Reduction of activated conjugated alkenes by the InCl3-NaBH 4 reagent system

Article abstract of DOI:10.1016/j.tet.2003.08.022

A combination of a catalytic amount of indium (III) chloride and sodium borohydride in acetonitrile reduces selectively the carbon-carbon double bonds in conjugated alkenes such as α,α-dicyano olefins, α,β-unsaturated nitriles, cyanoesters, cyanophosphonate and dicarboxylic esters. However, reduction of chalcones is little different. They are reduced to a mixture of saturated ketones and alcohols if the reaction mixture is quenched with H₂O, whereas quenching with MeOH leads to saturated alcohols only.

Full text of DOI:10.1016/j.tet.2003.08.022

Tetrahedron 59 (2003) 7901–7906
Reduction of activated conjugated alkenes by the InCl3–NaBH4
reagent system
*
Brindaban C. Ranu and Sampak Samanta
Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032, India
Received 12 June 2003; revised 16 July 2003; accepted 13 August 2003
Abstract—A combination of a catalytic amount of indium (III) chloride and sodium borohydride in acetonitrile reduces selectively the
carbon–carbon double bonds in conjugated alkenes such as a,a-dicyano olefins, a,b-unsaturated nitriles, cyanoesters, cyanophosphonate
and dicarboxylic esters. However, reduction of chalcones is little different. They are reduced to a mixture of saturated ketones and alcohols if
the reaction mixture is quenched with H2O, whereas quenching with MeOH leads to saturated alcohols only.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
As a part of our interest in indium-mediated reductions2d–f,
j–h we initiated an investigation to find applications for this
simple reagent3d and we have discovered that this system
InCl3–NaBH4 shows much improved activity towards
reduction of carbon–carbon double-bonds in conjugated
alkenes compared to metallic indium.2f A part of these
results has been reported recently in a communication4 and
we wish to present here further application of this reagent in
chalcone system together with the experimental details of
our earlier results (Scheme 1).
Reduction by indium metal is receiving more and more
attention in recent times because of its unique style of
action.1 Although metallic indium has been successfully
used for the reduction of various functionalities such as
aromatic nitro groups,2a quinolines,2b azides,2c vic-aryl
dibromides,2d terminal alkynes2e and conjugated olefins,2f
among others,2 two major drawbacks of these processes are
the use of a stoichiometric amount or more of the costly
indium and its limited applicability to specific types of
substrate. As these reactions are likely to proceed through
single electron transfer process, search for other indium
derivatives as better radical agents led to the discovery and
use of a couple of indium hydrides.3 Recently, dichloro-
indium hydride (Cl2InH) generated in situ from the
combination of sodium borohydride and a catalytic amount
of indium trichloride has been demonstrated to be a benign
alternative to tributyltin hydride in the dehalogenation of
alkyl halides and other radical cyclisations.3b
2. Results and discussion
The experimental procedure for this reduction is very
simple. The conjugated alkene was stirred with a solution of
a catalytic amount (10–15 mol%) of indium (III) chloride
and sodium borohydride in acetonitrile at room temperature
for the period of time required to complete the reduction
(Thin Layer Chromatography). The reaction mixture was
then quenched with water and extracted with ether. The
usual work-up and purification produced the corresponding
reduction product.
Several structurally diverse conjugated alkenes undergo
selective reduction of their carbon–carbon double bonds by
this procedure to provide the corresponding saturated
products. The alkenes include a,a-dicyano olefins, a,b-
unsaturated nitriles, cyanoesters, a cyanophosphonate, and
dicarboxylic esters. The results are summarized in Table 1.
As is evident from the results the conjugated monoester
(entry 17) remains inert, whereas the diester (entry 16) is
reduced easily. Apparently, this reagent system, InCl3–
NaBH4 is quite different from metallic indium in its course
of reduction as conjugated cyanoesters, diesters, nitriles
Scheme 1.
Keywords: indium chloride; sodium borohydride; reduction; conjugated
alkene; chalcone.
