Synthesis of 3-aryl-5-t-butylsalicylaldehydes and their chiral Schiff base compounds

Article abstract of DOI:10.1080/00397910701572423

Six meta-substituted salicylaldehyde compounds have been prepared in 68-90% yields by the Suzuki-Miyaura coupling reaction using 3-bromo-5-t- butylsalicylaldehyde (1a) and arylboronic acids (2a-f) as reactants. Among the obtained products, 3-(4-fluorophenyl)-5-t-butylsalicylaldehyde (3b), 3-(4-methylphenyl)-5-t-butylsalicylaldehyde (3d), 3-(1-naphthyl)-5-t- butylsalicylaldehyde (3e), and 3-(2-naphthyl)-5-t-butylsalicylaldehyde (3f) have not been reported so far. A series of new Schiff base ligands (L1-L10) were obtained in 51-89% yields from these salicylaldehyde derivatives. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701572423

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Synthesis of 3‐Aryl‐5‐t‐butylsalicylaldehydes
and their Chiral Schiff Base Compounds
Hai‐bin Liu a , Mei Wang a , Ying Wang a , Qiang Gu a & Li‐cheng Sun a b
a State Key Laboratory of Fine Chemicals, DUT‐KTH Joint Education and
Research Center on Molecular Devices , Dalian University of Technology
(DUT) , Dalian, China
b Department of Chemistry , Royal Institute of Technology (KTH) ,
Stockholm, Sweden
Published online: 19 Oct 2007.
To cite this article: Hai‐bin Liu , Mei Wang , Ying Wang , Qiang Gu & Li‐cheng Sun (2007) Synthesis of
3‐Aryl‐5‐t‐butylsalicylaldehydes and their Chiral Schiff Base Compounds, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 37:21, 3815-3826, DOI:
10.1080/00397910701572423
To link to this article: http://dx.doi.org/10.1080/00397910701572423
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Synthetic Communicationsw, 37: 3815–3826, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701572423
Synthesis of 3-Aryl-5-t-
butylsalicylaldehydes and their Chiral
Schiff Base Compounds
Hai-bin Liu, Mei Wang, Ying Wang, and Qiang Gu
State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and
Research Center on Molecular Devices, Dalian University of Technology
(DUT), Dalian, China
Li-cheng Sun
State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and
Research Center on Molecular Devices, Dalian University of Technology
(DUT), Dalian, China and Department of Chemistry, Royal Institute of
Technology (KTH), Stockholm, Sweden
Abstract: Six meta-substituted salicylaldehyde compounds have been prepared in
68–90% yields by the Suzuki–Miyaura coupling reaction using 3-bromo-5-t-
butylsalicylaldehyde (1a) and arylboronic acids (2a–f) as reactants. Among the
obtained products, 3-(4-fluorophenyl)-5-t-butylsalicylaldehyde (3b), 3-(4-methyl-
phenyl)-5-t-butylsalicylaldehyde (3d), 3-(1-naphthyl)-5-t-butylsalicylaldehyde (3e),
and 3-(2-naphthyl)-5-t-butylsalicylaldehyde (3f) have not been reported so far. A
series of new Schiff base ligands (L1–L10) were obtained in 51–89% yields from
these salicylaldehyde derivatives.
Keywords: 3-bromo-5-t-butylsalicylaldehyde,chiralSchiffbaseligands,meta-substituted
salicylaldehyde, Suzuki–Miyaura coupling reaction
Received January 5, 2007
Address correspondence to Mei Wang, State Key Laboratory of Fine Chemicals,
DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian Univer-
sity of Technology (DUT), Dalian 116012, China. E-mail: symbueno@dlut.edu.cn
3815

3816
H.-b. Liu et al.
