Biphenylꢀ2,2´ꢀdiolꢀbased iminophosphite ligand
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 4, April, 2004
817
leads to a substantial enhancement of the asymmetric
induction (see Table 3, run 4). To the best of our knowlꢀ
edge, this is the first example of Rhꢀcatalyzed allylic
sulfonylation.
completely homogeneous. The excess of PCl3 was removed
in vacuo (40 Torr), the residue was dissolved in 10 mL of toluꢀ
ene, and the solution was concentrated in vacuo (40 Torr) to
remove traces of PCl . The product was distilled in vacuo (b.p.
3
1
25—126 °C, 1 Torr). Yield 2.29 g (85%). The spectroscopic and
Our attempts to perform allylic amination of substrates
physicochemical characteristics of product 1 fully correspond to
6
a,b (Nu = PhCH NH ) failed even on refluxing the
16,17
2
2
published data.
reaction mixtures (cat* is [Pd(All)Cl] /2L or complex 5)
2
(2´S,3´S)ꢀ2ꢀ{2´ꢀ[(Ferrocenylidene)amino]ꢀ3´ꢀmethylpentylꢀ
oxy}dibenzo[d, f ][1,3,2]dioxaphosphepine (2). Reagent 1 (1 g,
in THF for 48 h. Generally, imino phosphite 2 can be
considered as a specific ligand for enantioselective cataꢀ
lytic processes involving Cꢀnucleophiles. Indeed, the level
of enantioselectivity equal to 88%, attained with this ligand
in the Pdꢀcatalyzed alkylation of 1,3ꢀdiphenylallyl acꢀ
etate with dimethyl malonate, is quite comparable with
that obtained for the aboveꢀmentioned best P,Nꢀbidentate
phosphiteꢀtype ligands (85—88%).
4 mmol) and Et N (0.56 mL, 4 mmol) were dissolved in 12 mL
3
of toluene, and (2S,3S)ꢀ3ꢀmethylꢀ2ꢀ(ferrocenylidenamino)penꢀ
tanꢀ1ꢀol (1.252 g, 4 mmol) was added with vigorous stirring and
cooling to 0 °C. The resulting solution was stirred for 10 min,
heated to boiling, and cooled to 20 °C, and Et N•HCl was
3
filtered off. Hexane (15 mL) was added to the filtrate, the preꢀ
cipitate was filtered off, and the filtrate was concentrated in
vacuo (40 Torr). The resulting solution was evacuated (1 h,
1
Torr) to give compound 2 in 1.935 g (92%) yield as a red resin.
Experimental
Found (%): C, 66.05; H, 5.73; N, 2.66. C H FeNO P. Calcuꢀ
lated (%): C, 66.21; H, 5.62; N, 2.54. C NMR (CDCl ), δ:
10.8, 15.5 (both s, Me); 25.4 (s, CH ); 35.9 (s, CH); 66.2
(s, CH O); 68.2, 68.4, 68.9, 70.1 (all s, CFс); 76.1 (s, CHN);
2
3
9
30
3
1
3
31Р and 13C NMR spectra were recorded on a Bruker
AMXꢀ400 spectrometer (161.98 and 100.61 МHz) relative to
2
2
8
5% H РO in D O and CDCl (δ 76.91), respectively. The
C NMR signals were assigned using the DEPT procedure; in
80.4 (s, CFc (ipso)); 121.6, 121.9, 124.7, 124.8, 129.0, 129.6 (all s,
3
4
2
3
C
13
3
3
CHPh); 130.6 (d, C , J = 2.7 Hz); 130.8 (d, C , J = 3.4 Hz);
Ph Ph
3
3
the assignment of signals of the coordinated cod ligand in the
spectrum of complex 4, data from a previous publication were
also used.21 The EI mass spectra (70 eV) were recorded on a
Varian MATꢀ311 instrument, while the electrospray ionization
149.6 (d, CPh, J = 4.9 Hz); 149.8 (d, C , J = 5.3 Hz); 161.5
Ph
(s, CH=). MS (EI, 70 eV), m/z (Irel (%)): 527 [M]+ (3), 443
+
(92), 377 [M – C H —C H + 2 H] (100).
6
4
6
4
(2´S,3´S)ꢀ2ꢀ{2´ꢀ[(Ferrocenylidene)amino]ꢀ3´ꢀmethylꢀ
4
(
ESI) mass spectra were run on a Micromass Bio IIꢀZS inꢀ
pentyloxy}dibenzo[d, f ][1,3,2]dioxaphosphepineꢀP,N)(η ꢀ
strument. The IR spectra of solutions in CHCl3 were reꢀ
corded on a Specord Mꢀ80 spectrophotometer in a polyethylene
cell. The optical yields of compounds 7а and 7с were deterꢀ
mined by GC (a DPꢀTFAꢀγꢀCD chiral column) and HPLC
cyclooctaꢀ1,5ꢀdiene)rhodium(1+) tetrafluoroborate (4). Yield
88%. Redꢀorange powder, m.p. 147—149 °C (with dec.).
