
Asymmetric Synthesis of Diarylmethyl Sulfones by Palladium-
Catalyzed Enantioselective Benzylic Substitution: A Remarkable
Effect of Water
Atifah Najib,[a] Koji Hirano,*[a] and Masahiro Miura*[a]
Dedication ((optional))
Abstract:
A
Pd/(R)-BINAP-catalyzed enantioselective benzylic
further developments of asymmetric benzylic sulfone synthesis.
On the other hand, our group recently developed the palladium-
catalyzed asymmetric benzylic substitution reactions of
secondary benzyl carbonates with carbon, nitrogen, and oxygen
nucleophiles.[9] The greatest feature of aforementioned catalysis
is stereoconvergency: through the epimerization of two
diastereomeric -benzylpalladium[10] intermediates the racemic
secondary benzylic electrophiles are converted into the
sulfonation of diarylmethyl carbonates with sodium sulfinates
proceeds to deliver the corresponding chiral diarylmethyl sulfones in
good yields with high enantioselectivity. The reaction occurs in a
dynamic kinetic asymmetric transformation (DYKAT) manner and
thus provides convergent access to optically active benzylic sulfones
from racemic secondary benzylic carbonates. Additionally, the
addition of H2O is found to be critical for high enantioselectivity.
substitution products in
a
dynamic kinetic asymmetric
transformation (DYKAT)[11] manner, and thus both yield and e.r.
can be theoretically reached to 100% and >99:1. Given our
previous success and reported asymmetric sulfonation of
isoelectronic -allylpalladiums,[4a,b] we have now found a Pd/(R)-
BINAP-catalyzed enantioselective benzylic substitution of
racemic diarylmethyl carbonates with sodium sulfonates
(Scheme 1c).[12] The present asymmetric catalysis occurs again
in DYKAT manner and thus provides a new repertoire of
stereoconvergent synthesis of chiral benzylic sulfones.
The sulfonyl group is among representative electron-withdrawing
groups and often used as a building block in synthetic organic
chemistry.[1] Additionally, it is frequently occurring in biologically
active compounds and pharmaceutical agents.[2] Thus, synthetic
chemists have developed numerous strategies for preparation of
various
sulfonyl
compounds,
including
oxidation
of
sulfides/sulfoxides and classical nucleophilic substitution
reactions.[3] However, catalytic synthesis of enantioenriched
sulfones has been less developed.[4] Particularly, -chiral
benzylic sulfones still remains challenging targets. In 2016, Yan
reported the chiral cation-binding poly ether catalyst for
enantioselective elimination of racemic -sulfonyl ketones.
Although the enantioselectivity was excellent, the reaction
proceeded in a kinetic resolution manner, thus giving the chiral
sulfones in chemical yields theoretically up to 50%.[5] The
stereoconvergent approaches to chiral sulfones from racemic
starting substrates are more attractive from the viewpoint of
atom economy (Scheme 1). Fu developed the nickel/box-type
ligand-catalyzed stereoconvergent cross-coupling of -
bromosulfones with arylzinc reagents via radical intermediates to
form the corresponding -chiral benzylic sulfones with yields and
enantiomeric ratios (e.r.) up to >99% and 99:1, respectively
(Scheme 1a).[6] Additionally, Liu and Li succeeded in a dynamic
kinetic resolution of 2-sulfonylalkyl phenols by using cinchonine-
derived nucleophilic catalysts and allenoate trapping reagents
(Scheme 1b).[7] In this case, the stereoconvergency was
induced through the formation of ortho-quinone methides (o-
QMs). Completely different enantioselective conjugate addition
of sulfinates across -unsaturated carbonyl compounds was
also possible in the presence of chiral NHC/thiourea/amine
complex multicatalysts,[8] but there still needs a large demand for
Scheme 1. Stereoconvergent approaches to -chiral benzylic sulfones.
