The first phosphiteꢀtype ligand
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 12, December, 2013
2629
Me4Si (1H and 13C). The signals in the 1H and 13C NMR spectra
were assigned using COSY, DEPT, and HSQC NMR techniques
and taking in account published data.9 Electron impact mass
spectra (EI, 70 eV) were obtained on a Varian MATꢀ311 instruꢀ
ment. Enantiomeric analyses of the product of allylic sulfonylaꢀ
tion were performed on a Stayer HPLC system. For elemental
analyses, Carlo Erba EA1108 CHNSꢀO microanalyzer was used.
All reactions were carried out in anhydrous solvents under
dry argon. ((4R,5S)ꢀ5ꢀ(Hydroxymethyl)ꢀ2,2ꢀdimethylꢀ1,3ꢀdiꢀ
oxolanꢀ4ꢀyl)diphenylmethanol (1) were synthesized by the
known procedure.9 The starting compounds, (E)ꢀ1,3ꢀdiphenylꢀ
allyl acetate (3) and complex [Pd(allyl)Cl]2, were synthesized as
earlier described.12 Pdꢀcatalyzed asymmetric allylic sulfonylaꢀ
tion of compound 3 with sodium pꢀtoluenesulfinate and deterꢀ
mination of enantiomeric excesses of product 4 were performed
following the published procedures.13
determined from 31P NMR (CDCl3) spectra of comꢀ
pound 2 exhibiting two narrow singlets at P 144.9 (95%)
and 137.3 (5%). It should be emphasized that the presence
of the P*ꢀstereogenic donor atom in the ligand 2 faciliꢀ
tates the chirality transfer on the key step of the catalytic
cycle.10,11
Stereodifferentiating ability of amidophosphite 2 was
estimated using enantioselective Pdꢀcatalyzed allylic sulꢀ
fonylation of (E)ꢀ1,3ꢀdiphenylallyl acetate (3) (Scheme 2,
Table 1) as a model reaction. It is of note that chiral allyl
sulfones are of considerable interest for the stereoselective
organic synthesis.11
Scheme 2
Pyrrolidine, Nꢀmethylpyrrolidone, and sodium pꢀtolueneꢀ
sulfinate are commercially available from Fluka and Aldrich.
(1R,7S)ꢀ9,9ꢀDimethylꢀ2,2ꢀdiphenylꢀ4ꢀ(pyrrolidinꢀ1ꢀyl)ꢀ
3,5,8,10ꢀtetraoxaꢀ4ꢀphosphabicyclo[5.3.0]decane (2). To a vigꢀ
orously stirred suspension of compound 1 (0.63 g, 2 mmol) in
PCl3 (4 mL, 45.5 mmol), Nꢀmethylpyrrolidone (0.01 g, 0.1 mmol)
was added and the mixture was refluxed for 5 min until homoꢀ
geneity. The PCl3 excess was removed in vacuo (40 Torr), the
residue was dried in vacuo (30 min, 1 Torr) to remove the PCl3
traces and dissolved in toluene (12 mL). To the obtained soluꢀ
tion, pyrrolidine (0.4 mL, 4.8 mmol) was added at 20 C under
vigorous stirring. The reaction mixture was refluxed for 15 min,
cooled to 20 C, and filtered through an alumina pad. The filꢀ
trate was concentrated in vacuo (40 Torr). Purification of the
residue by flash column chromatography (silica gel, elution with
CH2Cl2) afforded compound 2 in the yield of 0.59 g (71%),
colorless oil. Found (%): C, 67.05; H, 6.76; N, 3.24. C23H28NO4P.
Calculated (%): C, 66.82; H, 6.83; N, 3.39. 13C NMR (CDCl3),
Reagents and conditions: 1) [Pd(allyl)Cl]2, ligand 2, THF, 20 C,
15 min, 2) pꢀTolSO2Na, 20 C, 48 h.
As a preꢀcatalyst, [Pd(allyl)Cl]2 was used. Allylic sulꢀ
fone (S)ꢀ4 was obtained in high yield and high enantioseꢀ
lectivity up to 90% ee (see Table 1). In this reaction, the
known TADDOLꢀderived bisꢀphosphine ligand gives no
more than 68% ee.9 Thus, amidophosphite 2 is a promisꢀ
ing chiral ligand and its application in asymmetric catalyꢀ
sis is now extensively studied in our research group.
