Steric effects in the design of chiral Schiff base-titanium complexes: New catalysts for asymmetric trimethylsilylcyanation of aldehydes

Article abstract of DOI:10.1016/S0957-4166(02)00073-3

New chiral Schiff base ligands derived from salicylaldehydes bearing bulky ring substituents were synthesized by reaction with various amino alcohols. These new ligands were used with titanium tetraisopropoxide to study steric effects on the enantioselect

Full text of DOI:10.1016/S0957-4166(02)00073-3

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 13 (2002) 149–154
Steric effects in the design of chiral Schiff base–titanium
complexes: new catalysts for asymmetric trimethylsilylcyanation
of aldehydes
Angeles Gama,a Luc´ıa Z. Flores-Lo´pez,a Gerardo Aguirre,a Miguel Parra-Hake,a
Ratnasamy Somanathana,* and Patrick J. Walshb,*
aCentro de Graduados e Investigacio´n, Instituto Tecnolo´gic de Tijuana, Apartado postal 1166, 22000 Tijuana, BC Mexico
bDepartment of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA 19104-6323, USA
Received 20 December 2001; accepted 24 January 2002
Abstract—New chiral Schiff base ligands derived from salicylaldehydes bearing bulky ring substituents were synthesized by
reaction with various amino alcohols. These new ligands were used with titanium tetraisopropoxide to study steric effects on the
enantioselectivity of the trimethylsilylcyanation of aldehydes. © 2002 Published by Elsevier Science Ltd.
1. Introduction
In this study, we found that the enantioselectivity of the
trimethylsilylcyanation reaction was dependent on the
size of the R1 group on the Schiff base ligand 1, where
R3, R4=indanol backbone, Eq. (1).
Optically active cyanohydrins are very useful synthons
in organic synthesis, which can be transformed into
chiral a-hydroxy carboxylic acids,1,2 a-hydroxy alde-
hydes,3 a-hydroxy ketones,4 and b-amino alcohols.2,5,6
Numerous efficient asymmetric methods to these
molecules have been reported.7–14 Among these, the
Lewis acid-catalyzed addition of trimethylsilylcyanide
to aldehydes has been accomplished with excellent
enantioselectivity.15–18 This asymmetric carbonꢀcarbon
bond forming process finds wide synthetic application
in the pharmaceutical and agrochemical industries.19 In
a previous report from this laboratory we described the
catalyticenantioselectivetrimethylsilylcyanation of benz-
aldehyde with up to 85% e.e. using catalytic amounts of
titanium tetraisopropoxide and chiral Schiff-base lig-
ands derived from cis-1-amino-2-indanol.20
Through NMR and X-ray analyses we found that when
ligands with small R1 substituents (R1=H, Br, OCH3)
ortho to the phenolic OH were combined with an
equivalent of titanium tetraisopropoxide the predomi-
nant product was L*Ti with a ligand to titanium ratio
of 2:1. Only a small2amount of L*Ti(O-i-Pr)2, which is
believed to be the active catalyst, was observed by
NMR along with some unreacted titanium tetra-
isopropoxide. The L2*Ti complex was found to be a
very slow catalyst for the asymmetric addition of
trimethylsilylcyanide to aldehydes because the catalyst
is octahedral and sterically saturated. In contrast, when
R1 was large (e.g. tert-butyl), reaction of the ligand
R2
R1
R3
N
OH
(1)
*
*
1
R4 OH
H
OSi(CH3)3
PhCHO
+
TMSCN
Ph* CN
Ti(OiPr)4
* Corresponding authors. E-mail: somanatha@sundown.sdsu.edu; pwalsh@sas.upenn.edu
0957-4166/02/$ - see front matter © 2002 Published by Elsevier Science Ltd.
PII: S0957-4166(02)00073-3

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A. Gama et al. / Tetrahedron: Asymmetry 13 (2002) 149–154
with titanium tetraisopropoxide gave only L*Ti(O-i-Pr)2
by NMR. This species catalyzed the reaction efficiently
and with high enantioselectivity (Table 1, entries 1–3).