Our optimization studies began with tert-butyl diarylmethyl
carbonate 1a and sodium para-toluenesulfinate hydrate
(2a•xH2O) by screening chiral bisphosphine ligands, in
conjunction with a [{PdCl(3-C3H5)}2] catalyst and DMSO solvent,
at 60 ˚C (Table 1). Initial investigation of common BINAP-type
chiral biarylbisphosphine ligands (entries 1–5) revealed that the
parent (R)-BINAP was the most promising from the viewpoint of
enantioselectivity: the desired chiral benzylic sulfone 3aa was
obtained in 82% with 78:22 e.r. (entry 1). Although BINAP
analogues, H8-BINAP, SEGPHOS, MeO-BIPHEP, and
DIFLUOROPHOS, also promoted the reaction with good
[a]
A. Najib, Prof. Dr. K. Hirano, Prof. Dr. M. Miura
Department of Applied Chemistry
Graduate School of Engineering, Osaka University
Suita, Osaka 565-0871 (Japan)
Fax: (+81) 6-6879-7362
E-mail: k_hirano@chem.eng.osaka-u.ac.jp;
miura@chem.eng.osaka-u.ac.jp
Supporting information for this article is available on the WWW
under http://www.xxx.
This article is protected by copyright. All rights reserved.

10.1002/chem.201800744
Chemistry - A European Journal
COMMUNICATION
efficiency, but the enantioselectivity was somewhat lower (76–
93%, 51:49–74:26 e.r.; entries 2–5). The substitution product
3aa was formed also in the presence of (R,R)-DIOP that bears a
similar large bite angle to BINAP, albeit with 67:33
enantioselectivity (entry 6). The (S,S)-BDPP ligand, which was
employed in seminal work on the asymmetric benzylic
substitution reaction of secondary benzyl carbonates by Fiaud
and Legros,[13] showed a result comparable to that of (R)-
BINAP (94%, 79:21 e.r.; entry 7). On the other hand, no
reaction occurred with (R,R)-DPPBA (entry 8), which was
optimal in the asymmetric benzylic substitution of primary
benzylic electrophiles with prochiral nucleophiles.[14] We next
tested the reaction with anhydrous sulfinate 2a. However,
surprisingly, the enantiomeric ratio dramatically decreased to
56:44 e.r. (entry 9). On the other hand, the addition of H2O
recovered the enantioselectivity (entry 10). Thus, we added
other proton sources including MeOH, tBuOH, tAmOH, AcOH,
and HFIP, but almost racemic 3aa was formed in any cases (see
the Supporting Information for details). Thus, such a positive
effect on enantioselectivity is unique to H2O as far as we
examined. A similar trend was observed in another sulfinate:
anhydrous sodium benzenesulfinate (2b) provided the
completely racemate of 3ab (entry 11) while the enantiomeric
ratio increased to 89:11 e.r. in the presence of H2O (entry 12).
With benzenesulfinate 2b, (R)-BINAP showed a much better
selectivity than (S,S)-BDPP (entry 12 vs 13). Finally, the
reaction conducted at 60 ˚C further improved the
enantioselectivity, and we isolated 3ab in 98% yield with 91:9
enantiomeric ratio (entry 14). Additional observations are to be
noted: no back ground reaction occurred in the absence of any
palladium salts and ligands (entry 15); some other palladium
sources and polar solvents also work well but a combination of
[{PdCl(3-C3H5)}2] and DMSO was optimal in view of efficiency
and selectivity; more bulky substituents on phosphorus in
ligands were inferior to the parent Ph group; the use of OPiv
leaving group instead of OBoc was detrimental to the
enantioselectivity (see the Supporting information for more
detailed optimization studies).
5
2a•xH2O
2a•xH2O
2a•xH2O
2a•xH2O
2a
(R)-DIFLUOROPHOS
3aa, 91, 74:26
3aa, 87, 67:33
3aa, 94, 79:21
3aa, 0, n.d.
6
(R,R)-DIOP
(S,S)-BDPP
(R,R)-DPPBA
(R)-BINAP
(R)-BINAP
(R)-BINAP
(R)-BINAP
(S,S)-BDPP
(R)-BINAP
none
7
8
9
3aa, 79, 56:44
3aa, 92, 72:28
3ab, 71, 50:50
3ab, 86, 89:11
3ab, 83, 76:24
3ab, 98, 91:9
3aa, 0, n.d.
