A. Zulauf, M. Mellah, R. Guillot, E. Schulz
FULL PAPER
and Na2CO3 (180 mg, 1.69 mmol) and was maintained under argon
by successive vacuum–argon cycles (3 h). Thoroughly degassed
DME (2.1 mL) and degassed water (0.7 mL) were introduced
through a cannula into the Schlenk tube. The mixture was heated
at 100 °C for 24 h. Water (20 mL) was added and the aqueous layer
was extracted with CH2Cl2. The organic layer was dried with
MgSO4 and the solvents were removed under reduced pressure. The
residue was purified by flash chromatography on silica gel (pen-
tane/diethyl ether, 4:1) to afford 8a (218 mg, 61%) as a yellow oil.
1H NMR (300 MHz, CDCl3): δ = 11.81 (s, 1 H, OH), 9.89 (s, 1 H,
CHO), 7.85 (d, J = 2.1 Hz, 1 H, CH), 7.74 (d, J = 2.1 Hz, 1 H,
CH), 6.28 (s, 1 H, CH), 4.37–4.31 (m, 2 H, CH2), 4.31–4.25 (m, 2
H, CH2), 1.47 (s, 9 H, 3 ϫ CH3) ppm. 13C NMR (62.5 MHz,
CDCl3): δ = 197.1 (CH), 159.7 (Cq), 142.1 (Cq), 138.3 (Cq), 137.5
(Cq), 132.0 (CH), 129.0 (CH), 124.5 (Cq), 120.4 (Cq), 116.1 (Cq),
96.7 (CH), 64.7 (CH2), 64.3 (CH2), 34.8 (Cq), 29.0 (3ϫCH3) ppm.
HRMS (EI): calcd. for C17H18O4S 318.0920; found 318.0914.
39.0 (CH), 35.2 (CH2), 34.9 (Cq), 29.1 (CH3), 25.7 (CH2) ppm.
HRMS (EI): calcd. for C20H24O2S 328.1492; found 328.1500.
General Procedure for the Formation of the Ligands: The diamine
(0.52 equiv.) was added to a solution of the targeted aldehyde in
ethanol (0.07 ) with continuous stirring, and the mixture was
heated at 60 °C for 19 h. The reaction mixture was cooled to room
temperature. The solvents were removed under reduced pressure
and the residue was purified as described below.
(S,S)-N,NЈ-Bis[3-tert-butyl-5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-
yl)salicylidene]cyclohexane-1,2-diamine (9a): This product was ob-
tained using aldehyde 8a and (S,S)-cyclohexane-1,2-diamine. The
residue was recrystallized from 2-propanol to afford 9a (71%) as a
yellow powder; m.p. 148–150 °C. [α]2D0 = –28 (c = 0.99, CHCl3). 1H
NMR (300 MHz, CDCl3): δ = 13.97 (s, 2 H, OH), 8.35 (s, 2 H,
CH), 7.57 (s, 2 H, CH), 7.38 (s, 2 H, CH), 6.20 (s, 2 H, CH), 4.40–
4.18 (m, 8 H, CH2), 3.39–3.35 (m, 2 H, CH), 2.15–1.72 (m, 6 H,
CH2), 1.70–1.35 (m, 20 H, 6 ϫ CH3, CH2) ppm. 13C NMR
(62.5 MHz, CDCl3): δ = 165.6 (CH), 159.4 (Cq), 142.1 (Cq), 137.4
(Cq), 136.9 (Cq), 127.8 (CH), 127.6 (CH), 123.0 (Cq), 118.5 (Cq),
117.6 (Cq), 96.0 (CH), 72.3 (CH), 64.7 (CH2), 64.5 (CH2), 34.9
3-tert-Butyl-2-hydroxy-5-(3-octyl-2-thienyl)benzaldehyde (8b): A
Schlenk tube was charged with 3-tert-butyl-5-bromo-2-hydroxy-
benzaldehyde (281.5 mg, 1.09 mmol), 4,4,5,5-tetramethyl-2-(3-oc-
tyl-2-thienyl)-1,3,2-dioxaborolane (7b) (705.5 mg, 2.19 mmol),
[Pd(PPh3)4] (189.8 mg, 0.16 mmol) and Na2CO3 (174 mg,
1.64 mmol) and was maintained under argon by successive vac-
uum–argon cycles (3 h). Thoroughly degassed DME (2.1 mL) and
degassed water (0.7 mL) were introduced through a cannula into