INTRODUCTION
Salicylaldehyde and its derivatives can be transformed to Schiff bases and
salen ligands, which are important ligands and have been widely used in asym-
metric catalysis.[1] Transition-metal complexes containing chiral Schiff bases
or salen ligands can catalyze many enantioselective reactions, such as
asymmetric oxidation of sulfides,[2] epoxidation of olefins,[3] cyclopropana-
tion of styrene,[4] and asymmetric hetero-Diels–Alder reactions.[5] The
steric hindrance and inductive effect of the substituent on the ortho-position
of the OH group in a salen ligand have an important influence on asymmetric
catalytic reactions. For example, Katsuki found that Mn(salen) complexes
with large ortho-substituted 1-naphthyl groups could catalyze the epoxidation
of indene and N-tosyltetrahydropyridine in high ee values (.90% ee)
(Scheme 1).[6]
In modern organic synthesis, the Suzuki–Miyaura reaction is one of the
most important methods for formation of aryl-aryl bonds.[7] Compared with
other cross-coupling reactions, the Suzuki–Miyaura reaction attracts attention
because of its convenient manipulation and widely available organoboron
reagents, which are nontoxic and air stable.[8] There are few reports concerning
the synthesis of 3-aryl-5-t-butylsalicylaldehydes and the catalytic reactions
using their Schiff base ligands. In this article, we describe the synthesis of
3-aryl-5-t-butylsalicylaldehydes by the Suzuki–Miyaura coupling reaction
and the preparation of their Schiff base ligands.
RESULTS AND DISCUSSION
According to literature procedures,[9] the bromination of 4-t-butylphenol at the
ortho-position by bromine at 08C in the mixture of CCl4 and CHCl3 gave
4-t-butyl-2-bromophenol as the only product in excellent yields. Treatment of
4-t-Butyl-2-bromophenol with polyformaldehyde and Mg(OCH3)2 gave
3-bromo-5-t-butylsalicylaldehyde (1a) in 61% yield.
Scheme 1.

Synthesis of 3-Aryl-5-t-butylsalicylaldehydes
3817
Scheme 2.
The reaction of 1a and 2a catalyzed by Pd(PPh3)4 with various bases in
different solvents was investigated. In the Suzuki–Miyaura coupling
reaction of 1a and 2a, there was another reaction to give the by-product
biphenyl, which was formed by the self-coupling reaction of 2a (Scheme 2).
First, we studied the effect of solvents on this Suzuki–Miyaura coupling
reaction (Table 1). The solvent played an important role in the yield of the
cross-coupling reaction. Toluene is often used in the Suzuki–Miyaura
coupling reaction; however, the present coupling reaction in toluene gave
more by-product and a lower yield of the target product as compared to the
reaction in 1,2-dimethoxyethane (DME)/water. The best results were
obtained using DME/water (3/1, v/v) as solvent.
A suitable base was also essential for the Suzuki–Miyaura coupling
reaction as shown in Table 2. Although 1a contains an OH group, the
strong base NaOH can be used in this system to give 79% yield of product.
Compared with NaHCO3 and NaOH, K2CO3 was the optimal base to give
90% yield.
According to the obtained results, we studied the reactions of 1a with
2a–f, using 5 mol% of Pd(PPh3)4 as catalyst, K2CO3 as base, and DME/
water (3/1, v/v) as the mixture solvent (Scheme 3, Table 3). Arylboronic
acids, either with an electron-withdrawing group (F) or with an electron-
donating group (OCH3 or CH3) on the para-position of the phenyl group,
Table 1. Effect of solvents on the Suzuki–Miyaura coupling reaction of 1a and 2aa
Entry
Solvent
Temperature (8C)
Yield (%)b
1
2
3
DME/waterc
Toluene
Ethanol
90
90
80
90
38
51
aThe reactions were carried out using 1a (1 equiv), 2a (1.1 equiv), Pd(PPh3)4
(5 mol%), and K2CO3 (1.5 equiv) in Ar-degassed solvents for 10 h.
bYields are given for pure products isolated by chromatography on silica gel.
cDME/water ¼ 3/1 (v/v).

3818
H.-b. Liu et al.
Table 2. Effect of bases on the Suzuki–Miyaura coupling
reaction of 1a and 2aa
Entry
Base
Yield (%)b
1
2
3
K2CO3
NaHCO3
NaOH
90
61
79
aThe reactions were carried out at 908C using 1a (1 equiv), 2a (1.1
equiv), Pd(PPh3)4 (5 mol%), and base (1.5 equiv) in Ar-degassed
DME/water (3/1, v/v) for 10 h.
bIsolated yields.
Scheme 3.