*
Corresponding author. Tel.: þ91-33-24734971; fax: þ91-33-24732805;
e-mail: ocbcr@iacs.res.in
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.08.022

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B. C. Ranu, S. Samanta / Tetrahedron 59 (2003) 7901–7906
Table 1. The reduction of CvC bond in conjugated alkenes by
InCl3/NaBH4
Table 2. Reduction of chalcones by InCl3/NaBH4
Entry
Alkene
E1
Time
(h)
Yield
(%)a
Entry
R
R1
Time (h)
Yield (%)a
R1
R2
E2
1
2
3
4
5
6
7
Ph
Ph
Ph
p(Me)-C6H4
Ph
p(Me)-C6H4
1
2
2
2.5
4
1
94
93
92
91
92
95
94
1
2
3
4
5
6
7
8
Ph
p-(Cl)-C6H4
H
H
CN
CN
CN
CN
CN
CN
CN
CN
H
3
3
3.5
4
3.5
4
12
12
5
85
83
79
79
83
81
69
57
84
88
p(Cl)-C6H4
p(OMe)-C6H4
p(O-allyl)-C6H4
m(OBn)-C6H4
Ph Me CN
p-(Me)-C6H4 Me CN
Ph
Ph
Ph
Cy-C6H11
Me2CH
Ph
p-(Me)-C6H4
CN
Me CN
2
H
H
CN
H
CN
CN
H
H
9
H
Ph
Ph
(Ov)P(OMe)2
CO2Et
CO2Et
10
11
12
CN
3
Me CN
CN
4.5 82 (55:45)b
8
p(Me)-C6H4
2.5
1.5
2
91
91
89
H
CO2Et
5
87
9
Ph
Ph
13
14
15
16
17
18
19
Me2CH
cy-C6H10
cy-C8H14
Ph
Me CN
CN
CN
CO2Et
CO2Et
CO2Et
5
85 (60:40)b
4.5
4.5
6
84
81
87
H
H
H
H
CO2Et CO2Et
CO2Et
H
H
Ph
Ph
H
COPh
COPh
18 No reaction
0.5
0.75
10
96
88
11
Ph
3
89
a
Yields refer to those of pure isolated products characterized by spectral
data (IR, 1H NMR, 13C NMR).
The figure in parenthesis denotes the diastereometric ratio of the product.
b
which are reduced readily by this procedure do not undergo
reduction by indium metal.2f
12
13
14
Ph-CHvCH(t)
Ph-CHvCH(t)
Ph-CHvCH(t)
Ph
p(Me)-C6H4
p(OBn)-C6H4
2
2
2.5
88
85
81
More significantly, the reduction of chalcone which was
found to be problematic using indium metal2f,g though
successful using this reagent system, is very interesting. The
reduction of unsubstituted chalcone by this procedure
involves the reduction of double bond only to produce the
corresponding saturated ketones, whereas the substituted
chalcones underwent further reduction of the ketone
functionality to the extent of 20–25% producing a mixture
of saturated ketones and alcohols. This prompted us to look
into details of this reduction and we discovered that
chalcones, in general, are reduced directly to the corre-
sponding saturated alcohols in one pot by InCl3/NaBH4
system in acetonitrile if quenched with methanol in place
of water (Scheme 1). A wide range of structurally varied
chalcones underwent clean and complete reduction to the
corresponding saturated alcohols in high yields by this
procedure. The results are reported in Table 2. Hetero-
aromatic rings (entries 8–10) and ferrocene-substituted
chalcones are also reduced without any difficulty. Very
interestingly, the a,b,g,d-unsaturated analogues (entries
12–14) underwent selective reduction at the a,b-carbon–
carbon double bond producing the corresponding g,d-
a
Yields refer to those of pure isolated products properly characterized.
unsaturated alcohols. These reductions, when quenched
with H2O in place of MeOH led to the mixture of saturated
ketones and alcohols, ketones being the major component.
On the other hand, after the reaction, if the mixture was left
to open atmosphere containing moisture and filtered through
a short column of silica gel, mostly saturated ketones were
isolated. These observations demonstrate that this reagent
system, InCl3–NaBH4 in CH3CN, reduces chalcones to the
corresponding saturated ketones in the first phase, which on
addition of MeOH undergo further reduction by the hydride
ion released by the relatively slow decomposition of
remaining sodium borohydride with MeOH. However,
quenching with H2O leads to faster decomposition of
NaBH4 thus resulting in incomplete reduction of the CvO
groups.
The one-step reduction of chalcones to the saturated
alcohols by this reagent system is unique as other

B. C. Ranu, S. Samanta / Tetrahedron 59 (2003) 7901–7906
Table 4. Reduction by NaBH4/ZnCl2
7903
Table 3. Reduction of Chalcones by NaBH4
Entry
R
R1
Time (min)
Yield (%)
Entry
1
R
R1
Ph
Time (h)
2
Ratio of A/B (1H NMR)
72:28
1
2
p(Cl)-C6H4
Ph
Ph
30
30
93
91
3
4
m(OBn)-C6H4
Ph
Ph
30
30
94
92
2
m(OBn)-C6H4
Ph
2
60:40
3. Conclusion
In conclusion, the combination of sodium borohydride and a
catalytic amount of indium (III) chloride provides a highly
chemoselective reduction of the carbon–carbon double-
bonds in a wide range of activated conjugated alkenes such
as a,a-dicyano olefins, a,b-unsaturated nitriles, cyano-
esters, a cyanophosphonate, and dicarboxylic esters. On the
other hand, the substituted chalcones are cleanly reduced to
the corresponding saturated alcohols in one-step by this
reagent which is difficult to achieve by other conventional
reducing agents. Certainly, this reagent offers significant
improvements with regard to convenience, cost, mildness
and efficiency over the similar reduction by indium metal2
and leaves great promise for other applications.
conventional reducing agents failed to do this job cleanly.
