Highly stereoselective synthesis of 2,5-disubstituted (E, E)-penta-2,4-dienals

Article abstract of DOI:10.1007/s11172-010-0008-4

A condensation of α,β-unsaturated aldehydes with O-protected 4-hydroxybutanal N-(tert-butyl)-imine has been exemplified for the first time using (E)-cinnamic and (E)-4-methoxycinnamic aldehydes. (E,E)-2,5-Disubstituted penta-2,4-dienals, which are key intermediates in the synthesis of strobilurins A and X, were prepared in good yields and close to 100% stereoselectivity.

Full text of DOI:10.1007/s11172-010-0008-4

Russian Chemical Bulletin, International Edition, Vol. 58, No. 2, pp. 312—316, February, 2009
312
Highly stereoselective synthesis of 2,5ꢀdisubstituted
(E,E)ꢀpentaꢀ2,4ꢀdienals*
N. Ya. Grigorieva, A. G. Smirnov, V. A. Popovsky, and A. V. Stepanov
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Eꢀmail: ves@ioc.ac.ru
A condensation of α,βꢀunsaturated aldehydes with Oꢀprotected 4ꢀhydroxybutanal Nꢀ(tertꢀbutyl)ꢀ
imine has been exemplified for the first time using (E)ꢀcinnamic and (E)ꢀ4ꢀmethoxycinnamic
aldehydes. (E,E)ꢀ2,5ꢀDisubstituted pentaꢀ2,4ꢀdienals, which are key intermediates in the synꢀ
thesis of strobilurins A and X, were prepared in good yields and close to 100% stereoselectivity.
Key words: stereocontrolled synthesis, directed aldol condensation, strobilurins, 2,5ꢀdisubꢀ
stituted (E,E)ꢀpentaꢀ2,4ꢀdienals, α,βꢀunsaturated aldehydes, aldimines.
Earlier, it has been shown2 that the condensation of
Scheme 1
deprotonated Nꢀ(tertꢀbutyl)imines 2 with aliphatic aldeꢀ
hydes 3, including those containing several isolated C=С
bonds in the chain, leads to a predominant (>95%) forꢀ
mation of (E)ꢀα,βꢀdisubstituted enals 1a since they are
thermodynamically more stable, than the corresponding
(Z)ꢀisomers 1b (Scheme 1). It was also found that
enals 1a can be smoothly converted to the corresponding
(Z)ꢀtrisubstituted olefins 4 with complete retention of
configuration of the C=C bond (see Scheme 1).
The sequence of the reactions under consideration
allowed one to synthesize a representative set of lowꢀ
molecularꢀweight regulators of polyprenol series, i.e.,
dolichols,3—5 their analogs,6,7 as well as sex pheromones
of some insects.8,9
Condensation of aldimines with α,βꢀunsaturated
aldehydes 5 has not been studied earlier. At the same
time, this reaction is of considerable interest since it can
presumably lead to dienals 6 with high stereoselectivity
and further to dienes 7 containing a 2,5ꢀdisubstituted
pentadiene fragment, which is encountered with in
biologically active natural compounds. An example of
the latter are strobilurins,10,11 a group of antifungus antiꢀ
biotics of a general formula 8, which amounts at present
about 20 representatives differing in substituents in the
aromatic ring. As it can be seen from the retrosynthetic
analysis given in Scheme 2, the key intermediates deterꢀ
mining configuration of the molecules 8 can be dienals 9.
The present communication is devoted to the synthesis of
dienals 9a—e with various protecting groups R´ at the
hydroxyl of the C(2´) atom. The latter are precursors of
parent strobilurins A (8a) and X (8b).
In accordance with the approach chosen, dienals
9a—e can be obtained by the condensation of commerꢀ
cially available (E)ꢀcinnamic (10a) and (E)ꢀ4ꢀmethoxyꢀ
cinnamic aldehydes (10b) with Nꢀ(tertꢀbutyl)imines of
4ꢀbenzyloxyꢀ (11a), 4ꢀ(tertꢀbutyldimethylsilyloxy)ꢀ (11b)
and 4ꢀ(4ꢀmethoxybenzyloxy)butanals (11c), respectively.