Table 3. Suzuki–Miyaura coupling reactions of 1a with 2a–f catalyzed by
a
Pd(PPh3)4
Entry
Ar-B(OH)2
Time (h)
Product
Yield (%)b
1
2
3
4
5
6
C6H5B(OH)2
4-FC6H4B(OH)2
4-CH3OC6H4B(OH)2
4-CH3C6H4B(OH)2
1-C10H7B(OH)2
2a
2b
2c
2d
2e
2f
10
10
10
10
13
20
3a
3b
3c
3d
3e
3f
90
86
87
88
83
68
2-C10H7B(OH)2
aReaction conditions are the same as those for entry 1 in Table 2, with 1.1 equiv of
2a–f.
bIsolated yields based on the amount of 1a used.
Scheme 4.

Synthesis of 3-Aryl-5-t-butylsalicylaldehydes
Table 4. Synthesis of chiral Schiff base ligands
3819
Entry
Ar
R
Schiff base
Yield (%)a
1
2
3
4
5
6
7
8
9
10
Phenyl
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Bu
i-Bu
Bn
L1
L2
L3
L4
L5
L6
L7
L8
L9
L10
68
51
62
70
72
68
84
89
66
82
4-Flourophenyl
4-Methylphenyl
4-Methoxyphenyl
1-Naphthyl
2-Naphthyl
1-Naphthyl
4-Methoxyphenyl
1-Naphthyl
4-Methoxyphenyl
Bn
aIsolated yields.
were used for the coupling reaction. Consequently, 3b, 3c, and 3d were
successfully synthesized in good yields (86–90%, entries 2–4 in Table 3).
The results suggest that the inductive effect of the para-substituents on aryl-
boronic acids has no considerable influence on these coupling reactions. To
obtain derivatives of salicylaldehyde containing a large group on the
3-position, 2e and 2f were selected as organoboron reagents. Because 2e is
more active than 2f, 3e was given in a higher yield than 3f (entries 5 and 6
in Table 3).
The chiral Schiff base ligands derived from 3-aryl-5-t-butylsalicylaldehyde
(3a–f) and chiral aminoalcohols are our ultimate compounds, which were
prepared by the reaction as shown in Scheme 4 (Table 4). Equivalent amounts
of a chiral aminoalcohol and 3a–f were dissolved in an appropriate volume of
anhydrous ethanol and stirred for 4 h at 608C. After flash-column chromato-
graphy and drying in vacuo, the desired Schiff base ligands (L1–L10) were
obtained with moderate to high yields and characterized by MS, 1H NMR, and
13C NMR spectra.
In conclusion, six useful compounds were conveniently synthesized by
the Suzuki–Miyaura coupling reaction of 1a with 2a–f in 68–90% yields.
Among the meta-substituted salicylaldehydes obtained, 3b, 3d, 3e, and 3f
have not been reported so far. Ten new chiral Schiff base ligands (L1–L10)
have also been prepared. The application of these new chiral ligands is
currently explored for asymmetric oxidation of sulfides.
EXPERIMENTAL
General Procedures
Catalyst Pd(PPh3)4,[10] arylboronic acids,[11] and chiral aminoalcohols[12] were
obtained by literature procedures. Anhydrous THF and toluene were dried

3820
H.-b. Liu et al.
prior to use by distillation over sodium/benzophenone ketyl. Anhydrous ethanol
˚
was predried by 4-A molecular sieves for 1 day and then distilled over sodium/
diethyl phthalate. Toluene, ethanol, and DME/water were degassed before use
for Suzuki–Miyaura coupling reactions. Melting points were measured on an
XRc-1 melting-point apparatus and are uncorrected. NMR, mass spectroscopy
(MS), and high performance liquid chromatography (HPLC) spectra were
recorded on Unity Inova 400-Mz (TMS as internal standard), HP1100LC/
MSD, and Waters instruments, respectively. High-resolution mass spectra
were obtained on a Micromass GCT TOF mass spectrometer.
Data
4-t-Butylphenol.[9a] Yield: 80% as white needle crystals. Mp: 97–998C (lit.
1018C); 1H NMR (400 MHz, CDCl3): d 7.23 (d, J ¼ 8.8 Hz, 2H), 6.75
(d, J ¼ 12.8 Hz, 2H), 4.60 (s, 1H), 1.26 (s, 9H).
4-t-Butyl-2-bromophenol.[9b] Yield: 93% as colorless liquid. 1H NMR
(400 MHz, CDCl3): d 7.41 (s, 1H), 7.21 (d, J ¼ 13.2 Hz, 1H), 6.92
(d, J ¼ 8.4 Hz, 1H), 5.44 (s, 1H), 1.25 (s, 9H).
