Reduction of carboxylic acid derivatives using diphenylsilane in the presence of a Rh-PPh3 complex

Article abstract of DOI:10.1246/bcsj.78.1856

Reductions of carboxylic acid derivatives by silanes in the presence of rhodium complexes were studied. Carboxylic esters were reduced to alcohols by diphenylsilane catalyzed by [RhCl(cod)]₂/4PPh₃ or [RhCl(PPh₃)₃] at room temperature in up to 99% yields. For example, ethyl decanoate and ethyl phenylacetate were converted to decanol and 2-phenylethanol in 98 and 92% yields, respectively. Carboxylic acids were also reduced by this reducing system to the corresponding alcohols in high yields. Furthermore, N-monosubstituted amides were reduced to secondary amines in moderate to good yields. For sterically hindered amides, the yields were moderate, and imines were produced in competitive yields.

Full text of DOI:10.1246/bcsj.78.1856

1856 Bull. Chem. Soc. Jpn., 78, 1856–1861 (2005)
Ó 2005 The Chemical Society of Japan
Reduction of Carboxylic Acid Derivatives Using Diphenylsilane
in the Presence of a Rh–PPh3 Complex
ꢀ
Tetsuo Ohta, Masahiro Kamiya, Mami Nobutomo, Keisuke Kusui, and Isao Furukawa
Department of Molecular Science and Technology, Faculty of Engineering, Doshisha University,
Kyotanabe, Kyoto 610-0394
Received May 23, 2005; E-mail: tota@mail.doshisha.ac.jp
Reductions of carboxylic acid derivatives by silanes in the presence of rhodium complexes were studied. Carbox-
ylic esters were reduced to alcohols by diphenylsilane catalyzed by [RhCl(cod)]2/4PPh3 or [RhCl(PPh3)3] at room tem-
perature in up to 99% yields. For example, ethyl decanoate and ethyl phenylacetate were converted to decanol and 2-
phenylethanol in 98 and 92% yields, respectively. Carboxylic acids were also reduced by this reducing system to the
corresponding alcohols in high yields. Furthermore, N-monosubstituted amides were reduced to secondary amines in
moderate to good yields. For sterically hindered amides, the yields were moderate, and imines were produced in com-
petitive yields.
Catalytic reduction1 of carbonyl compounds is the most typ-
ical method of producing alcohols. Aldehydes and ketones are
reduced to the corresponding alcohols by hydrogenation,2
transfer hydrogenation,3 and reduction using silane in the pres-
ence of transition metal catalysts.4 On the other hand, carbox-
ylic acid derivatives are not easily reduced catalytically to al-
cohols or amines, and only a few examples have been reported
so far.5–7 Silane reduction catalyzed by metal halides, such as
ZnCl2, CsF, and KF, has been applied for the reduction of es-
ters to alcohols, but the reaction conditions are severe or a stoi-
chiometric amount of metal halides is used.8 Using silane in
the presence of a titanium complex has been developed for
the reduction of esters to alcohols by Buchwald,9 but an alkyl-
metal reagent, such as n-BuLi and EtMgBr or heating is need-
ed in order to produce an active catalyst. Nagashima et al. re-
ported the unique ruthenium catalyst for silane-reduction of
carboxylic acid derivatives.10 On the other hand, esters were
converted to ethers by Mn–silane system.11 Amides were re-
duced by combinations of transition-metals and silanes.12,13
We have preliminarily reported that esters were reduced to
alcohols in excellent yields using silane in the presence of a
rhodium complex. Now we wish to describe the details of this
reaction and their application to the reduction of carboxylic
acids and amides to alcohols and amines.14
= C9H19, R2 ¼ C2H5) was selected as the substrate. It
was reduced to decanol (3a) in 98% yield using 3 equiv of
diphenylsilane (2) as a reducing agent in the presence of
[RhCl(cod)]2/4PPh3 at room temperature in THF (Table 1,
Entry 3). Wilkinson’s complex [RhCl(PPh3)3] also showed
good catalytic activity enough to give the product in 96%
yield by the reaction for 6 h, while carbonyl complex [RhCl-
(CO)(PPh3)3] showed lower catalytic activity (Entry 8).
[RhCl(cod)]2–BINAP15 was effective for this reduction giving
3a in 95% yield for 120 h; employing 1,10-phenanthroline16 as
a ligand, however, resulted in 53% yield of the alcohol 3a
(Entry 14). The ratio of catalyst strongly affected the reaction.
