A new approach to the synthesis of racemic analogs of 1, 5-dimethyl-branched insect pheromones from 4-methyltetrahydropyran

Article abstract of DOI:10.1023/A:1023939730023

A new procedure was developed for the synthesis of racemic analogs of 1,5-dimethyl-branched insect pheromones based on monoalkylation of ethyl acetoacetate with 1-acetoxy-5-bromo-3-methylpentane produced upon decyclization of 4-methyltetrahydropyran.

Full text of DOI:10.1023/A:1023939730023

740
Russian Chemical Bulletin, International Edition, Vol. 52, No. 3, pp. 740—744, March, 2003
A new approach to the synthesis of racemic analogs
of 1,5ꢀdimethylꢀbranched insect pheromones from 4ꢀmethyltetrahydropyran*
G. Yu. Ishmuratov,aꢀ M. P. Yakovleva,a A. V. Galyautdinova,a R. R. Muslukhov,a and G. A. Tolstikovb
aInstitute of Organic Chemistry, Ufa Research Center of the Russian Academy of Sciences,
71 prosp. Oktyabrya, 450054 Ufa, Russian Federation.
Fax: +7 (347 2) 35 6066. Eꢀmail: kharis@anrb.ru
bN. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences,
9 prosp. Akad. Lavrent´eva, 630090 Novosibirsk, Russian Federation.
Fax: +7 (383 2) 34 4752
A new procedure was developed for the synthesis of racemic analogs of 1,5ꢀdimethylꢀ
branched insect pheromones based on monoalkylation of ethyl acetoacetate with 1ꢀacetoxyꢀ5ꢀ
bromoꢀ3ꢀmethylpentane produced upon decyclization of 4ꢀmethyltetrahydropyran.
Key words: 1ꢀacetoxyꢀ5ꢀbromoꢀ3ꢀmethylpentane, 8ꢀacetoxyꢀ6ꢀmethyloctanꢀ2ꢀone, ethyl
acetoacetate, racemic analogs of pheromones, 4ꢀmethyltetrahydropyran, Wittig reaction, crossꢀ
coupling.
4ꢀMethyltetrahydropyran (1) acidꢀcatalyzed ringꢀ
opening products, among them 1ꢀacetoxyꢀ5ꢀbromoꢀ3ꢀ
methylpentane (2), find rather wide use in the synthesis
of methylꢀbranched lowꢀmolecularꢀweight insect bioꢀ
regulators.1,2
In the present study, we examined new approaches to
the synthesis of biologically active3 racemic analogs of
1,5ꢀdimethylꢀbranched insect pheromones (3—5) based
on chemoselective transformations of the monoalkylaꢀ
tion product of ethyl acetoacetate with bromoacetate 2
(Scheme 1).
The NMR spectra of sample 6 have no signals for the
protons and carbon atoms of the starting compounds and
other structural impurities.
The reaction involving lowerꢀbasic EtOLi 4 instead of
EtONa proceeded much more slowly (∼50 h). However,
this process was not accompanied by the aboveꢀmenꢀ
tioned cyclization and a mixture of diastereomeric acetoxy
oxo esters 6 was obtained in 92% yield. Even a higher
yield (96%) was attained in the reaction performed in a
1 : 1 mixture of aprotic solvents DMF and benzene with
sodium hydride as a base.
It should be noted that the low yield (25%) of a mixꢀ
ture of diastereomeric ethyl 7ꢀacetoxyꢀ2ꢀacetylꢀ5ꢀmethylꢀ
heptanoates (6) obtained in the reaction performed under
standard conditions (EtONa/EtOH, 10 h) is attributed to
the fact that this transformation was accompanied by cyꢀ
clization of 2 as a side reaction giving rise to the starting
pyran 1.
The chemical shifts and multiplicities of the signals in
the 13C NMR spectrum of a mixture of diastereomers 6
are consistent with the assumed structure. The signals for
the C(4), C(5), C(6), and CH3C(5) atoms are observed as
pairs of closely spaced lines, which is attributable to the
difference in shielding of the aboveꢀmentioned nuclei of
diastereomers 6. Equal integral intensities of the signals
for the corresponding atoms in the 13C NMR spectra,
which were acquired using a longer pulse delay (20 s),
suggest that compound 6 represents a racemic mixture of
diastereomers.