3-Bromo-5-t-butylsalicylaldehyde (1a).[9a] Yield: 61% as light yellow solid.
1
Mp: 79–818C; H NMR (400 MHz, CDCl3): d 11.41 (s, 1H), 9.85 (s, 1H),
7.81 (d, J ¼ 1.6 Hz, 1H), 7.51 (d, J ¼ 2.4 Hz, 1H), 1.33 (s, 9H); MS
(APCI): m/z 255.0 [M–H]2.
General Procedure for the Reaction of 3-bromo-5-t-
butylsalicylaldehyde with Arylboronic Acids: 3-Phenyl-5-t-
butylsalicylaldehyde (3a)
3-Bromo-5-t-butylsalicylaldehyde (1a) (256 mg, 1.0 mmol), phenylboronic
acid (2a) (134 mg, 1.1 mmol), K2CO3 (207 mg 1.5 mmol), and
Pd(PPh3)4 (58 mg, 0.05 mmol, 5 mol%) were added to a Schlenk flask
with a stirring bar. The mixture was purged with argon. A degassed
solvent of DME/water (3/1, v/v, 8 mL) was then added. The mixture
was refluxed with stirring in the dark at 908C for 10 h under the protection
of argon. The organic layer was then separated, and the water layer was
extracted with CH2Cl2 (3 ꢀ 15 mL). The combined organic layers were
washed with brine and dried over anhydrous Na2SO4, and then the
solvent was removed under reduced pressure. The residue was purified
by chromatography on silica gel eluting with petroleum ether (60–
908C)/ethyl acetate (20/1, v/v) to give 229 mg of 3-phenyl-5-t-
butylsalicylaldehyde.
Products 3b–3f were prepared by the same procedure as 3a unless
otherwise noted.

Synthesis of 3-Aryl-5-t-butylsalicylaldehydes
3821
Data
3-Phenyl-5-t-butylsalicylaldehyde (3a). Yield 90% as a yellow oil; 1H
NMR (400 MHz, CDCl3): 11.36 (s, 1H), 9.95 (s, 1H), 7.65
d
(d, J ¼ 2.0 Hz, 1H), 7.59 (d, J ¼ 7.2 Hz, 2H), 7.53 (d, J ¼ 2.4 Hz, 1H),
7.46 (t, J ¼ 7.2 Hz, 2H), 7.38 (t, J ¼ 7.2 Hz, 1H), 1.37 (s, 9H); MS
(APCI): m/z 255.2 [M þ H]þ.
3-(4-Fluorophenyl)-5-t-butylsalicylaldehyde (3b). Yield 86% as a yellow
1
solid. Mp: 59–618C; H NMR (400 MHz, CDCl3): d 11.31 (s, 1H), 9.87
(s, 1H), 7.54 (d, J ¼ 2.4 Hz, 1H), 7.51–7.46 (m, 3H), 7.09–7.05 (m, 2H),
1.29 (s, 9H); 13C NMR (CDCl3): d 197.3 (CHO), 156.8, 143.0, 135.6,
132.9, 131.2, 131.1, 129.7, 129.1, 120.5, 115.5, 115.3, 34.4 [C(CH3)3], 31.5
[C(CH3)3]; EI-HRMS (C17H17O2F): calcd. m/z 272.1213, found 272.1219.
3-(4-Methoxyphenyl)-5-t-butylsalicylaldehyde (3c). Yield 87% as a yellow
1
solid. Mp: 118–1198C; H NMR (400 MHz, CDCl3): d 11.35 (s, 1H), 9.94
(s, 1H), 7.63 (d, J ¼ 2.4 Hz, 1H), 7.54 (d, J ¼ 8.8 Hz, 2H), 7.49
(d, J ¼ 2.4 Hz, 1H), 7.00 (d, J ¼ 8.8 Hz, 2H), 3.86 (s, 3H), 1.37 (s, 9H);
MS (APCI): m/z 285.2 [M þ H]þ.