That is, employing 2.5 mol % catalyst (Rh atom to substrate)
resulted in good yields of 3a, while using 1.0 mol % of catalyst
showed unsatisfactory yields of 3a (Entries 2 and 7). Using
other silanes decreased the yields of the alcohol 3a (Entries
10–13). For example, using trichlorosilane yielded a complex
mixture, while an employment of triethylsilane resulted in
trace amounts of alcohol. Interestingly, reduction using octyl-
silane proceeded well to give decanol in 98% yield, while
using phenylsilane, decanol was obtained in 42% yield accom-
panied with desyl ethyl ether in 41% yield. Silane 2 was need-
ed in more than 3 equiv to the ester for obtaining the highest
yield of the reduction, whereas the yield was lower using 2
equiv of 2 (Entry 5).
This reduction was applied to a variety of esters 1b–h; rep-
resentative results are listed in Table 2. Linear and aliphatic es-
ters 1a, 1b, and 1d were reduced smoothly to the correspond-
ing alcohols in good yields (Entries 1, 2, and 4). From isobutyl
decanoate (1b), ethyl phenylacetate (1e), and ethyl benzoate
(1f), the corresponding alcohols were obtained in moderate
yields by standard workup using 1 M NaOH aq, while workup
using 6 M NaOH aq gave better yields. That is, the yields
of the products from the reaction of 1b, 1e, and 1f by
[RhCl(cod)]2/4PPh3 increased from 70, 73, and 47 to 92, 92,
and 70%, respectively. This apparently is due to the hydrolysis
Results and Discussion
Reduction of Carboxylic Esters. Ethyl decanoate (1a, R1
Ph2SiH2 (2)
Rh catalyst
O
NaOH aq.
R1
OR2
THF, rt
ð1Þ
R2OH
1
R1CH2OH
+
3
Published on the web October 4, 2005; DOI 10.1246/bcsj.78.1856

T. Ohta et al.
Bull. Chem. Soc. Jpn., 78, No. 10 (2005) 1857
Table 1. Reduction of Ethyl Decanoate (1a) by Silane in the Presence of Rh ComplexesaÞ
Reaction
time/h
YieldcÞ/% of
3a
Entry
Ratio of Rh/1a/mol %bÞ
Silane/equiv
1
2
3
4
5
6
7
8
9
10
11
12
13
14
[RhCl(cod)]2/4PPh3 (2.5)
[RhCl(cod)]2/4PPh3 (1.0)
[RhCl(cod)]2/4PPh3 (2.5)
[RhCl(cod)]2/4PPh3 (2.5)
[RhCl(cod)]2/4PPh3 (2.5)
[RhCl(PPh3)3] (2.5)
[RhCl(PPh3)3] (1.0)
[RhH(CO)(PPh3)3] (2.5)
Ph2SiH2 (4)
Ph2SiH2 (4)
Ph2SiH2 (3)
Ph2SiH2 (3)
Ph2SiH2 (2)
Ph2SiH2 (3)
Ph2SiH2 (3)
Ph2SiH2 (3)
Ph2SiH2 (3.75)
PhSiH3 (3.75)
Cl3SiH (3.75)
Et3SiH (3.75)
C8H17SiH3 (4)
Ph2SiH2 (4)
72
72
72
6
72
6
92
40
98
90
72
96
51
30
6
48
120
120
120
90
144
72
[RhCl(cod)]2/2(S)-BINAP (2.5)
[RhCl(cod)]2/2(S)-BINAP (2.5)
[RhCl(cod)]2/2(S)-BINAP (2.5)
[RhCl(cod)]2/2(S)-BINAP (2.5)
[RhCl(cod)]2/2(S)-BINAP (2.5)
[RhCl(cod)]2/2(1,10-phenanthroline) (5)
95
42dÞ
0
trace
98
53
a) Reaction conditions: substrate 1a (2.0 mmol), Ph2SiH2, [RhCl(cod)]2, PPh3 (2 equiv to Rh atom), THF (2
1
mL), and room temperature. Workup: 1 M NaOH aq. b) Rh atom/1a. c) Determined by H NMR spectro-
scopic analysis by an internal standard (bibenzyl) method. d) Decyl ethyl ether was obtained in 41% yield.