Decarbethoxylation of 6 under the standard condiꢀ
tions5 afforded the key product, viz., 8ꢀacetoxyꢀ6ꢀmethylꢀ
octanꢀ2ꢀone (7). The Wittig olefination of the latter comꢀ
pound with ethylideneꢀ and nꢀhexylidenetriphenylphosꢀ
phoranes (0→20 °C) afforded mixtures (E : Z ∼ 1 : 1) of
unsaturated acetates 8 and 9, respectively. The ratios
of stereoisomers in these mixtures were determined
based on the GLC data and the integral intensity ratios
for the signals of the methyl groups at the double bond
1
(7ꢀCH3) in the H NMR spectra, which show resoꢀ
nances at δ 1.65 (for the Z isomer) and 1.56 (for the
E isomer).6
Alcohols 10 prepared by hydrolysis of acetates 8 were
further subjected to hydrogenation. Saturated alcohols 11
were transformed into a mixture of diastereomeric 4,8ꢀdiꢀ
methyldecanals 3 according to a procedure developed by
us earlier.7 The latter mixture is a biologically active anaꢀ
log of the aggregation pheromone of Tribolium flour
beetles, viz., of 4R,8Rꢀdimethyldecanal.3
Besides, pꢀtoluenesulfonates 13 and 14 prepared from
alcohols 10 as well from alkenols 12 corresponding to
* Dedicated to Academician I. P. Beletskaya on the occasion of
her anniversary.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 709—712, March, 2003.
1066ꢀ5285/03/5203ꢀ740 $25.00 © 2003 Plenum Publishing Corporation

1,5ꢀDimethylꢀbranched pheromones
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 3, March, 2003
741
Scheme 1
R1 = Me (8, 10, 13, 15), nꢀC5H11 (9, 12, 14, 16); R2 = H (10, 12), Ac (8, 9), Ts (13, 14); R3 = nꢀC8H17 (15), nꢀC7H15 (16)
Reagents and conditions: a) AcBr/ZnCl2 (see Ref. 2); b) AcCH2CO2Et/EtOLi or AcCH2CO2Et/NaH/PhH—DMF; c) LiI/DMF;
d) R1CH=PPh3 (R1 = Me, nꢀC5H11); e) KOH—MeOH; f ) TsCl/Py; g) H2/Pd—C; h) nꢀC6H13MgBr or nꢀC5H11MgBr/Li2CuCl4;
i) HBr/H2SO4; j) Mg; k) DMF (see Ref. 7); l) B2H6; m) H2O2; n) Ac2O/Py (see Ref. 6).
acetates 9 can be involved into catalyzed crossꢀcoupling
with nꢀhexylꢀ and nꢀpentylmagnesium bromides, respecꢀ
tively.
ethyl acetoacetate with 1ꢀacetoxyꢀ5ꢀbromoꢀ3ꢀmethylꢀ
pentane, which is a decyclization product of 4ꢀmethylꢀ
tetrahydropyran.
The first of the aboveꢀmentioned mixtures of monoꢀ
enes 15 and 16 thus synthesized was transformed into a
mixture of diastereomeric acetates 4 according to a proꢀ
cedure described earlier.6 The resulting mixture is a bioꢀ
logically active analog of diprionyl acetate, viz., of
2Sꢀacetoxyꢀ3S,7Sꢀdimethylpentadecane,3 which is the sex
pheromone of Diprion and Neodiprion pine sawflies.
Catalytic hydrogenation of a mixture of olefins 16
afforded diastereomeric 7,11ꢀdimethyloctadecanes 5,
which are analogs of the oviposition attractant of yellow
fever mosquito Aedes aegypti.8 The stereochemistry of the
latter compound remains to be established.
Experimental
The IR spectra were recorded on a URꢀ20 instrument in
thin layers. The NMR spectra were measured on a Bruker
AMꢀ300 spectrometer (300.13 MHz for 1H and 75.47 MHz
for 13C) in CDCl3 with Me4Si as the internal standard. The
GLC analysis was carried out on a Chromꢀ5 instrument (the
column length was 1.2 m; silicon SEꢀ30 (5%) on Chromaton
NꢀAWꢀDMCS (0.16—0.20 mm) as the stationary phase; the
column temperature was 50—300 °C) using helium as the
carrier gas. Column chromatography and TLC were carried
out with the use of light petroleum (LP), b.p. 40—70 °C.
