M. B. Andrus, D. Asgari / Tetrahedron 56 (2000) 5775±5780
5779
2H, J8.0, 7.5 Hz), 7.35±7.30 (m, 4H), 7.11 (d, 2H,
J9.5 Hz), 3.80±3.76 (m, 2H), 3.70±3.67 (m, 2H), 3.42±
3.38 (m, 2H), 2.30 (s, 2H), 1.93 (s, 6H), 0.72 (s, 18H); 13C
NMR (125 MHz, CDCl3) d 171.1, 136.8, 136.5, 136.3,
132.3, 128.1, 125.8, 62.8, 59.9, 33.5, 26.7, 20.1; HRMS
(FAB1) calcd for (MH1) C28H41 N2O4 469.3066, found
469.3056.
(7.0 g) and H2O (2.7 mL). The mixture was then gently
re¯uxed for 8 h, cooled to rt, and the solvent was removed
leaving a yellow residue containing K2CO3 and the product.
The residue was dissolved in EtOAc (150 mL) and water
(50 mL). The organic layer was then separated, dried over
MgSO4 and evaporation of the solvent afforded a light
yellow residue. Puri®cation using radial chromatography
(2 mm rotor, 5±35% EtOAc/hexane) produced a white oil
product 1a (0.3 g, 86% yield). Compounds 1b±d and 2a±d
were synthesized in similar fashion, and the overall yield for
the above two reactions were 65, 80, 71, 74, 62, 79 and 60,
respectively.
(S,S,S)-6,60-Dimethyl-biphenyl-2,20-dicarboxylic acid bis-
[(2-hydroxy-1-benzyl-ethyl)-amide] (5c). Rf0.47 in
1
100% EtOAc; H NMR (500 MHz, CDCl3) d 7.30 (d, 2H,
J8.5 Hz), 7.21±7.08 (m, 16H), 4.04±4.00 (m, 2H), 3.32±
3.20 (m, 4H), 2.67 (dd, 2H, J14.0, 6.5 Hz), 2.59 (dd, 2H,
J13.5, 6.5 Hz), 2.24 (s, 2H), 1.81 (s, 6H); 13C NMR
(125 MHz, CDCl3) d 170.9, 137.7, 137.0, 136.9, 136.1,
131.7, 129.1, 128.5, 127.9, 126.5, 124.2, 63.5, 52.9, 36.5,
19.9; HRMS (FAB1) calcd for (MH1) C34H37 N2O4
537.2753, found 537.2750.
(S,S,S)-2,20-Bi-o-tolyl-1,10-diphenyl bisoxazoline (1a). 1H
NMR (300 MHz, CDCl3) d 7.77 (dd, 2H, J12.5, 10.0 Hz),
7.30±7.11 (m, 10H), 6.98±6.94 (m, 4H), 5.04 (t, 2H,
J8.0 Hz), 4.29 (overlapt, 2H, J8.0 Hz), 3.75 (t, 2H,
J8.0 Hz), 1.91 (s, 6H); 13C NMR (75.4 MHz, CDCl3) d
165.7, 142.8, 140.1, 137.0, 132.3, 128.5, 127.8, 127.5,
127.3, 127.1, 126.9, 126.8, 74.7, 70.0, 20.5; IR (neat):
(S,R,S)-6,60-Dimethyl-biphenyl-2,20-dicarboxylic acid bis-
[(2-hydroxy-1-benzyl-ethyl)-amide] (6c). Rf0.35 in
3061, 2967, 2895, 1949, 1804, 1643, 1487, 1347 cm21
;
1
100% EtOAc; H NMR (500 MHz, CDCl3) d 7.27±7.11
HRMS (FAB1) calcd for (MH1) C32H28 N2O2 473.2229,
(m, 12H), 7.04 (d, 6H, J8.0 Hz), 3.99±3.94 (m, 2H),
3.43±3.27 (m, 4H), 2.44 (dd, 2H, J14.0, 8.5 Hz), 2.40
(dd, 2H, J14.0, 8.5 Hz), 2.38 (s, 2H), 1.84 (s, 6H); 13C
NMR (125 MHz, CDCl3) d 170.4, 137.7, 136.6, 136.5,
136.1, 132.1, 129.1, 128.5, 128.1, 126.6, 125.2, 63.6, 53.0,
36.4, 20.0; HRMS (FAB1) calcd for (MH1) C34H37N2O4
537.2753, found 537.2739.
found 473.2235. [a]D137.8 (c1.0, CHCl3).
(S,R,S)-2,20-Bi-o-tolyl-1,10-diphenyl bisoxazoline (2a). 1H
NMR (300 MHz, CDCl3) d 7.78 (dd, 2H, J12.5, 10.0 Hz),
7.42±7.22 (m, 10H), 6.95±6.91 (m, 4H), 5.17 (t, 2H,
J8.0 Hz), 4.43 (overlapt, 2H, J8.0 Hz), 3.78 (t, 2H,
J8.0 Hz), 2.1 (s, 6H); 13C NMR (75.4 MHz, CDCl3) d
165.7, 142.7, 139.6, 137.6, 132.0, 128.5, 128.0, 127.2,
127.1, 127.0, 126.7, 74.8, 70.0, 20.4; IR (neat): 3061,
(S,S,S)-6,60-Dimethyl-biphenyl-2,20-dicarboxylic acid bis-
[(2-hydroxy-1-i-propyl-ethyl)-amide] (5d). Rf0.33 in
2967, 2895, 1643, 1487, 1451, 1150 cm21
; HRMS
1
100% EtOAc; H NMR (500 MHz, CDCl3) d 7.36±7.26
(FAB1) calcd for (MH1) C32H28 N2O2 473.2229, found
(m, 8H), 3.72±3.67 (m, 2H), 3.48±3.44 (m, 2H), 3.37±
3.33 (m, 2H), 2.01 (s, 6H), 1.78±1.72 (m, 2H), 1.63 (s,
2H), 0.86 (d, 6H, J7.0 Hz), 0.83 (d, 6H, J7.0 Hz); 13C
NMR (125 MHz, CDCl3) d 171.4, 137.1, 136.3, 136.2,
131.6, 127.9, 124.3, 63.7, 56.9, 29.0, 20.1, 19.4, 18.7;
HRMS (FAB1) calcd for (MH1) C26H37 N2O4 441.2753,
found 441.2761.