Table 2. Reduction of Esters 1 by Diphenylsilane (2) in the Presence of Rhodium ComplexesaÞ
Substrate 1
R1
YieldbÞ/% of 3
[RhCl(cod)]2/4PPh3
Entry
R2
[RhCl(PPh3)3]
96 (91)cÞ
97dÞ
1
2
3
4
5
6
7
1a
1b
1c
1d
1e
1f
C9H19
C9H19
C13H27
CH3
C6H5CH2
C6H5
Br(CH2)6
C2H5
i-C4H9
i-C3H7
C10H21
C2H5
3a
3a
3b
3a
3c
3d
3e
98
92dÞ
66dÞ
94dÞ
92dÞ
70d),e)
92
90dÞ
97
86dÞ
C2H5
C2H5
56dÞ
1g
92dÞ
a) Reaction conditions for [RhCl(cod)]2/4PPh3: [RhCl(cod)]2 (0.025 mmol), PPh3 (0.10 mmol), Ph2SiH2
(6.0 mmol), an ester (2.0 mmol), THF (2.0 mL), 72 h, and rt. For [RhCl(PPh3)3]: [RhCl(PPh3)3] (0.05
mmol), Ph2SiH2 (6.0 mmol), an ester (2.0 mmol), THF (2.0 mL), 24 h, and 50 ꢁC. Work up with 1 M NaOH
aq. b) Determined by 1H NMR spectroscopic analysis by an internal standard (bibenzyl) method. c) Isolated
yield. d) Workup: 6 M NaOH aq. e) [RhCl(cod)]2 (0.05 mmol), PPh3 (0.20 mmol), and 144 h.
of the silicone–oxygen bond in alkoxysilane, in which the ster-
ically bulky alkoxy group prevents smooth hydrolysis. The
bromo substituent on the substrate did not suffer in the course
of this reaction (1g, Entry 7). When the ester substrates have a
carbon–carbon double bond, such as 2-ethylbutyl propenoate
and 2-pentenyl acetate, the reduction of ester function was
competing to the reduction of carbon–carbon double bond.
Lactone 1h was reduced by diphenylsilane in the presence of
this catalyst to the corresponding diol 3f in 63% yield.
Reduction of Carboxylic Acids. Reduction of carboxylic
Ph2SiH2 (2)
rhodium catalyst
O
1 M NaOH
R1
OH
THF, rt
ð3Þ
4
R1CH2OH
3
acids to the corresponding alcohols proceeded in good yields
as well. Results of the reaction under various conditions are
listed in Table 3. The use of a smaller amount of catalyst
(Entries 5 and 6) and less amount of silanes than 2 equiv to
the acid (Entries 3 and 4) decreased the yield of the alcohol.
In the case of decanoic acid, employment of phenylsilane
was as effective as the use of diphenylsilane, unlike the case
of ethyl decanoate (vide infra), while triphenylsilane and
triethylsilane showed no reduction ability (Entries 7–9).
Under the selecting reaction condition (2 mmol of substrate,
4 equiv of 2 to acid and 5 mol % of catalyst at room temper-
Ph2SiH2 (2)
[RhCl(cod)]2 / 4PPh3
O
1 M NaOH
O
5
THF, rt
1h
OH
5
OH
3f 63%
ð2Þ

1858 Bull. Chem. Soc. Jpn., 78, No. 10 (2005)
Table 3. Reduction of Decanoic Acid (4a) by HydrosilanesaÞ
Reduction of Acid Derivatives by Rh–Silane
Entry
Catalyst/mol %bÞ
Silane/equiv
YieldcÞ/% of 3a
1
2
3
4
5
6
7
8
9
10
[RhCl(cod)]2/4PPh3 (5)
[RhCl(cod)]2/4PPh3 (5)
[RhCl(cod)]2/4PPh3 (5)
[RhCl(cod)]2/4PPh3 (5)
[RhCl(cod)]2/4PPh3 (2.5)
[RhCl(cod)]2/4PPh3 (1)
[RhCl(cod)]2/4PPh3 (5)
[RhCl(cod)]2/4PPh3 (5)
[RhCl(cod)]2/4PPh3 (5)
[RhCl(cod)]2/2BINAP (5)
Ph2SiH2 (4)
Ph2SiH2 (3)
Ph2SiH2 (2)
Ph2SiH2 (1)
Ph2SiH2 (4)
Ph2SiH2 (4)
PhSiH3 (4)
Ph3SiH (4)
Et3SiH (4)
Ph2SiH2 (4)
95
90
52
20
73
50
92
0
0
97
a) Reaction conditions: decanoic acid 4a (2.0 mmol), silane, catalyst, THF (2 mL), room temper-
ature, and 48 h. Workup: 1 M NaOH aq. b) mol % of Rh atom to 4a. c) Determined by 1H NMR
spectroscopic analysis by an internal standard (bibenzyl) method.
