Electrochemical cleavage of double bonds in conjugated cycloalkenyl- and 1,2-alkenobenzenes

Article abstract of DOI:10.1021/jo951948s

The electrochemical cleavage of olefinic bonds in conjugated C₅-C₇-cycloalkenylbenzenes 1, indene 4a, and 1,2-dihydronaphthalene (4b) results from anodic oxidation of these compounds in MeOH in an undivided cell. The process includes the formation of (1,2-dimethoxycycloalkyl)benzenes 2a-c, 1,2-dimethoxyindan (5a), and 1,2-dimethoxytetralin (5b) as intermediates and leads to ω,ω-dimethoxy-ω-phenyl-n-C₅-C₇-alkanal dimethyl acetals 3a-c, [2-(dimethoxymethyl)phenyl]ethanal dimethyl acetal (6a), and 3-[2-(dimethoxymethyl)phenyl]propanal dimethyl acetal (6b) as major products, respectively. The best yields of 3a-c and 6a,b (58-76%) were obtained when the electrolysis was carried out at 60°C and 6 F/mol of electricity based on 1, 4a, and 4b was passed using C-anode and Bu₄NBF₄ as a supporting electrolyte. Compounds 2a-c and 5a,b as mixtures of cis and trans diastereomers were obtained as major products in 81-90% yield when the electrolysis was terminated after 2 F/mol of electricity based on 1, 4a, and 4b had been passed. The cis/trans ratio in 2a-c was increased with the increasing the size of cycloalkane rings in 1, 4a, and 4b and the obvious stereoselective effect of the anode nature (C or Pt) being observed in the case of dimethoxylation of 4a.

Full text of DOI:10.1021/jo951948s

3256
J . Org. Chem. 1996, 61, 3256-3258
Electr och em ica l Clea va ge of Dou ble Bon d s in Con ju ga ted
Cycloa lk en yl- a n d 1,2-Alk en oben zen es
Yuri N. Ogibin,* Alexey I. Ilovaisky, and Gennady I. Nikishin
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913, Russia
Received November 1, 1995X
The electrochemical cleavage of olefinic bonds in conjugated C5-C7-cycloalkenylbenzenes 1, indene
4a , and 1,2-dihydronaphthalene (4b) results from anodic oxidation of these compounds in MeOH
in an undivided cell. The process includes the formation of (1,2-dimethoxycycloalkyl)benzenes 2a -
c, 1,2-dimethoxyindan (5a ), and 1,2-dimethoxytetralin (5b) as intermediates and leads to ω,ω-
dimethoxy-ω-phenyl-n-C5-C7-alkanal dimethyl acetals 3a -c, [2-(dimethoxymethyl)phenyl]ethanal
dimethyl acetal (6a ), and 3-[2-(dimethoxymethyl)phenyl]propanal dimethyl acetal (6b) as major
products, respectively. The best yields of 3a -c and 6a ,b (58-76%) were obtained when the
electrolysis was carried out at 60 °C and 6 F/mol of electricity based on 1, 4a , and 4b was passed
using C-anode and Bu4NBF4 as a supporting electrolyte. Compounds 2a -c and 5a ,b as mixtures
of cis and trans diastereomers were obtained as major products in 81-90% yield when the
electrolysis was terminated after 2 F/mol of electricity based on 1, 4a , and 4b had been passed.
The cis/ trans ratio in 2a -c was increased with the increasing the size of cycloalkane rings in 1,
4a , and 4b and the obvious stereoselective effect of the anode nature (C or Pt) being observed in
the case of dimethoxylation of 4a .