3-(4-Methylphenyl)-5-t-butylsalicylaldehyde (3d). Yield 88% as a yellow
1
solid. Mp: 97–988C; H NMR (400 MHz, CDCl3): d 11.34 (s, 1H), 9.94
(s, 1H), 7.64 (d, J ¼ 2.4 Hz, 1H), 7.51–7.48 (m, 3H), 7.27 (d, J ¼ 9.2 Hz,
2H), 2.41 (s, 3H), 1.36 (s, 9H); 13C NMR (CDCl3): 197.3 (CHO), 157.0,
142.9, 137.6, 135.8, 134.0, 130.2, 129.3, 129.2, 120.4, 34.4 [C(CH3)3], 31.4
[C(CH3)3], 21.4 (CH3); EI-HRMS (C18H20O2): calcd. m/z 268.1463, found
268.1462.
3-(1-Naphthyl)-5-t-butylsalicylaldehyde (3e). Yield 83% as a yellow solid.
Mp: 114–1158C; 1H NMR (400 MHz, CDCl3): d 11.07 (s, 1H), 9.93
(s, 1H), 7.84 (d, J ¼ 8.4 Hz, 2H), 7.57–7.53 (m, 3H), 7.49 (t, J ¼ 7.2 Hz,
1H), 7.44–7.34 (m, 3H), 1.29 (s, 9H); 13C NMR (CDCl3): d 197.14 (CHO),
157.4, 142.78, 137.2, 135.1, 133.8, 131.9, 129.9, 129.2, 128.6, 127.8, 126.3,
126.1, 126.0, 125.6, 120.3, 34.4 [C(CH3)3], 31.5 [C(CH3)3]; EI-HRMS
(C21H20O2): calcd. m/z 304.1463, found 304.1467.
3-(2-Naphthyl)-5-t-butylsalicylaldehyde (3f). Yield 68% as a yellow solid.
1
Mp: 98–998C; H NMR (400 MHz, CDCl3): d 11.41 (s, 1H), 9.98 (s, 1H),
8.04 (s, 1H), 7.93–7.87 (m, 3H), 7.77–7.74 (m, 2H), 7.56 (d, J ¼ 2.4 Hz,
1H), 7.51–7.49 (m, 2H), 1.40 (s, 9H); 13C NMR (CDCl3): d 197.3 (CHO),
157.2, 143.1, 136.1, 134.6, 133.6, 132.9, 130.2, 129.7, 128.4, 127.9, 127.6,
126.4, 120.6, 34.5 [C(CH3)3], 31.6 [C(CH3)3]; EI-HRMS [C21H20O2]: calcd.
m/z 304.1463, found 304.1463.

3822
H.-b. Liu et al.
Data for Chiral Schiff Base Ligands
(S)-2-(N-3-Phenyl-5-t-butylsalicylidene)amino-3-methyl-1-butanol (L1).
1
Yield 68%. Mp: 139–1418C; H NMR (400 MHz, CDCl3): d 13.73 (s, 1H,
OH), 8.45 (s, 1H, CH55N), 7.63 (d, J ¼ 7.2 Hz, 2H), 7.47–7.43 (m, 3H),
7.35 (t, J ¼ 7.6 Hz, 1H), 7.30 (d, J ¼ 2.4 Hz, 1H), 3.83–3.72 (m, 2H,
CH2OH), 3.08–3.06 (m, 1H, CH-N), 1.96–1.91 [m, 1H, CH(CH3)2], 1.35
[s, 9H, C(CH3)3], 0.95 [dd, J ¼ 6.8, 6.8 Hz, 6H, CH(CH3)2]; 13C NMR
(CDCl3): d 166.7 (CH55N), 156.4 (C-OH), 141.5, 138.4, 131.2, 129.6,
129.5, 128.4, 127.7, 127.3, 118.2, 76.9 (CH-N), 64.9 (CH2OH), 34.3
[C(CH3)3], 31.7 [3C, C(CH3)3], 30.2 [CH(CH3)2], 20.0 and 18.9 [2C,
CH(CH3)2]; MS (API-ES): m/z 340.3 [M þ H]þ.