Alcohol 13a necessary for the synthesis of imine 11a
was obtained in 70% yield by the reductive cleavage of
acetal 12 following the Eliel method,12 whereas the
* On the occasion of the 75th anniversary of the foundation
of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences. For preliminary communication,
see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 310—314, February, 2009.
1066ꢀ5285/09/5802ꢀ0312 © 2009 Springer Science+Business Media, Inc.

2,5ꢀDisubstituted (E,E)ꢀpentaꢀ2,4ꢀdienals
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
313
Scheme 2
8, 10: R = H (a), OMe (b)
9
R
R´
a
H
Bn
b
OMe
Bn
c
H
d
e
H
OMe
SiMe2But
11: R´ = Bn (a), SiMe2But (b), 4ꢀMeOC6H4CH2 (c)
SiMe2But
4ꢀMeOC6H4CH2
Scheme 3
viii,
for
for
9, 16
R
R´
a
H
Bn
b
OMe
Bn
c
H
d
e
H
11,13,14,15: R´ = Bn (a), SiMe2But (b), 4ꢀMeOC6H4CH2 (c)
OMe
SiMe2But
SiMe2But
4ꢀMeOC6H4CH2
t
Reagents and conditions: i. PhCHO/PhH, cat. H SO , reflux, 12 h; ii. AlCl —LiAlH (3 : 1)/Et O, 0 °C, 30 min, then ~20 °C, 3 h; iii. Me Bu SiCl
2
4
3
4
2
2
t
or 4ꢀMeOC H CH Cl (0.3 equiv.)/NaH/THF, ~20 °C, 30 min; iv. PCC/AcONa/CH Cl , 3 h; v. Bu NH /Et O/mol.sieves 4 Å, ~20 °C, 7 h;
vi. LDA/Et O/0 °C, 45 min; vii. (E)ꢀPhCH=CHCHO (10a) or (E)ꢀ4ꢀMeOC H CH=CHCHO (10b), –80 °C, 40 min, then heating (4 h) to ~0 °C;
6
4
2
2
2
2
2
2
6 4
viii. 3% aq. HCl, 20 min; ix. H O—Me CO (1 : 4), cat. H SO , reflux 5 h; x. aq. solution of (COOH) to pH 4, ~20 °C, 2.5 h.
2
2
2
4
2
McDougal method13 modified by us proved optimum for
preparing alcohols 13b,c (Scheme 3). Alcohols 13b,c were
obtained without side bisꢀethers 14b,c. The oxidation of
alcohols 13a—c with PCC in the presence of AcONa
gives good yields of known aldehydes 15a—c, which were
converted to imines 11a—c upon action of tertꢀbutylꢀ
amine.
The condensation of the LDA deprotonated imines
11a,c with (E)ꢀcinnamic aldehyde under conditions deꢀ
scribed earlier2,3 leads to fairly stable aldimines 16a,e,
which were characterized by 1H NMR spectroscopy. The
latter were converted to the target dienals 9a,e on reflux
for 5 h in 20% aqueous acetone in the presence of H2SO4
in catalytic amounts. Similarly, the condensation of

314
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
Grigorieva et al.
over Na. Solution of LDA was prepared directly in the reactor
from equivalent amounts of diisopropylamine and 1.3—1.5 M
hexane solution of BuLi, which was obtained following a standard
procedure. Experiments which used BuLi, LDA, and NaH were
carried out under argon, using glassware dried at 160 °C for 12 h
and cooled in the flow of argon.
The following reactants used in this work were purchased
from Acros Organics: (E)ꢀcinnamic and (E)ꢀ4ꢀmethoxycinnamic
aldehydes (the latter was additionally recrystallized from diethyl
ether), NaH, ButNH2, and molecular sieves 4 Å.
deprotonated imine 11a with (E)ꢀ4ꢀmethoxycinnamic alꢀ
dehyde afforded dienal 9b through imine 16b. The conꢀ
densation of deprotonated imine 11b with (E)ꢀcinnamic
and (E)ꢀ4ꢀmethoxycinnamic aldehydes leads to the less
stable aldimines 16c,d, respectively, which were converted
to the target dienals 9c,d already upon treatment of the
reaction mixture with aq. oxalic acid at pH 4 for 2.5 h.