Table 4. Reduction of Carboxylic Acids 4 by Diphenylsilane (2) in the Presence of [RhCl(cod)]2/4PPh3
or [RhCl(PPh3)3]aÞ
Entry
Carboxylic acid
R =
YieldbÞ/% of 3
[RhCl(cod)]2/4PPh3
[RhCl(PPh3)3]
90
1
2
3
4
5
6
7
8
9
4a
4b
4c
4d
4f
4g
4h
4i
C9H19
C7H15
C15H31
3a
3g
3h
3i
95
85
87cÞ
75cÞ
63
90c),d)
79
62cÞ
86cÞ
70cÞ
67
C4H9CH(C2H5)
76cÞ
47cÞ
99cÞ;eÞ
80cÞ
Br(CH2)4
C8H17CH=CH(CH2)7
cyclohexyl-CH2
C6H5
C6H5(CH2)2
C6H5OCH(CH3)
4-BrC6H4CH2
3j
3k and 3l
3m
3d
4j
4k
4l
3n
3o
3p
93cÞ
77cÞ
10
11
a) Reaction conditions for [RhCl(cod)]2/4PPh3: [RhCl(cod)]2 (0.025 mmol), PPh3 (0.10 mmol),
Ph2SiH2 (8.0 mmol), carboxylic acid (2.0 mmol), THF (2.0 mL), 48 h, and rt. For [RhCl(PPh3)3]:
[RhCl(PPh3)3] (0.05 mmol), Ph2SiH2 (6.0 mmol), carboxylic acid (2.0 mmol), THF (2.0 mL), 24 h,
and 50 ꢁC. b) Determined by 1H NMR spectroscopic analysis by an internal standard (bibenzyl) meth-
od. c) Workup: 6 M NaOH aq. d) Oleyl alcohol (3k, 63%) and octadecanol (3l, 27%) were formed. e)
Oleyl alcohol (3k, 70%) and octadecanol (3l, 29%) were formed.
ature for 48 h in THF (2 mL)), various carboxylic acids were
reported that tertiary amide was reduced to tertiary amine by
hydrosilylation using Rh complex.13 In their reaction, primary
and secondary amides and esters were not reduced.
In our reduction, secondary amides 5 were reduced to sec-
ondary amines 6 in up to 97% yields (Table 5). When sub-
strates have bulky substituents, yields of amines 6 were mod-
erate, and some imines 7 were produced. [RhCl(cod)]2/4PPh3
showed better catalytic activity than [RhCl(PPh3)3] for this
reduction of amides.
allowed to be reduced (Table 4). Long chain carboxylic acids
were reduced efficiently to give the corresponding alcohols in
good yields, while sterically hindered carboxylic acids and
benzoic acids were reduced in lower yields. Bromo substitu-
ents on alkyl and aryl survived in this reduction (Entries 5
and 11). Substrate 4g with olefinic part (C=C) was reduced
to a mixture of unsaturated alcohol (3k) and saturated alcohol
(3l) (Entry 6).
Reduction of Amide to Amine. Carboxylic amides are
Reaction of primary amides, such as benzamide and octyl-
amide, gave a complex mixture. In the case of benzonitrile,
no reaction proceeded at all. This reduction system can be
applied to esters, carboxylic acids, and secondary amide at
Ph2SiH2 (2)
rhodium catalyst
NHR2
THF, rt
O
6 M NaOH
R1
ꢁ
room temperature and acetals and orthoesters14b at 50–60 C.
ð4Þ
At room temperature, halide, alkoxy, acetal, hydroxyl, amine,
and nitrile may survive during the reduction using diphenyl-
silane in the presence of rhodium complex.
Reaction Mechanism. The reaction mechanism is not
clear yet. Trichlorosilane under radiation of ꢀ-waves was
known to reduce esters to the corresponding ethers via a radi-
5
R1CH2NHR2
6
one of the carboxylic acid derivatives and can usually be
reduced to amines by the reduction with LiAlH4. Ito et al.