(S)-2-(N-3-(4-Fluorophenyl)-5-t-butylsalicylidene)amino-3-methyl-1-
butanol (L2). Yield 51%. Mp: 116–1178C; 1H NMR (400 MHz, CDCl3): d
13.82 (s, 1H, OH), 8.44 (s, 1H, CH55N), 7.60 (dd, J ¼ 6.0, 5.6 Hz, 2H), 7.41
(d, J ¼ 2.4 Hz, 1H), 7.30 (d, J ¼ 2.4 Hz, 1H), 7.13 (t, J ¼ 8.8 Hz, 2H), 3.86–
3.72 (m, 2H, CH2OH), 3.11–3.06 (m, 1H, CH-N), 1.96–1.91 [m, 1H,
CH(CH3)2], 1.35 [s, 9H, C(CH3)3], 0.95 [dd, J ¼ 6.8, 7.2 Hz, 6H,
CH(CH3)2]; 13C NMR (CDCl3): d 166.6 (CH55N), 156.4 (C-OH), 141.6,
134.3, 134.2, 131.2, 131.1, 130.9, 128.4, 127.8, 118.3, 115.3, 115.1, 76.9
(CH-N), 64.8 (CH2OH), 34.3 [C(CH3)3], 31.6 [3C, C(CH3)3], 30.2
[CH(CH3)2], 20.0 and 18.8 [2C, CH(CH3)2]; MS (API-ES): m/z 358.5
[M þ H]þ.
(S)-2-(N-3-(4-Methylphenyl)-5-t-butylsalicylidene)amino-3-methyl-1-
butanol (L3). Yield 62%. Mp: 138–1418C; 1H NMR (400 MHz, CDCl3): d
13.61 (s, 1H, OH), 8.36 (s, 1H, CH55N), 7.45 (d, J ¼ 8.0 Hz, 2H), 7.37
(d, J ¼ 2.4 Hz, 1H), 7.21–7.18 (m, 3H), 3.74–3.63 (m, 2H, CH2OH),
3.01–2.97 (m, 1H, CH-N), 2.32 (s, 3H, CH3), 1.89–1.81 [m, 1H,
CH(CH3)2], 1.27 [s, 9H, C(CH3)3], 0.86 [dd, J ¼ 6.8, 6.8 Hz, 6H,
CH(CH3)2]; 13C NMR (CDCl3): d 166.7 (CH55N), 156.4 (C-OH), 141.4,
136.9, 135.4, 131.0, 129.5, 129.4, 129.1, 127.4, 118.2, 76.9 (CH-N), 64.9
(CH2OH), 34.2 [C(CH3)3], 31.6 [3C, C(CH3)3], 30.2 [CH(CH3)2], 21.4
(CH3), 20.0 and 18.8 [2C, CH(CH3)2]; MS (API-ES): m/z 354.3 [M þ H]þ.
(S)-2-(N-3-(4-Methoxyphenyl)-5-t-butylsalicylidene)amino-3-methyl-1-
1
butanol (L4). Yield 70%. Mp: 141–1428C; H NMR (400 MHz, CDCl3): d
13.70 (s, 1H, OH), 8.44 (s, 1H, CH55N), 7.57 (d, J ¼ 7.6 Hz, 2H), 7.43
(s, 1H), 7.26 (s, 1H), 6.99 (d, J ¼ 7.6 Hz, 2H), 3.85 (s, 3H, OCH3),
3.83–3.74 (m, 2H, CH2OH), 3.07 (m, 1H, CH-N), 1.96–1.91 [m, 1H,
CH(CH3)2], 1.35 [s, 9H, C(CH3)3], 0.95 [t, J ¼ 8.0 Hz, 6H, CH(CH3)2]; 13C
NMR (CDCl3): d 166.7 (CH55N), 158.9 (C-OH), 156.4, 141.5, 130.9,
130.7, 130.6, 129.1, 127.3, 118.2, 113.9, 76.9 (CH-N), 64.8 (CH2OH), 55.5

Synthesis of 3-Aryl-5-t-butylsalicylaldehydes
3823
(OCH3), 34.2 [C(CH3)3], 31.6 [3C, C(CH3)3], 30.2 [CH(CH3)2], 20.0 and 18.8
[2C, CH(CH3)2]; MS (APCI): m/z 370.2 [M þ H]þ.
