A simple, concise, stereocontrolled synthesis of (8E,10Z)-pentadecadien-1- ol acetate

Article abstract of DOI:10.1081/SCC-200051715

A simple, concise, and stereocontrolled synthesis of (8E,10Z)- pentadecadien-1-ol acetate involving a Cadiot-Chodkiewicz reaction as the key step is described.

Full text of DOI:10.1081/SCC-200051715

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A Simple, Concise, Stereocontrolled Synthesis
of (8E,10Z)‐Pentadecadien‐1‐ol Acetate
Subhash P. Chavan a , Rajendra K. Kharul a , Subhash K. Kamat a , Uttam R.
Kalkote a & Ramesh R. Kale a
a Division of Organic Chemistry: Technology , National Chemical Laboratory ,
Pune, India
Published online: 21 Aug 2006.
To cite this article: Subhash P. Chavan , Rajendra K. Kharul , Subhash K. Kamat , Uttam R. Kalkote & Ramesh
R. Kale (2005) A Simple, Concise, Stereocontrolled Synthesis of (8E,10Z)‐Pentadecadien‐1‐ol Acetate,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
35:7, 987-994, DOI: 10.1081/SCC-200051715
To link to this article: http://dx.doi.org/10.1081/SCC-200051715
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Synthetic Communicationsw, 35: 987–994, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200051715
A Simple, Concise, Stereocontrolled
Synthesis of (8E,10Z)-Pentadecadien-1-ol
Acetate
Subhash P. Chavan, Rajendra K. Kharul, Subhash K. Kamat,
Uttam R. Kalkote, and Ramesh R. Kale
Division of Organic Chemistry: Technology, National Chemical
Laboratory, Pune, India
Abstract: A simple, concise, and stereocontrolled synthesis of (8E,10Z)-pentadecadien-
1-ol acetate involving a Cadiot–Chodkiewicz reaction as the key step is described
Keywords: Acetate, Acrobasis vaccini, Cadiot–Chodkiewicz reaction, diacetylene,
pheromone
INTRODUCTION
The cranberry fruitworm, Acrobasis vaccinni Riley, is a member of the
pyralidae family of the Lepidoptera.[1] It is the most important pest of cranber-
ries and blueberries and is capable of considerably decimating these crops.
Other host plants include huckleberries, dangleberries, beach plums, and
apples. An effective agent for detecting, monitoring, and controlling this
pest is needed.
McDonough et al.[2] reported that the composition of two compounds,
(8E,10Z)-pentadecadien-1-ol acetate (1) and (E)-9-pentadecen-1-ol acetate
(2), in a defined ratio range is a highly effective attractant for the male
cranberry fruitworm. This composition provides a sensitive tool for the
detection of this pest by attracting the male cranberry fruit worm moths to
Received in the USA December 9, 2004
Address correspondence to Subhash P. Chavan, Division of Organic Chemistry:
Technology, National Chemical Laboratory, Pune 411 008, India. E-mail:
spchavan@dalton.ncl.res.in

988
S. P. Chavan et al.
the field traps, thus helping the pest control. This composition also provides
a means to detect, survey, monitor, and control the cranberry fruitworm.[2]
(8E,10Z)-Pentadecadien-1-ol acetate (1) is a major component of this
composition. Lack of a good synthetic protocol to prepare compound (1)
will limit its usage. Only two syntheses of 1 have been reported in the litera-
ture.[2,3] Both involve Wadsworth–Horner–Emmons and Wittig reactions
respectively as the key steps to construct the olefin. However, these
methods lack stereoselectivity and are lengthy.
RESULTS AND DISCUSSION
Herein, we wish to report a simple, concise, and highly selective synthetic
strategy to prepare acetate 1 that utilizes the Cadiot–Chodkiewicz
reaction[4] as the key step (Scheme 1). The Cadiot–Chodkiewicz reaction of
1-halogenoacetylenes with terminal acetylenes is a widely used protocol[4c]
for the synthesis of asymmetrically disubstituted diacetylenes. This article
delineates our synthetic strategy, which hinges on the Cadiot–Chodkiewicz
reaction to assemble the required dialkynes, which then are preferentially
converted to cis- and trans olefins. The Cadiot–Chodkiewicz coupling
of 1-bromohexyne (3) with propargyl alcohol (4) is reported to furnish
2,4-nonadiyn-1-ol (7) in poor yield.[4f] We now report the synthesis of
2,4-nonadiyn-1-ol (7) in excellent yield, which is a marked improvement
over the reported method. Thus, coupling 1-bromo-1-hexyne (3) with
propargyl alcohol (4) or 3-bromoprop-2-yn-1-ol (5) and 1-hexyne (6) was
Scheme 1.