For comparison, a few representative chalcones were
subjected to reduction by NaBH4–MeOH and LiAlH4–
ether. Reduction by sodium borohydride furnished the
corresponding allyl alcohol (Table 3) while lithium
aluminium hydride produced a mixture of allyl alcohol,
saturated alcohol and saturated ketone together with other
unidentified products even after a reaction period of 12 h
(Scheme 2). In another comparison experiment when
indium (III) chloride has been replaced by zinc (II) chloride,
a mixture of allyl alcohol and saturated alcohols were
obtained (Table 4). Thus, a combination of indium (III)
chloride and sodium borohydride in acetonitrile followed
by quenching with methanol is very useful for the direct
reduction of chalcones to the saturated alcohols.
4. Experimental
4.1. General
In general, reductions by this procedure are clean, high
yielding and quite fast. The reactions proceed at room
temperature unlike using indium metal which requires a
temperature of 908C for a longer period.2f The reaction
conditions are mild enough to tolerate a sensitive furan ring.
Acetonitrile was distilled over anhydrous phosphorus
˚
pentoxide and stored over molecular sieves (4 A). Sodium
borohydride and indium (III) chloride (98%) was purchased
from Aldrich. The conjugated alkenes and chalcones are
prepared by standard methods. IR spectra were taken as thin
films for oils and as KBr pellet for solid compounds. 1H and
13C NMR spectra were recorded in CDCl3 solutions at 300
and 75 MHz respectively. Elemental Analyses were per-
formed on a Perkin–Elmer autoAnalyzer 2400 II.
To ascertain the role of indium (III) chloride a few reactions
were carried out with the conjugated nitrile (listed in entry
7), cyanoester (entry 10), dicyano-olefin (entry 1) and
chalchone (entry 18) under identical reaction conditions
without the indium (III) chloride and no reduction was
observed in each case.
Scheme 2.

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B. C. Ranu, S. Samanta / Tetrahedron 59 (2003) 7901–7906
4.1.1. General procedure for the reduction of activated
conjugated alkenes: representative one for the reduction
of 1,1-dicyano-2-phenylethylene (entry 1, Table 1). To a
stirred solution of anhydrous indium (III) chloride (30 mg,
0.135 mmol) and sodium borohydride (56 mg, 1.5 mmol) in
dry acetonitrile (3 mL) was added a solution of 1,1-dicyano-
2-phenylethylene (154 mg, 1 mmol) in acetonitrile (1 mL)
at room temperature (28–308C) under nitrogen. The
reaction mixture was stirred for another 3 h as monitored
by TLC and quenched with water (0.5 mL). The reaction
mixture was extracted with ether (3£10 mL) and ether
extract was washed with brine, dried (Na2SO4) and
evaporated to leave the crude product which was purified
by column chromatography over silica gel (hexane–ether
98:2) to provide the corresponding alkane (131 mg, 85%) as
a white solid, mp 87–888C (lit.,2f mp 878C) whose spectral
data are in good agreement with those reported earlier.2f
4.1.9. Dimethyl 2-cyanoethylphosphonate (entry 9).
1
Gummy liquid; IR 2247 cm21; H NMR d 3.68 (s, 3H),
3.64 (s, 3H), 2.46–2.56 (m, 2H), 1.92–2.03 (m, 2H); 13C
NMR d 118.5 (d, JCP¼16.87 Hz), 53.3 (d, JCP¼6.52 Hz,
2C), 21.7 (d, JCP¼145.27 Hz), 11.9 (d, JCP¼7.05 Hz). Anal.
calcd for C5H10NO2P: C, 40.82; H, 6.85; N, 9.52. Found: C,
40.77; H, 6.74; N, 9.39.
4.1.10. 1-Cyano-1-ethylcarboxy-2-phenylethane (entry
10). Gummy liquid; IR 2250, 1743 cm21 1H NMR d
;
7.25–7.36 (m, 5H), 4.22 (q, J¼7.14 Hz, 2H), 3.74 (d, J¼
5.88 Hz, 0.5H), 3.71 (d, J¼5.88 Hz, 0.5H), 3.14–3.30 (m,
2H), 1.25 (t, J¼7.14 Hz, 3H); 13C NMR d 165.9, 135.7,
129.4 (2C), 129.2 (2C), 128.1, 116.6, 63.3, 40.0, 36.1, 14.3.
Anal. calcd for C12H13NO2: C, 70.91; H, 6.44; N, 6.89.
Found: C, 70.82; H, 6.40; N, 6.81.