3
: 25.4 (s, CH3); 25.9 (d, CH2, JC,P = 5.4 Hz); 27.4 (s, CH3);
44.5 (d, CH2N, 2JC,P = 15.0 Hz); 65.6 (d, C(6), 2JC,P = 10.0 Hz);
3
2
31
1
P, H, and 13C NMR spectra were run on Bruker Avance
75.3 (d, C(7), JC,P = 3.8 Hz); 80.6 (d, C(2), JC,P = 5.7 Hz);
86.2 (d, C(1), 3JC,P = 19.1 Hz); 110.7 (s, C(9)); 126.8 (s, CHPh);
126.9 (s, CHPh); 127.0 (s, CHPh); 127.3 (s, CHPh); 128.0
(s, CHPh); 128.4 (s, CHPh); 141.3 (s, CPh); 146.7 (s, CPh). 1H NMR
(CDCl3), : 0.66 (s, 3 H, CH3); 1.46 (s, 3 H, CH3); 1.84—1.91
(m, 4 H, CH2); 3.24—3.29 (m, 2 H, CH2N); 3.39—3.44 (m, 2 H,
400 (161.98 (31P), 400.13 (1H), and 100.61 MHz (13C)) and
Bruker Avance III 600 (242.94 (31P), 600.13 (1H), and 150.9 MHz
13C)) spectrometers relative to 85% H3PO4 in D2O (31P) and
(
CH2N); 3.89 (ddd, 1 H, C(6)H, 2JH,H = 11.2 Hz, 3JH,H = 9.2 Hz,
Table 1. Pdꢀcatalyzed asymmetric allylic sulfonylationa of
diphenylallyl acetate 3 with sodium pꢀtoluenesulfinate in
the presence of ligand 2
3
3JH,P = 2.4 Hz); 4.18 (td, 1 H, C(7)H, JH,H = 9.2 Hz, 3JH,H
=
= 3.6 Hz); 4.33 (ddd, 1 H, C(6)H, 2JH,H = 11.2 Hz, 3JH,H = 3.6 Hz,
3JH,P = 28.2 Hz); 4.96 (dd, 1 H, C(1)H, 3JH,H = 9.1 Hz, 4JH,P
=
= 3.9 Hz); 7.22 (t, 1 H, CHPh, 3J = 7.4 Hz); 7.28 (t, 2 H, CHPh
3J = 7.4 Hz); 7.30—7.34 (m, 2 H, CHPh); 7.39 (t, 1 H, CHPh
3J = 7.5 Hz); 7.41 (d, 2 H, CHPh, 3J = 7.6 Hz); 7.65 (d, 2 H, CHPh
3J = 7.6 Hz). MS, m/z (Irel (%)): 413 [M]+ (100).
,
,
,
Entry
Ratio
ligand 2 : Pd
(mol/mol)
Yield of 4
ee (%)b,c
(%)
Asymmetric allylic sulfonylation of (E)ꢀ1,3ꢀdiphenylallyl acetꢀ
ate (3) with sodium pꢀtoluenesulfinate. A solution of [Pd(allyl)Cl]2
(0.0019 g, 0.005 mmol) and ligand 2 (0.004 g, 0.01 mmol or
0.008 g, 0.02 mmol) in THF (1.5 mL) was stirred for 40 min.
Then (E)ꢀ1,3ꢀdiphenylallyl acetate (3) (0.05 mL, 0.25 mmol)
was added. After 15 min stirring, sodium pꢀtoluenesulfinate
(0.089 g, 0.5 mmol) was added and stirring was continued for 48 h.
To the reaction mixture, brine (3 mL) was added, the mixture
was stirred for 1 h and extracted with THF (3×2 mL). The orꢀ
ganic layer was washed with brine (2×2 mL), dried with MgSO4,
and filtered through Celite. The solvent was removed in vacuo
1
2
1
2
87
92
90 (S)
85 (S)
a Reaction conditions: [Pd(allyl)Cl]2 (2 mol.%), THF,
20 C, 48 h.
b Enantiomeric excesses of product 4 were determined by
HPLC (chiral column Daicel Chiralcel ODꢀH, elution
with C6H14—PriOH (4 : 1), eluent flow rate 0.5 mL min–1
,
detection at = 254 nm, retention times t(R) = 16.3 min,
t(S) = 18.5 min).
c Configuration of the product is given in parentheses.