Synthesis of (8E,10Z)-Pentadecadien-1-ol Acetate
989
Scheme 2.
performed under modified Cadiot–Chodkiewicz conditions (Scheme 1). To
achieve better yields, we changed the sequence of addition of reagents and
varied molar quantities of reagents as well as the solvent. Under the
optimized conditions, propargyl alcohol (4) was first treated with ethyl
amine solution (70% w/w), then 1-bromo-1-hexyne (3) was added, and,
lastly, CuCl. It was observed that freshly prepared CuCl, successively
washed with glacial acetic acid, water, ethanol, and dry diethyl ether and
then dried in vacuum was found to give the best results. Use of excess of
ethyl-amine solution also was found to substantially increase the yield of
coupling reaction. Thus as depicted in Scheme 1, we have significantly
improved the yield in the coupling reaction.
The required (8E)-stereochemistry of the sex pheromone was obtained
[5]
easily by selectively reducing one of the triple bonds with LiAlH4
(Scheme 2). Trans geometry of the double bond was ascertained and
1
confirmed by analysis of the H NMR spectrum of (8).[6] Allyl alcohol (8)
[7]
thus obtained was brominated with PPh3Br2 at 08C to furnish (2E)-1-
bromo-2-nonen-4-yne (9), which was then coupled with the Grignard
reagent (10) catalyzed by Cu (I)[8] to get desired C15 skeleton (11).[9] The
required (10Z) geometry was easily obtained by reducing the triple bond by
P2-Ni catalyst.[10] One-pot deprotection and protection with AcCl/AcOH
led to the target molecule (1) in 88% yield (Scheme 2). Thus synthesis of
(8E,10Z)-pentadecadien-1-ol acetate (1) was accomplished, starting from
1-bromo-1-hexyne (3) and propargyl alcohol (4), in 16% overall yield.
CONCLUSIONS
As compared to the methods reported in literature that involve Wittig
reactions, lead to undesired isomers, and are lengthy, our protocol furnishes

990
S. P. Chavan et al.
the desired compound in a stereoseletive manner. Although the first step
of our synthetic sequence is known, we have significantly improved the
yield of 2,4-nonadiyn-1-ol (7). The chemistry utilized is operationally
simple, effective, and efficient, and we believe that the sequence described
here is a practical strategy for synthesis of (8E, 10Z)-pentadecadien-1-ol
acetate (1).
EXPERIMENTAL
General Information
IR spectra were recorded on Matteson, UK, model, research series FT-IR.
1H and 13C NMR spectra were recorded on Bruker AC 200 and MSL 300
spectrometers. The chemical shifts are reported in ppm (d) using tetramethyl-
silane as internal standard. Mass spectra were recorded on a Finnigan
MAT-1020-B-70 eV mass spectrometer. Propargyl alcohol and 1-hexyne
were purchased from Aldrich Chemical Co. and used without further
purification. 1-Bromo-1-hexyne (3) and 3-bromoprop-2-yn-1-ol (5) were
prepared by the literature method.[11]
2,4-Nonadiyn-1-ol (7): To a stirred mixture of propargyl alcohol (4)
(5.2 g, 92 mmol), ethyl amine (25 mL, aqueous solution, 70% w/w), and
1-bromo-1-hexyne (3) (13 g, 80 mmol) in MeOH (75 mL) in a round-
bottomed flask, freshly prepared CuCl (170 mg, 1.7 mmol) was added. The
reaction mixture turned yellowish green. At this point NH2OH.HCl (ꢀ1 g)
was added, upon which the reaction mixture instantly turned yellow.
The progress of the reaction was monitored by thin-layer chromatography.
After completion, the reaction mixture was filtered through a short bed of
celite. Methanol from the filtrate was removed on a rotary evaporator under
reduced pressure. The residue was extracted with ethyl acetate (100 mL).
The organic layer was washed with water (2 ꢀ 25 mL) and saturated brine
solution (2 ꢀ 25 mL). The organic layer was dried over anhydrous sodium
sulphate, filtered, and concentrated on a rotary evaporator to furnish crude dia-
cetylene compound (7). Column chromatography on silica gel (60–120 mesh)
(eluent: 10:90 ethyl acetate–petroleum ether) furnished 2,4-nonadiyn-1-ol
(7) as a colorless liquid. Yield: 9.38 g (86%). 2,4-nonadiyn-1-ol (7) was
also obtained by coupling 3-bromoprop-2-yn-1-ol (4) (6.80, 50 mmol) with
1-hexyne (5) (4.52 g, 55 mmol) under similar reaction conditions. Yield:
5.78 g (84%). IR nmax (CHCl3) cm21: 3540–3250 (broad band), 2933, 2867,
1
2254, 1458. H NMR: (CDCl3, 200 MHz) d: 0.91 (t, 3H, –CH3, J ¼ 6 Hz),
;;
1.35–1.62 (m, 4H), 2.08 (bs, –OH), 2.29 (t, 2H, –C C–CH2, J ¼ 6 Hz),
4.32 (s, 2H, –CH2OH). 13C NMR: (CDCl3, 50 MHz) d: 13.66 (q), 19.12 (t),
22.11 (t), 30.38 (t), 51.35 (t), 64.66 (s), 70.76 (s), 73.88 (s), 81.81 (s). Mass
(m/z): 136 (Mþ, 22), 121 (5), 117 (7), 107 (18), 91 (37), 77 (100), 65 (52).

