SYNTHESIS OF 2-METHYLHEPTADECANE AND 14-METHYLPENTADECAN-3-ONE

Full text of DOI:10.1135/cccc19940721

New Compounds
721
SYNTHESIS OF 2-METHYLHEPTADECANE
AND 14-METHYLPENTADECAN-3-ONE
Jasvinder SINGH*, Ajay K. ARORA, Amandeep KAUR and Goverdhan L. KAD
Department of Chemistry,
Panjab University, Chandigarh-160 014, India
Received May 26, 1993
Accepted July 21, 1993
2-Methylheptadecane (I) is the sex pheromone of the family Arctiidae (tiger moth) and
was isolated by Roelof and Carde1 and assigned structure I on the basis of spectral data.
Haque et al.2 isolated a granular white solid (m.p. 80 °C) from the ether extract of dried
and powdered plant of Parthenium hysterophorous L. (Compositae) and proposed its
structure, 14-methylpentadecan-3-one (II) on the basis of spectroscopic data. Literature
records3 – 5 a few synthesis of I and II. We report herein a short and facile synthesis of
these compounds. The sequence of reactions employed in their synthesis is outlined in
Scheme 1.
Coupling reaction6 of isopropylmagnesium bromide with 11-bromo-1-undecene at
−10 °C using catalytic amount of lithium tetrachlorocuprate in anhydrous tetrahydro-
furan afforded olefin III. Treatment of III with acetoxyborohydride7, prepared in situ
from sodium borohydride and mercuric acetate in tetrahydrofuran, followed by oxida-
tion with alkaline hydrogen peroxide resulted in the formation of alcohol IV in quanti-
tative yield. Alcohol IV was converted into corresponding bromide V in reaction with
phosphorus tribromide in ether. Coupling of bromide V with 1-butylmagnesium
bromide in dry tetrahydrofuran in the presence6 of catalytic amount of dilithium tetra-
chlorocuprate at −10 °C yielded hydrocarbon I.
Pyridinium chlorochromate8 oxidation of alcohol IV, in dry dichloromethane af-
forded aldehyde VI which on treatment with ethylmagnesium bromide in dry ether fol-
lowed by pyridinium chlorochromate oxidation in dichloromethane gave ketone II in
good yield (cf. ref.3).
EXPERIMENTAL
All the glassware used for the experiment was thoroughly dried in an oven and cooled under the
stream of nitrogen. Purity of the samples was checked by TLC using silica gel impregnated with 13%
calcium sulfate. Silica gel (Acme, 60 – 80 mesh) was used for column chromatography. IR spectra
1
were recorded in Perkin–Elmer 377 spectrophotometer (wavenumber in cm−1) and H NMR spectra
(in CCl4 or CDCl3) on a Varian EM-390 instrument using tetramethylsilane as an internal standard.
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Singh, Arora, Kaur, Kad:
Chemical shifts are given in ppm (δ-scale), J in Hz. Unless otherwise stated, all the organic extracts
were dried over anhydrous sodium sulfate.
12-Methyltridec-1-ene (III)
To the Grignard reagent (prepared from magnesium turnings (0.24 g, 10 mmol) and 2-bromopropane
(1.23 g, 10 mmol) in dry tetrahydrofuran (15 ml) under nitrogen) added 11-bromo-1-undecene
(2.33 g, 10 mmol) in dry tetrahydrofuran (5 ml) at −10 °C and stirred for 30 min. To this a catalytic
amount of 0.1 M dilithium tetrachlorocuprate in tetrahydrofuran (1.5 ml) was added, stirred for 4 h
SCHEME 1
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New Compounds
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and then left overnight. The resulting solution was decomposed with a saturated aqueous solution of
ammonium chloride (20 ml) and extracted with ether (4 × 25 ml), the combined ethereal extract was
washed with brine (2 × 10 ml) and dried. Evaporation of the solvent under reduced pressure followed
by chromatographic purification over silica gel employing light petroleum ether as eluent furnished
pure olefin III; yield 0.82 g (42%). IR spectrum (neat): 2 940, 2 845, 1 640, 1 420, 1 340, 1 250,
1 200, 1 070, 910, 790. 1H NMR spectrum: 5.6 – 6.0 m, 1 H (−CH=CH2); 4.9 – 5.2 m, 2 H
(−CH=CH2); 2.0 m, 2 H (allylic methylene); 1.27 bs, 17 H (8 × −CH2−, −CH<); 0.85 d, 6 H
(2 × CH3, J = 6). For C14H28 (196.4) calculated: 85.6% C, 14.4% H; found: 85.5% C, 14.5% H.
12-Methyltridecan-1-ol (IV)
A dry 100 ml flask equipped with magnetic stirring bar, septum inlet and reflux condenser was
flushed with nitrogen. The flask was charged under nitrogen with sodium borohydride (0.76 g,
20 mmol) followed by the addition of tetrahydrofuran (40 ml) via syringe. The flask is immersed in
an ice-bath, and mercuric acetate (3.18 g, 10 mmol) was added slowly under a blanket of nitrogen.
The contents were allowed to stir for 1 h at 0 °C. The reaction mixture was brought to room tem-
perature and the olefin III (3.9 g, 20 mmol) was added dropwise. The contents were further stirred
for 16 h at room temperature for complete hydroboration.
The organoborane solution prepared as above was cooled to 0 °C and 3 M aqueous sodium hydrox-
ide (8 ml) was added slowly to the reaction mixture. Hydrogen peroxide (8 ml, 30% aqueous solu-
tion) was introduced dropwise to the stirred reaction mixture. The temperature was then raised
slowly, and the reaction mixture was heated at 70 °C for 1 h, during which the mercury coagulated.
