Observations on the alkylation of β-acetalic carbanions: Monoalkylation versus dialkylation and elimination

Article abstract of DOI:10.1016/S0040-4020(01)00378-7

The reaction with methyl iodide and a base (t-BuOK) of 1,3-dioxolanes and 1,3-dithiolanes substituted at the β-position with an electron-withdrawing substituent (EWG=-CO₂Me, -SO₂Ph, -SO₂Ph-p-NO₂, -SO₂Ph-o-NO₂) leads to mono- or dialkylated or ring-opened products in good yield.

Full text of DOI:10.1016/S0040-4020(01)00378-7

TETRAHEDRON
Pergamon
Tetrahedron 57 )2001) 4461±4465
Observations on the alkylation of b-acetalic carbanions:
monoalkylation versus dialkylation and elimination
Roberto Ballini,a,p Giovanna Bosica,a Sergio Cossu,b,p Ottorino De Lucchib and Paola Pelusob
a
Á
Dipartimento di Scienze Chimiche dell'Universita, Via S. Agostino 1, I-62032 Camerino, Italy
Á
Dipartimento di Chimica, Universita Ca' Foscari di Venezia, Dorsoduro 2137, I-30123 Venezia, Italy
b
Received 23 November 2000;revised 9 March 2001;accepted 22 March 2001
AbstractÐThe reaction with methyl iodide and a base )t-BuOK) of 1,3-dioxolanes and 1,3-dithiolanes substituted at the b-position with an
electron-withdrawing substituent )EWGˆZCO2Me, ZSO2Ph, ZSO2Ph-p-NO2, ZSO2Ph-o-NO2) leads to mono- or dialkylated or ring-
opened products in good yield. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
compounds, the latter to ole®ns. Because of the interest in
the nucleophilic ring opening of cyclic acetals in stereo-
selective processes,1,6b,7,8 we have studied the role of the
electron-withdrawing group, with the aim to establish the
best reaction conditions to accomplish either one of the
transformations in a selective fashion.
Cyclic acetals are useful synthons in organic synthesis.1
They are extensively used as protective groups in carbo-
hydrate chemistry and in the preparation of other polyols.2
Chiral versions of cyclic acetals and thioacetals are of
particular interest owing to their applications in the asym-
metric synthesis of natural products and of biologically
active molecules.3,4
2. Results
Although the classical method of preparation of cyclic
acetals and thioacetals involves acidic catalysis,5 they can
also be obtained by Michael addition of diols or dithiols to
electron-poor acetylenes )Scheme 1).6 The resulting acetals
contain an electron-withdrawing group at the b-position
and represent interesting substrates for subsequent trans-
formations.7 For example, considering the formation of a
carbanionic species by an appropriate base, two competitive
pathways can be envisaged )Scheme 1): alkylation )path A)
and elimination )path B), the former leading to substituted
In order to investigate the role of the electron-withdrawing
group and of the acetalic heterocycles, we prepared acetals
or thioacetals 2a±d )Fig. 1) by reaction of either methyl
propiolate )1a), phenylsulfonyl acetylene )1b), p-nitro-
phenylsulfonyl acetylene )1c) or o-nitrophenylsulfonyl
acetylene )1d) with diols or thiols as shown in Scheme 1.6
In the present study the acetals derived from 1,2-ethanediol
)2aA, 2bA, 2cA), 1,2-benzenedithiol )2bB), hydrobenzoin
)2aC, 2bC, 2dC), and 2,20-binaphthol )2bD) were
considered.
Scheme 1.
Keywords: acetals;alkylation;elimination.
Corresponding authors. Tel.: 10737 40347;fax: 10737 637345;e-mail: ballini@camserv.unicam.it;
Tel.: 1041 2578647;fax: 1041 2578517;e-mail: cossu@unive.it
p
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020)01)00378-7

4462
R. Ballini et al. / Tetrahedron 57 .2001) 4461±4465
Figure 1.