Table 1, the e.e. of the trimethylsilylcyanation improved
with respect to ligands 1d–1f. The best results were
obtained when R1 was an adamantyl group (entries 7, 10
and 13).
2. Results and discussion
Next, a series of benzaldehyde derivatives was examined
with the catalyst formed from ligand 1b (Eq. (2)). The
product e.e.s were the highest with para substituted
aldehydes and were found to be lower when meta or ortho
substituted aldehydes were employed. para-Anisalde-
hyde was an excellent substrate for catalyst 1b, giving
95% e.e. in the asymmetric addition reaction.
As a continuation of our initial study, we were interested
in designing new Schiff base ligands, where R1 would be
very bulky (i.e. larger than tert-butyl). We have previ-
ously determined that the most enantioselective catalysts
incorporated ligands in which R1 was tert-butyl. Not
only would such large substituents favor the formation
of L*Ti(O-i-Pr)2 species, but based on our earlier inves-
tigations, we believed that they might form more enan-
tioselective catalysts. Aldehyde precursors for ligand
syntheses with large R1 substituents were prepared fol-
lowing the literature methods21 and converted to Schiff
base ligands on reaction with cis-1-amino-2-indanol. The
Schiff bases were then combined with an equivalent of
titanium isopropoxide to form the catalysts for the
asymmetric trimethylsilylcyanation of benzaldehyde.
The results of the asymmetric addition reactions are
shown in Table 1. The results in entries 4–6 indicate that
ligands with large R1 groups and the conformationally
rigid five-membered indanol did not result in an increase
in the enantioselectivity or efficiency of the catalyst
compared to the ligands where R1 was a tert-butyl group
(entries 1–3). A possible explanation for the low enan-
tioselectivity and conversion with ligands 1d–1f is that the
large R1 substituent does not allow facile coordination
and activation of the aldehyde substrate.
R1
O
H
OSi(CH3)3
CN
R2
R3
TMSCN
*
H
Ti(OiPr)4
(2)
N
OH
1b
*
*
OH
The results described in Tables 1 and 2 and our previous
study clearly indicate that steric crowding around
the metal center is necessary for the formation of active
and enantioselective catalysts in the asymmetric
trimethylsilylcyanation of aldehydes with Schiff-base
ligands and titanium isopropoxide. Similar effects have
also been reported for the salen ligands, where steric
factors play a major role in the asymmetric induction.23
From our work, it appears that the size of the R1
substituent and the bulk and conformational flexibility
of the amino alcohol backbone must be balanced in
designing new Schiff-base ligands. We are currently
working on a series of structurally similar ligands with
In order to explore the steric effects of the ligand on the
enantioselectivity of catalysts with different backbones,
we replaced the rigid indanol ring with conformationally
more flexible amino alcohol components. As shown in
Table 1. Enantioselective addition of trimethylsilylcyanide to benzaldehyde promoted by chiral Schiff base–titanium
complexesa
Entry
Schiff base
Configuration
R1
R2
R3
R4
Yield (%)
e.e.b (%)
(Configuration)
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
(R,S)
(R,S)
(R,S)
(R,S)
(R,S)
(R,S)
(S)
(S)
(S)
(R)
(R)
C(CH3)3
C(CH3)3
C(CH3)3
C(CH3)3
H
CH3
CH3
CH2C6H4
CH2C6H4
CH2C6H4
CH2C6H4
CH2C6H4
CH2C6H4
62
64
72
25
36
17
52
38
18
50
39
20
50
40
15
60
70 (R)c
85 (R)c
59 (R)c
44 (S)
27 (R)
12 (R)
68 (S)
55 (R)
17 (R)
55 (S)
52 (R)
15 (R)
66 (S)
54 (R)
12 (R)
65 (S)
Adamantyl
C(CH3)2CH2CH3
C(CH3)2Ph
Adamantyl
C(CH3)2CH2CH3
C(CH3)2Ph
Adamantyl
C(CH3)2CH2CH3
C(CH3)2Ph
Adamantyl
C(CH3)2CH2CH3
C(CH3)2Ph
Adamantyl
C(CH3)2CH2CH3
C(CH3)2Ph
CH3
C(CH3)2CH2CH3
C(CH3)2Ph
CH3
C(CH3)2CH2CH3
C(CH3)2Ph
CH3
C(CH3)2CH2CH3
C(CH3)2Ph
CH3
C(CH3)3
C(CH3)3
C(CH3)3
Ph
H
H
H
H
H
H
Ph
Ph
Ph
H
9
10
11
12
13
14
15
16
Ph
Ph
Ph
Ph
(R)
(S,R)
(S,R)
(S,R)
(S)
Ph
CH(CH3)2
a All reactions were performed using 20% mol titanium tetraisopropoxide at –78°C in dichloromethane for 36 h. Each e.e. value is the result of
a minimum of two runs.