10[d]
11
2a
2b
12[d]
13[d]
14[d,e]
15[f]
2b
2b
2b
2a•xH2O
[a] Conditions: 1a (0.25 mmol), 2 (0.30 mmol), [{PdCl(3-C3H5)}2] (0.0050
mmol), ligand (0.011 mmol), DMSO (1.0 mL), 80 ˚C, 6 h, N2. [b] Yields of the
isolated product are given. [c] Enantiomeric ratio (e.r.) was determined by
HPLC analysis on a chiral stationary phase. [d] In DMSO/H2O (1.0/0.050 mL).
[e] At 60 ˚C. [f] Without Pd and ligand. Boc = tert-butoxycarbonyl. n.d. = not
determined.
With the conditions in entry 14 of Table 1, we performed the
asymmetric benzylic sulfonation of several secondary benzylic
carbonates 1 with 2b.
The representative products are
Table 1. Optimization studies for palladium-catalyzed enantioselective
benzylic substitution of tert-butyl diarylmethyl carbonate 1a with sodium
sulfinates 2.[a]
illustrated in Scheme 2. In addition to 3ab, the methoxy-, chloro-,
and trifluoromethyl-substituted chiral benzylic sulfones 3bb–3db
were obtained in good yields with 82:18–86:14 e.r. while the
reaction should be conducted at 40 ˚C.[15]
The asymmetric
catalysis was compatible with the sterically demanding ortho-
methyl group, giving the desired 3eb with a good enantiomeric
ratio (93:7 e.r.).
Although the introduction of methoxy
substituent at the 2-naphthalene ring somewhat decreased the
enantioselectivity (3fb), 1-naphthylmethy carbonate provided the
substitution product 3gb with excellent enantioselectivity (99:1
e.r.). The higher fused phenanthrene derivative could also be
employed, and the corresponding sulfone 3hb was obtained with
a high enantiomeric ratio (98:2 e.r.). On the other hand, similar
in our previous work,[9] 1-(2-naphthyl)ethyl carbonate gave
nearly racemate (3ib).[16] The absolute configuration of 3gb was
determined to be R by single crystallographic X-ray analysis,
and others are tentatively assigned by analogy.[17]
Entry
2
Chiral ligand
3, Yield [%][b], e.r.[c]
3aa, 82, 79:21
3aa, 76, 51:49
3aa, 93, 63:37
3aa, 92, 74:26
1
2
3
4
2a•xH2O
2a•xH2O
2a•xH2O
2a•xH2O
(R)-BINAP
(R)-H8-BINAP
(R)-SEGPHOS
(R)-MeO-BIPHEP
Several sodium sulfinates 2 were also tested (Scheme 3).
The para-toluenesulfinate (2a) could be coupled with 1g to form
the chiral benzylic sulfone 3ga with a good enantiomeric ratio
This article is protected by copyright. All rights reserved.

10.1002/chem.201800744
Chemistry - A European Journal
COMMUNICATION
(87:13 e.r.). On the other hand, electron-withdrawing chloro-
substituted sulfinate 2c and aliphatic methanesulfinate 2d were
also reactive, but somewhat lower enantioselectivity was
observed (3gc and 3ad).
means the absolute configuration of the ligand L).[18] An
alternative
mechanism
includes
initial
-
coordination/ionization,[10,14] which can explain better reactivity of
naphthalene substrates.[16] They then undergo the epimerization
probably by the attack of additional [Pd(0)Ln] species.[19] During
this process, the stereochemical information on the starting
carbonate at the benzylic position is lost and DYKAT thus is
accessible. A related process is proposed in the isoelectronic -
allylpalladium chemistry.[20] The asymmetric induction arises
from a selective backside attack of sulfinate 2b with one (S,RL)-4
isomer to produce the observed major enantiomer (R)-3ab.
Scheme 4. Plausible mechanism. L = (R)-BINAP. The descriptor RL means
the absolute configuration of the ligand L.