Synthesis of (8E,10Z)-Pentadecadien-1-ol Acetate
991
(2E)- 2-Nonen-4-yn-1-ol (8): To LiAlH4 (3.23 g, 85.2 mmol) covered
with dry THF (10 mL), 2,4-nonadiyn-1-ol (7) (5.78 g, 42.6 mmol) in dry
THF (25 mL) was added dropwise over 30 min. The reaction mixture was
stirred at room temperature. The reaction was monitored by TLC. After
completion (40 min), the reaction mixture was filtered through a short bed
of celite. THF was removed on a rotary evaporator and the residue was
extracted with diethyl ether. The organic layer was washed with 1N HCl
(2 ꢀ 30 mL), water (2 ꢀ 30 mL water), brine (30 mL), dried over anhydrous
sodium sulphate, filtered, and concentrated to give crude product. Column
chromatography on silica gel (eluent: 8:92 ethyl acetate–petroleum ether)
furnished (2E)- 2-nonen-4-yn-1-ol (8) as colorless oil. Yield: 4.62 g (79%).
IR nmax, (CHCl3) cm21: 3540–3250 (broad band), 3010, 2954, 1626.
1H NMR: (CDCl3, 200 MHz) d: 0.91 (t, 3H, –CH3, J ¼ 6 Hz), 1.35–1.62
;;
(m, 4H), 2.01 (bs, –OH), 2.29 (t, 2H, –C C–CH2, J ¼ 6 Hz), 4.17
;;
(d, 2H, –C55C–CH2–OH, J ¼ 8 Hz), 5.72 (ddt, 1H, –C C–CH55CH–,
J1 ¼ 16 Hz, J2 ¼ 4 Hz, J3 ¼ 2 Hz), 6.15 (dt, 1H, –CH55CH–CH2,
J1 ¼ 14 Hz, J2 ¼ 6 Hz). 13C NMR: (CDCl3, 50 MHz) d: 13.62 (q), 19.10 (t),
22.00 (t), 30.86 (t), 62.73 (t), 78.50 (s), 91.21 (s), 111.14 (d), 140.32 (d).
Mass (m/z): 138 (Mþ, 11), 123 (5), 109 (7), 95 (100), 81 (22), 67 (20).
CHN analysis: C9H14O calcd: C, 78.21%; H, 10.21%. Found: C, 77.92%;
H, 10.46%.
(2E)-1-Bromo-2-nonen-4-yne (9): To an ice-cold stirred solution of
PPh3Br2 (10.77 g, 24.7 mmol) in dry dichloromethane (35 mL), (2E)-2-
nonen-4-yn-1-ol (8) (2.94 g, 21.3 mmol) in dry dichloromethane (15 mL)
was added dropwise over 10 min. After stirring at the same temperature for
10 min, the reaction mixture was warmed to room temperature. The progress
of the reaction was monitored by TLC. After completion, the reaction
mixture was diluted with ethyl acetate. The organic layer was washed with
sodium thiosulphate (10% solution, 2 ꢀ 25 mL), water (3 ꢀ 30 mL), and
brine (2 ꢀ 20 mL) and dried over anhydrous Na2SO4. The solvent, after
filtration, was removed on a rotary evaporator to furnish crude allyl
bromide. The crude product thus obtained was purified by column chromato-
graphy on silica gel (eluent: 4:96 ethyl acetate–petroleum ether) to get
(2E)-1-bromo-2-nonen-4-yne (9) as a colorless liquid. Yield: 3.6 g (84%).
1
IR nmax (CHCl3) cm21: 3020, 2954, 1626. H NMR: (CDCl3, 200 MHz)
d: 0.91 (t, 3H, –CH3, J ¼ 6 Hz), 1.35–1.61 (m, 4H), 2.29 (t, 2H,
2
;;
C–C C–CH –, J ¼ 6 Hz), 3.97 (d, 2H, –CH55CH–CH2–Br, J ¼ 8 Hz),
;;
5.72 (ddt, 1H, –C C–CH55CH–, J1 ¼ 16 Hz, J2 ¼ 4 Hz, J3 ¼ 2 Hz),
6.14 (dt, 1H, –CH55CH–CH2–, J1 ¼ 16 Hz, J2 ¼ 6 Hz). 13C NMR:
(CDCl3, 50 MHz) d: 13.66 (q), 19.21 (t), 22.07 (t), 30.75 (t), 32.07 (t),
77.87 (s), 93.64 (s), 115.25 (d), 136.61 (d). Mass (m/z): 202 (Mþ, 12),
200 (Mþ 2 2, 12), 137 (14), 121 (70), 91 (65), 77 (100), 65 (22).
1-[(Tetrahydro-2H-pyran-2-yl)-oxy)-(8E)-pentadecadien-10-yne (11):
Grignard reagent was prepared by refluxing Br-(CH2)6-OTHP (3.12 g,