Scheme 2.
The reactions were carried out by treating THF solutions of
acetals 2A±D with a stoichiometric amount of t-BuOK at
the indicated temperature and by quenching the resulting
species with methyl iodide. The reaction products were
puri®ed in all cases by chromatography and characterized
by NMR. The results obtained are summarised in Table 1.
Under the same reaction conditions, the p-nitrophenyl-
sulfonyl-substituted acetal 2cA )row 3, Table 1) led to a
mixture of mono- )3cA) and dimethylated )4cA) compounds
in 11% and 64% yields, respectively. In this case, the nitro
group appears to exert an additional effect in stabilizing the
anion derived from the monomethylated product in apparent
contrast to the standard stability of carbanions, but in
agreement with what is reported in the literature.9
The effect of the nature of the electron-withdrawing group
was comparatively tested on 2aA )EWGˆZCO2Me), 2bA
)EWGˆZSO2Ph) and 2cA )EWGˆZSO2Ph-p-NO2). The
reaction )Scheme 2) carried out on the methylester 2aA
)row 1, Table 1) afforded only the monomethylated deriva-
tive 3aA )46% yield);while acetal 2bA, containing the
phenylsulfonyl group )row 2, Table 1), furnished the mono-
methyl derivative 3bA in higher yield )80% yield) as the
sole product.
The product distribution is in¯uenced by the concentration
of MeI and by the sequence of addition of the reagents.
These aspects were studied in the methylation of 2cA in
experiments carried out at 08C. By treating a solution of
2cA anion with a fourfold excess of methyl iodide )row 5,
Table 1), the dimethylated compound 4cA )94% yield) was
formed predominantly with respect to the monomethylated
Table 1. Reaction conditions and product distribution )yields) in the reaction of 2aA±D, 6 with base and MeI
Number
Substrate
Method
Monoalkylated
product
)% yield)
Dialkylated
product
)% yield)
Ring-opened
product
)% yield)
1
2
3
4
5
6
7
8
2aA
2bA
2cA
2cA
2cA
2cA
2cA
6
2aC
2bC
2dC
2bB
2bD
2788C, THF, t-BuOK, CH3I )1 equiv.)
2788C, THF, t-BuOK, CH3I )1 equiv.)
2788C, THF, t-BuOK, CH3I )1 equiv.)
2788C, THF, t-BuOK, CH3I )2 equiv.)
08C, THF, t-BuOK, CH3I )4 equiv.)
08C, THF, t-BuOK, CH3I )4 equiv. inv. add.)
08C, THF, t-BuOK, IZ)CH2)4ZI
2788C, THF, t-BuOK, CH3I )1 equiv.)
2788C, THF, t-BuOK, CH3I )2 equiv.)
2788C, THF, t-BuOK, CH3I )2 equiv.)
2788C, THF, t-BuOK, CH3I )1 equiv.)
2788C, THF, t-BuOK, CH3I )1 equiv.)
2788C, THF, t-BuOK, CH3I )1 equiv.)
3aA )46)
3bA )80)
3cA )11)
3bA )11)
±
3bA )20)
±
±
3aC )quant.)
3bC )50)
3dC )quant.)
±
±
±
±
±
±
±
±
±
±
±
±
4cA )64)
4bA )54)
4cA )94)
4cA )65)
5 )20)
7 )60)
±
4bC )50)
±
±
9
±
±
±
10
11
12
13
8 )quant.)
9 )quant.)
±

R. Ballini et al. / Tetrahedron 57 .2001) 4461±4465
4463
Scheme 3.
Scheme 4.
sibility of alkylating the ethyl derivative 6 obtained by reac-
tion of 1-ethyl-1-p-toluensulfonyl-2-chloroethylene with
ethylene glycol, under standard conditions )Scheme 4).
This compound, treated with t-BuOK at 2788C and methyl
iodide, afforded 7 )row 8, Table 1). Also in this case, the
reactions of the anion derived from 6 with electrophiles
other then methyl iodide were unsuccessful.