The configurational purity of dienals 9a—e isolated in
1
70—80% yield was inferred from their H NMR spectral
Standard treatment of organic extracts included their washing
to pH ~7, drying with Na2SO4, and concentration in vacuo on a
rotary evaporator.
data, in which the ratio of peak intensities of the CHO
groups of possible isomers (δ 9.50 and 10.01) is 98.5 : 1.5.
The stereochemistry of predominant isomers was also
inferred from the NMR spectroscopic data. For example,
using the C—Hꢀcorrelation and the COSY, parameters δ
and J for the H atoms of the diene system were found for
dienal 9a (δ 7.04, d, J = 15.5 Hz; δ 7.12, d, J = 11.0 Hz;
δ 7.36, dd, J1 = 15.5 Hz, J2 = 11.0 Hz). From the pair of
the doublet signals given, only the second one with δ 7.12
reveals the NOE (∼10%) with HC(1), that, first, allows one
to assign this signal to the HC(3) group and, second, draw
a conclusion on the (E)ꢀconfiguration of the C(2)=C(3)
bond. This suggestion is confirmed by the presence of the
NOE (~6%) between the H2C(1´) and H2C(4) atoms
(δ ~7.36), as well as by the presence of the signal with
δ 9.5 in the 1H NMR spectrum of dienal 9a and the signal
with δ ~194 in its 13C NMR spectrum characteristic of the
CHO group of (E)ꢀenals, and signals of low intensities
(<1.5%) characteristic of the CHO group of (Z)ꢀenals
Alcohol 13a,12 aldehydes 15a,8 15b,16 and 15c17 were
obtained by known procedures.
4ꢀ(tertꢀButyldimethylsilyloxy)butanꢀ1ꢀol (13b). A suspension
of NaH (55%) in mineral oil was washed three times with hexane,
dried in the flow of argon, and then added in small portions
to a solution of butanꢀ1,4ꢀdiol (13.32 g, 150 mmol) in THF
(150 mL). The suspension obtained was stirred for 30 min
followed by a dropwise addition to it a solution of (tertꢀbutyl)ꢀ
chlorodimethylsilane (7.5 g, 50 mmol) in THF (50 mL). After
stirring for another 30 min, a water—methyl tertꢀbutyl ether
(MTBE) mixture (1 : 1, 150 mL) was added and after 30 min,
layers were separated. The aqueous layer was extracted with
MTBE (3×50 mL). After standard treatment of combined organic
extracts, alcohol 13b was obtained (10.2 g, ~100%) as an
1
individual compound according to the H and 13C NMR data,
which was dried in vacuo (1 Torr) at ~20 °C until the weight was
constant and was further used without additional purification.
Physicoꢀchemical characteristics of 13b agree with the literature
data.16,18
4ꢀ(4ꢀMethoxybenzyloxy)butanꢀ1ꢀol (13c) was obtained
similarly from butanꢀ1,4ꢀdiol and 4ꢀmethoxybenzyl chloride
(68% yield), its physicoꢀchemical parameters agree with the
literature data.17
1
(δ ~10 in the H NMR spectra and δ 191—192 in the
13C NMR spectra).14,15 The second doublet signal in
the 1H NMR spectrum of dienal 9a (δ 7.04) was assigned
to HC(5). Its spinꢀspin coupling constant value with
HC(4) (15.5 Hz) indicates the (E)ꢀconfiguration of the
C(4)=C(5) bond. Configurations of dienals 9b—e were
established similarly. In conclusion, the present study
resulted in the preparation of key intermediate products
for the synthesis of strobilurins A and X in high yield and
stereoselectivity close to 100%.