T. Ohta et al.
Bull. Chem. Soc. Jpn., 78, No. 10 (2005) 1859
Table 5. Reduction of Amides 5 in the Presence of Rh ComplexesaÞ
Amide 5
YieldbÞ/% of 6
[RhCl(cod)]2/4PPh3
Entry
R1
R2
[RhCl(PPh3)3]
1
2
3
4
5
6
7
5a
5b
5c
5d
5e
5f
C6H5
C6H5
C6H5
C6H5
C6H5
C9H19
C9H19
(CH3)2CH
(CH3)3C
C10H21
C6H5CH2
2,6-(CH3)2C6H3
(CH3)2CH
(CH3)3C
6a
6b
6c
6d
6e
6f
80
52eÞ
86
87
79
88
59
52c),d)
57c),f)
30cÞ
97cÞ
45c),g)
86cÞ
48c),h)
5g
6g
a) Reaction conditions for [RhCl(cod)]2/4PPh3: [RhCl(cod)]2 (0.025 mmol), PPh3 (0.10 mmol),
Ph2SiH2 (8.0 mmol), amide (2.0 mmol), THF (2.0 mL), 48 h, and rt. For [RhCl(PPh3)3]:
[RhCl(PPh3)3] (0.05 mmol), Ph2SiH2 (6.0 mmol), amide (2.0 mmol), THF (2.0 mL), 6 h, and 50
1
ꢁC. b) Determined by H NMR. c) Work up: 6 M NaOH aq. d) Imine 7a was formed in 5% yield.
e) Imine 7b was formed in 15% yield. f) Imine 7b was formed in 20% yield. g) Imine 7e was formed
in 40% yield. h) Imine 7g was formed in 10% yield.
H
LnRh
+
H2SiR''2
LnRh SiHR''2
8
H
H
LnRh SiHR''2
LnRh SiHR''2
O
H
C
OSiHR''2
8
8
C
R
R'
R
N
H
NR'
C
R'
-R''2HSiOSiHR''2
R
N
7
5
H
LnRh SiHR''2
NaOH aq.
H2
C
8
R
NHR'
6
Scheme 1.
cal mechanism.17 Even though the formation of a trace amount
of ethers was observed in our catalysis, high alcohol selectiv-
ities (more than 95% selectivities of alcohols in each case)
may rule out such a radical mechanism. Furthermore, the reac-
tions under light or under dark showed no difference in yields
of the products. In deoxylation of esters to ethers11 or of
amides to amines13 by hydrosilylation using Mn or Rh com-
plexes and in reduction of esters to alcohols by Ti complex,9
oxidative addition of silane to a metal complex was suggested.
It is considered that our reaction also proceeds through oxida-
tive addition of silane to a Rh complex producing hydrido-
(silyl)rhodium, followed by reduction of the ester with this
rhodium hydride species to give the aldehyde. Then, the alde-
hyde was reduced by hydrido(silyl)rhodium species again.
In the case of the reduction of carboxylic acid, the same
mechanism described above was again considered. That is,
the carboxylic acid reacts with silane to give silyl ester, and
then this silyl ester is reduced to the alcohol by hydrido(silyl)-
rhodium species.
ilar mechanism as LiAlH4. On the other hand, our system can
reduce the secondary amide to a secondary amine. Further-
more, amides with sterically bulky substituents were often
converted to imines. This indicates that the mechanism is dif-
ferent for the reductions of tertiary amide and for those of sec-
ondary amide.18 Basically, secondary amide may be reduced to
give the imine first, and then the imine is reduced to the amine
(Scheme 1). Although the reduction of imine may need the
coordination of the imine to catalyst center, the bulky group
substituted on the nitrogen atom of the imine makes the imine
difficult to coordinate to catalyst center. Therefore, reduction
of imine becomes slow, and such amides gave a mixture of
the amine and the imine.
Conclusion
Rh-catalyzed reduction of carboxylic acid derivatives, such
as ester, carboxylic acid, and amide, using diphenylsilane pro-
ceeded smoothly. Esters and carboxylic acids were reduced to
corresponding alcohols in up to 99% yields, while secondary
amides were converted to secondary amine in up to 97% yield.