(S)-2-(N-3-(1-Naphthyl)-5-t-butylsalicylidene)amino-3-methyl-1-butanol
(L5). Yield 72%. Mp: 79–818C; 1H NMR (400 MHz, CDCl3): d 13.49
(d, J ¼ 36.4 Hz, 1H, OH), 8.49 (s, 1H, CH55N), 7.89 (t, J ¼ 7.2 Hz, 2H),
7.70 (dd, J ¼ 8.4, 8.4 Hz, 1H), 7.56 (t, J ¼ 7.2 Hz, 1H), 7.51–7.40 (m, 5H),
3.82–3.69 (m, 2H, CH2OH), 3.09–3.07 (m, 1H, CH-N), 1.92–1.87 [m, 1H,
CH(CH3)2], 1.35 [s, 9H, C(CH3)3], 0.95 [t, J ¼ 6.8 Hz, 6H, CH(CH3)2]; 13C
NMR (CDCl3): d 166.7 (CH55N), 156.7 (C-OH), 141.6, 136.0, 133.7,
132.7, 131.4, 129.4, 128.3, 128.2, 127.9, 127.9, 127.8, 127.6, 126.1, 125.9,
118.3, 76.9 (CH-N), 64.9 (CH2OH), 34.3 [C(CH3)3], 31.7 [3C, C(CH3)3],
30.2 [CH(CH3)2], 20.0 and 18.9 [2C, CH(CH3)2]; MS (API-ES): m/z 390.3
[M þ H]þ.
(S)-2-(N-3-(2-Naphthyl)-5-t-butylsalicylidene)amino-3-methyl-1-butanol
1
(L6). Yield 68%. Mp: 121–1238C; H NMR (400 MHz, CDCl3): d 13.88
(s, 1H, OH), 8.60 (s, 1H, CH55N), 8.18 (s, 1H), 8.04–7.98 (m, 3H), 7.93
(d, J ¼ 8.4 Hz, 1H), 7.68 (d, J ¼ 2.4 Hz, 1H), 7.60 (t, J ¼ 4.4 Hz, 2H), 7.46
(d, J ¼ 2.8 Hz,, 1H), 3.98–3.88 (m, 2H, CH2OH), 3.21 (m, 1H, CH-N),
2.07–2.06 [m, 1H, CH(CH3)2], 1.50 [s, 9H, C(CH3)3], 1.08 [dd, J ¼ 7.2,
6.8 Hz, 6H, CH(CH3)2]; 13C NMR (CDCl3): d 166.6 (CH55N), 156.8
(C-OH), 141.2, 136.6, 133.9, 132.5, 132.2, 128.5, 128.1, 128.0, 127.9,
127.8, 126.5, 126.0, 125.9, 125.6, 118.1, 76.9 (CH-N), 64.8 (CH2OH), 34.3
[C(CH3)3], 31.7 [3C, C(CH3)3], 30.3 [CH(CH3)2], 20.0 and 18.9 [2C,
CH(CH3)2]; MS (API-ES): m/z 390.2 [M þ H]þ.
(R)-2-(N-3-(1-Naphthyl)-5-t-butylsalicylidene)amino-4-methyl-1-pentanol
(L7). Yield 84%. Mp: 60–628C; 1H NMR (400 MHz, CDCl3): d 13.49
(d, J ¼ 16.0 Hz, 1H, OH), 8.48 (s, 1H, CH55N), 7.86 (t, J ¼ 7.2 Hz, 2H),
7.67 (t, J ¼ 8.8 Hz, 1H), 7.52 (t, J ¼ 7.2 Hz, 1H), 7.46–7.36 (m, 5H),
3.64–3.55 (m, 2H, CH2OH), 3.41–3.39 (m, 1H, CH-N), 1.46–1.43 [m, 3H,
CH2CH(CH3)2], 1.32 [s, 9H, C(CH3)3], 0.83 [m, 6H, CH(CH3)2]; 13C NMR
(CDCl3): 166.2 (CH55N), 156.8 (C-OH), 141.3, 136.5, 136.4, 133.8, 132.4,
132.2, 128.5, 128.1, 127.9, 127.7, 126.5, 126.1, 125.9, 125.6, 117.9, 70.0
(CH-N), 66.7 (CH2OH), 41.0 (CH2), 34.3 [C(CH3)3], 31.7 [3C, C(CH3)3],
24.6 [CH(CH3)2], 23.8 and 21.7 [2C, CH(CH3)2]; MS (APCI): m/z 404.3
[M þ H]þ.