4.1.11. 1-Cyano-1-ethylcarboxy-2-phenylpropane (entry
11). Yellow liquid; IR 2248, 1743 cm21 1H NMR (a
;
This procedure is followed for the reduction of all
conjugated alkenes listed in Table 1. However, for the
reduction of substituted chalcones the reaction mixture at
the end of the reaction was quenched with methanol in place
of water. All the products have been characterized by their
spectroscopic (IR, 1H NMR, 13C NMR) data and elemental
analysis. The known compounds are in good agreement with
the values reported for them.2 Spectroscopic and analytical
data of the products whose data are not available for
comparison are presented below in order of their entries in
Tables 1 and 2.
mixture of diastereoisomer 55:45) d 7.27–7.41 (m, 5H),
4.17 (q, J¼7.11 Hz, 1.1H), 4.15 (q, J¼7.11 Hz, 0.9H), 3.70
(d, J¼6.72 Hz, 0.45H), 3.65 (d, J¼6.33 Hz, 0.55H), 3.47–
3.55 (m, 1H), 1.51 (d, J¼6.96 Hz, 0.55H), 1.50 (d, J¼7.14 Hz,
0.45H), 1.20 (t, J¼7.11 Hz, 1.65H), 1.18 (t, J¼7.11 Hz,
1.35H); 13C NMR (major isomer) d 165.8, 141.3, 129.1 (2C),
127.4 (2C), 125.9, 115.9, 63.1, 46.4, 40.8, 19.7, 14.3; minor
isomer: d 165.7, 140.8, 129.0 (2C), 127.5 (2C), 126.3, 115.9,
63.0, 46.1, 40.8, 19.7, 14.2. Anal. calcd for C13H15NO2: C,
71.86; H, 6.95; N, 6.44. Found: C, 71.68; H, 6.86; N, 6.31.
4.1.2. 2-(40-Chlorophenyl)-1,1-dicyanoethane (entry 2).
4.1.12. 1-Cyano-1-ethylcarboxy-2-(20-furyl)ethane (entry
12). Colourless liquid; IR 2251, 1743 cm21; 1H NMR d 7.35
(m, 1H), 6.31 (dd, J¼3.09, 2.97 Hz, 1H), 6.24 (d, J¼
3.09 Hz, 1H), 4.26 (q, J¼7.14 Hz, 2H), 3.83 (d, J¼6.18 Hz,
0.5H), 3.80 (d, J¼6.18 Hz, 0.5H), 3.24–3.36 (m, 2H), 1.29
(t, J¼7.14 Hz, 3H); 13C NMR d 165.1, 148.9, 142.5, 115.8,
110.6, 108.4, 63.0, 37.0, 28.5, 13.9. Anal. calcd for
C10H11NO3: C, 62.16; H, 5.73; N, 7.24. Found: C, 62.02;
H, 5.75; N, 7.21.
Pale yellow solid; mp 928C. (lit.,2f mp 928C).
4.1.3. 1,1-Dicyano-2-phenylpropane (entry 3). Light
yellow viscous oil.2f
4.1.4. 1,1-Dicyano-2-(40-methylphenyl)propane (entry 4).
Light yellow viscous oil.2f
4.1.5. 1,1-Dicyano-1-cyclohexylmethane (entry 5). Colour-
less liquid.2f
4.1.13. 1-Cyano-1-ethylcarboxy-2,3-dimethylbutane
1
(entry 13). Colourless oil; IR 2248, 1745 cm21; H NMR
4.1.6. 1,1-Dicyano-2,3-dimethylbutane (entry 6). Colour-
less oil; IR 2250 cm21; 1H NMR d 3.57 (d, J¼5.49 Hz, 1H),
2.30–2.35 (m, 1H), 1.62–1.73 (m, 1H), 0.85–1.11 (m, 9H);
13C NMR d 112.2 (2C), 39.8, 29.8, 25.9, 18.1, 17.1 (2C).
Anal. calcd for C8H12N2: C, 70.55; H, 8.88; N, 20.56.
Found: C, 70.42; H, 8.72; N, 20.48.
(a mixture of diastereoisomers 6:4) d 4.27 (2q, J¼7.14 Hz,
2H), 3.48 (d, J¼4.44 Hz, 0.6H), 3.43 (d, J¼5.01 Hz,
0.4 Hz), 2.31–2.35 (m, 1H), 1.60–1.71 (m, 1H), 1.31
(t, J¼7.14 Hz, 1.8H), 1.30 (t, J¼7.14 Hz, 1.2H), 1.10 (d,
J¼6.78 Hz, 1.8H), 1.05 (d, J¼6.66 Hz, 1.2H), 0.87–0.98
(m, 6H); 13C NMR (major isomer) d 166.6, 115.7, 63.0,
44.3, 32.6, 27.6, 18.1, 17.7 (2C); (minor isomer) d 166.3,
116.1, 62.9, 44.2, 32.8, 27.6, 18.3, 17.6 (2C). Anal. calcd for
C10H17NO2: C, 65.54; H, 9.35; N, 7.64. Found: C, 65.38; H,
9.31; N, 7.53.