For esters and carboxylic acids, reduction of sterically bulky
substrates was sluggish. Amides with a bulky substituent on ni-
Reduction of tertiary amide was reported by Ito et al. using
a similar rhodium phosphine complex as a catalyst.13 In their
report, hydrido(silyl)rhodium species reduced amide by a sim-

1860 Bull. Chem. Soc. Jpn., 78, No. 10 (2005)
Reduction of Acid Derivatives by Rh–Silane
Hexadecanol (3h): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼ 6:8 Hz,
3H, –CH3), 1.20–1.40 (m, 26H, –CH2(CH2)13CH3), 1.52–1.61
(m, 2H, –CH2CH2OH), 3.61 (t, J ¼ 6:4 Hz, 2H, –CH2OH).
2-Ethylhexanol (3i): 1H NMR (CDCl3) ꢁ 0.85–0.93 (m, 6H,
–(CH2)3CH3 and –CHCH2CH3), 1.2–1.4 (m, 8H, –(CH2)3CH3
and –CHCH2CH3), 1.64 (m, 1H, –CH(CH2)3CH3), 3.54 (d, J ¼
6:8 Hz, 2H, –OCH2–).
5-Bromopentanol (3j): 1H NMR (CDCl3) ꢁ 1.45–1.60 (m,
4H, –(CH2)2–), 1.86–1.90 (m, 2H, –CH2CH2Br or –CH2CH2OH),
3.41 (t, J ¼ 7:2 Hz, 2H, –CH2OH or –CH2Br), 3.64 (t, J ¼ 7:2
Hz, 2H, –CH2OH or –CH2Br).
trogen gave a mixture of corresponding amines and imines.
Applicability of this reduction system to other functionalities
is now underway.
Experimental
General. All solvents were dried by standard methods and
were distilled under argon.19 Commercially available compounds
were used without purification. Substrates without amides were
purchased from Wako Pure Chemical Industries, Ltd. or Tokyo
Kasei Kogyo Co., Ltd. [RhCl(cod)]2,20 [RhCl(PPh3)3],21 [RhH-
(CO)(PPh3)3],22 and amide substrates23 were prepared by the liter-
ature method. All products were known and identified by mp, bp,
IR, and/or 1H NMR analyses by comparison with that of authentic
samples as purchased from Aldrich or Tokyo Kasei Kogyo Co. 1H
nuclear magnetic resonance spectra were measured on a JEOL
JNM A-400 (400 MHz) spectrometer using tetramethylsilane as
an internal standard. IR spectra were measured on a Shimadzu
IR-408 spectrometer. Analyses by gas chromatography were per-
formed on a Shimadzu GC-14A (Column packing: 5% Silicone
SE-30 on Chromosorb W AW DMCS (80–100 mesh)). Melting
points were measured on a Yanako Model MP and were not
corrected.
Reduction of Esters by Diphenylsilane in the Presence of
[RhCl(cod)]2 and PPh3. This is a typical procedure for reduc-
tion of esters, carboxylic acids, and amides. In a 20-mL Schlenk
tube were placed [RhCl(cod)]2 (12.3 mg, 0.025 mmol), PPh3
(26.2 mg, 0.10 mmol), and THF (2 mL). To the resulting clear so-
lution were added ethyl decanoate (1a) (0.46 mL, 2.0 mmol) and
Ph2SiH2 (2) (1.11 mL, 6.0 mmol), and the solution was stirred at
room temperature for 3 d. Bibenzyl (0.342 g, 2 mmol, as an inter-
nal standard), THF (10 mL), and 1 M NaOH aq (10 mL) were add-
ed, and the mixture was stirred for 3 h. A mixture of the products
and bibenzyl was obtained by extraction with diethyl ether, fol-
lowed by concentration. The yield was determined by 1H NMR
spectroscopic analysis using an internal standard method. Other-
wise, 6 M NaOH aq was used for hydrolysis, when 1 M NaOH
aq did not work well. Furthermore, 8.0 mmol of diphenylsilane
was used for the reduction of carboxylic acids and amides, and
the reaction mixture was stirred for 48 h.
Oleyl Alcohol (3k): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼ 7:2 Hz,
3H, –CH3), 1.20–1.40 and 1.54–1.62 (m, 24H, methylene), 1.95–
2.10 (m, 4H, –CH2CH=CHCH2–), 3.63 (t, J ¼ 6:4 Hz, 2H,
–CH2OH), 5.37–5.40 (m, 2H, –CH=CH–).
Octadecanol (3l): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼ 7:2 Hz,
3H, –CH3), 1.20–1.40 (m, 30H, –CH2(CH2)15CH2–), 1.54–1.62
(m, 2H, –CH2CH2OH), 3.63 (t, J ¼ 6:4 Hz, 2H, –CH2OH).