473.2234. [a]D2193.5 (c1.0, CHCl3).
(S,S,S)-2,20-Bi-o-tolyl-1,10-di t-butyl bisoxazoline (1b).
1H NMR (500 MHz, CDCl3) d 7.67 (d, 2H, J8.0 Hz),
7.22 (d, 2H, J7.5 Hz), 7.17 (q, 2H, J4.0 Hz), 3.88 (t,
2H, J8.5 Hz), 3.74 (t, 2H, J9.0 Hz), 3.68 (t, 2H,
J9.0 Hz), 1.84 (s, 3H), 0.63 (s, 18); 13C NMR
(125 MHz, CDCl3) d 163.5, 140.2, 136.6, 131.6, 127.7,
126.9, 126.6, 76.1, 68.1, 33.7, 25.7, 20.3; IR (neat): 3065,
(S,R,S)-6,60-Dimethyl-biphenyl-2,20-dicarboxylic acid bis-
[(2-hydroxy-1-i-propyl-ethyl)-amide] (6d). Rf0.22 in
2950, 2867, 2359, 1731, 1656, 1478, 1207, 1002 cm21
;
1
100% EtOAc; H NMR (500 MHz, CDCl3) d 7.47 (d, 2H,
HRMS (FAB1) calcd for (MH1) C28H37N2O2 433.2855,
J7.0 Hz), 7.35±7.30 (m, 4H), 7.20 (d, 2H, J9.0 Hz),
3.64±3.59 (m, 2H), 3.50±3.48 (m, 4H), 2.62 (s, 2H), 1.94
(s, 6H), 1.68±1.61 (m, 2H), 0.75 (d, 6H, J7.0 Hz), 0.71 (d,
6H, J7.0 Hz); 13C NMR (125 MHz, CDCl3) d 170.9,
136.7, 136.5, 136.2, 132.2, 128.1, 125.4, 63.7, 57.4, 28.9,
20.0, 19.2, 18.6; HRMS (FAB1) calcd for (MH1) C26H37
N2O4 441.2753, found 441.2767.
found 433.2863. [a]D185.5 (c1.0, CHCl3).
(S,R,S)-2,20-Bi-o-tolyl-1,10-di t-butyl bisoxazoline (2b).
1H NMR (500 MHz, CDCl3) d 7.55 (d, 2H, J7.0 Hz),
7.20 (t, 2H, J7.0 Hz), 7.15 (t, 2H, J7.0 Hz), 3.92 (t,
2H, J8.5 Hz), 3.70±3.61 (m, 4H), 1.89 (s, 3H), 0.56 (s,
18H); 13C NMR (125 MHz, CDCl3) d 163.6, 139.8, 137.4,
131.4, 127.7, 126.7, 126.6, 76.4, 68.1, 33.4, 25.6, 20.3; IR
(neat): 3065, 2950, 2867, 1731, 1656, 1478, 1207,
1002 cm21; HRMS (FAB1) calcd for (MH1) C28H37N2O2
433.2855, found 433.2845. [a]D2193.5 (c1.0, CHCl3).
General procedure for synthesis of ligands 1a±d and 2a±d
Thionyl chloride (1.51 g, 12.7 mmol) was added to a solu-
tion of 5a (0.43 g, 0.84 mmol) in dichloromethane (8 mL)
under N2. The solution was stirred for 24 h at rt, dichloro-
methane was added (50 mL) and then water (11 mL). The
organic layer was washed with 4 M NaOH (5 mL), brine,
and dried over MgSO4. Evaporation of the solvent afforded
a dichloro intermediate as a light yellow solid, 0.4 g, 87%
yield. To the solution of this intermediate (0.40 g,
0.73 mmol) in acetonitrile (30 mL), were addded K2CO3
1
(S,S,S)-2,20-Bi-o-tolyl-1,10-dibenzyl bisoxazoline (1c). H
NMR (500 MHz, CDCl3) d 7.62 (d, 2H, J8.0 Hz), 7.26±
7.08 (m, 10), 7.05 (d, 4H, J8.0 Hz), 4.22±4.16 (m, 2H),
3.83 (t, 2H), 3.63 (dd, 2H, J8.0, 7.5 Hz), 2.89 (dd, 2H,
J14.0, 12.5 Hz), 2.36 (dd, 2H, J14.0, 10.0 Hz), 1.89 (s,
6H); 13C NMR (125 MHz, CDCl3) d 164.7, 139.8, 138.4,
136.7, 131.8, 129.1, 128.4, 127.8, 126.9, 126.8, 126.2, 71.7,