b Enantioselectivities were determined as described in the Section 3.
c Ref. 20.

A. Gama et al. / Tetrahedron: Asymmetry 13 (2002) 149–154
151
Table 2. Enantioselectivities in the asymmetric cyanohydration of different aldehydes
a
Configuration was determined using Oguni’s ligand.15
b
Absolute configuration not assigned.
c
Determined by comparison of the sign of specific rotation value with the literature value.22
subtle variations in the size of the substituents to opti-
mize the catalysts and understand their mechanisms in
the trimethylsilylcyanation of aldehydes.
Details of the general procedure for the synthesis of the
Schiff bases, for the trimethylsilylcyanation reaction,
and the experimental data for ligands 1a–1c are
reported in a previous work.20
3. Experimental
3.1. Data for (1R,2S)-(+)-1-[N-(3%-adamantyl-5%-methyl-
salicylidene)amino]-2-indanol, 1d
All manipulations involving titanium complexes were
carried out under an inert atmosphere using standard
Schlenk and vacuum line techniques.
Yellow solid (0.31 g, 95% yield): mp 220–225°C; [h]2D5=
+76.9 (c=0.5, CH2Cl2); IR (KBr) 3586, 2901, 2845,
1621 and 745 cm−1; 1H NMR (200 MHz, CDCl3) l
13.10 (brs, 1H), 8.60 (s, 1H), 7.30 (d, 1H, J=7.2 Hz),
7.28 (t, 1H, J=7.4 Hz), 7.22 (t, 1H, J=7.3 Hz), 7.18 (d,
1H, J=7.2 Hz), 7.10 (d, 1H, J=1.5 Hz), 6.96 (d, 1H,
J=1.5 Hz), 4.78 (d, 1H, J=5.2 Hz), 4.65 (q, 1H, J=5.2
Hz), 3.23 (dd, 1H, J1=5.9 Hz and J2=15.9 Hz), 3.12
(dd, 1H, J1=5.9 Hz and J2=15.9 Hz), 2.29 (s, 3H),
2.13 (s, 6H), 2.05 (s, 3H) and 1.76 (s, 6H) ppm; 13C
NMR (50 MHz, CDCl3) l 168.07, 158.42, 140.98,
140.88, 137.70, 131.25, 130.01, 128.57, 127.12, 127.06,
125.50, 124.95, 118.37, 75.74, 75.22, 40.23, 39.66, 37.07,
39.90, 29.00 and 20.59 ppm. Anal. calcd for
Enantiomeric excesses were determined using
a
Hewlett–Packard 6890 gas chromatograph with a 30 m
Supelco b-DEX column. The silyloxy cyanides were
hydrolyzed with 1N HCl for 3 h to the alcohol and
derivatized with acetic anhydride. The GC conditions
were: oven temperature 150°C, flow rate 3 mL/min. The
retention times (min) of the enantiomers derived from
benzaldehyde were 11.42 (R) and 12.07 (S); 3a 12.60
(R) and 13.15 (S); 3b 17.00 (R) and 17.20 (S); 3c 15.45
(R) and 15.77 (S); 3d 15.00 (R) and 15.40 (S); 3e 14.80
(R) and 15.10 (S).