4.1.7. 1-Cyano-2-phenylethane (entry 7). Colourless oil;
1
IR 2248, 1602 cm21; H NMR d 7.22–7.47 (m, 5H), 2.95
(t, J¼7.41 Hz, 2H), 2.61 (t, J¼7.41 Hz, 2H); 13C NMR d
138.5, 129.3 (2C), 128.7 (2C), 127.6, 119.6, 31.9, 19.7.
Anal. calcd for C9H9N: C, 82.40; H, 6.91; N, 10.67. Found:
C, 82.43; H, 6.88; N, 10.59.
4.1.14. 1-Cyano-1-ethylcarboxy-1-cyclohexylmethane
1
(entry 14). Colourless oil; IR 2251, 1743 cm21; H NMR
d 4.11 (q, J¼7.14 Hz, 2H), 3.30 (d, J¼5.61 Hz, 1H), 1.41–
2.11 (m, 5H), 0.96–1.24 (m, 9H); 13C NMR d 166.1, 116.0,
62.7, 44.7, 39.0, 31.2, 28.2, 26.0, 25.9, 25.8, 14.3. Anal.
calcd for C11H17NO2: C, 67.66; H, 8.77; N, 7.17. Found: C,
67.45; H, 8.65; N, 7.05.
4.1.8. 1-Cyano-2-(40-methylphenyl)ethane (entry 8).
Colourless oil; IR 2246, 1602 cm21 1H NMR d 7.05–
;
7.38 (m, 4H), 2.91 (t, J¼7.44 Hz, 2H), 2.58 (t, J¼7.44 Hz,
2H), 2.34 (s, 2H); 13C NMR d 137.1, 135.4, 129.9 (2C),
128.5 (2C), 119.5, 31.6, 21.4, 19.8. Anal. calcd for
C10H11N: C, 82.71; H, 7.63; N, 9.64. Found: C, 82.59; H,
7.66; N, 9.70.
4.1.15. 1-Cyano-1-ethylcarboxy-1-cyclooctylmethane
1
(entry 15). Colourless oil; IR 2249, 1743 cm21; H NMR

B. C. Ranu, S. Samanta / Tetrahedron 59 (2003) 7901–7906
7905
d 4.19 (q, J¼7.17 Hz, 2H), 3.34 (d, J¼5.40 Hz, 1H), 2.16–
2.28 (m, 1H), 1.41–1.68 (m, 14H), 1.24 (t, J¼7.17 Hz, 3H);
13C NMR d 166.4, 116.5, 62.8, 45.9, 38.3, 32.0, 29.2, 26.7
(2C), 26.6, 26.5, 24.0, 14.4. Anal. calcd for C13H21NO2: C,
69.92; H, 9.47; N, 6.27. Found: C, 69.78; H, 9.35; N, 6.19.
4.1.23. 3-(40-Allyloxyphenyl)-1-phenylpropan-1-ol (entry
1
5). Colourless oil; IR 3377, 1642, 1597 cm21; H NMR d
7.23–7.24 (m, 5H), 6.99 (d, J¼8.52 Hz, 2H), 6.74 (d,
J¼8.52 Hz, 2H), 5.89–6.02 (m, 1H), 5.16–5.34 (m, 2H),
4.56 (d, J¼5.4 Hz, 0.5H), 4.54 (d, J¼5.4 Hz, 0.5H), 4.40 (d,
J¼5.28 Hz, 2H), 2.47–2.60 (m, 2H), 1.84–2.03 (m, 2H);
13C NMR d 157.2, 145.0, 134.4, 133.9, 129.7 (2C), 128.9
(2C), 128.0, 126.4 (2C), 117.9, 115.1 (2C), 74.2, 69.3, 41.0,
31.5. Anal. calcd for C18H20O2: C, 80.56; H, 7.51. Found: C,
80.38; H, 7.46.
4.1.16. 1,1-Diethylcarboxy-2-phenylethane (entry 16).
Colourless oil; IR 1749, 1604 cm21 1H NMR d 7.16–
;
7.29 (m, 5H), 4.18 (q, J¼7.14 Hz, 2H), 4.16 (q, J¼7.14 Hz,
2H), 3.64 (t, J¼7.86 Hz, 1H), 3.21 (d, J¼7.86 Hz, 2H), 1.18
(t, J¼7.14 Hz, 6H); 13C NMR d 169.2 (2C), 138.3, 129.2
(2C), 128.9 (2C), 127.1, 61.8 (2C), 54.2, 35.1, 14.4 (2C).
Anal. calcd for C14H18O4: C, 67.18; H, 7.24. Found: C,
67.11; H, 7.15.