Sch em e 1
Electrooxidation of conjugated arylalkenes in alcohols
is a convenient and efficient method for the electrochemi-
cal cleavage of a double bond and for the conversion of
the compounds to acetals of aromatic aldehydes (eq 1)1
which are versatile starting materials in organic synthe-
sis.2
Now we report a new approach based on this method-
ology to acetal and ketal derivatives with acetal and ketal
groups in one molecule, namely, to the respective deriva-
tives of aromatic 1,5-, 1,6-, and 1,7- dicarbonyl compounds
which could be of interest as precursors for a wide variety
of carbocycles and heterocycles.3 The derivatives are still
fairly unaccessible since they cannot be derived from the
respective dicarbonyl compounds by their acetalization
and ketalization because of faster conversion into oxacy-
cloalkanes. 1,3-Dimethoxyisochroman was formed by the
reaction of homophthalic aldehyde with MeOH,4 and
4-benzoylbutanal was found to give 2,6-dimethoxy-2-
phenyltetrahydropyran under these reaction conditions.
Presuming that the derivatives could be prepared from
the readily available conjugated cycloalkenyl- and 1,2-
alkenobenzenes, we undertook the present investigation
and report here the results of our work.
We have found that conjugated phenylcycloalkenes
1a -c and 1,2-alkenobenzenessindene 4a and 1,2-dihy-
dronaphthalene 4b being electrolyzed in MeOH under
galvanostatic conditions using an undivided cellsundergo
a consecutive electrochemical cleavage of benzylic π- and
σ-carbon-carbon bonds to give at first (1,2-dimethoxy-
cycloalkyl)benzenes 2a -c, 1,2-dimethoxyindan (5a ), and
1,2-dimethoxytetralin (5b) and then ω,ω-dimethoxy-ω-
phenylalkanal acetals 3a -c and 2-(ω,ω-dimethoxyalkyl)-
benzaldehyde acetals 6a ,b (Scheme 1).
The best yields of acetals 3 (58-76%) and 6 (61-75%)
were obtained when electrolysis was carried out at 60
°C using a graphite anode, tetrabutylammonium tet-
rafluoroborate as a supporting electrolyte, current density
of 100 mA/cm2, and 6 F/mol of electricity based on the
starting substrate (Table 1). The optimization of the
electrochemical process was performed for 1b testing C-
and Pt-anodes, Bu4NBF4, KF, CF3COONa, and TsONa
as electrolytes, room and elevated (60 °C) temperature,
X Abstract published in Advance ACS Abstracts, April 15, 1996.
(1) (a) Inoue, T.; Koyama, K.; Matsuoka, T.; Tsutsumi, S. Bull. Chem
Soc. J pn. 1967, 40, 162. (b) Ogibin, Yu. N.; Elinson, M. N.; Sokolov, A.
B.; Nikishin, G. I. Izv. Akad. Nauk SSSR, Ser. Khim. 1990, 494 (Bull.
Acad. Sci. USSR, Div. Chem. Sci. 1990, 39, 432). (c) Ogibin, Yu. N.;
Sokolov, A. B.; Ilovaisky, A. I.; Elinson, M. N.; Nikishin, G. I. Izv. Akad.
Nauk SSSR, Ser. Khim. 1991, 644 (Bull. Acad. Sci. USSR, Div. Chem.
Sci. 1991, 40, 561). (d) Ogibin, Yu. N.; Ilovaisky, A. I.; Nikishin, G. I.
Izv. Russ. Akad. Sci., Ser. Khim. 1994, 1624 (Russ. Chem. Bull. 1994,
43, 1536). (e) Barba, I.; Chinchilla, R.; Gomez, C. J . J . Org. Chem. 1990,
55, 3270. (f) Bornewasser, U.; Steckhan, E. In Electroorganic Synthesis;
Baizer, M. M., Little, R. D., Weiberg, N. L., Eds.; Marcel Dekker: New
York, 1991; p 205.
(2) Electrochemical cleavage of double bonds was also observed for
alkyl-substituted allenes (Becker, J . Y.; Zinger, B. Tetrahedron 1982,
38, 1677), for cyclic enol ethers (Shono, T.; Matsumura, Y.; Hamaguchi,
H.; Imanishi, T.; Yoshida, K. Bull. Chim. Soc. J pn. 1978, 51, 2179),
and for different olefins under conditions of indirect anodic oxidation
5-
using SiRu(H2O)W11O39 and NaIO3 as mediators (Steckhan, E.;
Kandzia, C. Synlett 1992, 139).