4ꢀMethyltetrahydropyran was prepared according to a known
procedure.9
To summarize, we developed a new approach to the
synthesis of racemic analogs of acyclic 1,5ꢀdimethylꢀ
branched insect pheromones based on monoalkylation of

742
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 3, March, 2003
Ishmuratov et al.
Ethyl 7ꢀacetoxyꢀ2ꢀacetylꢀ5ꢀmethylheptanoates (6). A. Ethyl
(CDCl3), δ: 0.88 (d, 3 H, 6ꢀCH3, J = 6.5 Hz); 1.05—1.70 (m,
7 H, H(4), H(5), H(6), H(7)); 2.01 (s, 3 H, CH3CO); 2.13 (s,
3 H, CH3CO2); 2.44 (t, 2 H, H(3), J = 7.0 Hz); 3.99—4.10 (m,
2 H, H(8)). 13C NMR (CDCl3), δ: 18.93 (q, CH3C(6)); 20.55
(q, CH3CO2); 20.67, 34.93, and 35.85 (all t, C(4), C(5), C(7));
29.30 (q, C(1)); 29.44 (d, C(6)); 43.33 (t, C(3)); 62.34 (t, C(8));
170.58 (s, CH3CO2); 208.32 (s, C(2)).
acetoacetate (9.42 g, 72.5 mmol) was added dropwise to a stirred
(Ar, 20 °C) solution of EtONa prepared from Na (1.55 g,
67.3 mgꢀat.) in anhydrous EtOH (34 mL). Then bromide 2
(10.00 g, 44.8 mmol), which was prepared from 4ꢀmethyltetraꢀ
hydropyran (1) according to a known procedure,2 was added
with refluxing. The reaction mixture was refluxed for 10 h (TLC
control on SiO2, LP—Et2O, 1 : 1), cooled, and filtered. The
precipitate was washed on a filter with EtOH and the filtrate was
concentrated. The residue was chromatographed on a column
with SiO2 (LP—Et2O, 5 : 1). A mixture of diastereomers 6 was
obtained in a yield of 2.45 g (25%), Rf 0.18 (LP—Et2O, 1 : 1).
Found (%): C, 61.61; H, 8.83. C14H24O5. Calculated (%):
C, 61.74; H, 8.88. IR, ν/cm–1: 1755, 1745 (O—C=O); 1718
(C=O); 1245, 1140, 1055 (C—O—C). 1H NMR (CDCl3), δ:
0.91 (d, 2 H, H3C(5), J = 6.5 Hz); 1.27 (t, 3 H, CH3CH2O, J =
7.0 Hz); 1.39—1.99 (m, 7 H, H(3), H(4), H(5), H(6)); 2.03 (s,
3 H, CH3CO); 2.22 (s, 3 H, CH3CO2); 3.36 (t, 1 H, H(2), J =
7.0 Hz); 4.03—4.12 (m, 2 H, H(7)); 4.19 (q, 2 H, CH3CH2O,
J = 7.0 Hz). 13C NMR (CDCl3), δ: 13.81 (q, CH3CH2O2C);
18.95 (18.89) (q, CH3C(5)); 20.68 (q, CH3CO2); 25.23 (t, C(3));
28.54 (q, CH3CO); 29.48 (29.43) (d, C(5)); 34.08 (34.00)
(t, C(4)); 34.91 (34.86) (t, C(6)); 59.62 (d, C(2)); 61.01
(t, CH3CH2O2C); 62.33 (t, C(7)); 169.47 (s, C(1)); 170.78
(s, CH3CO2); 202.75 (s, CH3CO).
B. Ethyl acetoacetate (9.09 g, 70.0 mmol) was added
dropwise to a stirred (Ar, 20 °C) solution of EtOLi prepared
from Li (0.38 g, 53.8 mgꢀat.) in anhydrous EtOH (27 mL). Then
bromoacetate 2 (10.00 g, (44.8 mmol) was added with refluxing.
The reaction mixture was refluxed for 50 h and then treated as
described in the method A. A mixture 6 was obtained in a
yield of 11.17 g (92%). According to the spectroscopic data,
this mixture is identical with that prepared according to the
method A.