To support the proposed mechanism, some additional
experiments were implemented. When the enantiomerically
pure (S)-1a was subjected to conditions with (R)-BINAP or (S)-
BINAP-ligated palladium catalyst, the obtained major enantiomer
of 3ab was dependent on the absolute configuration of ligand:
(R)-BINAP and (S)-BINAP mainly provided (R)-3ab and (S)-3ab,
respectively, thus suggesting operation of DYKAT [Eqs. (1) and
(2)]. However, a significant match/mismatch phenomenon was
also observed. This is probably because the epimerization
between (S,RL)-4 and (R,RL)-4 is not much more rapid than the
sulfonation with 2b, and thus enantiospecific pathway
competitively occurs. Actually, the reaction of (S)-1a with 2b in
the presence of Pd/rac-BINAP catalyst resulted in a partial but
significant chirality transfer likely through double inversion
process (net retention) [Eq. (3)].
Scheme 2. Palladium-catalyzed enantioselective benzylic substitution of tert-
butyl diarylmethyl carbonate 1 with sodium benzenesulfinate 2b. Conditions: 1
(0.25 mmol), 2b (0.30 mmol), [{PdCl(3-C3H5)}2] (0.0050 mmol), (R)-BINAP
(0.011 mmol), DMSO/H2O (1.0/0.050 mL), 60 ˚C, 6 h, N2. Yields of the isolated
product are given. Enantiomeric ratio (e.r.) was determined by HPLC analysis
on a chiral stationary phase. [a] At 40 ˚C.
Finally, we performed some control studies to get insight into
the role of H2O. One possibility is to suppress the racemization
of initially formed enantioenriched product, however, this is
unlikely since the independently prepared (R)-3ab (89:11 e.r.)
underwent no racemization in the presence or absence of H2O
[Eq. (4)]. Others are in situ conversions of starting reagents and
catalysts to truly active and selective species, but any attempts
with the free carbinol 5, sulfinic acid 6, or (R)-BINAP monoxide
(R)-BINAP(O)[21] did not furnish the substitution product 3ab at
all [Eq. (5)]. Thus, although details are still unclear, H2O may
play a pivotal role in the sulfonation step to increase the
difference of reaction rates between (S,RL)-4 and (R,RL)-4 with
2b (Scheme 4).
Scheme 3. Palladium-catalyzed enantioselective benzylic substitution of 1a
and 1g with several sodium sulfinate 2. Conditions: see the footnote of
Scheme 2.
On the basis of our previous findings and literature
information, we are tempted to assume the reaction mechanism
of 1a with 2b as follows (Scheme 4). Initial SN2-type substitution
of the secondary benzyl carbonates (R)-1a and (S)-1a with
[Pd0Ln] [L = (R)-BINAP] is followed by decarboxylation and -to-
 isomerization to form the corresponding diastereomeric -
benzyl intermediates (S,RL)-4 and (R,RL)-4, respectively (RL
In conclusion, we have developed a palladium-catalyzed
asymmetric benzylic substitution of diarylmethyl carbonates with
sodium sulfinates in a DYKAT manner to form the -chiral
This article is protected by copyright. All rights reserved.

10.1002/chem.201800744
Chemistry - A European Journal
COMMUNICATION
Tetrahedron 1980, 36, 723; c) R. W. Murray, R. Jeyararnan, M. K.
Pilley, J. Org. Chem. 1987, 52, 746.
benzylic sulfones, which are difficult to prepare by the
conventional methods. The present asymmetric catalysis can
provide an additional stereoconvergent approach to chiral
sulfones from racemic starting substrates. Further elucidation of
mechanism, particularly role of H2O, and development of other
types of DYKAT process are now ongoing in our laboratory.
[4]
For asymmetric allylic sulfonation of -allylpalladiums and-iridiums, see:
a) B. M. Trost, M. G. Organ, G. A. O’Doherty, J. Am. Chem. Soc. 1995,
117, 9662; b) H.-J. Gais, T. Jagusch, N. Spalthoff, F. Gerhards, M.
Frank, G. Raabe, Chem. Eur. J. 2003, 9, 4202; c) M. Ueda, J. Hartwig,
Org. Lett. 2010, 12, 92.
