R. K. Sharma et al. / Tetrahedron: Asymmetry 19 (2008) 655–663
661
1H, CHOP) 31P NMR (162.02 MHz, CDCl3) d 127.1 (s)
Anal. Calcd for C38H32P2O2PdCl2ꢂCHCl3: C, 53.27; H,
3.78. Found: C, 53.19; H, 3.89.
[Pd(PPh2Cl)2Cl2] (0.071 mmol) under nitrogen for 48 h at
room temperature. The solvent was removed under vac-
uum and ether (10 mL) added to the residue which resulted
in a gummy solid. The addition of chloroform gave a hazy
solution that gradually precipitated the complex. The pre-
cipitate was filtered and washed with cold chloroform to
4.3. General procedure for the synthesis of bisphosphinite
complexes 6–9
give an off white powder 10, 0.016 g, yield 32%,
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4.3.1. [(S)-1,2-Bis(diphenylphosphinooxy)-1,1,2-triphenyl-
ethane PdCl2] 6. The bisphosphinite ligand 6a (0.157
mmol) was dissolved in 1 mL of dry THF and added to
THF (5 mL) containing Pd(COD)Cl2 (0.157 mmol) under
dry nitrogen. The solution was stirred till it became a clear
yellow solution (5 h). After 2 h, a yellow precipitate
appeared which was filtered and washed with cold THF
(5 mL) and diethyl ether (5 mL) to give a light yellow pow-
½aꢀD ¼ þ21:2 (c 1.0, DMSO); 1H NMR (400 MHz, CDCl3)
d 7.87–7.35 (m, 20H, Harom) 4.97 (br s, 1H, CHOP) 4.63 (s,
1H, CHOC) 4.38 (m, 1H, CHHOP) 4.06 (m, 1H, CHHOP)
31P NMR (162.02 MHz, CDCl3) d 120.5 (d) and 116.1 (d)
J = 27.5 Hz. Anal. Calcd for C30H26P2O6PdCl2: C, 49.92;
H, 3.63. Found: C, 49.96; H, 3.68.
4.4.2.
[(R)-5-((S)-1,2-Bis(diphenylphosphinooxy)ethyl)-3-
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1
der 6, yield 77%. ½aꢀD ¼ þ12:8 (c 2.0, CH2Cl2); H NMR
(400 MHz, CDCl3) d 7.82–6.53 (m, 35H, Ph) 6.38 (d,
J = 16.0 Hz 1H, CHOP). 31P NMR (162.02 MHz, CDCl3)
d 138.1 (d) JPP = 38.8 Hz and 112.1 (d) JPP = 42.0 Hz.
Anal. Calcd for C44H36P2O2PdCl2: C, 63.21; H, 4.34.
Found: C, 63.16; H, 4.37.
(benzyloxy)-4-hydroxyfuran-2(5H)-one PdCl2] 11. White
25
powder, yield 61%, ½aꢀD ¼ þ19:9 (c 1.6, CH2Cl2); 1H
NMR (400 MHz, CDCl3) d 7.89–7.31 (m, 25H, Harom
)
5.46 (br s, 1H, CHOP) 4.83 (d, J = 11.2 Hz, 1H, CHOC)
4.70 (d, J = 11.6 Hz, 2H, CH2Ph) 4.39 (m, 1H, CHHOP)
3.84 (m, 1H, CHHOP). 31P NMR (162.02 MHz, CDCl3)
d 123.6 (d) and 112.5 (d) JPP = 29.1 Hz. Anal. Calcd for
C37H32P2O6PdCl2ꢂCH2Cl2: C, 54.73; H, 3.97. Found: C,
54.79; H, 3.92.
4.3.2. [(3S,6S)-3,6-Bis(diphenylphosphinooxy)-hexahydro-
furo[3,2-b]furan PdCl2] 7. Yellow crystalline solid, yield
25
1
81%, ½aꢀD ¼ þ28:2 (c 1.0, CHCl3); H NMR (400 MHz,
CDCl3) d 7.93–7.23 (m, 20H, Harom) 5.30 (d, J = 12.0 Hz,
2H, CHOP) 4.58 (s, 2H, CHOC) 3.97 (d, J = 9.2 Hz, 4H,
CH2O). 31P NMR (162.02 MHz, CDCl3) d 104.0 (s). Anal.
Calcd for C30H28P2O4PdCl2: C, 52.08; H, 4.07. Found: C,
52.16; H, 4.27.
4.4.3.