The chiral substrates 2aC, 2bC and 2dC in Fig. 1, obtained
employing )R,R)-hydrobenzoin as chiral diol, were prepared
in order to evaluate the degree of the stereoselectivity in the
alkylation step. Relatively to the nature of electron-
withdrawing substituents, the behaviour of 2a±dC was
quite different: while 2aC )EWGˆZCO2Me) )row 9,
Table 1) and 2dC )EWGˆZSO2Ph-o-NO2) )row 11,
Table 1) selectively lead to the monomethylated product
3aC and 3dC )Fig. 2), 2bC )EWGˆZSO2Ph) gave a 1:1
mixture of monomethyl )3bC), and dimethyl )4bC) deriva-
tives )row 10, Table 1). In all cases diastereoselectivity was
poor )6:4 diastereoselective ratio for 3aC, 7:3 for 3bC and
1:1 for 3dC).
Figure 2.
one, showing that the formation of the dimethylated product
is favoured at higher concentration of methyl iodide. By
using 2 equiv. of methyl iodide )row 4, Table 1), the mono-
methylated 3cA and dimethylated 4cA derivatives were
formed in about 1:5 ratio. Differently, the formation of the
dimethylated derivative was slightly disfavoured by the
inverse addition of the reagents. In fact, by using the same
fourfold excess of methyl iodide )row 6, Table 1), the mono-
)3cA) and dimethylated )4cA) derivatives, were obtained in
1:3 ratio, respectively.
Acetals 2bB and 2bD )rows 12 and 13, Table 1) exclusively
afforded O- and S-methylated products 8 and 9 )Fig. 3)
through a b-elimination pathway )path B in Scheme 1) in
almost quantitative yields.7c The stereochemistry of the
double bond in 8 and 9 was assigned E, as suggested by
the coupling constants of the vinylic protons )8: Jˆ14.6 Hz;
9: Jˆ12.0 Hz).
While alkylating agents different from methyl iodide, such
as ethyl bromide, butyl bromide, benzyl bromide, benzoyl
choride or benzaldehyde were totally unreactive with 2bA
and 2cA under the same reaction conditions, the quenching
of 2cA with 1,4-diiodobutane )row 7, Table 1) afforded the
cyclic derivative 5 )20% yield) through an intramolecular
second nucleophilic substitution )Scheme 3).
In conclusion, in the present study we have observed that the
reaction of anions derived from b-electron-withdrawing
substituted acetals may occur through different competitive
reaction routes, involving either mono-, dialkylation and
On the basis of these results, it is not possible to introduce
two different electrophiles;therefore we checked the pos-
Figure 3.

4464
R. Ballini et al. / Tetrahedron 57 .2001) 4461±4465
b-elimination processes. These reactions can be moderatly
shifted to a predominant species under appropriate
conditions.
762, 758, 702 cm21; dH )200 MHz, CDCl3) 7.45±7.10
)10H, series of m, Ar), 5.93 )1H, t, Jˆ5.2 Hz), 4.81 )2H,
s), 3.78 )3H, s), 2.98 )1H, d, Jˆ5.2 Hz); dC )50 MHz,
CDCl3) 169.7, 137.6, 136.3, 128.6, 128.3, 128.11, 126.9,
126.8, 126.4, 102.0, 86.9, 85.0, 51.9, 40.4.
3. Experimental
3.2.4.