[5]
[6]
[7]
[8]
[9]
L. Li, Y. Liu, Y. Peng, L. Yu, X. Wu, H. Yan, Angew. Chem. Int. Ed.
2016, 55, 331; Angew. Chem. 2016, 128, 339.
J. Choi, P. Martín-Gago, G. C. Fu, J. Am. Chem. Soc. 2014, 136,
12161.
P. Chen, K. Wang, W. Guo, X. Liu, Y. Liu, C. Li, Angew. Chem. Int. Ed.
2017, 56, 3689; Angew. Chem. 2017, 129, 3743.
Z. Jin, J. Xu, S. Yang, B.-A. Song, Y. R. Chi, Angew. Chem. Int. Ed.
2013, 52, 12354; Angew. Chem. 2013, 125, 12580.
a) S. Tabuchi, K. Hirano, M. Miura, Angew. Chem. Int. Ed. 2016, 55,
6973; Angew. Chem. 2016, 128, 7087; b) A. Najib, K. Hirano, M. Miura,
Org. Lett. 2017, 19, 2438.
[10] Reviews: a) B. M. Trost, L. C. Czabaniuk, Angew. Chem. Int. Ed. 2014,
53, 2826; Angew. Chem. 2014, 126, 2868; b) J. L. Le Bras, J. Muzart, E.
J. Org. Chem. 2016, 2565.
[11] a) K. Faber, Chem. Eur. J. 2001, 7, 5004; b) B. M. Trost, D. R. Fandrick,
Aldrichimica 2007, 40, 59; c) J. Steinreiber, K. Faber, H. Griengl, Chem.
Eur. J. 2008, 14, 8060.
[12] Kuwano reported the palladium-catalyzed benzylic sulfonation of benzyl
carbonates with sodium sulfinates, but the substrates were limited to
primary ones, and the stereochemical control was not mentioned; R.
Kuwano, Y. Kondo, T. Shirahama, Org. Lett. 2005, 7, 2973.
[13] a) J.-Y. Legros, A. Boutros, J.-C. Fiaud, M. Toffano, J. Mol. Catal. A:
Chem. 2003, 196, 21; b) J.-Y. Legros, M. Toffano, J.-C. Fiaud,
Tetrahedron 1995, 51, 3235.
[14] a) B. M. Trost, L. C. Czabaniuk, J. Am. Chem. Soc. 2010, 132, 15534;
b) B. M. Trost, L. C. Czabaniuk, J. Am. Chem. Soc. 2012, 134, 5778.
[15] We confirmed the racemization by subjection of isolated 3db (64:36
e.r.) to standard conditions (60 ˚C), giving the recovered 3db with 52:48
e.r. However, other products hardly underwent the racemization as far
as we tested.
[16] As far as we tested, the present catalyst system did not address the
“naphthalene
problem”:
diphenylmethyl
and
(4-
biphenylyl)(phenyl)methyl carbonates gave no desired products. Such
a reactivity difference can be associated with weaker aromaticity of
naphthalene and related fused aromatics, which accelerates the
formation of -benzyl intermediates. Similar trends are often observed
in metal-catalyzed cross-coupling reactions with C–O electrophiles.
See: a) M. Tobisu, N. Chatani, Acc. Chem. Res. 2015, 48, 1717; b) S.
N. Mendis, J. A. Tunge, Org. Lett. 2015, 17, 5164.
Acknowledgements ((optional))
This work was supported by JSPS KAKENHI Grant Nos. JP
15H05485 (Grant-in-Aid for Young Scientists (A)) to K.H. and JP
17H06092 (Grant-in-Aid for Specially Promoted Research) to
M.M. We thank Misaki Terada, Kazutaka Takamatsu, and Dr.
Yuji Nishii for their assistance with X-ray analysis.
[17] Crystallographic data for the structure of 3gb have been deposited with
the Cambridge Crystallographic Data Centre (CCDC 1823024). See
the Supporting Information for details.