[(R)-5-((S)-1,2-Bis(diphenylphosphinooxy)ethyl)-4-
(benzyloxy)-4-hydroxyfuran-2(5H)-one PdCl2] 12. White
25
powder, yield 58%, ½aꢀD ¼ þ31:2 (c 1.8, CHCl3); 1H
NMR (400 MHz, CDCl3) d 7.91–7.13 (m, 25H, Harom
)
5.35 (d, J = 12 Hz, 1H, CHHOPh) 5.21 (d, J = 11.6 Hz,
1H, CHHOPh) 4.57 (m, 1H, CHOP) 4.50 (m, 1H, CHOC)
4.27 (m, 1H, CHHOP) 4.22 (m, 1H, CHHOP). 31P NMR
(162.02 MHz, CDCl3)
J = 35.6 Hz. Anal. Calcd for C37H32P2O6PdCl2: C, 54.73;
4.3.3. [N-((1R,2R)-1,3-Bis(benzhydryloxy)-1-(4-nitrophenyl)-
propan-2-yl)-2,2-dichloroacetamide PdCl2] 8. Yellow
25
d 121.7 (d) and 121.2 (d)
crystalline solid, yield 71%, ½aꢀD ¼ þ57:3 (c 1.0, DMSO);
1H NMR (400 MHz, CDCl3+DMSO-d6) d 8.08–7.12 (m,
24H, Harom) 6.37 (s, 1H, CHCl2) 5.54 (d, 1H, J = 6.4 Hz,
CHOP) 4.31 (m, 2H, CH2OP) 3.73 (m, 1H, CHN). 31P
NMR (162.02 MHz, CDCl3+DMSO-d6) d 123.1 (d) and
121.8 (d) JPP = 38.8 Hz. Anal. Calcd for C35H30-
P2N2O5PdCl4: C, 48.38; H, 3.48; N, 3.22. Found: C,
48.32; H, 3.52; N, 3.19.
H, 3.97. Found: C, 54.70; H, 4.00.
4.4.4. [(S)-5-((R)-1,2-Bis(diphenylphosphinooxy)ethyl)-3,4-
bis(benzyloxy)furan-2(5H)-one PdCl2] 13. Off white pow-
25
1
der, yield 77%, ½aꢀD ¼ þ42:1 (c 1.4, CHCl3); H NMR d
7.90–7.12 (m, 30H, Harom) 5.15 (d, J = 11.6 Hz, 1H,
CHHOPh) 5.06 (m, 2H, CH2OPh) 4.76 (d, J = 11.2 Hz,
1H, CHHOPh) 4.54 (m, 1H, CHOP) 4.49 (s, 1H, CHOC)
4.19 (m, 2H, CH2OP). 31P NMR (162.02 MHz, CDCl3) d
122.0 (d) JPP = 34.0 Hz and 121.3 (d) JPP = 35.6 Hz. Anal.
Calcd for C44H38P2O6PdCl2: C, 58.59; H, 4.25. Found: C,
58.54; H, 4.44.
4.3.4. [(S)-4-((1R,2S)-2-((R)-2,2-Dimethyl-1,3-dioxolan-4-
yl)-1,2-bis(diphenylphosphinooxy)ethyl)-2,2-dimethyl-1,3-di-
oxolane PdCl2] 9. Colorless crystalline solid, yield 65%,
25
1
½aꢀD ¼ þ28:4 (c 0.5, CHCl3); H NMR (400 MHz, CDCl3)
d 7.99–7.34 (m, 20H, Harom) 4.13 (d, 1H, J = 5.2 Hz,
CHHC) 4.01 (d, 1H, J = 4.8 Hz, CHHC) 3.69 (dd, 1H,
J = 6.8, 8.4 Hz, CHOC) 3.56 (dd, 2H, J = 5.6, 8.4 Hz,
2H, CHOP) 1.18 (s, 3H, CH3) 1.03 (s, 3H, CH3). 31P
NMR (162.02 MHz, CDCl3) d 125 (s). Anal. Calcd for
C36H40P2O6PdCl2: C, 53.51; H, 4.99. Found: C, 56.54; H,
5.16.
4.4.5. (R)-5-((R)-1,2-Bis(diphenylphosphinooxy)ethyl)-3,4-
dihydroxyfuran-2(5H)-one PdCl2] 14. Procedure was sim-
ilar to 10 (in place of HMPA, DBU was used), light yellow
25
powder, yield 34%, ½aꢀD ¼ ꢁ18:6 (c 0.6, DMSO); 1H NMR
(400 MHz, CDCl3) d 7.90–7.23 (m, 20H, Harom) 5.39 (br s,
1H, CHOP) 4.91 (s, 1H, CHOC) 4.25 (m, 1H, CHHOP)
3.73 (m, 1H, CHHOP). 31P NMR (162.02 MHz, CDCl3)
d 120.5 (d) and 116.1 (d) JPP = 27.5 Hz. Anal. Calcd for
C30H26P2O6PdCl2: C, 49.92; H, 3.63. Found: C, 49.89; H,
3.66.
4.4. Synthesis of bisphosphinite complexes derived from
ascorbic and isoascorbic acid
4.4.1. [(R)-5-((S)-1,2-Bis(diphenylphosphinooxy)ethyl)-3,4-
dihydroxyfuran-2(5H)-one PdCl2] 10. L-Ascorbic acid
(0.012 g, 0.070 mmol) was dissolved in dry degassed THF
(2 ml) containing DMF (0.1 mL) and HMPA (0.01 mL),
4.4.6.
[(R)-5-((R)-1,2-Bis(diphenylphosphinooxy)ethyl)-3-
(benzyloxy)-4-hydroxyfuran-2(5H)-one PdCl2] 15. Light
yellow powder, yield 61%, ½aꢀD ¼ ꢁ23:6 (c 1.1, CHCl3);
25
and added dropwise to
a
stirred solution of