C. Ethyl acetoacetate (4.77 g, 36.7 mmol) was added
dropwise to a stirred (Ar, 0 °C) suspension of NaH (0.88 g,
36.7 mmol) in anhydrous benzene (37 mL) and anhydrous DMF
(37 mL). The reaction mixture was kept at ∼20 °C until the
reaction mixture became homogeneous (∼3 h). Then comꢀ
pound 2 (7.96 g, 36.7 mmol) was added dropwise to the resulting
solution at 0 °C. The reaction mixture was kept at ∼20 °C for
11 h and then refluxed for 12 h, after which water (40 mL) was
added. Then the reaction mixture was extracted with benzene
(4×40 mL). The combined extracts were washed with water
(20 mL), dried with MgSO4, filtered, and concentrated. The
residue was chromatographed on SiO2 (LP—Et2O, 5 : 1). A mixꢀ
ture 6 was obtained in a yield of 9.58 g (96%). According to the
spectroscopic data, this mixture is identical with that prepared
according to the method A.
3,7ꢀDimethylnonꢀ7Z/Eꢀenꢀ1ꢀyl acetates (8). A 1 M BunLi
solution in hexane (33.0 mL, 33.0 mmol) was added dropwise
with stirring to a suspension of ethyltriphenylphosphonium broꢀ
mide (12.24 g, 33.0 mmol) in anhydrous THF (100 mL)
(Ar, 0 °C). The reaction mixture was stirred at ∼20 °C for 1 h
and cooled to 0 °C. Then a solution of acetoxy ketone 7 (4.00 g,
20.0 mmol) in anhydrous THF (14 mL) was added dropwise.
The reaction mixture was stirred at 0 °C for 15 min, kept at
∼20 °C for 12 h, diluted with light petroleum (200 mL), and
filtered through a layer of SiO2. The solvent was evaporated and
the residue was chromatographed on SiO2 (LP—Et2O, 10 : 1).
A mixture of acetates 8 (Z/E ∼ 1 : 1) was obtained in a yield of
3.60 g (85%), Rf 0.78 (LP—Et2O, 1 : 1). Found (%): C, 73.46;
H, 11.35. C13H24O2. Calculated (%): C, 73.53; H, 11.39. IR,
ν/cm–1: 1745 (C=O); 1658 (C=C); 1240, 1055 (C—O—C).
1H NMR (CDCl3), δ: 0.90 (d, 3 H, H3C(3), J = 6.5 Hz); 1.25
(br.s, 7 H, H(2), H(3), H(4), H(5)); 1.55 and 1.66 (both s,
1.5 H each, H3C(7)); 1.50—1.65 (m, 3 H, H(9)); 1.88—2.00 (m,
2 H, H(6)); 2.02 (s, 3 H, CO2CH3); 4.03—4.15 (m, 2 H, H(1));
5.12—5.25 (m, 1 H, H(8)). 13C NMR (CDCl3), δ: 13.24 (13.32)
(q, C(9)); 15.51 (E) (23.35 (Z )) (q, CH3C(7)); 19.47 (19.50)
(q, CH3C(3)); 21.03 (q, CH3CO2); 25.17, 35.49, and 36.68
(all t, C(2), C(4), C(5)); 29.73 (29.76) (d, C(3)); 35.49 (39.84)
(t, C(6)); 63.07 (t, C(1)); 118.24 (118.93) (d, C(8)); 135.85
(136.06) (s, C(7)); 171.27 (s, CH3CO2).
3,7ꢀDimethylnonꢀ7Z/Eꢀenꢀ1ꢀols (10). A mixture of acetates 8
(3.56 g, 16.8 mmol) was dissolved in MeOH (17 mL), KOH
(0.98 g, 17.5 mmol) was added, and the reaction mixture was
refluxed for 4 h. Then MeOH was evaporated and the residue
was extracted with Et2O (3×30 mL). The combined extracts
were washed with a saturated NaCl solution, dried with Na2SO4,
filtered, and concentrated. A mixture of alcohols 10 was obꢀ
tained in a yield of 2.51 g (88%), Rf 0.52 (LP—Et2O, 1 : 1).
Found (%): C, 77.47; H, 12.99. C11H22O. Calculated (%):
C, 77.58; H, 13.02. IR, ν/cm–1: 3450—3300 (OH); 1650 (C=C).