(R)-2-(N-3-(4-Methoxyphenyl)-5-t-butylsalicylidene)amino-4-methyl-1-
pentanol (L8). Yield 89%. Mp: 121–1228C; 1H NMR (400 MHz, CDCl3): d
13.78 (s, 1H, OH), 8.47 (s, 1H, CH55N), 7.58 (d, J ¼ 8.8 Hz, 2H), 7.44
(d, J ¼ 2.4 Hz, 1H), 7.27 (d, J ¼ 2.4 Hz, 1H), 7.00 (d, J ¼ 8.8 Hz, 2H),
3.86 (s, 3H, OCH3), 3.73–3.61 (m, 2H, CH2OH), 3.45–3.40 (m, 1H, CH-N),
1.64–1.51 [m, 3H, CH2CH(CH3)2], 1.36 [s, 9H, C(CH3)3], 0.91 [t,

3824
H.-b. Liu et al.
J ¼ 6.8 Hz, 6H, CH(CH3)2]; 13C NMR (CDCl3): d 166.3 (CH55N), 158.9
(C-OH), 156.4, 141.5, 130.9, 130.7, 130.6, 129.1, 127.2, 118.1, 113.8, 69.9
(CH-N), 66.8 (CH2OH), 55.5 (OCH3), 41.0 (CH2), 34.2 [C(CH3)3], 31.6
[3C, C(CH3)3], 24.6 [CH(CH3)2], 23.8 and 21.6 [2C, CH(CH3)2]; MS
(APCI): m/z 384.2 [M þ H]þ.
(S)-2-(N-3-(1-Naphthyl)-5-t-butylsalicylidene)amino-3-phenyl-1-propanol
1
(L9). Yield 66%. Mp: 171–1728C; H NMR (400 MHz, CDCl3): d 13.35
(s, 1H, OH), 8.15 (d, J ¼ 3.2 Hz, 1H, CH55N), 7.82–7.78 (m, 2H), 7.62–
7.57 (m, 1H), 7.49–7.29 (m, 5H), 7.19–7.02 (m, 6H), 3.69–3.54 (m, 2H,
CH2OH), 3.46–3.40 (m, 1H, CH-N), 2.85–2.66 (m, 2H, PhCH2), 1.21 [s,
9H, C(CH3)3]; 13C NMR (CDCl3): d 166.7 (CH55N), 156.7 (C-OH), 141.3,
138.1, 136.6, 133.8, 132.5, 132.2, 129.6, 128.6, 128.5, 128.4, 128.1, 128.0,
127.8, 127.7, 126.6, 126.4, 126.1, 126.0, 125.9, 125.6, 117.9, 73.5 (CH-N),
66.0 (CH2OH), 39.2 (PhCH2), 34.3 [C(CH3)3], 31.6 [3C, C(CH3)3]; MS
(APCI): m/z 438.4 [M þ H]þ.
(S)-2-(N-3-(4-Methoxyphenyl)-5-t-butylsalicylidene)amino-3-phenyl-1-
propanol (L10). Yield 82%. Mp: 54–568C; 1H NMR (400 MHz, CDCl3): d
13.60 (s, 1H, OH), 8.16 (s, 1H, CH55N), 7.55 (d, J ¼ 8.4 Hz, 2H), 7.39
(d, J ¼ 2.0 Hz, 1H), 7.23–7.09 (m, 6H), 6.98 (d, J ¼ 8.8 Hz, 2H), 3.83
(s, 3H, OCH3), 3.79–3.68 (m, 2H, CH2OH), 3.54–3.48 (m, 1H, CH-N),
2.96–2.79 (m, 2H, PhCH2), 1.28 [s, 9H, C(CH3)3]; 13C NMR (CDCl3): d
166.9 (CH55N), 159.0 (C-OH), 156.2, 141.5, 138.1, 131.0, 130.7, 130.6,
129.6, 129.0, 128.7, 127.3, 126.6, 118.1, 113.9, 73.4 (CH-N), 66.2
(CH2OH), 55.5 (OCH3), 39.3 (PhCH2), 34.2 [C(CH3)3], 31.6 [3C,
C(CH3)3]; MS (APCI): m/z 418.4 [M þ H]þ.
ACKNOWLEDGMENTS
We are grateful to the Chinese National Natural Science Foundation (Grant
Nos. 20471013 and 20633020), the Swedish Energy Agency, the Swedish
Research Council, and the K & A Wallenberg Foundation for financial
support of this work.
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