992
S. P. Chavan et al.
11.85 mmol) prepared from 1,6-hexanediol with 47% HBr[12] followed by
[9]
protection with 3,4-dihydro-2H-pyran
and Mg turnings (0.285 g,
11.85 mmol) in dry THF for 5 h with a catalytic amount of 1,2-dibromoethane
under an inert atmosphere. The reaction mixture was cooled to room
temperature and then gradually to 2788C. CuBr (41 mg, 0.27 mmol) was
added followed by (2E)-1-bromo-2-nonen-4-yne (9) (0.518 g, 2.6 mmol) in
THF (2 mL) dropwise over a 10-min period. The reaction mixture was
stirred at –788C for 2 h, slowly warmed to 2408C over a period of 30 min,
and finally brought to room temperature and stirred for 2 h. The reaction
was quenched with saturated NH4Cl (1 mL) and extracted with ethyl
acetate. The organic layer was washed with saturated NH4Cl solution
(2 ꢀ 1 mL), dried over anhydrous Na2SO4, filtered, and concentrated under
vacuum. The title compound was purified by silver nitrate impregnated
silica gel[13] (60–120 mesh) (eluent: 5:95 ethyl acetate–petroleum ether) to
afford the title compound as a colorless liquid. Yield: 0.313 g (40%). IR:
nmax (CHCl3) cm21: 3020, 2954, 1430, 1390, 1220. 1H NMR: (CDCl3,
200 MHz) d: 0.91 (t, 3H, –CH3, J ¼ 6 Hz), 1.16–1.35 (m, 12H), 1.41–1.82
;;
(m, 8H), 2.05 (q, 2H, J ¼ 6 Hz), 2.28 (dt, 2H, –C C–CH2–, J1 ¼ 6 Hz,
J2 ¼ 2 Hz), 3.33–3.61 (m, 2H), 3.62–3.98 (m, 2H). 4.56 (t, 1H, J ¼ 4 Hz),
;;
5.44 (ddt, 1H, –C C–CH ¼ CH–, J1 ¼ 16 Hz, J2 ¼ 4 Hz, J3 ¼ 2 Hz),
6.08 (dt, 1H, –CH55CH–CH2-, J1 ¼ 16 Hz, J2 ¼ 6 Hz). 13C NMR:
(CDCl3, 50 MHz) d: 13.66 (q), 19.21 (t), 19.83 (t), 22.15 (t), 25.79 (t),
26.37 (t), 29.02 (t), 29.20 (t), 29.46 (t), 29.94 (t), 31.01 (t), 31.19 (t), 33.06
(t), 62.39 (t), 67.69 (t), 79.45 (s), 88.68 (s), 98.93 (d), 110.29 (d), 143.08
(d). Mass (m/z): 306 (2), 288 (2), 263 (2), 191 (2), 171 (3), 135 (6), 119
(5), 85 (100), 67 (12), 56 (12). CHN analysis: C20H34O2 calcd. C, 78.38%;
H, 11.18%. Found: C, 78.62%; H, 11.32%.
1-[(Tetrahydro-2H-pyran-2-yl)-oxy]-(8E,10Z)-pentadecadiene (12):
A two-necked round-bottomed flask (50 mL) was flushed with hydrogen.
.
Ni(OAc)2 4H2O (204 mg) was dissolved in ethanol (8 mL), stirred at
room temperature for 5 min, and again flushed with hydrogen. NaBH4 (1M
in ethanol, 0.5 mL) was added followed by ethylene diamine (3 drops).
Immediately, the acetylenic compound (11) (300 mg) in ethanol (8 mL) was
added and the resultant solution was stirred at room temperature. The
progress of the reaction was monitored by TLC. After completion (30 min),
the reaction mixture was filtered through short a bed of celite. Ethanol was
removed and the residue was extracted with ethyl acetate. The organic layer
was washed with water (10 mL) and then with brine (10 mL). The organic
layer was dried over anhydrous Na2SO4 and concentrated in vacuum. The
diene thus obtained was purified by column chromatography silica gel
(eluent: 2:98 ethyl acetate–pet. ether). Yield: 234 mg (79%). 1H NMR:
(CDCl3, 200 MHz) d: 0.91 (t, 3H, –CH3, J ¼ 6 Hz), 1.25–1.48 (m, 10H),
1.53–1.1.99 (m, 8H), 2.11–2.26 (m, 4H), 3.27–3.61 (m, 4H), 3.67–3.98
(m, 2H), 4.56 (t, 1H, J ¼ 4 Hz), 5.29 (dt, 1H, J1 ¼ 12 Hz, J2 ¼ 6 Hz), 5.63