4ꢀBenzyloxybutanal Nꢀ(tertꢀbutyl)imine (11a). A solution of
tertꢀbutylamine (5.11 g, 70 mmol) in diethyl ether (20 mL) was
added dropwise to a vigorously stirred mixture of granulated
molecular sieves 4 Å (35 g, calcined for 5 h at 300 °C), aldehyde
15a (8.9 g, 50 mmol), and diethyl ether (200 mL) cooled to
–15 °C. After 15 min, the temperature was raised to ~20 °C
followed by stirring for 8 h. Then molecular sieves were filtered
off and washed with MTBE. The filtrate was dried with K2CO3
and concentrated in vacuo to obtain aldimine 11a (11.4 g, 97%)
Experimental
1
(see Ref. 8), b.p. 98—100 °C (6•10–2 Torr). H NMR, δ: 1.13
(s, 9 H, CMe3); 1.83 (m, 2 H, H2C(3)); 2.32 (m, 2 H, H2C(2));
UV spectra were recorded on a Specord UVꢀVIS spectroꢀ
meter in ethanolic solution, IR spectra were recorded on
a Perkin—Elmer 577 spectrometer for neat samples. 1H and
13C NMR spectra were recorded on a Bruker ACꢀ200 spectroꢀ
meter for solutions in CDCl3 using signals of the solvent
as a reference (δ 7.27 and 77.0, respectively). Mass spectra (EI,
70 eV) were recorded on a Kratos MSꢀ30 instrument; there are
given peaks with relative intensities >10% with the peaks of
molecular ions being an exception. Melting points were measured
using a Kofler apparatus. Column chromatography was performed
on Silica gel 60 (0.04—0.06 mm, Fluka). The solvents used were
purified as follows: diethyl ether and THF were stored over
KOH, subsequently distilled over Na and LiAlH4, then refluxed
with sodium benzophenone ketyl until a persistent blue color,
and distilled directly into the reaction flask; hexane was distilled
3.46 (t, 2 H, H2C(4), J = 7.4 Hz); 4.46 (s, 2 H, CH2Ph); 7.26
1
(br.s, 5 H, Ph); 7.60 (t, 1 H, HC(1), J = 5.5 Hz). H NMR
(literature data8), δ: 1.5 (s, 9 H); 1.85 (m, 2 H); 2.35 (m, 2 H);
3.5 (t, 2 H); 4.5 (s, 2 H); 7.3 (s, 5 H); 7.6 (t, 1 H).
4ꢀ(tertꢀButyldimethylsilyloxy)butanal Nꢀ(tertꢀbutyl)imine
1
(11b) was obtained similarly, the yield was 98%. H NMR, δ:
0.05 (s, 6 H, Me2Si); 0.90 (s, 9 H, Me3CSi); 1.20 (s, 9 H,
Me3C); 1.75 (m, 2 H, H2C(3)); 2.30 (m, 2 H, H2C(2)); 3.64
(t, 2 H, H2C(4), J = 7.2 Hz); 7.60 (t, 1 H, HC(1), J = 5.5 Hz).
13C NMR, δ: –5.48 (Me2Si); 20.00 (Me3CSi); 25,80 (Me3CSi);
29.42 (C(3)); 32.81 (C(2)); 62.02 (Me3CN); 62.47 (C(4)); 158.63
(C(1)).
4ꢀ(4ꢀMethoxybenzyloxy)butanal Nꢀ(tertꢀbutyl)imine (11c)
1
was obtained similarly, the yield was 91%. H NMR, δ: 1.15 (s,

2,5ꢀDisubstituted (E,E)ꢀpentaꢀ2,4ꢀdienals
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
315
9 H, Me3C); 1.82 (m, 2 H, H2C(3)); 2.32 (m, 2 H, H2C(2));
3.47 (t, 2 H, H2C(4), J = 7.2 Hz); 3.80 (s, 3 H, MeO); 4.45 (s,
2 H, CH2Ph); 6.88, 7.26 (both d, 2 H each, Ar, J1 = J2 = 8.5 Hz);
7.62 (t, 1 H, HC(1), J = 5.5 Hz).