(3) (a) J ung, M. E. Tetrahedron 1976, 32, 3. Molander, G. A.;
Schubert, D. C. J . Am. Chem. Soc. 1980, 45, 5312. (b) Epsztain, J . A.;
Bienick, A.; Brzezinski, J . Z. Pol. J . Chem. 1980, 54, 341. (c) Anderson,
D. N.; Sharp, J . T.; Sood, H. R. Synthesis 1985, 106.
(4) Hatsui, T.; Takeshita, H. Bull. Chem. Soc. J pn. 1980, 53, 2655.
S0022-3263(95)01948-7 CCC: $12.00 © 1996 American Chemical Society

Cleavage of Double Bonds in Conjugated Benzenes
J . Org. Chem., Vol. 61, No. 10, 1996 3257
Ta ble 1. Electr ooxid a tion of Cycloa lk en ylben zen es 1a -c
of type 3a -c and 6a ,b. However, higher oxidative
potentials for the intermediates (e.g., 1.80 V vs Ag/Ag+
for (1,2,3-trimethoxypropyl)benzene7 ) in comparison with
those for conjugated alkenylbenzenes (1.42 V vs Ag/Ag+
for (3-methoxypropenyl)benzene7) essentially increase the
consumption of electricity by the side anodic oxidation
of methanol (solvent)8 and consequently decrease the
conversion of 2 and 5 and the yields of 3 and 6 on the
basis of 1 and 4 when the theoretical amount of electricity
was passed (4 F/mol based on the starting materials) (see
Table 1). To provide higher yields of 3 and 6 based on
starting 1 and 4, we increased the electricity passed to 6
F/mol.
a n d 1,2-Alk en oben zen es 4a ,ba
electricity conversn (%), products, yield cis/trans ratio,c
passed
(F/mol)
C-anode
(Pt-anode)
(%),b C-anode
(Pt-anode)
C-anode
(Pt-anode)
substr
1a
1a
1a
1b
1b
1b
1c
1c
4a
4a
4b
4b
2
4
6
2
4
6
2
6
2
6
2
6
85 (78)
100
100
80 (75)
100
100
93 (90)
100
95 (83)
100
95 (80)
100
2a , 81 (75)
1.3 (0.8)
2a , 58; 3a , 33
2a , 3; 3a , 62
2b, 76 (70)
2b, 56; 3b, 34
2b, 4; 3b, 58
2c, 90 (85)
2c, 13; 3c, 76
5a , 88 (74)
5a , 17; 6a , 75
5b, 90 (76)
3.2 (2.5)
6.1 (5.1)
1.4 (1.05)
1.8 (1.9)
5b, 11; 6b, 61
Exp er im en ta l Section
a
b
60 °C, Bu4NBF4. Isolated yields based on the substrate.
c Determined by GLC and 1H NMR.
The electrochemical undivided cell was described previously.1d
The anodes were a 15-mm-diameter graphite rod or a platinum
plate (ca. 10 cm2); the cathode was a stainless steel plate. H
Ta ble 2. Electr ooxid a tion of Cycloh ex-1-en ylben zen e
(1b) Usin g Differ en t Electr olytes, An od ic Ma ter ia ls, a n d
Tem p er a tu r ea
1
NMR spectra were recorded in CDCl3 at 300 MHz using TMS
as the internal standard; 13C NMR spectra were recorded at
75 MHz. Mass spectra were determined at 70 eV. Gas
chromatography was performed using 5% Carbowax 20M on
Inerton AW and 5% XE-60 on Chromaton N-AW columns (200
× 0.3 cm). For flash column chromatography silica gel (40-
100 mesh) was used. Compounds 1a and 1c were prepared
by the reaction of the corresponding cycloalkanones with
PhMgBr followed by dehydratation with HCOOH;9 4b was
synthesized from R-tetralone.10 Solvents were distilled by
using the usual procedures. All other materials were com-
mercially available and used as received.
