Lithium amidoborane, a highly chemoselective reagent for the reduction of α,β-unsaturated ketones to allylic alcohols

Article abstract of DOI:10.1039/c1ob06368e

Lithium amidoborane (LiNH₂BH₃, LiAB for short), is capable of chemoselectively reducing α,β-unsaturated ketones to the corresponding allylic alcohols at ambient temperature. A mechanistic study shows that the reduction is via a double hydrogen transfer process. The protic H(N) and hydridic H(B) in amidoborane add to the O and C sites of the carbonyl group, respectively.

Full text of DOI:10.1039/c1ob06368e

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Lithium amidoborane, a highly chemoselective reagent for the reduction of
a,b-unsaturated ketones to allylic alcohols†
Weiliang Xu,b Yonggui Zhou,a Ruimin Wang,c Guotao Wua and Ping Chen*a
Received 11th August 2011, Accepted 6th October 2011
DOI: 10.1039/c1ob06368e
Lithium amidoborane (LiNH2BH3, LiAB for short), is capable of chemoselectively reducing
a,b-unsaturated ketones to the corresponding allylic alcohols at ambient temperature. A mechanistic
study shows that the reduction is via a double hydrogen transfer process. The protic H(N) and hydridic
H(B) in amidoborane add to the O and C sites of the carbonyl group, respectively.
Introduction
The chemoselective reduction of a,b-unsaturated carbonyl com-
pounds to allylic alcohols is one of the important processes
in synthetic organic chemistry.1 Catalytic hydrogenation,2 trans-
fer hydrogenation3 and borohydride reduction1a are traditional
methods that can be applied for this transformation. Metal
borohydrides, such as NaBH4, are usually employed as the primary
choice due to its low cost and convenient operation.1a Reduction
Scheme 1 1,2- and 1,4-reduction of a,b-unsaturated ketones.
of a,b-unsaturated ketones by metal borohydrides generally gives
two possible products, i.e., the corresponding allylic alcohol a
through a 1,2-reduction and the corresponding saturated carbonyl
compound b after a 1,4-reduction (Scheme 1). Which product
is formed depends on the steric hindrance of the double bonds
and the reaction conditions.4 Meanwhile, a substantial amount of
fully reduced alcohols are also produced in some cases.5 Improved
1,2-selective reductions of a,b-unsaturated carbonyl groups can
be achieved by introducing additives, such as stoichiometric
lanthanide chlorides (CeCl3) developed by Luche and his co-
workers,6 to the NaBH4 reaction system. One of the disadvantages
of such a process is the formation of toxic cerium byproducts.
Besides lanthanide chlorides, other additives such as calcium
chloride (CaCl2),7 guanidine chloride8 and pentafluorophenol,9
are also employed to achieve high selectivity towards the 1,2-
reduction route. Another reliable reagent for the 1,2-reduction of
conjugated carbonyl compounds is a lithium aminoborohydride
(LiNRR¢BH3), such as lithium pyrrolidinoborohydride,10 which
can be applied to most of the a,b-unsaturated carbonyl com-
pounds with an essentially quantitative yield of allylic alcohols
upon hydrolysis/solvolysis of the intermediate borates. Herein, we
report an effective chemoselective reagent, lithium amidoborane
(LiNH2BH3, or LiAB for short), which can directly reduce
a,b-unsaturated carbonyl compounds to allylic alcohols under
ambient conditions.
Ammonia borane (NH3BH3, AB for short), a promising solid-
state hydrogen storage material,11 has been used to reduce unsat-
urated organic functional groups for a long time.12 Berke and his
co-workers recently reported that AB reduces C N groups13a and
◦
polarizes C C groups13b at 60 C or room temperature through
a double hydrogen transfer process, due to the coexistence of a
protic H(N) and hydridic H(B) in the AB structure. Recently,
metal amidoboranes (M(NH2BH3)n, or MAB for short), which are
synthesized by substituting one of the protic hydrogen atoms of
AB by an alkali or alkaline-earth element, have been investigated
intensively for hydrogen storage due to their high hydrogen
content and mild dehydrogenation conditions.14 LiAB can release
◦
hydrogen at ca. 90 C in the solid-state15 or at ca. 40 ◦C when
in a THF solution.15a Notably, lithium amidoborane can be
conveniently obtained by reacting LiH with AB in THF (Reaction
(1)).