[18] a) P. K. Wong, K. S. Y. Lau, J. K. Stille, J. Am. Chem. Soc. 1974, 96,
5956; b) A. López-Pérez, J. Adrio, J. C. Carretero, Org. Lett. 2009, 11,
5514.
Keywords: asymmetric catalysis • benzylic substitution •
DYKAT • palladium • sulfones
[19] I. M. Yonova, A. G. Johnson, C. A. Osborne, C. E. Moore, N. S.
Morrissette, E. R. Jarvo, Angew. Chem. Int. Ed. 2014, 53, 2422; Angew.
[1]
[2]
[3]
a) N. S. Simpkins, Sulfones in Organic Synthesis, Pergamon, Oxford,
1993; b) Organosulfur Chemistry in Asymmetric Synthesis, (Eds.: T.
Toru, C. Bolm), Wiley-VCH, Weinheim, 2008; c) P. Vogel, M. Turks, L.
Bouchez, D. Marković, A. Varela-Álvarez, J. Á. Sordo, Acc. Chem. Res.
2007, 40, 931; d) J. D. Wilden, J. Chem. Res. 2010, 34, 541.
Chem. 2014, 126, 2454.
However, we observed no positive
dependence of enantioselectivity on the catalyst loading. See the
Supporting Information for details.
[20] a) T. Takahashi, Y. Jinbo, K. Kitamura, J. Tsuji, Tetrahedron Lett. 1984,
25, 5921; b) K. L. Granberg, J.-E. Bäckvall, J. Am. Chem. Soc. 1992,
114, 6858; c) M. Moreno-Mañas, L. Morral, R. Pleixats, J. Org. Chem.
1998, 63, 6160; d) H. Kurosawa, S. Ogoshi, Y. Kawasaki, S. Murai, M.
Miyoshi, I. Ikeda, J. Am. Chem. Soc. 1990, 112, 2813.
[21] It is known that H2O promotes the reduction of PdII into Pd0 with
concomitant oxidation of phosphine ligands; a) F. Ozawa, A. Kubo, T.
Hayashi, Chem. Lett. 1992, 2177; b) B. P. Fors, P. Krattiger, E. Strieter,
S. L. Buchwald, Org. Lett. 2008, 10, 3505.
a) S. Trivedi, P. C. Patidar, P. K. Chaurasiya, Pharma Chem. 2010, 2,
369; b) M. Teall, P. Oakley, T. Harrison, D. Shaw, E. Kay, J. Elliott, U.
Gerhard, J. L. Castro, M. Shearman, R. G. Ball, N. N. Tsou, Bioorg.
Med. Chem. Lett. 2005, 15, 2685; c) M. Yamada, T. Ichikawa, M. Ii, K.
Itoh, N. Tamura, T. Kitazaki, Bioorg. Med. Chem. 2008, 16, 3941.
a) H. Fukuda, F. J. Frank, W. E. Truce, J. Org. Chem. 1963, 28, 1420;
b) J. J. Burger, T. B. R. A. Chen, E. R. De Waard, H. O. Huisman,
This article is protected by copyright. All rights reserved.

10.1002/chem.201800744
Chemistry - A European Journal
COMMUNICATION
This article is protected by copyright. All rights reserved.

10.1002/chem.201800744
Chemistry - A European Journal
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
Layout 1:
COMMUNICATION
Text for Table of Contents
Author(s), Corresponding Author(s)*
Page No. – Page No.
Title
Layout 2:
COMMUNICATION
A. Najib, K. Hirano,* M. Miura*
Page No. – Page No.
Asymmetric Synthesis of
Diarylmethyl Sulfones by Palladium-
Catalyzed Enantioselective Benzylic
Substitution: A Remarkable Effect of
Water
Dynamic road to sulfones: A Pd/(R)-BINAP-catalyzed enantioselective benzylic
sulfonation of diarylmethyl carbonates with sodium sulfinates proceeds in a
dynamic kinetic asymmetric transformation (DYKAT) manner to deliver the
corresponding chiral diarylmethyl sulfones in good yields with high
enantioselectivity. The key to success is addition of H2O as well as judicious choice
of ancillary chiral ligand.
This article is protected by copyright. All rights reserved.