Imines 11b,c decompose on distillation. Therefore, they were
dried for 12 h in vacuo (1 Torr) at ~20°C, then dissolved in THF,
stored over molecular sieves 4 Å for 12 h at 4—5 °C, and used for
obtaining dienals 9c—e.
(CH2Ph); 123.99 (C(4)); 136.10 (C(2)); 141.62 (C(5)); 150.37
(C(3)); 194.09 (C(1)). MS, m/z (Irel (%)): 292 [M]+ (3), 201
(13.5), 186 (52), 171 (15), 143 (34.5), 142 (15), 141 (19), 129
(13), 128 (74), 127 (15), 117 (34), 115 (18), 91(100), 76 (15), 65
(56.5), 55 (25), 53 (19), 51 (15), 46 (18), 44 (15), 43 (31).
(E,E)ꢀ2ꢀ(2ꢀBenzyloxyethyl)ꢀ5ꢀ(4ꢀmethoxyphenyl)pentaꢀ
2,4ꢀdienal (9b) was obtained similarly, the yield was 90%,
m.p. 64—65 °C (from diethyl ether—hexane (1 : 1)). Found (%):
C, 78.07; H, 6.88. C21H22O3. Calculated (%): C, 78.23; H, 6.88.
UV (λmax/nm (ε)): 252 (7400), 362 (43500). IR, ν/cm–1: 3036,
3000, 2964, 2936, 2900, 2836, 2792, 2760, 1660, 1620, 1600,
1512, 1464, 1452, 1428, 1408, 1380, 1364, 1312, 1284, 1256,
(E,E)ꢀ2ꢀ(2ꢀBenzyloxyethyl)ꢀ5ꢀphenylpentaꢀ2,4ꢀdienal (9a).
A solution of aldimine 11a (9.9 g, 42.5 mmol) in THF (100 mL)
was slowly added dropwise to a solution of LDA (prepared
according to a standard procedure from BuLi (50 mmol)
and Pri NH (50 mmol) in THF—hexane (3 : 1 v/v, 120 mL))
1188, 1176, 1108, 1012, 972, 820, 748, 700, 520. H NMR, δ:
1
2
at –15 °C, the reaction mixture was heated to 0 °C, stirred for
45 min, and cooled to –80 °C followed by a dropwise addition to
it a solution of freshly distilled (E)ꢀcinnamic aldehyde (3.7 g,
28 mmol) in THF (50 mL). The mixture was stirred for 30 min
at –80 °C, then heated to 0 °C over 4 h, and kept for 15 h at
4—5 °C. A reddishꢀbrown solution obtained was poured into a
cold mixture of 3% aq. HCl (380 mL) and MTBE (200 mL), this
was stirred for 30 min followed by separation of the layers. The
aqueous layer was sequentially extracted with MTBE (3×150 mL)
and chloroform (3×150 mL). After standard treatment of
combined ethereal extracts, an oily mixture of the reaction
products was obtained (1.2 g), which contained (1H NMR data)
dienal 9a, the starting (E)ꢀcinnamic aldehyde (10a), and
aldehyde 15a in the ratio (1 : 1 : 2). After standard treatment of
combined chloroform extracts, an oily mixture of the reaction
products was obtained (8.97 g), which contained (1H NMR
data) 80—85% of aldimine 16a. 1H NMR, δ: 1.20 (s, 9 H,
Me3C); 3.00 (t, 2 H, H2C(1´), J = 7.2 Hz); 3.66 (t, 2 H, H2C(2´),
J = 7.2 Hz); 4.66 (s, 2 H, CH2Ph); 6.60 (d, 1 H, HC(3), J = 10 Hz);
6.73 (d, 1 H, HC(5), J = 15 Hz); 7.40 (m, 11 H, Ph + HC(4));
7.85 (s, 1 H, HC(1)).