LiH + NH3BH3 ⎯T⎯HF⎯→LiNH2BH3 + H2
(1)
aDalian Institute of Chemical Physics, Dalian, China. E-mail: pchen@
dicp.ac.cn; Fax: +86 411-84379583; Tel: +86 411-84379905
In comparison with lithium aminoborohydrides, LiAB has two
protic Hs bonded with N. It is of interest to figure out whether
the dissociation of the B–H and N–H of LiAB, and the transfer
of those oppositely charged Hs to unsaturated functional groups
can be realized.
bNational University of Singapore, Singapore
cInner Mongolia University, Huhhot, China
† Electronic supplementary information (ESI) available: See DOI:
10.1039/c1ob06368e
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Table 1 Reducing 1a by LiAB in different solventsa
Table 2 Reduction of a,b-unsaturated ketones by LiABa
Entry
R1/R2
Time/h
Yield %b
Entry
Solvent
Time/h
Conv. %
2a/3a
1
2
3
4
5
6
7
8
Ph/Ph
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
85c
86
87
88
92
90
80
78
82
88
91
90
90
93
86
88
86
1
2
3
4
5
6
CH2Cl2
CHCl3
CCl4
Et2O
Glyme
THF
3
3
3
3
3
0.5
78
45
25
93
93
>99
52/26
26/19
2/23
36/57
85/8
o-MeC6H4/Ph
m-MeC6H4/Ph
p-MeC6H4/Ph
p-MeOC6H4/Ph
p-ClC6H4/Ph
p-NO2C6H4/Ph
p-CH3C(O)NHC6H4/Ph
Ph/p-MeC6H4
Ph/p-MeOC6H4
Ph/p-ClC6H4
> 99/1
a Reaction conditions: 1 mmol of 1a reacted with 0.5 mmol of LiAB in
5 ml of solvent at ambient temperature. Conversion rates of 1a and 2a/3a
were determined by GC analysis.
9
10
11
12
13
14
15
16
17
Ph/p-NO2C6H4
Ph/p-CNC6H4
Ph–CH CH/Ph
Ph/CH3
Results and Discussion
We first performed the reduction of chalcone 1a by LiAB in a
number of common solvents to figure out the solvent effect. The
results are listed in the Table 1. Protic solvents, such as methanol,
are unsuitable due to the solvolysis of LiAB. Ether solvents (Table
1, entries 4–6) gave higher conversion rates of 1a than others which
is probably due to the facile solubility of LiAB in those solvents.
1,3-Diphenylpropanol 3a, the fully reduced product, was observed
in most cases (Table 1, entries 1–5). However, the THF mediated
reaction showed the best performance, i.e., fastest reaction rate,
highest chemoselectivity and 3a was almost undetectable.
In light of this result, a series of a,b-unsaturated ketones were
chosen to react with LiAB in THF at ambient temperature. The
molar ratio of ketone and LiAB was 2 : 1. The results are listed
in Table 2. In all the cases, it took ca. half an hour to reach 99%
conversion rates of ketones giving rise to the corresponding allylic
alcohols regardless of the steric and electronic effect of substituents
R1 and R2.
n-C5H11/n-C4H9
18
0.5
90
a The ratio of substrate and LiAB was 2 to 1 and the concentration of LiAB
was 0.083 M. b Isolated overall yields. c The yield of the allylic alcohol was
87% when the molar ratio of LiAB and chalcone was 1 : 1.
was obtained (see ESI†). It shows the transfer of the deuterium on
the B of the LiAB to the C of the carbonyl group in the reduction.
These experimental results confirm that both the protic H(N) and
hydridic H(B) in LiAB participate in the reduction and add directly
to the O and C sites of the ketone, respectively (Scheme 2). Our
interpretation is that the first step of the reduction may be the
dissociation of the B–H bond of LiAB with the assistance of the
metal cation.17 According to the HSAB (hard and soft acids and
bases) concept, the hard nucleophile hydride has a higher chance
In 1996, Myers and his co-workers reported that LiAB provides
a nucleophilic hydride that reduces tertiary amides into primary
alcohols.16 To the best of our knowledge, this is the first report on
using LiAB to selectively reduce a,b-unsaturated ketones to allylic
alcohols.
It is noted that the selective reduction of a,b-unsaturated
ketones can also be carried out on an enlarged scale. We up-
scaled the reduction to 30 mmol of 1a and 15 mmol of LiAB
under the same conditions and obtained an 87% isolated yield of
2a in 30 min. Noting that LiAB can be facilely produced, it can be
considered that the method demonstrated here may be a practical
and viable route for the selective reduction of conjugated ketones.
As discussed in the introduction section, the distinction of LiAB
and LiNRR¢BH3 lies in the presence of two protic Hs in LiAB.
Moreover, allylic alcohols were obtained directly from ketones–
LiAB without hydrolysis. Therefore, it can be deduced that the
protic H(N) of LiAB transfers to the O site of the carbonyl
group. In order to prove this deduction, LiND2BH3 (LiA(D)B)
was employed to react with 1a in THF. A singlet at d = 0.45
ppm, attributed to O–D, was observed in the 2H NMR spectrum
evincing the transfer of deuterium from N to the O of the carbonyl
group upon reduction (see ESI†). In a related experiment, reacting
LiNH2BD3 (LiAB(D)) and 1a in THF, a deuterated product at the
carbon end of the C O bond, which was of 88% isolated yield,
Scheme 2 The deuterium labelling study and the reaction model for LiAB
with ketones.