4.1.24. 3-(30-Benzyloxyphenyl)-1-phenylpropan-1-ol
1
(entry 6). Colourless oil; IR 3398, 1608 cm21; H NMR d
7.15–7.40 (m, 11H), 6.75–6.79 (m, 3H), 4.98 (s, 2H), 4.59
(d, J¼5.4 Hz, 0.5H), 4.56 (d, J¼5.4 Hz, 0.5H), 2.58–2.70
(m, 2H), 1.91–2.09 (m, 2H); 13C NMR d 159.4, 145.0,
144.0, 137.6, 129.9, 129.0 (2C), 128.9 (2C), 128.4, 128.0,
127.9 (2C), 126.4 (2C), 121.6, 115.7, 112.6, 74.2, 70.3,
40.8, 32.5. Anal. calcd for C22H22O2: C, 82.98; H, 6.96.
Found: C, 82.78; H, 6.84.
4.1.17. 1,3-Diphenylpropan-1-one (entry 18). Colourless
solid; mp 738C (lit.,5 mp 738C).
4.1.18. 3-Naphthyl-1-phenylpropan-1-one (entry 19).
1
Low melting solid; IR 1681, 1596 cm21; H NMR d 8.19
(d, J¼8.61 Hz, 1H), 8.08 (d, J¼8.1 Hz, 2H), 7.99 (d, J¼
7.56 Hz, 1H), 7.86–7.89 (m, 1H), 7.53–7.70 (m, 7H),
3.61–3.70 (m, 2H), 3.50–3.58 (m, 2H); 13C NMR d 199.7,
137.8, 137.2, 134.3, 133.5, 132.1, 129.4, 129.0 (2C), 128.4
(2C), 127.4, 126.6, 126.5, 126.1, 126.0, 123.9, 40.1, 27.6.
Anal. calcd for C19H16O: C, 87.66; H, 6.19. Found: C,
87.69; H, 6.16.
4.1.25. 3-(30,40-Dioxymethylnephenyl)-1-phenylpropan-
1
1-ol (entry 7). Colourless oil; IR 3381, 1602 cm21; H
NMR d 7.29–7.36 (m, 5H), 6.62–6.75 (m, 3H), 5.89 (s,
2H), 4.66 (d, J¼2.04 Hz, 0.5H), 4.63 (d, J¼5.1 Hz, 0.5H),
2.58–2.69 (m, 2H), 1.93–2.11 (m, 2H); 13C NMR d 147.9,
146.0, 145.0, 136.0, 128.9 (2C), 128.0, 126.4 (2C), 121.6,
109.4, 108.6, 101.1, 74.0, 41.1, 32.2. Anal. calcd for
C16H16O3: C, 74.98; H, 6.29. Found: C, 74.76; H, 6.18.
4.1.19. 1,3-Diphenylpropan-1-ol (entry 1, Table 2).
Colourless oil; IR 3395, 1608 cm21 1H NMR d 7.24–
;
7.47 (m, 10H), 4.72 (d, J¼5.58 Hz, 0.5H), 4.70 (d, J¼
5.79 Hz, 0.5H), 2.71–2.81 (m, 2H), 2.04–2.22 (m, 2H); 13C
NMR d 145.0, 142.3, 128.9 (4C), 128.8, 128.0, 126.4 (2C),
126.3 (2C), 74.2, 40.9, 35.5. Anal. calcd for C15H16O: C,
84.86; H, 7.59. Found: C, 84.58; H, 7.47.
4.1.26. 1-(40-Methylphenyl)-3-(20-thiophenyl)propan-1-ol
1
(entry 8). Colourless oil; IR 3378, 1596 cm21; H NMR d
7.25 (d, J¼8.04 Hz, 2H), 7.17 (d, J¼8.04 Hz, 2H), 7.11–
7.13 (m, 1H), 6.91–6.93 (m, 1H), 6.80–6.81 (m, 1H), 4.71
(d, J¼5.49 Hz, 0.5H), 4.68 (d, J¼5.49 Hz, 0.5H), 2.89–2.95
(m, 2H), 2.35 (s, 3H), 2.03–2.22 (m, 2H); 13C NMR d
145.1, 141.7, 137.8, 129.7 (2C), 127.1, 126.3 (2C), 124.7,
123.5, 73.8, 41.0, 26.7, 21.6. Anal. calcd for C14H16SO: C,
73.37; H, 6.94. Found: C, 73.52; H, 6.84.
4.1.20. 1-(40-Methylphenyl)-3-phenylpropan-1-ol (entry
1
2). Colourless oil; IR 3385, 1593 cm21; H NMR d 7.02–
7.19 (m, 9H), 4.51 (d, J¼5.7 Hz, 0.5H), 4.49 (d, J¼5.7 Hz,
0.5H), 2.52–2.61 (m, 2H), 2.23 (s, 3H), 1.87–2.04 (m, 2H);
13C NMR d 142.3, 142.0, 137.7, 129.6 (2C), 128.9 (2C),
128.8 (2C), 126.4 (2C), 126.3, 74.1, 40.8, 32.5, 21.6. Anal.
calcd for C16H18O: C, 84.91; H, 8.01. Found: C, 84.76; H,
8.08.