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A. Gama et al. / Tetrahedron: Asymmetry 13 (2002) 149–154
C27H31NO2: C, 78.02; H, 7.96. Found: C, 77.99; H,
7.95%.
CDCl3) l 8.80 (s, 1H), 7.71 (d, 1H, J=2.6 Hz), 7.51 (d,
1H, J=2.2 Hz), 4.36 (dd, 1H, J1=3.0 Hz and J2=11.0
Hz), 4.19 (t, 1H, J=11.0 Hz), 3.36 (dd, 1H, J1=2.8 Hz
and J2=9.4 Hz), 2.36 (q, 2H, 7.2 Hz), 2.06 (q, 2H,
J=7.2 Hz), 1.84 (s, 6H), 1.72 (s, 6H), 1.42 (s, 9H), 1.14
3.2. Data for (1R,2S)-(−)-1-[N-(3%,5%-di-tert-amylsalicyl-
idene)amino]-2-indanol, 1e
(t, 3H, J=7.2 Hz) and 1.12 (t, 3H, J=7.8 Hz) ppm; 13
C
Yellow solid (1.20 g, 90% yield); mp 78–80°C; [h]2D5=
–21.8 (c=1.2, CH2Cl2); IR (KBr) 3576, 3450, 2949,
NMR (50 MHz, CDCl3) l 167.46, 158.28, 138.39,
135.14, 129.25, 127.20, 117.73, 81.58, 62.75, 38.75,
37.44, 37.06, 33.43, 32.81, 28.77, 28.67, 28.55, 27.64,
27.33, 9.72 and 9.37 ppm. Anal. calcd for C23H39NO2:
C, 76.45; H, 7.10. Found: C, 76.88; H, 7.40%.
1
2884, 1620, 1457, 1158 and 750 cm−1; H NMR (200
MHz, CDCl3) l 8.60 (s, 1H), 7.26–7.17 (m, 5H), 7.10
(d, 1H, J=2.3 Hz), 4.70 (d, 1H, J=5.3 Hz), 4.60 (q,
1H, J=5.6 Hz), 3.20 (dd, 1H, J1=5.6 Hz and J2=15.9
Hz), 3.10 (dd, 1H, J1=5.6 Hz and J2=15.9 Hz), 1.87
(q, 2H, J=6.5 Hz), 1.60 (q, 2H, J=6.5 Hz), 1.36 (s,
6H), 1.27 (s, 6H), 0.69 (t, 6H, J=7.1 Hz) ppm; 13C
NMR (50 MHz, CDCl3) l 168.40, 158.07, 141.01,
140.88, 138.52, 135.22, 129.67, 128.51, 127.34, 127.01,
125.46, 124.98, 117.76, 75.60, 75.11, 39.60, 38.51, 37.21,
36.80, 32.54, 28.45, 27.37, 9.37 and 9.03 ppm. Anal.
calcd for C26H35NO2: C, 79.38; H, 8.90. Found: C,
79.42; H, 8.99%.