368 | Org. Biomol. Chem., 2012, 10, 367–371
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of bonding with the C of the C O, which is a hard electrophile,
giving rise to the 1,2-reduction product.6a
The solution can be directly used in the reducing reaction without
further purification.
The direct reduction of ketones to alcohols by LiAB through a
dissociation of both the B–H and N–H bonds resembles the double
hydrogen transfer (DHT) hydrogenation of carbonyl compounds,
which is via a dihydride route catalyzed by transitional metals18 or
the Meerwein–Ponndorf–Verley (MPV) reduction.19 2-Propanol,
formic acid and its salts, and the Hantzsch ester are traditional
hydrogen donors in hydrogen transfer reactions which provide
two hydrogens to the reactants.20 However, vigorous conditions or
catalysts are needed to complete the reduction. LiAB rapidly trans-
fers two hydrogens to the ketones at ambient temperature without
the employment of catalysts, showing superior performances in
both reactivity and selectivity.
General experimental procedure for reducing a,b-unsaturated
ketones with LiAB
5 ml 0.1 M LiAB solution (THF as solvent) was added to 1 ml 1 M
ketone solution (THF as solvent) at room temperature in a closed
glass bottle under argon gas protection. A FT-IR spectrometer
was used to monitor the consumption of the C O group and
the formation of the OH group. After the reaction was complete
the THF was evaporated. Then diethyl ether (3 ¥ 10 ml) was
added to the glass bottle to extract the alcohol. The diethyl ether
solution also underwent centrifugation to remove any suspended
substances. Next, the diethyl ether mixture was evaporated to leave
a transparent liquid residue which was further purified by column
chromatography (silica gel, 200–300 mesh, hexane/EtOAc (v/v,
Conclusion
1
10 : 1) as an eluent). Alcohol products were characterized by H
NMR, 13C NMR, FT-IR and GC-MS.
In summary, the highly chemoselective reduction of a,b-
unsaturated ketones to allylic alcohols was successfully achieved
by using lithium amidoborane as the reducing reagent. High
reducibility, double hydrogen transfer and chemoselectivity makes
this approach practical for the synthesis of allylic alcohols. Efforts
into exploring the use of MAB in other chemoselective reductions
of organic compounds are ongoing.
Products characterization
1,3-Diphenylprop-2-en-1-ol (entry 1, Table 2). 1H NMR (500
MHz, CDCl3, 25 ◦C; TMS): d = 2.07 (s, 1H; OH), 5.38 (s, 1H; CH),
6.36–6.40 (m, 1H; CH), 6.68 (d, 3JHH = 15.80 Hz, 1H; CH), 7.24–
7.42 ppm (m, 10H; ArH); 13C NMR (126 MHz, CDCl3, 25 ◦C;
CDCl3): d = 75.11, 126.32, 126.59, 127.75, 127.77, 128.54, 128.60,
130.56, 131.51, 136.53, 142.78 ppm; FT-IR (film): nmax = 3342,
3077, 3059, 3027, 1599, 1449, 1493, 1092, 1067, 1009, 966, 744,
695 cm-1; MS (EI): m/z (%) 209 [M–H]+ (47), 105 (100), 191 (67),
178 (27), 77 (33), 115 (30).
Experimental section
General remarks
Solvents and some of the reagents were purchased commercially
and used without further purification: THF (Honywell, HPLC,
further dried over NaH), diethyl ether (Honeywell, HPLC),
hexane (Beijing HuaGong, AR), EtOAc (Beijing HuaGong, AR),
ammonia borane (Sigma–Aldrich, 97%), lithium hydride (Alfa,
98%), chalcone (Table 2, entry 1, Alfa, 97%), 4-nitrochalcone
(Table 2, entry 7, Alfa, 99%), 4¢-methoxychalcone (Table 2, entry
10, Alfa, 97%), 3-methyl-2-cyclohexen-1-one (Table 2, entry 17,
Alfa, 98%), 2-benzylidenecyclohexanone (Table 2, entry 18, Alfa,
98%), 4-phenyl-3-buten-2-one (Table 2, entry 15, Sigma–Aldrich,
99%). Other a,b-unsaturated ketones were synthesized from
corresponding aldehydes and ketones. The synthetic procedures
are mentioned in the ESI†.