1H NMR (CDCl3), δ: 0.91 (d, 3 H, H3C(3), J = 6.5 Hz); 1.29
(br.s, 6 H, H(2), H(4), H(5)); 1.56 and 1.65 (both s, 1.5 H each,
H3C(7)); 1.54 (s, 3 H, H(9)); 1.61—1.67 (m, 1 H, H(3)); 1.87 (t,
2 H, H(6), J = 7 Hz); 3.53 (br.s, 1 H, OH); 3.79 (t, 2 H, H(1),
J = 6.5 Hz); 5.15—5.25 (m, 1 H, H(8)). 13C NMR (CDCl3), δ:
13.00 (13.20) (q, C(9)); 15.40 (E) (23.30 (Z )) (q, CH3C(7));
19.55 (19.57) (q, CH3C(3)); 25.40, 35.56, and 36.80 (all t, C(2),
C(4), C(5)); 27.40 (27.41) (d, C(3)); 33.68 (Z ) (39.20 (E))
(t, C(6)); 59.57 (t, C(1)); 118.40 (119.20) (d, C(8)); 136.21
(136.70) (d, C(7)).
8ꢀAcetoxyꢀ6ꢀmethyloctanꢀ2ꢀone (7). Lithium iodide (12.87 g,
95.5 mmol) was added in one portion to a stirred (20 °C) soluꢀ
tion of ester 6 (10.00 g, 36.8 mmol) in anhydrous DMF (104 mL).
The reaction mixture was refluxed until liberation of CO2 ceased
(∼12 h). Then the resulting mixture was cooled and extracted
with Et2O (4×50 mL). The combined extracts were washed sucꢀ
cessively with saturated solutions of Na2S2O3 and NaCl, dried
with Na2SO4, and filtered. The solvent was evaporated. Acetoxy
ketone 7 was obtained in a yield of 5.96 g (81%), Rf 0.23
(LP—Et2O, 1 : 1). Found (%): C, 65.70; H, 10.11. C11H20O3.
Calculated (%): C, 65.97; H, 10.07. IR, ν/cm–1: 1740
(O—C=O); 1720 (C=O); 1250, 1055 (C—O—C). 1H NMR
3,7ꢀDimethylꢀ1ꢀtosyloxyꢀ7Z/Eꢀnonenes (13). A mixture of
alcohols 10 (2.00 g, 11.6 mmol) was dissolved in dry Py (3.5 mL).
Then TsCl (2.43 g, 12.8 mmol) was added portionwise at 0—5 °C.
The reaction mixture was kept at 0 °C for 12 h, diluted with
Et2O (50 mL), washed successively with saturated solutions of
CuSO4, Na2CO3, and NaCl, dried with MgSO4, filtered, and
concentrated. A mixture of pꢀtoluenesulfonates 13 was obtained
in a yield of 3.16 g (84%). IR, ν/cm–1: 1660 (C=C); 1600 (Ar);
1350, 1180 (S=O).

1,5ꢀDimethylꢀbranched pheromones
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 3, March, 2003
743
3,7ꢀDimethyltridecꢀ7Z/Eꢀenꢀ1ꢀyl acetates (9). nꢀHexylꢀ
triphenylphosphonium bromide (6.80 g, 15.9 mmol) was conꢀ
verted into phosphorane and the reaction of the latter with keꢀ
tone 7 (1.93 g, 9.7 mmol) was performed analogously to the
synthesis of 8. A mixture of acetates Zꢀ9/Eꢀ9 (∼ 1 : 1) was obꢀ
tained in a yield of 1.69 g (65%), Rf 0.79 (LP—Et2O, 1 : 1).