2-Cyclohexylethanol (3m): 1H NMR (CDCl3) ꢁ 0.88–1.00
(m, 2H), 1.10–1.72 (m, 11H), 3.67 (t, J ¼ 6:8 Hz, 2H, –CH2OH).
3-Phenylpropanol (3n): 1H NMR (CDCl3) ꢁ 1.82–1.92 (m,
2H, –CH2CH2OH), 2.72 (t, J ¼ 7:2 Hz, 2H, –CH2(CH2)2OH),
3.67 (t, J ¼ 7:2 Hz, 2H, –CH2OH), 7.20–7.35 (m, 5H, –C6H5).
2-Phenoxypropanol (3o): 1H NMR (CDCl3) ꢁ 1.27 (d, J ¼
6:4 Hz, 3H, –CH3), 3.70 (d, J ¼ 7:2 Hz, 2H, –CH2OH), 4.46–
4.54 (m, 1H, –OCH–), 7.2–7.36 (m, 5H, –C6H5).
2-(4-Bromophenyl)ethanol (3p): 1H NMR (CDCl3) ꢁ 2.82
(t, J ¼ 6:4 Hz, 2H, –CH2CH2OH), 3.83 (m, 2H, –CH2OH),
7.20–7.40 (m, 4H, –C6H4Br).
N-Benzylisopropylamine (6a): 1H NMR (CDCl3) ꢁ 1.06 (d,
J ¼ 6:0 Hz, 6H, –CH(CH3)2), 2.79–2.91 (m, 1H, –CH(CH3)2),
3.72 (s, 2H, –CH2Ph), 7.26–7.81 (m, 5H, –C6H5).
N-Bezyl-t-butylamine (6b): 1H NMR (CDCl3) ꢁ 1.18 (s, 9H,
–C(CH3)3), 3.72 (s, 2H, –NHCH2–), 7.26–7.74 (m, 5H, –C6H5).
N-Benzyldecylamine (6c): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼
6:8 Hz, 3H, –CH3), 1.26–1.38 (m, 14H, –(CH2)7CH3), 1.59–
1.67 (m, 2H, –CH2(CH2)7CH3), 2.32 (t, J ¼ 8:0 Hz, 2H,
–CH2(CH2)8CH3), 3.76 (s, 2H, –CH2Ph), 7.27–7.77 (m, 5H,
–C6H5).
Dibenzylamine (6d):
(–CH2Ph)2), 7.26–7.81 (m, 10H, (–C6H5)2).
N-(2,6-Dimethylphenyl)benzylamine (6e):
1H NMR (CDCl3) ꢁ 3.80 (s, 4H,
Decanol (3a): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼ 6:8 Hz, 3H,
–CH3), 1.18–1.38 (br, 14H, –CH2(CH2)7CH3), 1.54–1.68 (m,
2H, –CH2CH2OH), 3.63 (t, J ¼ 6:8 Hz, 2H, –CH2OH).
1H NMR
(CDCl3) ꢁ 2.27 (s, 6H, –C6H3(CH3)2), 4.10 (s, 2H, –CH2Ph),
7.11–7.93 (m, 8H, –C6H5 and –C6H3(CH3)2).
Tetradecanol (3b): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼ 6:8 Hz,
3H, –CH3), 1.14–1.32 (br, 24H, –CH2(CH2)12CH3), 1.44–1.57 (m,
2H, –CH2CH2OH), 3.64 (t, J ¼ 6:8 Hz, 2H, –CH2OH).
N-Isopropyldecylamine (6f): 1H NMR (CDCl3) ꢁ 0.88 (t,
J ¼ 6:8 Hz, 3H, –CH3), 0.99 (d, J ¼ 6:8 Hz, 6H, –CH(CH3)2),
1.18–1.29 (m, 14H, –(CH2)7CH3), 1.57–1.65 (m, 2H, –CH2-
(CH2)7CH3), 2.46 (t, J ¼ 8:0 Hz, 2H, –NHCH2–), 2.60–2.75
(m, 2H, –NHCH(CH3)2).
2-Phenylethanol (3c): 1H NMR (CDCl3) ꢁ 2.87 (t, J ¼ 6:6
Hz, 2H, –CH2CH2O–), 3.86 (q, J ¼ 6:6 Hz, 2H, –CH2CH2O–),
7.18–7.32 (m, 5H, –C6H5).