1-Phenyl-3-o-tolylprop-2-en-1-ol (entry 2, Table 2). 1H NMR
(500 MHz, CDCl3, 25 ◦C; TMS): d = 2.07 (s, 1H; OH), 2.37 (s, 3H;
3
CH3), 5.41 (s, 1H; CH), 6.30–6.40 (m, 1H; CH), 6.92 (d, JHH
=
15.60 Hz, 1H; CH), 7.15–7.44 ppm (m, 9H; ArH); 13C NMR (126
MHz, CDCl3, 25 ◦C; CDCl3): d = 19.78, 75.33, 125.79, 126.06,
126.34, 127.65, 127.77, 128.41, 128.61, 130.28, 132.87, 135.62,
142.86 ppm; FT-IR (film): nmax = 3349, 3061, 3062, 2969, 2863,
1601, 1487, 1463 cm-1; MS (EI): m/z (%) 224 [M]+ (3), 105 (100),
206 (16), 77 (26).
1-Phenyl-3-m-tolylprop-2-en-1-ol (entry 3, Table 2). 1H NMR
(500 MHz, CDCl3, 25 ◦C; TMS): d = 2.16 (s, 1H; OH), 2.34 (s, 3H;
NMR spectra were recorded on a Bruker DRX-500 instrument.
Chemical shifts, quoted in ppm, are relative to the internal or
external standard (only for 2H NMR): singlet d = 0 ppm of TMS
3
CH3), 5.38 (s, 1H; CH), 6.37–6.40 (m, 1H; CH), 6.66 (d, JHH
=
15.55 Hz, 1H; CH), 7.07–7.44 ppm (m, 9H; ArH); 13C NMR (126
MHz, CDCl3, 25 ◦C; CDCl3): d = 21.35, 75.16, 123.81, 126.34,
127.30, 127.76, 128.46, 128.60, 130.68, 131.36, 136.48, 138.11,
142.85 ppm; FT-IR (film): nmax = 3350, 3056, 3028, 2955, 2919,
2862, 1602, 1491, 1453 cm-1; MS (EI): m/z (%) 224 [M]+ (15), 105
(100), 119 (36), 77 (33).
for 1H NMR; the middle of the CDCl3 triplet d = 77 ppm for 13
C
2
NMR; singlet d = 7.26 ppm of CDCl3 for H NMR. IR spectra
were obtained by a Varian 3100 FTIR spectrophotometer using
a Resolution Pro program. GC results were detected using the
RAMIN 2060 series. The model of the capillary column was HP-
5. MS analyses were performed on an Agilent 6890–5973 GC–MS.
1-Phenyl-3-p-tolylprop-2-en-1-ol (entry 4, Table 2). 1H NMR
(500 MHz, CDCl3, 25 ◦C; TMS): d = 1.99 (s, 1H; OH), 2.33 (s, 3H;
Synthesis of LiAB, LiA(D)B and LiAB(D)
3
CH3), 5.38 (s, 1H; CH), 6.31–6.36 (m, 1H; CH), 6.66 (d, JHH
=
1 mmol NH3BH3, ND3BH3 or NH3BD3 was first dissolved in
10 ml THF in a metal jar in a glove box. Then, 1 mmol LiH
was quickly added into the solution and the jar cap was closed.
The system was stirred at room temperature. After one equivalent
of H2 was released and detected by a pressure gauge, a clear 1
M LiAB solution was obtained and characterized by 11B NMR.
15.80 Hz, 1H; CH), 7.11–7.44 ppm (m, 9H; ArH); 13C NMR (126
MHz, CDCl3, 25 ◦C; CDCl3): d = 21.71, 75.23, 126.31, 126.51,
127.73, 128.58, 129.25, 130.50, 130.59, 133.78, 137.66, 142.88 ppm;
FT-IR (film): nmax = 3342, 2081, 3026, 2919, 2859, 1513, 1493, 1451
cm-1; MS (EI): m/z (%) 223 [M–H]+ (47), 105 (100), 207 (50), 119
(60), 77 (40).
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3
3-(4-Methoxyphenyl)-1-phenylprop-2-en-1-ol (entry 5, Table 2).
1H NMR (500 MHz, CDCl3, 25 ◦C; TMS): d = 2.04 (s, 1H; OH),
3.80 (s, 3H; CH3), 5.37 (s, 1H; CH), 6.23–6.27 (m, 1H; CH), 6.63
(d, 3JHH = 15.80 Hz, 1H; CH), 6.84 (d, 3JHH = 8.35 Hz, 2H; ArH),
7.29–7.44 ppm (m, 7H; ArH); 13C NMR (126 MHz, CDCl3, 25 ◦C;
CDCl3): d = 55.27, 75.30, 113.98, 126.28, 127.69, 127.81, 128.57,
5.37 (s, 1H; CH), 6.31–6.35 (m, 1H; CH), 6.67 (d, JHH = 15.80
Hz, 1H; CH), 7.25–7.27 ppm (m, 9H; ArH); 13C NMR (126 MHz,
CDCl3, 25 ◦C; CDCl3): d = 74.48, 126.62, 127.69, 127.97, 128.61,
128.71, 131.03, 131.08, 133.49, 136.25, 141.16 ppm; FT-IR (film):
nmax = 3334, 3078, 3059, 3027, 2957, 2925, 2870, 1597, 1490, 1449,
1404 cm-1; MS (EI): m/z (%) 244 [M]+ (36), 139 (100), 105 (60),
192 (60), 77 (33).