Found (%): C, 75.96; H, 11.98. C17H32O2. Calculated (%):
C, 76.06; H, 12.02. IR, ν/cm–1: 1750 (C=O); 1660 (C=C);
1245, 1050 (C—O—C). 1H NMR (CDCl3), δ: 0.90 (d, 3 H,
H3C(3), J = 6.0 Hz); 0.93 (t, 3 H, H3C(13), J = 7.0 Hz); 1.26
(br.s, 13 H, H(2), H(3), H(4), H(5), H(10), H(11), H(12));
1.48 and 1.63 (both s, 1.5 H each, H3C(7)); 1.88—2.01 (m, 4 H,
H(6), H(9)); 2.03 (s, 3 H, CH3CO2); 4.03—4.15 (m, 2 H, H(1));
5.12—5.25 (m, 1 H, H(8)). 13C NMR (CDCl3), δ: 14.05
(q, C(13)); 15.42 (E) (23.30 (Z)) (q, CH3C(7)); 19.70 (19.73)
(q, CH3C(3)); 21.04 (q, CH3CO2); 22.80, 25.42, 29.56, 29.70,
and 30.89 (all t, C(2), C(4), C(5), C(10)—C(12)); 27.40 (27.48)
(d, C(3)); 33.68 (39.20) (t, C(6)); 35.56 (36.80) (t, C(9)); 63.02
(t, C(1)); 126.72 (127.00) (d, C(8)); 134.47 (134.77) (s, C(7));
170.96 (s, CH3CO2).
3,7ꢀDimethyltridecꢀ7Z/Eꢀenꢀ1ꢀols (12). A mixture of acꢀ
etates 9 (1.60 g, 6.0 mmol) was treated with KOH in MeOH as
described in the synthesis of 10. A mixture of alcohols 12 was
obtained in a yield of 1.22 g (90%), Rf 0.54 (LP—Et2O, 1 : 1).
Found (%): C, 79.51; H, 13.39. C15H30O. Calculated (%):
C, 79.57; H, 13.36. IR, ν/cm–1: 3450—3300 (OH); 1645 (C=C).
1H NMR (CDCl3), δ: 0.90 (d, 3 H, H3C(3), J = 6.0 Hz); 0.94 (t,
3 H, H3C(13), J = 7.0 Hz); 1.31 (br.s, 13 H, H(2), H(3), H(4),
H(5), H(10), H(11), H(12)); 1.50 and 1.61 (both s, 1.5 H each,
H3C(7)); 1.88—2.00 (m, 4 H, H(6), H(9)); 3.80 (t, 2 H, H(1),
J = 6.5 Hz); 5.10—5.20 (m, 1 H, H(8)). 13C NMR (CDCl3), δ:
14.00 (q, C(13)); 15.38 (E) (23.00 (Z)) (q, CH3C(7)); 19.54
(19.60) (q, CH3C(3)); 22.85, 25.40, 29.50, 29.85, 30.85, 35.56
(all t, C(2), C(4), C(5), C(10)—C(12)); 28.50 (28.55) (d, C(3));
33.70 (39.12) (t, C(6)); 35.50 (36.80) (t, C(9)); 59.57 (t, C(1));
118.30 (119.10) (d, C(8)); 134.45 (135.00) (s, C(7)).
rated and the aqueous layer was extracted with Et2O (3×20 mL).
The combined extracts were washed successively with saturated
solutions of Na2CO3 and NaCl, dried with MgSO4, and concenꢀ
trated. The residue was chromatographed on neutral Al2O3 (penꢀ
tane—Et2O, 9 : 1). A mixture of alkenes 15 was obtained in a
yield of 1.90 g (83%), Rf 0.78 (pentane—Et2O, 9 : 1). Found (%):
C, 85.61; H, 14.30. C17H34. Calculated (%): C, 85.63; H, 14.37.
The parameters of the IR and 1H NMR spectra are virtually
identical with those described earlier.6
7,11ꢀDimethylꢀ6ꢀoctadecenes (16). Analogously to the
aboveꢀdescribed synthesis, the reaction of pꢀtoluenesulfonates
14 (1.70 g, 4.5 mmol) in anhydrous Et2O (18 mL) with a 0.1 M
Li2CuCl4 solution in THF (1.2 mL), Mg (0.27 g, 11.2 mgꢀat.),
and nꢀC5H11Br (1.34 g, 8.1 mmol) afforded a mixture of alkenes
16 in a yield of 1.02 g (81%), Rf 0.77 (pentane—Et2O, 9 : 1).