3.6. Data for (S)-(+)-2-[N-(3%,5%-Bis(a,a-dimethylbenzyl-
salicylidene)amino]-3,3-dimethyl-1-butanol, 1i
Yellow solid (0.54 g, 92% yield); mp 50–53°C; [h]2D5=
−34.75 (c=1.85, CH2Cl2); IR (KBr) 3412, 2963, 2871,
1
1628, 1458, 1045 and 697 cm−1; H NMR (200 MHz,
CDCl3) l 8.23 (s, 1H), 7.29–7.19 (m, 11H), 7.05 (d, 1H,
J=2.4 Hz), 3.81 (dd, 1H, J1=3.0 Hz and J2=11.2 Hz),
3.63 (t, 1H, J=9.4 Hz), 2.82 (dd, 1H, J1=3.0 Hz and
J2=9.4 Hz), 1.73 (s, 3H), 1.69 (s, 6H), 1.63 (s, 3H) and
0.83 (s, 9H) ppm; 13C NMR (50 MHz, CDCl3) l
166.87, 157.92, 150.72, 150.55, 139.74, 136.56, 129.55,
128.07, 127.81, 126.77, 125.85, 125.69, 125.08, 117.86,
81.57, 62.37, 42.37, 42.22, 33.13, 30.87, 30.80, 30.31,
28.29 and 27.03 ppm. Anal. calcd for C31H39NO2: C,
81.40; H, 8.53. Found: C, 81.80; H, 8.90%.
3.3. Data for (1R,2S)-(−)-1-[N-(3%,5%-Bis(a,a-dimethyl-
benzylsalicylidene)amino]-2-indanol, 1f
Yellow solid (1.48 g, 93% yield); mp 60–62°C; [a]2D5=
−42.4 (c=0.5, CH2Cl2); IR (KBr) 3549, 3387, 3033,
1
2960, 1630, 1458, 1093 and 761 cm−1; H NMR (200
MHz, CDCl3) d 8.46 (s, 1H), 7.35 (d, 1H, J=2.39 Hz),
7.29–7.10 (m, 14H), 7.08 (d, 1H, J=2.39 Hz), 4.69 (d,
1H, J=5.6 Hz), 4.57 (q, 1H, J=5.6 Hz), 3.15 (dd, 1H,
J1=5.9 Hz and J2=15.9 Hz), 3.00 (dd, 1H, J1=5.9 Hz
and J2=15.9 Hz), 1.71 (s, 6H), 1.64 (s, 6H) ppm; 13C
NMR (50 MHz, CDCl3) d 167.88, 157.79, 150.69,
150.41, 140.92, 140.69, 140.06, 136.40, 129.86, 128.53,
128.11, 127.88, 126.97, 126.76, 125.80, 125.69, 125.46,
125.16, 125.03, 118.03, 75.51, 75.06, 42.42, 42.14, 39.56,
30.85, 29.55 and 29.03 ppm. Anal. calcd for
C34H35NO2: C, 83.43; H, 7.15. Found: C, 83.55; H,
7.20%.
3.7. Data for (R)-(+)-2-[N-(3%-adamantyl-5%-methyl-
salicylidene)amino]-2-phenyl-1-ethanol, 1j
Yellow solid (0.38 g, 67% yield); mp 75–77°C. [h]2D5=
+126.5 (c=0.8, CH2Cl2); IR (KBr) 3366, 3036, 2889,
1
2849, 1623, 1444, 1244, 1059 and 692 cm−1; H NMR
(200 MHz, CDCl3) l 8.42 (s, 1H), 7.39–7.24 (m, 5H),
7.08 (s, 1H), 6.90 (s, 1H), 4.44 (t, 1H, J=6.6 Hz), 3.91
(d, 2H, J=7.0 Hz), 2.26 (s, 3H), 2.17 (s, 6H), 2.08 (s,
3H), and 1.79 (s, 6H) ppm; 13C NMR (50 MHz,
CDCl3) l 167.72, 158.60, 139.79, 137.76, 131.28, 130.16,
129.08, 128.09, 127.50, 127.29, 118.59, 67.97, 40.51,
37.34, 37.15, 29.28 and 20.79 ppm. Anal. calcd for
C26H31NO2: C, 80.79; H, 7.73. Found: C, 80.91; H,
7.79%.