129.26, 129.40, 130.26, 142.99, 159.38 ppm; FT-IR (film): nmax
=
3374, 3060, 3030, 3005, 2956, 2935, 2836, 1606, 1511, 1250 cm-1;
MS (EI): m/z (%) 239 [M–H]+ (43), 121 (100), 222 (36), 178 (36),
77 (38), 105 (37).
1-(4-Nitrophenyl)-3-phenylprop-2-en-1-ol (entry 12, Table 2).
1H NMR (500 MHz, CDCl3, 25 ◦C; TMS): d = 2.19 (s, 1H; OH),
3
5.49 (s, 1H; CH), 6.27–6.32 (m, 1H; CH), 6.73 (d, JHH = 15.80
3-(4-Chlorophenyl)-1-phenylprop-2-en-1-ol (entry 6, Table 2).
Hz, 1H; CH), 7.25–7.37 ppm (m, 5H; ArH), 7.61 (d, 3JHH = 7.90
Hz, 2H; ArH), 8.22 (d, 3JHH = 7.85 Hz, 2H; ArH); 13C NMR (126
MHz, CDCl3, 25 ◦C; CDCl3): d = 74041, 123.76, 126.69, 126.96,
128.34, 128.69, 130.07, 132.30, 135.82, 147.39, 149.71 ppm; FT-IR
(film): nmax = 3427, 3107, 3081, 3027, 1855, 1600, 1519, 1345 cm-1;
MS (EI): m/z (%) 237 [M–H2O]+ (98), 105 (100), 150 (65), 77 (40).
1H NMR (500 MHz, CDCl3, 25 ◦C; TMS): d = 2.07 (s, 1H; OH),
3
5.37 (d, JHH = 6 Hz, 1H; CH), 6.33–6.37 (m, 1H; CH), 6.64 (d,
3JHH = 15.80 Hz, 1H; CH), 7.25–7.42 ppm (m, 9H; ArH); 13C
NMR (126 MHz, CDCl3, 25 ◦C; CDCl3): d = 74.99, 126.32, 127.79,
127.93, 128.69, 128.71, 129.19, 132.16, 133.40, 135.05, 142.58 ppm;
FT-IR (film): nmax = 3338, 3060, 3029, 2958, 2924, 2856, 1593, 1491,
1452, 1404 cm-1; MS (EI): m/z (%) 244 [M]+ (37), 105 (100), 139
(32), 190 (27), 77 (33).
4-(1-Hydroxy-3-phenylallyl)benzonitrile (entry 13, Table 2). 1H
NMR (500 MHz, CDCl3, 25 ◦C; TMS): d = 2.31 (s, 1H; OH), 5.43
(d, 3JHH = 6.85 Hz, 1H; CH), 6.26–6.31 (m, 1H; CH), 6.70 (d, 3JHH
=
3-(4-Nitrophenyl)-1-phenylprop-2-en-1-ol (entry 7, Table 2). 1H
NMR (500 MHz, CDCl3, 25 ◦C; TMS): d = 2.15 (s, 1H; OH), 5.44
(s, 1H; CH), 6.55–6.58 (m, 1H; CH), 6.78 (d, 3JHH = 15.80 Hz, 1H;
CH), 7.33–8.17 ppm (m, 9H; ArH); 13C NMR (126 MHz, CDCl3,
25 ◦C; CDCl3): d = 74.68, 123.97, 126.40, 127.10, 127.85, 128.24,
15.80 Hz, 1H; CH◦), 7.26–7.65 ppm (m, 9H; ArH); 13C NMR (126
MHz, CDCl3, 25 C; CDCl3): d = 74.51, 111.37, 118.78, 126.68,
126.89, 128.26, 128.68, 130.25, 132.05, 132.37, 135.92, 147.87 ppm;
FT-IR (film): nmax = 3426, 3059, 3027, 2924, 2229, 1607, 1494, 967
cm-1; MS (EI): m/z (%) 235 [M]+ (100), 105 (98), 217 (50), 130
(60), 91 (50).
128.85, 136.23, 142.03, 143.12, 147.02 ppm; FT-IR (film): nmax
=
3392, 3105, 3062, 3030, 2931, 2850, 1596, 1514, 1342 cm-1; MS
1,5-Diphenylpenta-2,4-dien-1-ol (entry 14, Table 2). 1H NMR
(EI): m/z (%) 254 [M–H]+ (30), 105 (100), 178 (12), 77 (35).