2.81 (t, 2 H, H2C(1´), J = 6.7 Hz); 3.61 (t, 2 H, H2C(2´), J = 6.7 Hz);
3.86 (s, 3 H, MeO); 4.58 (s, 2 H, H2CPh); 6.96 (d, 1 H, HC(5),
J = 15.2 Hz); 7.05 (d, 1 H, HC(3)***, J = 10.7 Hz); 7.20 (dd,
1 H, HC(4), J1 = 15.2 Hz, J2 = 10.7 Hz); 7.28 (m, 2 H, Ph); 7.44
(d, 2 H, Ph, J = 9.1 Hz); 9.49 (s, 1 H, HC(1)). 13C NMR, δ**:
25.08(C(1´)); 55.31 (MeO); 68.94 (C(2´)); 72.80 (CH2 Ph);
121.74 (C(4)); 137.50 (C(2)); 141.61 (C(5)); 151.28 (C(3));
194.20 (C(1)). MS, m/z (Irel (%)): 322 [M]+ (10), 231 (22.5),
216 (50), 213 (11), 202 (11), 201 (29), 188 (17), 186 (11), 185
(59), 174 (11), 173 (55), 172 (21.5), 171 (19), 160 (12), 159 (25),
158(61) 157 (12), 149 (11), 147 (67), 145 (17), 142 (11), 141
(24), 135 (11), 134 (17), 128 (26.5), 127 (26.5), 121 (65.5), 115
(30), 108 (14), 92 (13), 91(100), 89 (11), 77 (15), 65 (22.5), 58
(15), 57 (11), 44 (13.5), 43 (27), 42 (19), 40 (12), 39 (25).
(E,E)ꢀ2ꢀ[2ꢀ(4ꢀMethoxybenzyloxy)ethyl]ꢀ5ꢀphenylpentaꢀ
2,4ꢀdienal (9e) was obtained similarly, the yield was 78%,
m.p. 98—99 °C (from hexane—MTBE (3 : 1)). Found (%): C,
78.38; H, 6.96. C21H22O3. Calculated (%): C, 78.23; H, 6.88.
UV (λmax/nm (ε)): 229 (20930), 337 (49105). IR, ν/cm–1: 3028,
2986, 2964, 2932, 2896, 2836, 2816, 2720, 1676, 1624, 1584,
1512, 1464, 1428, 1400, 1376, 1360, 1248, 1172, 1112, 1100,
1064, 1032, 964, 824, 748, 688. 1H NMR, δ: 2.81 (t, 2 H,
H2C(1´), J = 6.7 Hz); 3.57 (t, 2 H, H2C(2´), J = 6.7 Hz); 3.75
(s, 3 H, MeO); 4.45 (s, 2 H, H2CPh); 6.78 (d, 2 H, Ar, J = 8.6
Hz); 7.01 (d, 1 H, HC(5), J = 15.5 Hz); 7.09 (d, 1 H, HC(3)****,
J = 11.2 Hz); 7.23 (d, 2 H, Ar, J = 8.6 Hz); 7.34 (dd, 1 H,
HC(4), J1 = 15.5 Hz, J2 = 11.2 Hz); 7.35—7.60 (m, 5 H,
PhC(5)); 9.51 (s, 1 H, HC(1)). 13C NMR, δ**: 25.17 (C(1´));
55.14 (MeO); 68.66 (C(2´)); 72.53 (CH2Ph); 124.02 (C(4));
138.79 (C(2)); 141.62 (C(5)); 150.52 (C(3)); 194.22 (C(1)).
MS, m/z (Irel (%)): 322 [M]+ (10), 233 (14), 187 (14), 186 (97),
185 (14), 158 (22), 157 (16), 154 (28), 143 (23), 142 (21), 141
(23), 137 (32), 130 (16), 129 (22), 128 (42), 127 (11), 122 (25),
121 (100), 115 (19), 101 (15), 95 (21), 91 (62), 83 (11.5), 81
(27), 79 (33), 78 (54), 77 (55.5), 70 (14), 69 (27), 68 (20), 67
(63), 65 (38), 57 (46), 56 (35), 55 (58), 54 (12), 53 (46), 52 (21),
51 (45), 50 (14), 45 (14), 43 (23), 42 (18).