3.4. Data for (S)-(+)-2-[N-(3%-adamantyl-5%-methyl-
salicylidene)amino]-3,3-dimethyl-1-butanol, 1g
Yellow solid (0.31 g, 95% yield); mp 73–75°C; [h]2D5=
+0.5 (c=1.61, CH2Cl2); IR (KBr) 3403, 2908, 1628,
1
1454 and 1050 cm−1; H NMR (200 MHz, CDCl3): l
8.27 (s, 1H), 7.07 (d, 1H, J=2.2 Hz), 6.91 (d, 1H,
J=2.2 Hz), 3.86 (dd, 1H, J1=3.0 Hz and J2=11.4 Hz),
3.79 (t, 1H, J=9.4 Hz), 2.87 (dd, 1H, J1=2.8 Hz and
J2=9.0 Hz), 2.27 (s, 3H), 2.16 (s, 6H), 2.12 (s, 3H), 1.78
(s, 6H) and 0.95 (s, 9H) ppm; 13C NMR (50 MHz,
CDCl3): l 167.01, 158.63, 137.59, 130.71, 129.86,
126.89, 118.37, 81.56, 62.61, 40.45, 37.30, 33.36, 29.24,
27.25 and 20.85 ppm. Anal. calcd for C24H35NO2: C,
88.27; H, 8.04. Found: C, 88.35; H, 8.13%.
3.8. Data for (R)-(+)-2-[N-(3%,5%-di-tert-amylsalicyl-
idene)amino]-2-phenyl-1-ethanol, 1k
Yellow oil (0.64 g, 93% yield); [h]2D5=+95.4 (c=1.9,
CH2Cl2); IR (KBr) 3397, 2947, 2870, 1623, 1425, 1271,
1
1057, 738 and 700 cm−1; H NMR (200 MHz, CDCl3)
l 8.46 (s, 1H), 7.34–7.27 (m, 6H), 7.05 (s, 1H), 4.39 (t,
1H, J=6.8 Hz), 3.84 (d, 2H, J=7.6 Hz), 1.94 (q, 2H,
J=7.2 Hz), 1.59 (q, 2H, J=7.4 Hz), 1.40 (s, 6H), 1.25
(s, 6H) and 0.65 (t, 6H, J=6.4 Hz) ppm; 13C NMR (50
MHz, CDCl3) l 167.49, 157.86, 139.60, 138.34, 134.88,
129.30, 128.69, 128.55, 127.68, 127.18, 117.73, 67.55,
50.39, 38.54, 37.22, 36.85, 32.60, 28.50, 27.48, 9.52, and
9.11 ppm. Anal. calcd for C25H35NO2: C, 78.74; H,
9.18. Found: C, 78.90; H, 9.48%.
3.5. Data for (S)-(−)-2-[N-(3%,5%-di-tert-amylsalicyl-
idene)amino]-3,3-dimethyl-1-butanol, 1h
Yellow solid (0.47 g, 99% yield); mp 70–73°C. [h]2D5=
−33.7 (c=0.6, CH2Cl2). IR (KBr) 3387, 2947, 2870,
1633, 1461 and 1276 cm−1; 1H NMR (200 MHz,

A. Gama et al. / Tetrahedron: Asymmetry 13 (2002) 149–154
153
3.9. Data for (R)-(+)-2-[N-(3%,5%-Bis(a,a-dimethyl-
128.02, 127.91, 127.78, 127.14, 126.74, 125.78, 125.64,
125.05, 117.96, 80.18, 78.14, 42.33, 42.17, 30.78, 30.06
and 28.54 ppm. Anal. calcd for C39H39NO2: C, 84.63;
H, 7.05. Found: C, 85.01; H, 7.55%.