the Schlenk tube. The mixture was heated at 100 °C for 24 h. Water
(20 mL) was added and the aqueous layer was extracted with
CH2Cl2. The organic layer was dried with MgSO4 and the solvents
were removed under reduced pressure. The residue was purified by
flash chromatography on silica gel (pentane/diethyl ether, 9:1) to
afford 8b (349 mg, 86 %) as a yellow oil. 1H NMR (250 MHz,
CDCl3): δ = 11.93 (s, 1 H, OH), 9.93 (s, 1 H, CHO), 7.68 (d, J =
2.3 Hz, 1 H, CH), 7.50 (d, J = 2.3 Hz, 1 H, CH), 7.26 (d, J =
5.1 Hz, 1 H, CH), 7.04 (d, J = 5.1 Hz, 1 H, CH), 2.69 (t, J =
7.9 Hz, 2 H, CH2-C7H15), 1.83–1.62 (m, 2 H, CH2-CH2-C6H13),
1.53 (s, 9 H, 3ϫCH3), 1.49–1.26 (m, 10 H, 5ϫCH2), 1.04–0.85 (m,
3 H, CH3) ppm. 13C NMR (62.5 MHz, CDCl3): δ = 196.8 (CHO),
160.3 (Cq), 138.5 (Cq), 138.3 (Cq), 136.4 (Cq), 135.2 (CH), 132.2
(CH), 129.4 (CH), 125.8 (Cq), 123.3 (CH), 120.4 (Cq), 34.8 (Cq),
31.7 (CH2), 31.1 (CH2), 29.5 (CH2), 29.3 (CH2), 29.2 (CH2), 29.1
(CH3), 28.6 (CH2), 22.5 (CH2), 14.0 (CH2-CH3) ppm. HRMS (EI):
calcd. for C23H32O2S 372.2118; found: 372.2119.
(C ), 33.1 (CH ), 29.4 (CH ), 24.3 (CH ) ppm. IR (KBr): ν = 2930,
˜
q
2
3
2
2865, 1629, 1594, 1501, 1434, 1364, 1075 cm–1. Probably as a result
of low stability of ligand 9a, all attempts to obtain a correct HRMS
or elemental analysis failed.
(S,S)-N,NЈ-Bis[3-tert-butyl-5-(3-octyl-2-thienyl)salicylidene]cyclo-
hexane-1,2-diamine (9b): This product was obtained using aldehyde
8b and (S,S)-cyclohexane-1,2-diamine. The residue was purified by
flash chromatography on silica gel (heptane/diethyl ether, 98:2) to
afford 9b (81%) as yellow oil. [α]2D0 = +49 (c = 0.99, CHCl3). 1H
NMR (360 MHz, CDCl3): δ = 14.0 (s, 2 H, OH), 8.39 (s, 2 H, CH),
7.38 (d, J = 2.1 Hz, 2 H, CH), 7.18 (d, J = 5.1 Hz, 2 H, CH), 7.14
(d, J = 2.1 Hz, 2 H, CH), 6.98 (d, J = 5.1 Hz, 2 H, CH), 3.53–3.29
(m, 1 H, CH), 2.72–2.48 (m, 4 H, CH2-C7H15), 2.05–1.85 (m, 4 H,
CH2-CH2-C6H13), 1.80–1.06 (m, 46 H, 10 ϫ CH2, 6 ϫ CH3,
4 ϫ CH2), 0.92 (t, J = 7 Hz, 6 H, CH2-CH3) ppm. 13C NMR
(62.5 MHz, CDCl3): δ = 165.4 (CH), 159.9 (Cq), 138.0 (Cq), 137.9
(Cq), 137.3 (Cq), 130.8 (CH), 130.5 (CH), 129.4 (CH), 124.3 (Cq),
122.8 (CH), 118.5 (Cq), 72.4 (CH), 34.9 (Cq), 33.2 (CH2), 31.9
(CH2), 31.3 (CH2), 29.6 (CH2), 29.5 (CH2), 29.4 (CH2), 29.3
(4 ϫ CH3), 28.7 (CH2), 24.3 (CH2), 22.7 (CH2), 14.2 (CH2-
CH3) ppm. HRMS (ESI): calcd. for C52H75N2O2S2 [M + H]+
823.5264; found 823.5256. IR (KBr): ν = 2948, 2929, 2863, 1635,
˜
3-tert-Butyl-5-(3-cyclopentyl-2-thienyl)-2-hydroxybenzaldehyde (8c):
A Schlenk tube was charged with 3-tert-butyl-5-bromo-2-hydroxy-
benzaldehyde (42 mg, 0.16 mmol), 2-(3-cyclopentyl-2-thienyl)-
4,4,5,5-tetramethyl-1,3,2-dioxaborolane (7c) (90 mg, 0.32 mmol),
[Pd(PPh3)4] (28 mg, 0.02 mmol) and Na2CO3 (25 mg, 0.24 mmol)
and was maintained under argon by successive vacuum–argon cy-
cles (3 h). Thoroughly degassed DME (320 µL) and degassed water
(110 µL) were introduced through a cannula into the Schlenk tube.