E lect r olysis of Cycloa lk en ylb en zen es 1a -c a n d 1,2-
Alk en oben zen es 4a ,b (Typ ica l P r oced u r e). A stirred 0.1
M solution (30 mL) of Bu4NBF4 or another electrolyte in MeOH
containing 15 mmol of 1 or 4 was electrolyzed at 60 °C in the
undivided cell at a constant current with a current density of
100 mA/cm2. The solvent was then removed, the residue was
extracted with hexane (2 × 30 mL), the combined extracts were
concentrated, and the products were isolated by vacuum
distillation and purified by flash chromatography with hex-
ane-ethyl acetate (0-2%) as eluent (Table 1). The stereo-
chemistry of 2 and 5 was determined by comparison of 1H
NMR signals for the methine protons of cis and trans 2 with
those for the authentic sample of cis-2b prepared from cis-1-
phenylcyclohexane-1,2-diol11,12 and for cis and trans dimethox-
yindans.13
1,2-Dim eth oxy-1-p h en ylcyclop en ta n e (2a ): mixture of
cis and trans isomers (1:1.3); bp 128-30 °C/10 mmHg; nD20
1.5276; MS, m/z (relative intensity) 206 (33, M+), 175 (14), 174
(79), 173 (15), 160 (12), 159 (17), 148 (13), 147 (100), 143 (51),
142 (34), 131 (47), 121 (26), 117 (53). Anal. Calcd for
C13H18O2: C, 75.69; H, 8.79. Found: C, 75.33; H, 8.57. cis-
2a : 1H NMR δ 1.65-2.05 (m, 2H), 2.07-2.30 (m, 4H), 3.02
(m, 1H), 3.10 (s, 3H), 3.32 (s, 3H), 7.25-7.52 (m, 5H); 13C NMR
δ 19.01, 27.30, 30.18, 51.33, 57.97, 79.95, 90.00, 126.95, 128.08,
128.53, 141.53. tr a n s-2a : 1H NMR δ 1.65-2.05 (m, 2H),
2.07-2.30 (m, 4H), 2.97 (s, 3H), 3.02 (s, 3H), 3.65 (m, 1H),
7.25-7.52 (m, 5H); 13C NMR δ 20.10, 28.26, 29.24, 49.78, 57.21,
86.54, 88.74, 127.45, 127.83, 128.08, 139.51.
temperature, yield of 2b, yield of 3b,
b
b
anode
C
electrolyte
°C
%
%
Bu4NBF4
Bu4NBF4
KF
CF3COONa
TsONa
Bu4NBF4
KF
CF3COONa
TsONa
20
60
60
60
60
60
60
60
60
34
6
8
83
45
21
23
32
28
38
62
54
15
37
53
54
48
53
Pt
a
b
6 F/mol, conversion of 1b 100%. GLC data.
and 2, 4 and 6 F/mol of electricity passed (Tables 1 and
2). The data obtained give evidence to faster anodic
oxidation of intermediate 2b on the C-anode in the
presence of Bu4NBF4 or KF than on the Pt-anode using
the same electrolytes. With CF3COONa and TsONa as
electrolytes, an opposite result is observed.
The formation of acetals 3 and 6 in substantial
amounts has been observed only after the exhaustion of
substrates 1 and 4; this occurred when a little more than
2 F/mol was passed. When the electrolysis was discon-
tinued at this moment, compounds 2 and 5 were isolated
as major products in 81-90% yield. They were formed
as mixtures of cis and trans diastereomers, the cis/trans
ratio of the isomers being increased with increasing the
size of the cycloalkane ring in 2 and 5 whether the anode
was graphite or platinum and the obvious stereoselective
effect of the anode nature (C or Pt) being observed in the
case of dimethoxylation of 1a (Table 1). The same effect
of the anode material was reported for dimethoxylation
of acenaphthylene.5 The stereochemistry observed for the
electrochemical conversion of 1 and 4 into 2 and 5
confirmes that the process proceeds mainly at the anode
surface and it is affected essentially by the starting
material structure. The latter seems to control the
adsorbing ability of the substrate at the anode surface,
which results in the attack at the side of the molecule
not protected by the electrode. This is supported by the
fact that no stereoselective effect took place for chemical
dimethoxylation of 4a .6
1,2-Dim et h oxy-1-p h en ylcycloh exa n e (2b): mixture of
cis and trans isomers (2.5:1); bp 110-3 °C/0.7 mmHg; nD20
(7) Elinson, M. N.; Makhova, I. V.; Nikishin, G. I. Izv. Akad Nauk
SSSR, Ser. Khim. 1987, 1569 (Bull. Acad. Sci. USSR, Div. Chem. Sci.
