Asymmetric Tsuji-Trost substitution in 3-acetoxy-1,3-diphenylpropene under phase-transfer conditions

Article abstract of DOI:10.1016/j.mencom.2012.01.015

P*-Chiral diamidophosphite ligand-assisted Pd-catalyzed Tsuji-Trost reaction between dimethyl malonate and prochiral 3-acetoxy-1,3-diphenylpropene in organic solvents using potassium carbonate as the base affords the substitution product in quantitative y

Full text of DOI:10.1016/j.mencom.2012.01.015

Mendeleev
Communications
Mendeleev Commun., 2012, 22, 39–40
Asymmetric Tsuji–Trost substitution in
3-acetoxy-1,3-diphenylpropene under phase-transfer conditions
a
b
a
Andrei A. Vasil’ev,* Sergey E. Lyubimov, Edward P. Serebryakov,
b
a
Vadim A. Davankov and Sergei G. Zlotin
a
b
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 499 135 5328; e-mail: vasiliev@ioc.ac.ru
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow,
Russian Federation
DOI: 10.1016/j.mencom.2012.01.015
P*-Chiral diamidophosphite ligand-assisted Pd-catalyzed Tsuji–Trost reaction between dimethyl malonate and prochiral 3-acetoxy-
,3-diphenylpropene in organic solvents using potassium carbonate as the base affords the substitution product in quantitative yields
1
and with enantioselectivities up to 99% ee.
Asymmetric Tsuji–Trost reaction of prochiral substrates using
chiral catalysts is nowadays a well-recognized methodology to
access non-racemic molecules. Replacement of acetoxy group
Me
N
N
N
N
N
N
Ph
Ph
1
P
P
P
OPh
L1
OCy
L2
OBut
of prochiral 3-acetoxy-1,3-diphenylpropene 1 (1,3-diphenylallyl
acetate) by dimethyl malonate 2 fragment is mostly employed as
a model reaction for testing new catalysts, ligands and reaction
conditions (Scheme 1). Excellent yields and ee values have been
L3
Me
1
(c)
currently achieved.
However, the best ligands are usually
N
N
Ph
H
O
P
N
P
O
poorly accessible, and most of standard procedures are based
on generation of malonate carbanion using highly flammable or
expensive bases such as NaH or BSA–AcOK system. This brings
certain restrictions to wide use of such a promising type of reaction.
N
P
O
N
H
O
N
Me
O
L5
Me
Me
Ph
L4
OAc
Ph
MeO2C
CO2Me
Ph
Pd/P*
+
2 2
CH(CO Me)
Ph
*
selectivity. We suppose that both reacting species, namely, p-ally-
lic Pd complex and carbanion, are generated during the course
of the reaction and definitely are present in low concentrations.
On carrying out the process in less polar solvents such as THF
and CH Cl (entries 2 and 3), application of phase transfer catalyst,
Ph
1
3
Base
CH2(CO2Me)2
2
2
2
Scheme 1
for example Bu NBr, was required. Although yield of product 3
4
remained quantitative, ee values were somewhat lower.
2
Recently, we have shown that phase-transfer methodology
for generation of CH-acid carbanion using cheap and safe bases
such as alkali carbonates or phosphates (cf. ref. 3) can be suc-
cessfully employed in the Tsuji–Trost reaction even in the case
of problematic substrates. Based on this principle, we pioneered
in carrying out reaction between the reactants 1 and 2 in super-
critical carbon dioxide thus providing reasonable yields and ee
Testing of other diamidophosphites L2–L5 (Table 1, entries 4–7)
showed that bidentate dianhydromannitol-tethered one L5 was
the ligand of choice. Interestingly, l-menthol-derived ligand L4
also containing additional chiral centers proved to be inefficient
in view of enantioselectivity (entry 6). Further optimization of
reaction conditions (entries 8–10) by varying solvent and palla-
4
†
values of the product 3. Herein, we report our latest results on
A Schlenk tube equipped with a stirring magnet and charged with dimethyl
this reaction in conventional organic solvents using potassium
carbonate as the base and readily accessible P*-chiral diamido-
phosphite ligands L1–L5. Such ligands proved to be very efficient
malonate 2 (0.3 mmol), an appropriate solvent (0.7 ml) and Bu NBr
4
(0.025 mmol, if necessary) was three times deaerated by evacuation and
filling with argon (special care should be taken in case of volatile solvents).