◦
(500 MHz, CDCl3, 25 C; TMS): d = 2.01 (s, 1H; OH), 5.32 (d,
N-(4-(3-Hydroxy-3-phenylprop-1-enyl)phenyl)acetamide (entry
8, Table 2). 1H NMR (500 MHz, CDCl3, 25 ◦C; TMS): d =
2.04 (s, 1H; OH), 2.15 (s, 3H; CH3), 2.19 (s, 1H; NH), 5.36 (s, 1H;
CH), 6.29–6.33 (m, 1H; CH), 6.63 (d, 3JHH = 15.80 Hz, 1H; CH◦ ),
7.25–7.58 ppm (m, 9H; ArH); 13C NMR (126 MHz, CDCl3, 25 C;
CDCl3): d = 24.52, 75.13, 119.85, 125.89, 126.31, 127.20, 127.74,
128.45, 129.41. 129.91, 130.85, 132.69, 142.86 ppm; FT-IR (film):
nmax = 3303, 3113, 3030, 2975, 2871, 1669, 1597, 1534, 1513, 1410
cm-1; MS (EI): m/z (%) 267 [M]+ (30), 105 (100).
3JHH = 6.35 Hz, 1H; CH), 5.98–6.02 (m, 1H; CH), 6.45–6.50 (m,
3
1H; CH), 6.58 (d, JHH = 15.65 Hz, 1H; CH), 6.75–6.81 (m, 1H;
CH), 7.21–7.42 ppm (m, 10H; ArH); 13C NMR (126 MHz, CDCl3,
25 ◦C; CDCl3): d = 74.86, 126.30, 126.39, 127.65, 127.78, 128.07,
128.60, 130.98, 133.23, 135.49, 137.08, 142.79 ppm; FT-IR (film):
nmax = 3290, 3080, 3059, 3026, 1599, 1492, 1449 cm-1; MS (EI):
m/z (%) 235 [M–H]+ (25), 105 (100), 217 (90), 128 (50), 202 (50),
77 (33).
4-Phenylbut-3-en-2-ol (entry 15, Table 2). 1H NMR (500 MHz,
CDCl3, 25 ◦C; CHCl3): d = 1.36 (d, 3JHH = 6.39 Hz, 3H; CH3), 1.56
(s, 1H; O–H), 4.47–4.45 (m, 1H; CH), 6.23–6.28 (m,1H, CH), 6.56
3-Phenyl-1-p-tolylprop-2-en-1-ol (entry 9, Table 2). 1H NMR
(500 MHz, CDCl3, 25 ◦C; TMS): d = 1.98 (d, 3JHH = 3.45 Hz, 1H;
3
OH), 2.35 (s, 3H; CH3), 5.36 (t, JHH = 4.52 Hz, 1H; CH), 6.36–
(d, 3JHH = 15.93 Hz, 1H; CH), 7.21–7.38 ppm (m, 5H; ArH); 13
C
6.41 (m, 1H; CH), 6.68 (d, JHH = 15.85 Hz, 1H; CH), 7.18–7.39
NMR (126 MHz, CDCl3, 25 ◦C; CDCl3): d = 23.42, 68.94, 126.46,
127.64, 128.59, 129.41, 133.58, 136.72 ppm; FT-IR (film): nmax
3
ppm (m, 9H; ArH); 13C NMR (126 MHz, CDCl3, 25 ◦C; CDCl3):
d = 21.11, 74.96, 136.31, 126.58, 127.70, 128.53, 129.30, 130.31,
131.66, 136.60, 137.56, 139.86 ppm; FT-IR (film): nmax = 3338,
3083, 3026, 2971, 2919, 1599, 1578, 1509 cm-1; MS (EI): m/z (%)
223 [M–H]+ (47), 119 (100), 206 (98), 105 (60), 191 (70), 77 (40).
=
3342, 3078, 3058, 3026, 2972, 2926, 2871, 1493, 1449, 1141, 1059,
967, 748, 693 cm-1; MS (EI): m/z (%) 148 [M]+ (50), 129 (100), 105
(67), 115 (50), 132 (25), 77 (25), 91 (33).
Dodec-6-◦en-5-ol (entry 16, Table 2). 1H NMR (500 MHz,
CDCl3, 25 C; TMS): d = 0.8 (s, 6H), 1.29–1.33 (m, 12H), 2.01–
2.07 (m, 4H), 4.02 (s, 2H; OH), 5.39 ppm (s, 1H; CH); 13C NMR
(126 MHz, CDCl3, 25 ◦C; CDCl3): d = 13.94, 13.98, 22.53, 22.84,
27.38, 27.76, 29.42, 30.83, 31.56, 67.30, 127.09, 139.09 ppm; FT-
IR (film): nmax = 3344, 2928, 2397, 1378, 1331, 1086 cm-1; MS (EI):
m/z (%) 184 [M]+ (9), 57 (100), 81 (39), 71 (76), 94 (35).