benzyl)salicylidene)amino]-2-phenyl-1-ethanol, 1l
Yellow solid (0.27 g, 51% yield); mp 56–58°C; [h]2D5=
+79.8 (c=1.61, CH2Cl2); IR (KBr) 3406, 3033, 2956,
1
2861, 1628, 1447, 1033, 761 and 704 cm−1; H NMR
3.13. Data for S-(−)-2-[N-3%-adamantyl-5%-methylsali-
cylidene)amino]-3-methyl-1-butanol, 1p
(200 MHz, CDCl3) l 8.31 (s, 1H), 7.46 (d, 1H, J=2.4
Hz), 7.43–7.17 (m, 15H), 7.12 (d, 1H, J=2.2 Hz), 4.30
(t, 1H, J=6.0 Hz), 3.74 (d, 2H, J=6.2 Hz), 1.71 (s,
3H), 1.68 (s, 3H) and 1.64 (s, 6H) ppm; 13C NMR (50
MHz, CDCl3) l 167.13, 157.49, 150.60, 150.47, 139.92,
139.43, 136.03, 129.40, 128.65, 128.40, 128.00, 127.85,
127.69, 127.16, 126.67, 125.63, 125.09, 118.00, 78.04,
67.34, 42.40, 42.16, 30.87, 30.28 and 28.54 ppm. Anal.
calcd for C33H35NO2: C, 83.02; H, 7.34. Found: C,
83.41; H, 7.84%.
Yellow solid (0.47 g, 61% yield); mp 58–60°C; [h]2D5=
−26.3 (c=0.13, CH2Cl2); IR (KBr) 3373, 2960, 2906,
1
2860, 1630, 1453, 1246, 1026 and 740 cm−1; H NMR
(200 MHz, CDCl3) l 8.29 (s, 1H), 7.08 (d, 1H, J=2.0
Hz), 6.92 (d, 1H, J=2.2 Hz), 3.77 (2dd, 2H, J1=2.4 Hz
and J2=10.4 Hz), 3.01 (t, 1H, J=10.0 Hz), 2.28 (s,
3H), 2.17 (s, 6H), 2.08 (s, 3H), 1.9 (m, 1H), 1.78 (s, 6H),
0.95 (d, 3H, J=2.8 Hz) and 0.92 (d, 3H, J=2.8 Hz)
ppm; 13C NMR (50 MHz, CDCl3) l166.97, 158.63,
137.63, 130.78, 129.84, 126.97, 118.41, 78.14, 64.78,
40.49, 37.34, 37.12, 30.26, 29.27, 20.86, 19.97 and 19.05
ppm. Anal. calcd for C23H33NO2: C, 77.74; H, 9.29.
Found: C, 77.80; H, 9.33%.
3.10. Data for (1S,2R)-(+)-2-[N-3%-adamantyl-5%-methyl-
salicylidene)amino]-1,2-diphenylethanol, 1m
Yellow solid (0.39 g, 89% yield); mp 75–77°C. [h]2D5=
+0.75 (c=0.4, CH2Cl2); IR (KBr) 3422, 2899, 2844,
1
1628, 1449, 1045 and 701 cm−1; H NMR (200 MHz,
CDCl3) l 8.02 (s, 1H), 7.40–7.22 (m, 10H), 7.03 (d, 1H,
J=2.02 Hz), 6.70 (d, 1H, J=2.4 Hz), 5.05 (d, 1H,
J=6.6 Hz), 4.43 (d, 1H, J=6.4 Hz), 3.43 (s, 1H), 2.22
(s, 3H), 2.18 (s, 6H), 2.12 (s, 3H) and 1.8 (s, 6H) ppm;
13C NMR (50 MHz, CDCl3) l 167.21, 166.74, 158.48,
140.54, 139.76, 137.52, 131.18, 130.80, 130.11, 129.85,
129.16, 128.67, 128.45, 128.17, 127.67, 127.17, 126.87,
118.49, 118.52, 80.90, 80.42, 78.84, 78.19, 40.88, 40.47,
40.09, 37.83, 37.43, 37.16, 29.54, 29.15, 21.04, 20.66,
0.40 and 0.10 ppm. Anal. calcd for C32H35NO2: C,
77.80; H, 9.48. Found: C, 77.96; H, 9.57%.
Acknowledgements
We gratefully acknowledge support for this project by
COSNET grant (498.01-P) 2001, CONACyT grant
(37827-E) 2001 and graduate fellowship by CONACyT
for A.G.
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1
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