Diamidophosphite L1–L4 (0.01 mmol) or L5 (0.005 mmol) and Pd dba
3
5
in various versions of Pd-catalyzed allylic substitution.
2
or [Pd(C H )Cl] (0.0025 mmol) were added, and the mixture was stirred
Experiments using the simplest ligand L1 with Pd dba (two
3
5
2
2
3
for ca. 5 min until change in the colour occurred. Then (E)-3-acetoxy-
,3-diphenylpropene 1 (50 mg, 0.25 mmol) was added, and the mixture
P atoms per one Pd, Pd:L = 1:2) showed (Table 1, entry 1) that
quantitative yield and very good enantiomeric purity of the product
1
was stirred for 10 min, followed by addition of finely powdered potassium
carbonate (69 mg, 0.5 mmol). Each opening of the Schenk tube was carried
out under argon flushing. The mixture was stirred at ambient temperature
for 18 h, after which it was treated with water, extracted with benzene and
3
can be truly achieved in DMF using potassium carbonate as the
†
base. Apparently, the carbonate basicity is not sufficient to fully
deprotonate malonate 2, however, it is enough to maintain neces-
sary steady-state concentration of the carbanion thus allowing
the reaction to proceed. Low concentration of reacting species is
usually recognized as an important factor providing high enantio-
dried with CaCl . To determine conversion of substrate 1 and enantiomeric
2
excess (ee) of product 3, an aliquote was analyzed by chiral HPLC (Daicel
Chiralcel OD-H column) as described previously.6
©
2012 Mendeleev Communications. All rights reserved.
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Mendeleev Commun., 2012, 22, 39–40
Table 1 Enantioselective Tsuji–Trost substitution in 3-acetoxy-1,3-diphenyl-
References
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1
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ee (%)b
Entry Ligand Solvent
Conversion (%)
1
2
3
4
5
6
7
8
9
0
L1
L1
L1
L2
L3
L4
L5
L5
L5
L5
DMF
THF (+ Bu NBr)
100
100
100
100
100
100
100
100
90
84
77
76
68
30
92
95
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Int. Ed., 2010, 59, 605).
4
CH Cl (+ Bu NBr)
2
2
4
DMF
DMF
DMF
DMF
3
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(
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4 (a) S. E. Lyubimov, I. V. Kuchurov, A. A. Vasil’ev, A. A. Tyutyunov, V. N.
4
CH Cl (+ Bu NBr)
100 (100)c
96 (99)c
2
2
4
95 (100)c
94 (97)c
1
toluene (+ Bu NBr)
4
Kalinin, V. A. Davankov and S. G. Zlotin, J. Organomet. Chem., 2009,
a
Reaction conditions: 0.25 mmol of 3-acetoxy-1,3-diphenylpropene 1, 0.3 mmo
of dimethyl malonate 2, 0.5 mmol of K CO , 0.7 ml of solvent, 0.025 mmol of
Bu NBr (if specified), 1 mol% of Pd dba (2 g-at% Pd per 1), 4 mol% of
ligand (or 2 mol% of bidentate ligand L5), 20°C, 18 h. Major isomer had
S)-configuration. Parentheses are related to when [Pd(C H )Cl] was used
as the Pd source.
l
6
94, 3047; (b) S. E. Lyubimov, I. V. Kuchurov, A. A. Vasil’ev, S. G. Zlotin
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3
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4
2
3
5
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Bondarev, V. A. Davankov, A. A. Kabro, S. K. Moiseev, V. N. Kalinin and
K. N. Gavrilov, Eur. J. Org. Chem., 2004, 2214; (b) K. N. Gavrilov, V. N.
Tsarev, A. A. Shiryaev, O. G. Bondarev, S. E. Lyubimov, E. B. Benetsky,
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Davankov and M. T. Reetz, Adv. Synth. Catal., 2007, 349, 609; (f) K. N.