The residue from the chloroform extract was dissolved in
acetone (180 mL) followed by addition to it a solution of H2SO4
(0.7 mL) in water (45 mL), this was refluxed for 5 h. Then, the
solution was cooled and neutralized with NaHCO3, acetone was
evaporated in vacuo, the residue was diluted with equal amount
of water and extracted with MTBE (5×50 mL). After standard
treatment of combined extracts, a residue was obtained (7.58 g),
from which crystalline dienal 9a (6.3 g) was isolated using flashꢀ
chromatography on SiO2 (100 g) with a gradient (0 → 30%) elution
of MTBE in light petroleum. Flashꢀchromatography of the
mixture of substances from the MTBE extract gave addiꢀ
tionally 0.2 g of dienal 9a, the overall yield of which was ∼80%,
m.p. 94—95 °C (from hexane—MTBE (3 : 1)). Found (%):
C, 82.15; H, 6.92. C20H20O2. Calculated (%): C, 82.16; H, 6.89.
UV (λmax/nm (ε)): 238 (11540), 330 (44240). IR, ν/cm–1: 3060,
3025, 2930, 2860, 2780, 1660, 1615, 1500, 1480, 1450, 1410,
1375, 1360, 1310, 1190, 1185, 1115, 1105, 1050, 980, 840, 740,
(E,E)ꢀ2ꢀ[2ꢀ(tertꢀButyldimethylsilyloxy)ethyl]ꢀ5ꢀphenylpentaꢀ
2,4ꢀdienal (9c). The reaction mixture obtained similarly to that
described for 9a was treated by a (1 : 1) mixture of MTBE and
aq. (COOH)2•2H2O. The amount of the latter corresponded to
a total molar amount of the bases used in the reaction. The
mixture was stirred for 2.5 h followed by separation of the layers.
1
695. H NMR, δ: 2.82 (t, 2 H, H2C(1´), J = 6.7 Hz); 3.59 (t,
2 H, H2C(2´), J = 6.7 Hz); 4.52 (s, 2 H, H2CPh); 7.04 (d, 1 H,
HC(5), J = 15.5 Hz); 7.12 (d, 1 H, HC(3)*, J = 11.0 Hz);
7.20—7.42 (m, 5 H, PhCH2), 7.36 (dd, 1 H, HC(4), J1 = 15.5 Hz,
J2 = 11.0 Hz); 7.35—7.55 (m, 5 H, PhC(5)); 9.52 (s, 1 H,
HC(1)). 13C NMR, δ**: 25.22(C(1´)); 68.95 (C(2´)); 72.87
*** The signal was assigned based on the Overhauser effect
(~10%) HC(3)/HC(1).
**** The signal was assigned based on the Overhauser effect
(7.3%) HC(3)/HC(1).
* The signal was assigned based on the NOE experiment.
** The signals for the C atoms of the Ph rings are also present in
the spectrum.

316
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
Grigorieva et al.
The aqueous layer was extracted with MTBE. After standard
treatment of combined extracts, the residue was chromatoꢀ
graphed on SiO2 with gradient elution from light petroleum to
MTBE (up to 30% of the latter). Dienal 9c was isolated in 65%
yield, b.p. 140—145 °C (7•10–2 Torr (bath)). Found (%): C,
71.92; H, 8.86; Si, 8.76. C19H28O2Si. Calculated (%): C, 72.09;
References
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H, 8.91; Si, 8.87. UV (λ /nm (ε)): 205 (12000), 238 (7270),
max
330 (18800). IR, ν/cm–1: 3024, 3016, 2952, 2944, 2856, 2760,
2712, 1680, 1624, 1556, 1520,1496, 1484, 1472, 1448, 1384,
1363, 1308, 1280, 1256, 1180, 1100, 1045, 1010, 968, 932, 896,
840, 776, 752, 688, 672. 1H NMR, δ: 0.01 (s, 6 H, Me2Si); 0.85
(s, 9 H, Me3C); 2.70 (t, 2 H, H2C(1´), J = 6.5 Hz); 3.70 (t, 2 H,
H2C(2´), J = 6.5 Hz); 7.00 (d, 1 H, HC(5), J = 15.4 Hz); 7.09
(d, 1 H, HC(3)*, J = 11.10 Hz); 7.34 (dd, 1 H, HC(4),
J1 = 15.4 Hz, J2 = 11.10 Hz); 7.30—7.60 (m, 5 H, Ph); 9.50 (s,
1 H, HC(1)). 13C NMR, δ**: –5.38 (Me2Si); 18.23 (Me3C);
25.83 (Me); 28.11 (C(1´)); 61.76 (C(2´)); 124.17 (C(4)); 138.81
(C(2)); 141.41 (C(5)); 150.80 (C(3)); 194.44 (C(1)). MS, m/z
(Irel (%)): 301 [M – 15]+ (<1), 259 (28), 141 (11), 129 (12.5),
128 (11), 115 (29), 101 (27), 89 (24), 77 (18), 75 (100), 73 (44),
61 (12), 58 (15), 57 (24), 56 (11), 55 (16), 51 (14), 47 (14), 43 (14).