Found (%): C, 53.85; H, 5.13; N, 1.70. C H BF FeN OPRh.
3
7
42
4
3
13
Calculated (%): C, 54.03; H, 5.27; N, 1.58. C NMR (CDCl ),
3
(
a (R,R)ꢀWHELKꢀ01 chiral column), respectively, according to
δ: 10.7, 14.2 (both s, Me); 25.3 (s, CH ); 26.1, 29.2, 29.6, 34.1
2
1
3,19
recommendations from published studies.
The degree of conꢀ
(all s, CH (cod)); 38.4 (s, CH); 67.5 (s, CH O); 69.4, 70.1,
2
2
version of substrate 6b and the optical yield of product 7b were
found by HPLC (a Daicel Chiralcel ODꢀH chiral column), as
described previously.22
70.5, 72.1 (all s, C ); 77.5 (s, CHN); 79.0 (s, CFc (ipso)); 74.8 (d,
Fс
1
1
JC,Rh = 10.4 Hz) and 80.1 (d, J
10.8 Hz) (CH= (cod)
C,Rh =
1
2
transꢀN); 113.4 (dd, J
13.8 Hz, J
3.0 Hz) and 114.0
C,Rh =
C,Р =
(dd, JC,Rh = 11.2 Hz, 2JC,Р = 4.2 Hz) (CH= (cod) transꢀР);
1
All reactions were carried out under dry argon in anhydrous
solvents; PCl was distilled directly prior to use. Biphenylꢀ2,2´ꢀ
120.7—148.1 (CPh); 174.1 (s, CH=).
3
diol and (2S,3S)ꢀ2ꢀ(ferrocenylideneamino)ꢀ3ꢀmethylpentanꢀ
(2´S,3´S)ꢀ2ꢀ{2´ꢀ[(Ferrocenylidene)amino]ꢀ3´ꢀmethylpentylꢀ
oxy}dibenzo[d, f ][1,3,2]dioxaphosphepineꢀP,N)(πꢀallyl)palꢀ
ladium(2+) tetrafluoroborate (5). Yield 85%. Red powder,
m.p. 167—169 °C (with dec.). Found (%): C, 50.46; H, 4.63;
N, 1.84. C32H35BF FeN OPPd. Calculated (%): C, 50.62;
1
4
1
ꢀol were dried in vacuo (1 h, 1 Torr) before being used in the
reaction; Et N was distilled over КOH and then, immediately
3
prior to use, over LiAlH . The initial complexes, [Rh(CO) Cl] ,
4
2
2
+
–
[
Rh(thf) (cod)] BF , [Pd(All)Cl] , and [Pd (dba) ]•CHCl
2 4 2 2 3 3
were prepared by known procedures.
4
3
2
3—26
Rhodium complex 3
H, 4.81; N, 2.02.
was prepared and characterized by spectroscopy in a solution in
Palladiumꢀ and rhodiumꢀcatalyzed allylic alkylation of
1,3ꢀdiphenylallyl acetate with dimethyl malonate (general proceꢀ
dure). A solution of [Pd(All)Cl]2 (3.7 mg, 0.01 mmol)
or [Pd (dba) ]•CHCl (10.3 mg, 0.01 mmol) and ligand 2
2
7
CHCl without isolation, as described previously. Complexes
3
4
and 5 were synthesized according to the corresponding proꢀ
1
9,28
tocols.
2
3
3
Catalytic experiments on allylic alkylation of compound 6а
with dimethyl malonate and allylic sulfonylation of 6b with
sodium pꢀtoluenesulfinite was carried out by reported proceꢀ
(0.02—0.04 mmol) in 5 mL of the corresponding solvent
was stirred for 40 min (alternatively, ready complex 4 or 5
(0.02 mmol) was dissolved). 1,3ꢀDiphenylallyl acetate (6b)
(0.1 mL, 0.5 mmol) was added and the mixture was stirred for
15 min. Dimethyl malonate (0.1 mL, 0.87 mmol), BSA (0.22 mL,
0.87 mmol) and NaOAc (2 mg) were added. The reaction mixꢀ
ture was stirred for 48 h, diluted with 5 mL of the same solvent,
and filtered through a column with Celite. The filtrate was conꢀ
centrated in vacuo (40 Torr) and the residue was dried in vacuo
(12 h, 10 Torr). The product was a colorless oil that solidified on
storage.
dures.1
3,19
The initial substrate 6b (1,3ꢀdiphenylallyl acetate)
2
5
was synthesized by a known protocol. Bis(trimethylsilyl)acetꢀ
amide (BSA) and dimethyl malonate (Acros Organics) were
used as received.
2
ꢀChlorodibenzo[d, f ][1,3,2]dioxaphosphepine (1). NꢀMeꢀ
thylpyrrolidone (0.01 g, 0.1 mmol) was added to a suspension
of biphenylꢀ2,2´ꢀdiol (2 g, 10.7 mmol) in PCl3 (3.3 mL,
3
7.5 mmol), and the mixture was refluxed for 15 min to become