Found (%): C, 85.61; H, 14.30. C20H40. Calculated (%):
1
C, 85.63; H, 14.37. H NMR (CDCl3), δ: 0.88 (t, 9 H, H(1),
H3C(11), H(18), J = 7.0 Hz); 1.26 (br.s, 22 H, H(2), H(3),
H(4), H(9), H(10), H(12), H(13), H(14), H(15), H(16), H(17));
1.50 and 1.61 (both s, 1.5 H each, H3C(7)); 1.87—2.10 (m, 4 H,
H(5), H(8)); 5.15—5.20 (m, 1 H, H(6)). 13C NMR (CDCl3), δ:
14.05 and 14.12 (both q, C(1), C(18)); 19.28 (q, H3CC(11));
22.71, 24.73, 25.42, 27.53, 30.56, 31.91, 33.00, 36.48, 36.80,
37.07, and 37.63 (all t, C(2), C(3), C(4), C(9), C(10), C(12),
C(13), C(14), C(15), C(16), C(17)); 28.26 (d, C(11)); 33.00
(39.20) (t, C(8)); 35.49 (39.72) (t, C(5)); 118.30 (119.10)
(d, C(6)); 134.47 (134.92) (s, C(7)).
4,8ꢀDimethyldecanals (3) were prepared in 70% yield from a
mixture of diastereomeric alcohols 11 according to a procedure
developed earlier.7 The parameters of the IR and 1H NMR
spectra are virtually identical with those described earlier.7
2ꢀAcetoxyꢀ3,7ꢀdimethylpentadecanes (4) were prepared in
76% yield from a mixture of alkenes 15 according to a procedure
developed earlier.6 The parameters of the IR and 1H NMR
spectra are virtually identical with those described earlier.6
7,11ꢀDimethyloctadecanes (5). A mixture of alkenes 16
(0.50 g, 1.8 mmol) and 5% Pd—C (0.18 g) in anhydrous EtOH
(36 mL) was stirred under an atmosphere of hydrogen until
adsorption of the latter ceased (∼3 h). The precipitate was filꢀ
tered off, the filtrate was concentrated, and a mixture of alꢀ
kanes 5 was obtained in a yield of 0.49 g (97%), Rf 0.80 (hexꢀ
ane—Et2O, 7 : 3). Found (%): C, 84.98; H, 14.95. C20H42. Calꢀ
3,7ꢀDimethylꢀ1ꢀtosyloxytridecꢀ7Z/Eꢀene (14). A mixture of
alcohols 12 (1.20 g, 5.3 mmol) was transformed into a mixture
of pꢀtoluenesulfonates 14 according to the procedure used for
the preparation of sulfonates 13. The yield was 1.73 g (86%). IR,
ν/cm–1: 1665 (C=C); 1600 (Ar); 1360, 1185 (S=O).
3,7ꢀDimethylnonanꢀ1ꢀols (11). A mixture of unsaturated
alcohols 10 (0.50 g, 2.9 mmol) and 5% Pd—C (0.15 g) in anꢀ
hydrous MeOH (15 mL) was stirred under H2 until absorption
of the latter ceased (∼20 h). The precipitate was filtered off and
the filtrate was concentrated. A mixture of diastereomers 11 was
obtained in a yield of 0.48 g (97%), Rf 0.28 (hexane—Et2O,
7 : 3). Found (%): C, 76.58; H, 13.94. C11H24O. Calculated (%):
C, 76.67; H, 14.04. The parameters of the IR and 1H NMR
spectra are virtually identical with those described earlier.7
3,7ꢀDimethylpentadecꢀ2Z/Eꢀenes (15). A 0.1 M Li2CuCl4
solution in THF (2.4 mL) was added to a stirred solution of a
mixture of pꢀtoluenesulfonates 13 (3.12 g, 9.6 mmol) in anhyꢀ
drous Et2O (38 mL) (–78 °C, Ar). Then a solution of hexylꢀ
magnesium bromide, which was prepared from Mg (0.58 g,
24 mgꢀat.) and nꢀC6H13Br (2.85 g, 17.3 mmol), was added
dropwise. The reaction mixture was stirred at –70 °C for 2 h and
then at ∼20 °C for 12 h. Then Et2O (20 mL) was added. The
reaction mixture was stirred for 0.5 h and poured into a cooled
saturated NH4Cl solution (15 mL). The organic layer was sepaꢀ
1
culated (%): C, 85.02; H, 14.98. The parameters of the H and
13C NMR and IR spectra are virtually identical with those deꢀ
scribed earlier.10,11
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Received October 30, 2001;
in revised form December 9, 2002