4.1.27. 3-(20-Furyl)-1-phenylpropan-1-ol (entry 9). Colour-
1
less oil; IR 3377, 1598 cm21; H NMR d 7.18–7.31 (m,
6H), 6.22–6.23 (m, 1H), 5.93–5.94 (m, 1H), 4.57 (t, J¼
6.63 Hz, 1H), 2.57–2.66 (m, 2H), 1.92–2.07 (m, 2H); 13C
NMR d 156.0, 144.8, 141.4, 129.0 (2C), 128.0, 126.4 (2C),
110.6, 105.5, 74.0, 37.5, 24.8. Anal. calcd for C13H14O2: C,
77.20; H, 6.97. Found: 77.32; H, 7.01.
4.1.21. 3-(40-Chlorophenyl)-1-phenylpropan-1-ol (entry
1
3). Colourless oil; IR 3381, 1596 cm21; H NMR d 7.22–
7.24 (m, 5H), 7.15 (d, J¼8.34 Hz, 2H), 7.03 (d, J¼8.34 Hz,
2H), 4.60 (d, J¼5.4 Hz, 0.5H), 4.57 (d, J¼5.4 Hz, 0.5H),
2.55–2.64 (m, 2H), 1.87–2.04 (m, 2H); 13C NMR d 144.8,
140.6, 132.5, 130.2 (2C), 129.0 (2C), 128.9 (2C), 128.1,
126.3 (2C), 74.1, 40.7, 31.8. Anal. calcd for C15H15ClO: C,
73.01; H, 6.12. Found: C, 73.26; H, 6,05.
4.1.28. 3-(30-N-Methylindolyl)-1-phenylpropan-1-ol
1
(entry 10). Colourless oil; IR 3393, 1610 cm21; H NMR
d 7.05–7.51 (m, 9H), 6.83 (s, 1H), 4.76 (d, J¼5.58 Hz,
0.5H), 4.73 (d, J¼5.61 Hz, 0.5H), 3.72 (s, 3H), 2.70–2.93
(m, 2H), 2.05–2.26 (m, 2H); 13C NMR d 145.2, 137.5,
128.8 (2C), 128.2, 127.9, 126.5, 126.4 (2C), 121.9, 119.4,
119.0, 114.8, 109.5, 74.5, 39.8, 33.0, 21.8. Anal calcd for
C18H19NO: C, 81.47; H, 7.21; N, 5.27. Found: C, 81.51; H,
7.16; N, 5.25.
4.1.22. 1-(40-Methylphenyl)-3-(40-methoxyphenyl)pro-
pan-1-ol (entry 4). Colourless oil; IR 3376, 1601 cm21
;
1H NMR d 7.28 (d, J¼7.95 Hz, 2H), 7.25 (d, J¼7.95 Hz,
2H), 7.16 (d, J¼8.49 Hz, 2H), 6.89 (d, J¼8.49 Hz, 2H), 4.67
(d, J¼5.7 Hz, 0.5H), 4.65 (d, J¼5.7 Hz, 0.5H), 3.83 (s, 3H),
2.64–2.73 (m, 2H), 2.41 (s, 3H), 2.01–2.16 (m, 2H); 13C
NMR d 158.2, 142.2, 137.6, 134.4, 129.8 (2C), 129.7 (2C),
126.4 (2C), 114.3 (2C), 74.0, 41.1, 31.6, 21.6. Anal. calcd
for C17H20O2: C, 79.65; H, 7.86. Found: C, 79.45; H, 8.75.
4.1.29. 3-(20-Ferrocenyl)-1-phenylpropan-1-ol (entry 11).
Brown viscous oil; IR 3392, 1602 cm21; 1H NMR d 7.25–
7.36 (m, 5H), 4.69–4.71 (m, 1H), 4.19 (broad, 9H), 2.30–
2.39 (m, 2H), 1.81–1.95 (m, 2H); 13C NMR d 145.0, 128.9
(2C), 128.0, 126.4 (2C), 88.1, 69.9 (5C), 69.2 (2C), 68.4

7906
B. C. Ranu, S. Samanta / Tetrahedron 59 (2003) 7901–7906
(2C), 40.3, 26.1. Anal. calcd for C19H20FeO: C, 71.26; H,
6.29. Found: C, 71.22; H, 6.28.
CSIR, New Delhi [Grant No. 01(1739)/02]. S. S. is also
thankful to CSIR for his fellowship.
4.1.30. 1,5-Diphenyl-pent-4-en-1-ol (entry 12). Colourless
1
viscous oil; IR 3363, 1651 cm21; H NMR d 7.23–7.37
(m, 10H); 6.42 (d, J¼15.84 Hz, 1H), 6.25 (dt, J¼15.84,
6.78 Hz, 1H), 4.74 (dd, J¼7.38, 7.41 Hz, 1H), 2.24–2.29
(m, 2H), 1.84–2.04 (m, 2H); 13C NMR d 145.0, 138.0,
130.8, 130.4, 128.8 (4C), 128.0, 127.4, 126.4 (4C), 74.4,
38.8, 29.7. Anal. calcd for C17H18O: C, 85.67; H, 7.61.