34R,5R)-4,4-Diphenyl-2-32-nitrophenylsulfonyl-
methyl)-1,3-dioxolane 32dC). Yield, 93%. Pale yellow
oil: [Found: C, 62.27;H, 4.65;N, 3.43. C 22H19NO6S
requires C, 62.11;H, 4.50;N, 2.29%]; nmax )neat, NaCl)
3093, 3053, 2916, 1539, 1451, 1322, 1147, 1104, 762,
702, 645 cm21; dH )200 MHz, CDCl3) 8.30±8.20, 7.95±
7.62, 7.55±7.00 )14H, series of m, Ar), 6.02 )1H, t,
Jˆ4.9 Hz), 4.75 )1H, d, 1/2 AB system, Jˆ8.3 Hz), 4.69
)1H, d, 1/2 AB system, Jˆ8.3 Hz), 4.29 )1H, dd, 1/2 AB
system, Jˆ14.6, 5.3 Hz), 4.18 )1H, dd, 1/2 AB system,
Jˆ14.6, 5.3 Hz); dC )50 MHz, CDCl3) 139.9, 136.4,
135.3, 1134.8, 133.9, 132.9, 132.5, 128.7, 128.6, 128.6,
126.9, 126.5, 126.3, 124.7, 99.7, 86.7, 84.7, 60.8.
3.1. General methods
Melting points were determined on a BuÈchi 535 apparatus
and are uncorrected. Known compounds used in this
research were either purchased from standard chemical
suppliers or prepared according to literature procedures.
1
The H and 13C NMR were performed with a Bruker AC
200 at 200 MHz )1H) and 50 MHz )13C), respectively, in
deuterochloroform solution. IR spectra were recorded on a
Biorad FTS 40 spectrophotometer. Known compounds,
including optically active compounds, were prepared
according to literature procedures or purchased from
standard chemical suppliers and puri®ed to match the
reported physical and spectral data. NaH was purchased as
a dispersion in mineral oil and washed with pentane prior to
use. Microanalyses were performed on a Perkin±Elmer
2400 CHN elemental analyzer.
3.3. Alkylation of acetals. General procedure
A solution of acetal 2b )1.5 mmol) in freshly dried THF,
stirred under argon at the appropriate temperature, was
treated with t-BuOK )1.5 mmol) and the resulting solution
was stirred at the same temperature for 1 h. The methyl
iodide )1 equiv.) was added to the carbanion solution and
the mixture was stirred until the reaction reached room
temperature.The resulting mixture was treated with water
)5 mL), extracted with diethyl ether )3£25 mL), dried
)Na2SO4) and concentrated at reduced pressure. The residue
was puri®ed by ¯ash chromatography )eluting with a
gradient of n-hexane±ethyl acetate starting from n-hexane).
3.2. Reaction of 1a±c with RXH 3XˆO, S). General
procedure for the preparation of 2a±d 3A±D)
A stirred solution of the appropriate diol )or thiol) )5 mmol)
in anhydrous THF )20 mL) was treated at 08C, with NaH
)0.1 equiv. or stoichiometric amount for ethylenes) under
argon. After 15 min, a solution of 1 )5 mmol) in THF
)20 mL) was slowly added by syringe at 08C and the reac-
tion was monitored by TLC. The crude reaction mixture was
treated with brine )15 mL) and extracted with Et2O
)3£60 mL), dried, ®ltered and concentrated at reduced pres-
sure. Flash chromatography )eluant dichloromethane, silica
gel 60 mesh) was performed in order to obtain analytically
pure samples.
3.3.1. 2-310-Methoxycarbonylethyl)-1,3-dioxolane 33aA).
Colourless oil: [Found: C, 52.12;H, 7.36. C 7H12O4 requires
C, 52.49;H, 7.55%]; nmax )neat, NaCl) 2985, 2957, 2885,
1744, 1700,1640, 1438, 1293, 1253, 1189, 1124, 798 cm21
;
dH )200 MHz, CDCl3) 5.11 )1H, d, Jˆ5.1 Hz), 4.12±3.85
)4H, m), 3.72 )3H, s, OMe), 2.76 )1H, qd, Jˆ7.1, 5.1 Hz),
1.26 )6H, d, Jˆ7.1 Hz); dC )50 MHz, CDCl3) 157.5, 104.3,
73.2, 71.6, 65.2, 51.1, 44.1.
3.2.1. 2-Methoxycarbonylmethyl-1,3-dioxolane 32aA).