(E,E)ꢀ2ꢀ[2ꢀ(tertꢀButyldimethylsilyloxy)ethyl]ꢀ5ꢀ(4ꢀmethoxyꢀ
phenyl)pentaꢀ2,4ꢀdienal (9d) was obtained similarly, the yield
was 67%, b.p. 150 °C (7•10–2 Torr (bath)). Found (%): C,
68.98; H, 8.76; Si, 7.86. C20H30O3Si. Calculated (%): C, 69.32;
H, 8.73; Si, 8.10. UV (λmax/nm (ε)): 248(3120), 357 (27720).
IR, ν/cm–1: 3012, 2950, 2932, 2856, 2724, 1672, 1620, 1596,
1512, 1464, 1444, 1424, 1388, 1372, 1308, 1284, 1256, 1172,
1
1096, 1048, 1008, 968, 936, 896, 836, 664. H NMR, δ: 0.01
(s, 6 H, Me2Si); 0.84 (s, 9 H, Me3C); 2.69 (t, 2 H, H2C(1´),
J = 6.5 Hz); 3.69 (t, 2 H, H2C(2´), J = 6.5 Hz); 3.85 (s, 3 H,
MeO); 6.91 (d, 2 H, Ar, J = 8.8 Hz); 6.95 (d, 1 H, HC(5),
J = 14.8 Hz); 7.07 (d, 1 H, HC(3)*, J = 10.90 Hz); 7.21 (dd, 1
H, HC(4), J1 = 14.8 Hz, J2 = 10.90 Hz); 7.48 (d,
2 H, Ar, J = 8.8 Hz); 9.47 (s, 1 H, HC(1)). 13C NMR, δ**:
–5.38 (Me2Si); 18.22 (Me3C); 25.93 (Me); 28.12 (C(1´));
55.32 (MeO); 61.83 (C(2´)); 122.08 (C(4)); 137.73 (C(2));
141.31 (C(5)); 151.51 (C(3)); 194.43 (C(1)). MS, m/z (Irel (%)):
346 [M]+ (<1), 290 (32.5), 289 (80), 259 (35), 245 (10.5),
215 (17.5), 201 (10.5), 197 (30), 186 (12.5), 185 (38), 181 (11),
173 (16), 172 (17.5), 171 (53), 165 (11.5), 154 (14), 146 (12.5),
141 (11), 135 (22), 121 (31), 101 (16.5), 89 (12.5), 83 (22.5),
77 (40), 76 (21), 75 (100), 74 (17.5), 73 (92), 69 (18), 65 (11.5),
63 (11), 57 (45), 56 (40), 55 (46), 53 (11), 51 (13.5), 43 (14).
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This work was financially supported by the Russian
Foundation for Basic Research (Project No. 07ꢀ03ꢀ00454).
* The signal was assigned based on the Overhauser effect (~7%)
HC(3)/HC(1).
Received July 14, 2008;
in revised form September 11, 2008
** The signals for the C atoms of the Ph rings are also present in
the spectrum.