1987, 36, 1449).
(8) Sasaki, K.; Urata, H.; Uneyama, K.; Nagaura, S. Electrochim.
Acta 1967, 12, 137.
(9) Baddeley, G.; Chadwick, J .; Taylor, H. T. J . Chem. Soc. 1956,
451.
(10) Hauser, F. M.; Prasanna, S. Synthesis 1990, 621.
(11) Davies, M. T.; Dobson, D. F.; Hayman, D. F.; J ackman, G. B.;
Lester, M. G.; Petrov, V.; Stephanson, O.; Webb, A. A. Tetrahedron
1962, 18, 751.
Theoretically, 2 F/mol of electricity are required for
transforming intermediates 2a -c and 5a ,b to products
(5) Guirado, A.; Barba, F.; Franco, J . A. Electrochim. Acta 1982, 27,
1621.
(6) Mizuno, K.; Yoshioka, K.; Otsuji, Y. Chem. Lett. 1983, 941.
(12) Ceccarelli, G.; Macchia, B.; Macchia, F.; Monti, L. Org. Magn.
Reson. 1975, 7, 548.
(13) Austin, R. A.; Lillya, C. P. J . Org. Chem. 1969, 34, 1327.

3258 J . Org. Chem., Vol. 61, No. 10, 1996
Ogibin et al.
1.5282; MS, m/z (relative intensity) 220 (27, M+), 188 (9), 184
(5), 154 (18), 147 (61), 84 (100). Anal. Calcd for C14H20O2: C,
76.32; H, 9.15. Found: C, 76.39; H, 9.35. cis-2b: 1H NMR δ
1.25-2.15 (m, 8H), 2.99 (s, 3H), 3.06 (m, 1H), 3.15 (s, 3H),
7.20-7.50 (m, 5H); 13C NMR δ 20.90, 24.68, 26.56, 31.58, 50.13,
57.91, 80.09, 85.99, 126.71, 127.22, 127.79, 142.45. The same
spectra were obtained for the authentic sample of cis-2b .
tr a n s-2b: 1H NMR δ 1.25-2.15 (m, 8H), 2.86 (s, 3H), 2.93 (s,
3H), 3.27 (m, 1H), 7.20-7.50 (m, 5H); 13C NMR δ 19.31, 20.59,
24.89, 25.00, 48.93, 57.49, 78.92, 83.16, 126.85, 127.08, 127.79,
143.68.
intensity) 237 (2, M+ - OMe), 224 (9), 173 (8), 172 (100), 151
(10), 131 (12), 130 (75), 118 (40); 1H NMR δ 1.05 (m, 2H), 1.48
(m, 2H), 1.91 (m, 2H), 3.16 (s, 6H), 3.22 (s, 6H), 4.22 (t, 1H),
7.27-7.48 (m, 5H); 13C NMR δ 18.59, 32.26, 36.93, 48.60, 52.59,
103.49, 104.28, 126.96, 127.60, 127.96, 141.10. Anal. Calcd
for C15H24O4: C, 67.13; H, 9.01. Found: C, 67.09; H, 8.89.