Gavrilov, S. E. Lyubimov, S. V. Zheglov, E. B. Benetsky, P. V. Petrovskii,
E. A. Rastorguev, T. B. Grishina and V. A. Davankov, Adv. Synth. Catal.,
2007, 349, 1085; (g) K. N. Gavrilov, S. V. Zheglov, P. A. Vologzhanin,
E. A. Rastorguev, A. A. Shiryaev, M. G. Maksimova, S. E. Lyubimov,
E. B. Benetsky,A. S. Safronov, P.V. Petrovskii,V.A. Davankov, B. Schäffner
and A. Börner, Izv. Akad. Nauk, Ser. Khim., 2008, 2266 (Russ. Chem. Bull.,
Int. Ed., 2008, 57, 2311); (h) K. N. Gavrilov, S.V. Zheglov, P.A.Vologzhanin,
M. G. Maksimova,A. S. Safronov, S. E. Lyubimov,V.A. Davankov, B. Schäffner
and A. Börner, Tetrahedron Lett., 2008, 49, 3120.
b
c
(
3 5 2
dium source {Pd dba or [Pd(C H )Cl] } revealed that the use
of [Pd(C H )Cl] , CH Cl , Bu NBr (cat.) and K CO provided
2
3
3
5
2
3
5
2
2
2
4
2
3
excellent enantioselectivity (99% ee) and complete conversion
of 2 within 18 h at ambient temperature (entry 9). Note that
the use of [Pd(C H )Cl] as the palladium source brought about
slightly better results under the same reaction conditions (see
entries 9–10).
The results obtained are superior to previous not only for
excellent yields and enantioselectivities, but also for availability
and easiness-to-handle of the ligands, low price and safety of the
base and room temperature processing. Several precedents of
using alkali carbonates in asymmetric Tsuji–Trost substitution
in 3-acetoxy-1,3-diphenylpropene 1 were documented, though.
With aqueous K CO , cetyltrimethylammonium hydrosulfate,
Pd(C H )Cl] and R-BINAP at 25°C, the product 3 was obtained
quantitatively with 91% ee. Without phase transfer catalyst,
analogous to 3 ethyl diester of 80% ee was formed in 21% yield
on heating at 70°C for 12 h. In ionic liquids, 74–86% ee values
were achieved at yields of 27–81% on using of very expensive
chiral ferrocene phosphine ligands. It is worth noting that diamido-
3
5
2
6 H. Kodama, T. Taiji, T. Ohta and I. Furukawa, Tetrahedron: Asymmetry,
000, 11, 4009.
7 (a) D. Sinou, C. Rabeyrin and C. Nguefack, Adv. Synth. Catal., 2003, 345,
57; (b) C. Rabeyrin and D. Sinou, Tetrahedron: Asymmetry, 2003, 14, 3891.
2
3
2
[
3 5 2
7
3
8
9
F.-X. Felpin and Ya. Landais, J. Org. Chem., 2005, 70, 6441.
(a) Š. Toma, B. Gotov, I. Kmentová and E. Sol cˇ ániová, Green Chem.,
2000, 2, 149; (b) I. Kmentová, B. Gotov, S. E. Sol cˇ ániová and Š. Toma,
Green Chem., 2002, 4, 103.
8
9
phosphite ligands L1 and L5 on conventional manner of 1+2
coupling (BSA–AcOK system as the base, ambient temperature)
provided 74–98% ee of the product 3, with the conversion having
never reached its completion (72–90%) even upon 48 h of the
5
(a),(g),(h)
processing.
To conclude, we believe that our findings will promote wider
application of the Tsuji–Trost allylic substitution in the total
synthesis of useful biologically active compounds.
Received: 27th June 2011; Com. 11/3752
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40 –