Benzyl Alcohol (3d):
1H NMR (CDCl3) ꢁ 4.51 (s, 2H,
N-t-Butyldecylamine (6g): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼
6:8 Hz, 3H, –CH3), 1.09 (s, 9H, –C(CH3)3), 1.19–1.31 (m, 14H,
–(CH2)7CH3), 1.57–1.70 (m, 2H, –CH2(CH2)7CH3), 2.52 (t, J ¼
7:2 Hz, 2H, –NHCH2–).
–CH2OH), 7.17–7.35 (m, 5H, C6H5).
7-Bromoheptanol (3e): 1H NMR (CDCl3) ꢁ 1.23–1.48 (m,
8H, –(CH2)4), 1.78–1.82 (m, 2H, –CH2CH2Br or –CH2CH2OH),
3.36 (t, J ¼ 6:8 Hz, 2H, –CH2OH or –CH2Br), 3.45 (t, J ¼ 6:8
Hz, 2H, –CH2OH or –CH2Br).
N-Isopropylbenzaldimine (7a): 1H NMR (CDCl3) ꢁ 1.25 (d,
J ¼ 6:0 Hz, 6H, –CH(CH3)2), 3.48–3.60 (m, 1H, –CH(CH3)2),
7.26–7.81 (m, 5H, –C6H5), 8.29 (s, 1H, –N=CH–).
1,4-Undecanediol (3f): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼ 6:8
Hz, 3H, –CH3), 1.29–1.70 (m, 16H, –(CH2)6CH3 and
–(CH2)2CH2OH), 3.59–3.80 (m, 3H, –CH(CH2)6CH3 and
–CH2OH).
N-t-Butylbenzaldimine (7b): 1H NMR (CDCl3) ꢁ 1.30 (s, 9H,
–C(CH3)3), 7.26–7.74 (m, 5H, –C6H5), 8.28 (s, 1H, –N=CH–).
N-(2,6-Dimethylphenyl)benzaldimine (7e):
1H NMR
Octanol (3g): 1H NMR (CDCl3) ꢁ 0.88 (t, J ¼ 6:8 Hz, 3H,
–CH3), 1.20–1.40 (m, 10H, –(CH2)5CH3), 1.52–1.60 (m, 2H,
–CH2CH2OH), 3.62 (t, J ¼ 6:8 Hz, 2H, –CH2OH).
(CDCl3) ꢁ 2.14 (s, 6H, –C6H3(CH3)2), 7.11–7.93 (m, 8H, –C6H5
and –C6H3(CH3)2), 8.22 (s, 1H, –CH=N–).
N-t-Butyldecylaldimine (7g): 1H NMR (CDCl3) ꢁ 0.88 (t,

T. Ohta et al.
Bull. Chem. Soc. Jpn., 78, No. 10 (2005) 1861
J ¼ 6:8 Hz, 3H, –CH3), 1.05 (s, 9H, –C(CH3)3), 1.19–1.31 (m,
14H, –CH2(CH2)7CH3), 1.57–1.70 (m, 2H, –CH2(CH2)7CH3),
8.28 (s, 1H, –CH=N–).
558. c) C. Chuit, R. J. P. Corriu, R. Perz, and C. Reye, Synthesis,
1982, 981.
9
a) S. C. Berk, K. A. Kreutzer, and S. L. Buchwald, J. Am.
Chem. Soc., 113, 5093 (1991). b) S. C. Berk and S. L. Buchwald,
J. Org. Chem., 57, 3751 (1992). c) X. Verdaguer, S. C. Berk,
and S. L. Buchwald, J. Am. Chem. Soc., 117, 12641 (1995). d)
X. Verdaguer, M. C. Hansen, S. C. Berk, and S. L. Buchwald,
J. Org. Chem., 62, 8522 (1997), and references cited therein.
10 a) K. Matsubara and H. Nagashima, J. Synth. Org. Chem.
Jpn., 63, 122 (2005). b) H. Nagashima and K. Matsubara, Jpn.
Kokai Tokkyo Koho, JP2003261578 (2003); Chem. Abstr., 139,
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Nagashima, J. Org. Chem., 67, 4985 (2002).
We are grateful to Dr. Takayuki Yamashita for helpful dis-
cussions during the course of this work. This work was partial-
ly supported by Doshisha University’s Research Promotion
Fund and by a grant to RCAST at Doshisha University from
the Ministry of Education, Culture, Sports, Science and Tech-
nology of Japan.
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