6,6-Dim et h oxy-6-p h en ylh exa n a l d im et h yl a cet a l
(3b): bp 133-5 °C/0.1 mmHg; n2D0 1.4882; MS, m/z (relative
intensity) 251 (10, M+ - OMe), 233 (19), 220 (9), 219 (51), 204
(13), 179 (49), 165 (64), 151 (100), 145 (16), 105 (30), 91 (12);
1H NMR δ 1.01 (m, 2H), 1.22 (m, 2H), 1.47 (m, 2H), 1.89 (m,
2H), 3.14 (s, 6H), 3.25 (s, 6H), 4.24 (t, 1H), 7.27-7.48 (m, 5H);
13C NMR δ 23.12, 24.43, 32.18, 37.02, 48.48, 52.47, 103.42,
104.24, 126.82, 127.45, 127.80, 140.80. Anal. Calcd for
C16H26O4: C, 64.98; H, 8.39. Found: C, 64.75; H, 8.17.
7,7-Dim et h oxy-7-p h en ylh ep t a n a l d im et h yl a cet a l
(3c): bp 140-3 °C/0.07 mmHg; n2D0 1.4880; MS, m/z (relative
intensity) 265 (5, M+ - OMe), 234 (6), 233 (20), 152 (18), 151
(100), 105 (15); 1H NMR δ 0.97 (m, 2H), 1.19 (m, 4H), 1.48 (m,
2H), 1.87 (m, 2H), 3.13 (s, 6H), 3.25 (s, 6H), 4.27 (t, 1H), 7.22-
7.47 (m, 5H); 13C NMR δ 23.29, 24.44, 29.43, 32.36, 37.15,
48.60, 52.55, 103.62, 104.42, 126.95, 127.53, 127.70, 141.01.
Anal. Calcd for C17H28O4: C, 68.89; H, 9.52. Found: C, 68.78;
H, 9.37.
1,2-Dim eth oxy-1-p h en ylcycloh ep ta n e (2c): mixture of
cis and trans isomers (5.1:1); bp 154-7 °C/8 mmHg; nD20
1.5319; MS, m/z (relative intensity) 234 (23, M+), 203 (10), 202
(45), 172 (20), 170 (25), 147 (100), 121 (28), 105 (26), 91 (30).
Anal. Calcd for C15H22O2: C, 76.88; H, 9.47. Found: C, 76.69;
H, 9.37. cis-2c: 1H NMR δ 1.40-1.97 (m, 8H), 2.07 (m, 2H),
3.01 (s, 3H), 3.05 (m, 1H), 3.17 (s, 3H), 7.23-7-47 (m, 5H); 13
C
NMR δ 20.36, 23.60, 26.11, 26.93, 33.69, 50.83, 57.70, 82.11,
89.51, 126.46, 127.25, 127.54, 144.05. tr a n s-2c: 1H NMR δ
1.40-1.97 (m, 8H), 2.07 (m, 2H), 2.89 (s, 3H), 3.02 (s, 3H), 3.30
(m, 1H), 7.23-7.47 (m, 5H); 13C NMR δ 19.51, 24.64, 26.73,
29.15, 32.83, 49.82, 57.35, 82.30, 86.90, 127.07, 128.02, 128.68,
145.15.
1,2-Dim eth oxyin d a n (5a ): mixture of cis and trans iso-
mers (1.4:1); bp 125-8 °C/12 mmHg (lit.6 bp 134-6 °C/22
mmHg); n2D0 1.5358; MS, m/z (relative intensity) 178 (100,
M+), 147 (85), 146 (74), 131 (90), 117 (81), 116 (93), 115 (57),
105 (69), 104 (53), 103 (78), 91 (60). cis-5a : 1H NMR δ 2.75-
3.38 (m, 2H), 3.43 (s, 3H), 3.52 (s, 3H), 4.09 (m, 1H), 4.62 (d,
1H, J ) 4.97 Hz), 7.20-7.42 (m, 4H); 13C NMR δ 35.31, 56.95,
57.24, 82.05, 86.95, 124.89, 125.23, 127.75, 128.45, 139.49,
140.12. tr a n s-5a : 1H NMR δ 2.75-3.38 (m, 2H), 3.47 (s, 3H),
3.57 (s, 3H), 4.09 (m, 1H), 4.77 (d, 1H, J ) 4.18 Hz), 7.20-
7.42 (m, 4H); 13C NMR δ 35.86, 56.05, 56.95, 81.54, 88.02,
124.89, 126.22, 126.67, 128.89, 139.80, 140.75.
