a
Pr C O (CH ) CH
2 5
PrCOOH + CH (CH ) OH
3
3
2 5
O
b
CH (CH ) COOH
2 2
CH (CH ) COOK
2 2
3
3
d
Pr C O (CH ) CH
2 5
3
c
O
CH (CH ) Br
2 6
CH (CH ) OH
2 5
3
3
a. C6H6, 10% H2SO4; b. KOH, H2O; c. PBr3/Et2O, Py; d. TBAB
The potassium salt of butyric acid was isolated. The reaction of PBr with hexanol gave 1-bromohexane. The
3
esterification was performed under PTC conditions. The reaction was carried out for 5 h at 160oC with TBAB catalyst. The
yield was 81%.
The usual esterification [6] took 30 h and gave a yield of 73%. Therefore, performing the esterification under PTC
conditions significantly simplified and accelerated production of the ester.
Thus, a new method for synthesizing the sex pheromone of the bug
using a PTC version of the
Lygus lineolaris
Wittig—Horner reaction has been developed.
EXPERIMENTAL
PMR spectra were recorded on a Varian XL-200 spectrometer at working frequency 200 MHz. The solvent was CCl
with HMDS as an internal standard. Analysis of all compounds agreed with the calculated values.
4
E-2-Hexenic Acid Ethyl Ester. A mixture of TBAB (0.966 g, 0.003 mol), NaOH (50%, 71 mL), and CH Cl (106
2
2
mL) was stirred until the solution was homogeneous. A solution of butanal (4.62 g, 0.06 mol) and the triethyl ester of
phosphonoacetic acid (12.85 g, 0.06 mol) in CH Cl (160 mL) was added dropwise. The mixture was refluxed for 2 h and
2
2
washed with water. The organic layer was dried over MgSO . The solvent was removed under reduced pressure. The solid
4
was distilled under vacuum, bp 65-67oC at 7 mm Hg, yield 5.5 g (68%).
PMR (ppm): 6.87 (1H, dt, J = 16.0, 6.5, H ), 5.75 (1H, d, J = 16.0 Hz, H ), 4.09 (2H, q, J = 6.2 Hz, OCH ), 2.20 (2H,
A
B
2
m, C–CH ), 1.1-1.6 (4H, m, CH ), 1.27 (3H, t, J = 6.3 Hz, OCH –CH ), 0.98 (3H, t, J = 6.9 Hz, CH ).
2
2
2
3
3
Trans-2-hexen-1-ol. A suspension of LiAlH (2 g, 0.052 mol) in anhydrous ether (50 mL) at room temperature was
4
treated dropwise with the ethyl ester of trans-2-hexenic acid (4.2 g, 0.029 mol) and refluxed for 3 h. The cooled mixture was
treated with water. The organic layer was separated. The aqueous layer was extracted with ether (3×50 mL). The combined
extracts were dried over MgSO . After solvent was removed, the solid was vacuum distilled, bp 65-67oC at 2 mm. Yield
4
1.3 g (55%), nD20 = 1.4274.
Trans-2-hexenylbutyrate. A solution of E-2-hexen-1-ol (1.33 g, 0.014 mol) and butyric acid (1.21 g, 0.014 mol) in
benzene (10 mL) and H SO (0.55 g, 10%) was refluxed for 3 h with a Dean—Stark trap. The cooled solution was poured onto
2
4
ice, extracted with ether, and dried over MgSO . Solvent was removed. The crude product was chromatographed with elution
4
by hexane—acetone (4:1) on Chemapol L100/250 silica gel, R = 0.95. Yield 0.91 g (40%), nD20 = 1.4076.
f
Hexylbutyrate. Potassium butyrate (3.02 g, 0.024 mol), TBAB (0.16 g), and bromohexane (4 g, 0.024 mol) were
mixed. The reaction mixture was held on a glycerine bath at 160oC for 5 h. After the reaction was complete, the solid mixture
was filtered off and washed with anhydrous ether. The solvent was removed. The solid was distilled, bp 178oC. Yield
3.34 g (81%).
REFERENCES
1.
2.
3.
A. Sh. Khamraev, Zashch. Rast., 25 (1993).
R. J. Freeman and A. J. Mueller, J. Entomol. Sci., 218 (1989).
A. V. Skirkyavichus, Pheromone Handbook [in Russian], Vilnius, Institute of Zoology and Parasitology, Academy
of Sciences of the Lithuanian SSR (1988).
4.
5.
6.
R.C. Gueldner and W. Parrott, Insect Biochem., 4, 389 (1978).
Z. Mouloungui, M. Delmas, and A. Gaset, J. Org. Chem., 68, 3936 (1989).
Weygand-Hilgetag, Experimental Methods in Organic Chemistry [in Russian], Khimiya, Moscow (1968).
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