Found: C, 85.63; H, 7.63.
References
1. (a) Ranu, B. C. Eur. J. Org. Chem. 2000, 2347. (b) Podlech, J.;
Maier, T. C. Synthesis 2003, 633.
2. (a) Moody, C.-J.; Pitts, M. R. Synlett 1998, 1028. (b) Moody,
C. J.; Pitts, M. R. Synlett 1998, 1029. (c) Reddy, G. V.; Rao,
G. V.; Iyengar, D. S. Tetrahedron Lett. 1999, 40, 3937. (d)
Ranu, B. C.; Guchhait, S. K.; Sarkar, A. Chem. Commun. 1998,
2113. (e) Ranu, B. C.; Dutta, J.; Guchhait, S. K. J. Org. Chem.
2001, 66, 5624. (f) Ranu, B. C.; Dutta, J.; Guchhait, S. K. Org.
Lett. 2001, 3, 2603. (g) Pitts, M. R.; Harrison, J. R.; Moody, C. J.
J. Chem. Soc., Perkin Trans. 1 2001, 955. (h) Ranu, B. C.;
Dutta, P.; Sarkar, A. J. Chem. Soc., Perkin Trans. 1 1999, 1139.
(i) Ranu, B. C.; Samanta, S.; Guchhait, S. K. J. Org. Chem.
2001, 66, 4102. (j) Ranu, B. C.; Samanta, S.; Das, A.
Tetrahedron Lett. 2002, 43, 5993. (k) Khan, F. A.; Dash, J.;
Sahu, N.; Gupta, S. Org. Lett. 2002, 4, 1015. (l) Cho, S.; Kang,
S.; Keum, G.; Kang, S. B.; Han, S.-Y.; Kim, Y. J. Org. Chem.
2003, 68, 180. (m) Cicchi, S.; Bonanni, M.; Cardona, F.;
Revuelta, J.; Goti, A. Org. Lett. 2003, 5, 1773.
4.1.31. 1-(40-Methylphenyl)-5-phenylpent-4-en-1-ol
1
(entry 13). Viscous oil; IR 3363, 1651 cm21; H NMR d
7.13–7.40 (m, 9H), 6.40 (d, J¼15.81 Hz, 1H), 6.22 (dt,
J¼15.81, 6.81 Hz, 1H), 4.70 (dd, J¼7.20, 7.32 Hz, 1H),
2.35 (s, 3H), 2.22–2.31 (m, 2H), 1.81–2.05 (m, 2H); 13C
NMR d 141.9, 138.0, 137.7, 130.7, 130.5, 129.7 (2C), 128.9
(2C), 127.3, 126.6 (4C), 74.3, 38.8, 29.7, 21.6. Anal. calcd
for C18H20O: C, 85.67; H, 7.98. Found: C, 85.71; H, 7.91.
4.1.32. 1-(40-Benzyloxyphenyl)-5-phenylpent-4-en-1-ol
(entry 14). Colourless viscous oil; IR 3361, 1651 cm21
;
1H NMR d 7.19–7.46 (m, 12H), 6.97 (d, J¼8.67 Hz, 2H),
6.41 (d, J¼15.84 Hz, 1H), 6.22 (dt, J¼15.84, 6.69 Hz, 1H),
5.07 (s, 2H), 4.69 (dd, J¼7.29, 7.20 Hz, 1H), 2.17–2.36 (m,
2H), 1.81–2.06 (m, 2H); 13C NMR d 158.7, 138.0, 137.4,
130.7, 130.4, 128.9 (4C), 128.4, 127.9 (2C), 127.8 (2C),
127.6, 126.4 (2C), 115.0 (2C), 74.0, 70.4, 38.7, 29.8. Anal.
calcd for C24H24O2: C, 83.68; H, 7.02. Found: C, 83.57; H,
7.08.
3. (a) Inoue, K.; Sawada, A.; Shibata, I.; Baba, A. Tetrahedron
Lett. 2001, 42, 4661. (b) Inoue, K.; Sawada, A.; Shibata, I.;
Baba, A. J. Am. Chem. Soc. 2002, 124, 906. (c) Takami, K.;
Yorimitsu, H.; Oshima, K. Org. Lett. 2002, 4, 2993. (d) Ranu,
B. C.; Das, A.; Hajra, A. Synthesis 2003, 1012. (e) Abernethy,
C. D.; Cole, M. L.; Davies, A. J.; Jones, C. Tetrahedron Lett.
2000, 41, 7567.
4. Ranu, B. C.; Samanta, S. Tetrahedron Lett. 2002, 43, 7405.
5. Furniss, B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R.
Vogel’s Textbook of Practical Organic Chemistry. 5th ed.;
Longman: England, 1989; p 1035.
Acknowledgements
We are pleased to acknowledge the financial support from