Synthesis of (8E,10Z)-Pentadecadien-1-ol Acetate
993
(dt, 1H, J1 ¼ 15 Hz, J2 ¼ 6 Hz), 5.93 (m, 1H), 6.23–6.39 (m, 1H). 13C NMR:
(CDCl3, 50 MHz) d: 13.66 (q), 19.37 (t), 22.00 (t), 25.23 (t), 25.90 (t), 27.09
(t), 28 86 (t), 29.05 (t), 29.44 (t), 30.48 (t), 31.61 (t), 32.56 (t), 61.95 (t), 67.32
(t), 98.48 (d), 125.31 (d), 128.30 (d), 129.67 (d), 132.22 (d). Mass (m/z): 308
(Mþ, 4), 290 (5), 252 (4), 224 (4), 163 (4), 149 (6), 135 (8), 121 (8), 110 (12),
95 (10), 85 (100), 67 (15), 55 (8).
(8E,10Z)-Pentadecadien-1ol acetate (1): A mixture of diene (12)
(225 mg, 0.72 mmol), acetyl chloride (87 mg, 1.08 mmol), and glacial acetic
acid (1.5 mL) was stirred overnight at room temperature. The reaction
mixture was poured on crushed ice and extracted with diethyl ether. The
organic layer was washed with aqueous sodium bicarbonate (5%, 5 mL),
water (5 mL), and brine (5 mL), dried over anhydrous Na2SO4, and concen-
trated in vacuum. Column chromatography on silica gel (eluent 5:95 ethyl
acetate–pet. ether) furnished the title compound. Yield: 180 mg (92%). IR
n
max: (CHCl3) cm21: 3010, 2954, 1730, 1215,756. 1H NMR: (CDCl3,
200 MHz) d: 0.91 (t, 3H, CH3, J ¼ 12 Hz, J ¼ 6 Hz), 1.28–1.36 (m, 12 H),
1.63 (m, 2H), 2.03 (s, 3H), 2.03–2.16 (m, 4H), 4.05 (t, 2H, –CH2–O–
COCH3, J ¼ 6 Hz), 5.29 (dt, 1H, J1 ¼ 12 Hz, J2 ¼ 6 Hz), 5.63 (dt, 1H,
J1 ¼ 15 Hz, J2 ¼ 6 Hz), 5.93 (m, 1H), 6.23–6.39 (m, 1H). 13C NMR:
(CDCl3, 50 MHz) d: 13.64 (q), 20.66 (q), 22.07 (t), 25.58 (t), 27.09 (t),
28.20 (t), 28.77 (t), 29.00 (t), 31.86 (t), 32.74 (t), 64.54 (t), 125.70 (d),
128.57 (d), 130.04 (d), 134.38 (d), 171.10 (s). Mass (m/z): 266 (M þ , 22),
206 (12), 177 (5), 163 (7), 149 (13), 136 (25), 121 (50), 109 (69), 95 (100),
81 (60), 67 (40).
ACKNOWLEDGMENT
R.K.K. and R.R.K. thank CSIR, New Delhi, India for senior research fellow-
ships. Funding from the Young Scientist Award, CSIR, New Delhi, India
is also gratefully acknowledged.
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