1-(4-Methoxyphenyl)-3-phenylprop-2-en-1-ol (entry 10, Table 2).
1H NMR (500 MHz, CDCl3, 25 ◦C; TMS): d = 1.96 (s, 1H; OH),
3.81 (s, 3H; CH3), 5.35 (s, 1H; CH), 6.36–6.41 (m, 1H; CH), 6.67
(d, 3JHH = 15.85 Hz, 1H; CH), 6.91 (d, 3JHH = 7.90 Hz, 2H; ArH),
7.23–7.39 ppm (m, 7H; ArH); 13C NMR (126 MHz, CDCl3, 25 ◦C;
CDCl3): d = 55.31, 74.66, 114.01, 126.57, 127.69, 128.54, 130.20,
131.69, 135.01, 136.61, 159.28 ppm; FT-IR (film): nmax = 3379,
3059, 3026, 2956, 2908, 2835, 1610, 1511, 1449 cm-1; MS (EI):
m/z (%) 239 [M–H]+ (43), 223 (100), 135 (85), 178 (50), 77 (35).
3-Methylcyclohex-2-enol (entry 17, Table 2). 1H NMR (500
MHz, CDCl3, 25 ◦C; TMS): d = 1.38 (s, 1H; CH), 1.55–1.61 (m,
2H, CH2), 1.68 (s, 3H; CH3), 1.72–1.92 (m, 4H), 4.17 ◦(s, 1H; OH),
5.49 (s, 1H, CH); 13C NMR (126 MHz, CDCl3, 25 C; CDCl3):
d = 18.89, 23.60, 30.06, 31.67, 65.86, 124.23, 138.72 ppm; FT-IR
1-(4-Chlorophenyl)-3-phenylprop-2-en-1-ol (entry 11, Table 2).
1H NMR (500 MHz, CDCl3, 25 ◦C; TMS): d = 2.04 (s, 1H; OH),
370 | Org. Biomol. Chem., 2012, 10, 367–371
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(film): nmax = 3342, 2935, 2862, 1447, 1376, 1033 cm-1; MS (EI):
m/z (%) 112 [M]+ (30), 97 (100), 79 (80), 69 (25).
7 H. Fujii, K. Oshima and K. Utimoto, Chem. Lett., 1991, 1847–1848.
8 A. Heydari, A. Arefi and M. Esfandyari, J. Mol. Catal. A: Chem., 2007,
274, 169–172.
2-Benzylidenecyclohexanol (entry 18, Table 2). 1H NMR (500
MHz, CDCl3, 25 ◦C; TMS): d = 1.48–1.68 (m, 5H), 1.85–2.12 (m,
3H), 2.72 (s, 1H; OH), 4.24 (s, 1H; CH), 6.52 (s, 1H; CH); 7.22–7.32
9 J. Fuller, S. Williamson and B. Singaram, J. Fluorine Chem., 1994, 68,
265–268.
10 J. C. Fuller, E. L. Stangeland, C. T. Goralski and B. Singaram,
Tetrahedron Lett., 1993, 34, 257–260.
◦
(m, 5H; ArH) 13C NMR (126 MHz, CDCl3, 25 C; CDCl3): d =
11 (a) F. H. Stephens, V. Pons and R. T. Baker, Dalton Trans., 2007,
2613; (b) A. Gutowska, L. Y. Li, Y. S. Shin, C. M. M. Wang, X. H.
S. Li, J. C. Linehan, R. S. Smith, B. D. Kay, B. Schmid, W. Shaw, M.
Gutowski and T. Autrey, Angew. Chem., Int. Ed., 2005, 44, 3578; (c) D.
W. Himmelberger, L. R. Alden, M. E. Bluhm and L. G. Sneddon, Inorg.
Chem., 2009, 48, 9883; (d) T. He, Z. T. Xiong, G. T. Wu, H. L. Chu,
C. Z. Wu, T. Zhang and P. Chen, Chem. Mater., 2009, 21, 2315; (e) R.
J. Keaton, J. M. Blacquiere and R. T. Baker, J. Am. Chem. Soc., 2007,
129, 1844.
12 (a) G. C. Andrews, Tetrahedron Lett., 1980, 21, 697; (b) G. C. Andrews
and T. C. Crawford, Tetrahedron Lett., 1980, 21, 693; (c) B. L. Allwood,
H. Shahriarizavareh, J. F. Stoddart and D. J. Williams, J. Chem. Soc.,
Chem. Commun., 1984, 1461–1464.
23.18, 26.96, 27.34, 36.58, 73.74, 120.81, 126.21, 128.07, 128.91,
137.66, 144.34 ppm; FT-IR (film): nmax = 3360, 3058, 3020, 2938,
2853, 1598, 1494 cm-1; MS (EI): m/z (%) 188 [M]+ (36), 91(100),
115 (40), 97 (80).