The contents were brought to room temperature, decanted to separate mercury, and saturated with
sodium chloride. Isolation of the product was accomplished by a separatory funnel, and the aqueous
layer was extracted with ethyl ether (3 × 20 ml). The combined tetrahydrofuranethyl ether extract
was washed with water (2 × 10 ml) and brine (1 × 10 ml). The organic layer was concentrated under
reduced pressure and purified by column chromatography to yield 3.6 g (85%) of alcohol IV.
1
IR spectrum (neat): 3 380, 2 940, 2 860, 1 470, 1 330, 1 090, 800, 770. H NMR spectrum: 3.7 t,
2 H (−CH2OH, J = 6); 1.27 bs, 21 H (10 × −CH2−, −CH<); 0.8 d, 6 H (2 × CH3, J = 6). For
C14H30O (214.4) calculated: 78.4% C, 14.1% H; found: 78.5% C, 14.2% H.
12-Methyl-1-bromotridecane (V)
Phosphorus tribromide (1.2 g, 4.4 mmol) was added dropwise to an ice-cold and well stirred solution
of compound IV (1.98 g, 9.2 mmol) and pyridine (0.1 ml) in anhydrous ether (50 ml). After keeping
it overnight, the resulting solution was refluxed for 4 h. It was cooled, decomposed with cold
aqueous 10% sodium hydrogen carbonate solution (20 ml), extracted with ether (4 × 10 ml) and
dried. Evaporation of the solvent under reduced pressure afforded bromide V; yield 2.4 g (93%).
1
IR spectrum (neat): 3 060, 2 940, 1 470, 1 455, 1 270, 1 050, 920, 805. H NMR spectrum: 3.5 t,
2 H (−CH2Br, J = 6); 1.8, 2 H (−CH2CH2Br); 1.2 bs, 18 H (9 × −CH2−); 0.8 d, 6 H (2 × CH3, J = 6).
For C14H29Br (277.3) calculated: 60.6% C, 10.5% H; found: 60.7% C, 10.4% H.
2-Methylheptadecane (I)
To the Grignard reagent (prepared from magnesium turnings (0.29 g, 12 mmol) and 1-bromobutane
(1.64 g, 12 mmol) in dry tetrahydrofuran (15 ml) under nitrogen bromide V (3.32 g, 12 mmol) in dry
tetrahydrofuran (5 ml) was added at −10 °C and stirred for 30 min. To this a catalytic amount of
0.1 M dilithium tetrachlorocuprate in tetrahydrofuran (2 ml) was added, stirred for 4 h and then left
overnight. The resulting solution was decomposed with a saturated aqueous solution of ammonium
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Singh, Arora, Kaur, Kad:
chloride (20 ml) and extracted with ether (4 × 25 ml), the combined ethereal extract was washed with
brine (2 × 10 ml) and dried. Evaporation of the solvent under reduced pressure followed by chroma-
tographic purification over silica gel using light petroleum ether furnished pure compound I; yield
1
1.22 g (40%). IR spectrum (neat): 2 850, 2 780, 1 450, 1 250, 1 090, 1 015, 900, 815, 720. H NMR
spectrum: 1.2 bs, 30 H (15 × −CH2−); 0.85 m, 9 H (3 × CH3).
12-Methyltridecan-1-al (VI)
To pyridinium chlorochromate (3.6 g, 16.7 mmol) in methylene chloride (40 ml) alcohol IV
(2.68 g, 12.5 mmol) in dichloromethane (15 ml) was added under stirring. In a short time a black
mass separated and the stirring continued further for 2 h. Hexane (50 ml) was added, the mixture
was allowed to settle and then passed through a short pad of silica gel. Removal of the solvent
under reduced pressure afforded aldehyde VI; yield 2.4 g (84%). IR spectrum (neat): 2 950, 2 890,
2 705, 1 730, 1 470, 1 360, 1 180, 910, 740. 1H NMR spectrum: 9.87 bs, 1 H (−CHO); 2.2 m,
2 H (−CH2−CH=O); 1.25 bs, 19 H (9 × −CH2−, −CH<); 0.85 d, 6 H (2 × CH3, J = 6). For
C14H28O (212.4) calculated: 79.2% C, 13.3% H; found: 79.0% C, 13.4% H.
14-Methylpentadecan-3-one (II)
Aldehyde VI (2.12 g, 10 mmol) on reaction with ethylmagnesium bromide (1.33 g, 10 mmol) in
dry tetrahydrofuran (40 ml) followed by pyridinium chlorochromate oxidation of the obtained
alcohol in dichloromethane afforded the desired ketone II after chromatographic purification.
IR spectrum (CCl4): 2 850, 1 715, 1 440, 1 340, 1 100, 740. 1H NMR spectrum: 2.2 m, 4 H
(−CH2−C(=O)−CH2); 1.25 bs, 19 H (9 × −CH2−, −CH<); 0.83 m, 9 H (3 × CH3). For
C16H32O (240.4) calculated: 79.9% C, 13.4% H; found: 80.2% C, 13.2% H.
The financial support from UGC and CSIR, New Delhi is highly acknowledged.
REFERENCES
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4. Subramanian G. B. V., Mehrotra K.: Indian J. Chem., B 23, 665 (1984).
5. Kad G. L., Gupta S.: Indian J. Chem., B 28, 581 (1989).
6. Tamura M., Kochi J.: Synthesis 1971, 303.
7. Gautam V. K., Singh J., Dhillon R. S.: J. Org. Chem. 53, 187 (1988).
8. Corey E. J., Suggs J. W.: Tetrahedron Lett. 1975, 2647.
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