1,2-Dim eth oxy-1,2,3,4-tetr ah ydr on aph th alen e (5b): mix-
ture of cis and trans isomers (1.8:1); bp 130-5 °C/10 mmHg;
n2D0 1.5345; MS, m/z (relative intensity) 192 (7, M+), 160 (40),
134 (100), 119 (55), 91 (31). Anal. Calcd for C12H16O2: C,
74.96; H, 8.39. Found: C, 74.88; H, 8.27. cis-5b: 1H NMR δ
2.08 (m, 2H), 2.70-3.15 (m, 2H), 3.49 (s, 3H), 3.56 (s, 3H), 3.77
(m, 1H), 4.29 (d, 1H, J ) 4.98 Hz); 13C NMR δ 23.47, 25.38,
56.59, 57.50, 77.63, 79.69, 125.90, 127.67, 128.51, 129.81,
134.60, 136.65. tr a n s-5b: 1H NMR δ 2.08 (m, 2H), 2.70-3.15
(m, 2H), 3.51 (s, 3H), 3.53 (s, 3H), 3.67 (m, 1H), 4.39 (d, 1H, J
) 2.84 Hz), 7.12-7.42 (m, 4H); 13C NMR δ 22.36, 27.22, 56.43,
57.19, 77.67, 78.26, 125.41, 128.19, 128.86, 129.92, 133.90,
135.85.
2-(2,2-Dim eth oxyeth yl)ben za ld eh yd e d im eth yl a ceta l
(6a ): bp 81-3 °C/0.07 mmHg (lit.14 bp 74-6 °C/0.05 mmHg);
MS, m/z (relative intensity) 209 (3, M+ - OMe), 208 (2), 207
(3), 193 (5), 178 (7), 177 (56), 146 (10), 134 (17), 115 (15), 91
(16), 75 (100); 1H NMR δ 2.99 (d, 2H), 3.29 (s, 6H), 3.32 (s,
6H), 4.48 (t, 1H), 5.54 (s, 1H), 7.15-7.55 (m, 4H); 13C NMR δ
35.94, 53.05, 53.64, 101.84, 105.58, 125.99, 126.57, 128.17,
130.94, 135.21, 136.09.
2-(3,3-Dim eth oxyp r op yl)ben za ld eh yd e d im eth yl a c-
eta l (6b): bp 125-8 °C/1 mmHg; n2D0 1.4968; MS, m/z (rela-
tive intensity) 254 (5, M+), 252 (22), 242 (21), 241 (25), 191
(15), 190 (18), 176 (17), 175 (18), 164 (19), 156 (25), 149 (37),
1
141 (30), 117 (85), 89 (92), 75 (100); H NMR δ 1.91 (m, 2H),
2.77 (m, 2H), 3.33 (s, 6H), 3.36 (s, 6H), 4.42 (t, 1H), 5.52 (s,
1H), 7.18-7.58 (m, 4H); 13C NMR δ 26.93, 33.85, 52.50, 52.94,
101.39, 103.86, 125.55, 126.71, 128.44, 129.51, 135.29, 139.82.
Anal. Calcd for C14H22O4: C, 66.11; H, 8.72. Found: C, 66.02;
H, 8.58.
Ack n ow led gm en t. This work was supported by the
International Science Foundation (Grant MHY-000) and
the Russian Foundation for Fundamental Research
(Grant 95-03-08444a).
J O951948S
5,5-Dim et h oxy-5-p h en ylp en t a n a l d im et h yl a cet a l
(14) Ogibin, Yu. N.; Ilovaisky, A. I.; Nikishin, G. I. Izv. Russ. Akad.
Sci., Ser. Khim. 1993, 140 (Russ. Chem. Bull. 1993, 42, 126).
(3a ): bp 118-20 °C/0.1 mmHg; n2D0 1.4905; MS, m/z (relative