Acknowledgements
The authors thank the financial supports from the CAS Hundred
Talents Project (KGCX2-YW-806) and the Knowledge Innovation
Program of CAS (KJCX2-YW-H21). W. Xu thanks the schol-
arship of the National University of Singapore and the help in
experiments from Professor Zhitao Xiong (Dalian Institute of
Chemical Physics).
13 (a) X. H. Yang, L. L. Zhao, T. Fox, Z. X. Wang and H. Berke, Angew.
Chem., Int. Ed. Engl., 2010, 49, 2058; (b) X. Yang, T. Fox and H. Berke,
Chem. Commun., 2011, 47, 2053–2055.
14 (a) Z. T. Xiong, C. K. Yong, G. T. Wu, P. Chen, W. Shaw, A. Karkamkar,
T. Autrey, M. O. Jones, S. R. Johnson, P. P. Edwards and W. I. F. David,
Nat. Mater., 2008, 7, 138–141; (b) H. V. K. Diyabalanage, R. P. Shrestha,
T. A. Semelsberger, B. L. Scott, M. E. Bowden, B. L. Davis and A. K.
Burrell, Angew. Chem., Int. Ed., 2007, 46, 8995–8997; (c) Y. S. Chua,
P. Chen, G. Wu and Z. Xiong, Chem. Commun., 2011, 47, 5116–5129;
(d) H. No¨th, S. Thomas and M. Schmidt, Chem. Ber., 1996, 129, 451–
458.
Notes and references
1 (a) M. Johnson and B. Rickborn, J. Org. Chem., 1970, 35, 1041–
1045; (b) A. V. Malkov, Angew. Chem., Int. Ed., 2010, 49, 9814–
9815.
15 (a) Z. T. Xiong, Y. S. Chua, G. T. Wu, W. L. Xu, P. Chen, W. Shaw,
A. Karkamkar, J. Linehan, T. Smurthwaite and T. Autrey, Chem.
Commun., 2008, 5595–5597; (b) X. Kang, Z. Fang, L. Kong, H. Cheng,
X. Yao, G. Lu and P. Wang, Adv. Mater., 2008, 20, 2756–2759; (c) H.
Wu, W. Zhou and T. Yildirim, J. Am. Chem. Soc., 2008, 130, 14834–
14839; (d) A. Luedtke and T. Autrey, Inorg. Chem., 2010, 49, 3905–3910.
16 A. G. Myers, B. H. Yang and D. J. Kopecky, Tetrahedron Lett., 1996,
37, 3623–3626.
2 (a) P. G. N. Mertens, P. Vandezande, X. P. Ye, H. Poelman, I. F. J.
Vankelecom and D. E. De Vos, Appl. Catal., A, 2009, 355, 176–183;
(b) A. Deshmukh, A. Kinage, R. Kumar and R. Meijboom, Polyhedron,
2010, 29, 3262–3268; (c) J. H. van Tonder, C. Marais, D. J. Cole-
Hamilton and B. C. B. Bezuidenhoudt, Synthesis-Stuttgart, 2010, 421–
424.
3 (a) X. F. Li, L. C. Li, Y. F. Tang, L. Zhong, L. F. Cun, J. Zhu, J. Liao and
J. G. Deng, J. Org. Chem., 2010, 75, 2981–2988; (b) Z. Baan, Z. Finta,
G. Keglevich and I. Hermecz, Green Chem., 2009, 11, 1937–1940; (c) X.
Wu, J. Liu, X. Li, A. Zanotti-Gerosa, F. Hancock, D. Vinci, J. Ruan
and J. Xiao, Angew. Chem., Int. Ed., 2006, 45, 6718–6722.
4 D. Ward and C. Rhee, Can. J. Chem., 1989, 67, 1206–1211.
5 A. Aramini, L. Brinchi, R. Germani and G. Savelli, Eur. J. Org. Chem.,
2000, 1793–1797.
17 D. Kim, N. Singh, H. Lee and K. Kim, Chem. Eur. J., 2009, 15, 5598–
5604.
18 J. S. M. Samec, J. E. Backvall, P. G. Andersson and P. Brandt, Chem.
Soc. Rev., 2006, 35, 237–248.
19 T. Kamitanaka, T. Matsuda and T. Harada, Tetrahedron, 2007, 63,
1429–1434.
20 (a) M. J Palmer and M. Wills, Tetrahedron: Asymmetry, 1999, 10, 2045;
(b) S. Gladiali and E. Alberico, Chem. Soc. Rev., 2006, 35, 226; (c) S.
L. You, Chem. Asian J., 2007, 2, 820–827.
6 (a) A. L. Gemal and J. L. Luche, J. Am. Chem. Soc., 1981, 103,
5454–5459; (b) J. L. Luche, J. Am. Chem. Soc., 1978, 100, 2226–
2227.
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