The mixture was heated at 100 °C for 22 h. Water (15 mL) was
added and the aqueous layer was extracted with CH2Cl2. The or-
ganic layer was dried with MgSO4 and the solvents were re-
moved under reduced pressure. The residue was purified by flash
chromatography on silica gel (pentane/diethyl ether, 99:1) to afford
1619, 1593, 1471, 1456, 1424 cm–1.
(S,S)-N,NЈ-Bis[3-tert-butyl-5-(3-cyclopentyl-2-thienyl)salicylidene]-
cyclohexane-1,2-diamine (9c): This product was obtained using al-
dehyde 8c and (S,S)-cyclohexane-1,2-diamine. The residue was
recrystallized from ethanol to afford 9c (72%) as a yellow solid;
m.p. 103 °C. [α]2D0 = +49 (c = 0.99, CHCl3). H NMR (360 MHz,
1
CDCl3): δ = 14.08 (br. 2 H, OH), 8.42 (s, 2 H, CH), 7.40 (s, H,
CH), 7.23 (d, J = 4.8 Hz, 2 H, CH), 7.17 (s, H, CH), 7.05 (d, J =
4.8 Hz, 2 H, CH), 3.52–3.38 (m, 2 H, CH), 3.08–3.03 (m, 2 H, CH),
2.13–1.91 (m, 8 H, CH2), 1.91–1.76 (m, 4 H, CH2), 1.75–1.60 (m,
4 H, CH2), 1.48 (s, 18 H, CH3) ppm. 13C NMR (360 MHz, CDCl3):
δ = 165.3 (CH), 159.9 (Cq), 142.2 (Cq), 137.5 (Cq), 137.2 (Cq), 131.1
(CH), 130.6 (CH), 126.8 (CH), 124.2 (Cq), 123.2 (CH), 118.4 (Cq),
72.4 (CH), 39.0 (CH), 35.3 (CH2), 34.8 (Cq), 33.2 (CH2), 29.3
(CH3), 25.7 (CH2), 24.2 (CH2) ppm. HRMS (EI): calcd. for
C46H58N2O2S2 734.3934; found 734.3892. IR (CaF2 cell, CHCl3):
1
8c (42.4 mg, 80%) as a yellow oil. H NMR (300 MHz, CDCl3): δ
= 11.83 (s, 1 H, OH), 9.89 (s, 1 H, CHO), 7.58 (d, J = 1.9 Hz, 1
H, CH), 7.44 (d, J = 1.9 Hz, 1 H, CH), 7.22 (d, J = 5.3 Hz, 1 H,
CH), 7.02 (d, J = 5.3 Hz, 1 H, CH), 3.12–2.97 (m, 1 H, CH), 2.07–
1.89 (m, 2 H, CH2), 1.89–1.72 (m, 2 H, CH2), 1.71–1.48 (m, 4 H,
ν = 2977, 2896, 1630, 1602, 1476, 1424, 1045 cm–1.
˜
CH2), 1.44 (s, 9 H, CH3) ppm. 13C NMR (300 MHz, CDCl3): δ = General Procedure for the Formation of the Complexes: The chiral
197.0 (Cq), 160.5 (Cq), 142.8 (Cq), 138.3 (Cq), 136.1 (Cq), 135.6 ligand in dry, degassed THF (0.08 ) was added to a solution of
(CH), 132.4 (CH), 126.9 (CH), 125.8 (Cq), 123.8 (CH), 120.4 (Cq), anhydrous CrCl2 (1.15 equiv.) in dry, degassed THF (0.04 ). The
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Eur. J. Org. Chem. 2008, 2118–2129