Yield, 84%. Colourless oil: [Found: C, 44.99;H, 7.70.
C5H10O4 requires C, 44.77;H, 7.51%]; nmax )neat, NaCl)
2956, 2893, 1738, 1439, 1136, 845, 745, 694 cm21; dH
)200 MHz, CDCl3) 5.25 )1H, t, Jˆ5.2 Hz), 4.04±3.78
)4H, m), 3.68 )3H, s), 2.65 )2H, d, Jˆ5.2 Hz). dC
)50 MHz, CDCl3) 169.7, 100.8, 64.9, 51.7, 39.6.
3.3.2. 2-310-Phenylsulfonylethyl)-1,3-dioxolane 33bA).
Colourless oil: [Found: C, 54.32;H, 6.04. C 11H14SO4
requires C, 54.53;H, 5.82%]; nmax )neat, NaCl) 3057,
2948, 2880, 1620, 1446, 1382, 1304, 1205, 1169, 758,
726, 689 cm21; dH )200 MHz, CDCl3) 7.96±7.85, 7.70±
7.50 )5H, series of m, Ar), 5.30 )1H, d, Jˆ3.3 Hz), 3.91±
3.79 )4H, m), 3.39 )1H, qd, Jˆ7.1, 3.3 Hz), 1.30 )6H, d,
Jˆ7.1 Hz); dC )50 MHz, CDCl3) 133.7, 129.2, 128.9, 128.2,
100.7, 68.0, 65.7, 65.0, 26.6.
3.2.2. 2-34-Nitrophenylsulfonylmethyl)-1,3-dioxolane
32cA). Pale yellow oil: [Found: C, 44.12;H, 4.15;N,
5.25. C10H11NO6S requires C, 43.95;H, 4.06;N, 5.13%];
n
max )neat, NaCl) 2990, 2995, 1520, 1351, 1306, 1130, 767,
740, 705 cm21; dH )200 MHz, CDCl3) 8.47±8.38, 8.20±
8.11 )4H, series of m, AA0BB0 system, Ar), 5.33 )1H, t,
Jˆ4.7 Hz), 3.87 )4H, bs), 3.53 )2H, d, Jˆ4.7 Hz); dC
)50 MHz, CDCl3) 145.9, 129.8, 125.8, 124.1, 98.5, 65.0,
59.6.
3.3.3. 2-[10-34-Nitrophenylsulfonyl)ethyl]-1,3-dioxolane
33cA). White solid, mp 101±1038C )Et2O±n-hexane):
[Found: C, 45.77;H, 4.65;N, 5.15. C 11H13NO6S requires
C, 45.99;H, 4.56;N, 4.88%]; nmax )KBr) 3010, 2985, 2896,
1523, 1354, 1297, 1128, 1078, 846, 770, 742, 706,
677 cm21; dH )200 MHz, CDCl3) 8.41±8.37, 8.13±8.09
)4H, series of m, AA0BB0 system, Ar), 5.29 )1H, d,
Jˆ3.6 Hz), 3.88±3.79 )4H, m), 3.43 )1H, qd, Jˆ7.2,
3.6 Hz), 1.37 )6H, d, Jˆ7.2 Hz). dC )50 MHz, CDCl3)
144.0, 130.9, 123.9, 100.9, 65.6, 65.2, 63.6, 8.0.
3.2.3. 34R,5R)-4,4-Diphenyl-2-methoxycarbonylmethyl-
1,3-dioxolane 32aC). Yield, 93%. White solid, mp 82±
838C )Et2O±petrol. ether): [Found: C, 72.76;H, 6.31.
C18H18O4 requires C, 72.47;H, 6.08%]; nmax )KBr disk)
3085, 3033, 2953, 2880, 1740, 1455, 1430, 1253, 1132,

R. Ballini et al. / Tetrahedron 57 .2001) 4461±4465
4465
3.3.4. 2-[10-Methyl-10-34-nitrophenylsulfonyl)ethyl]-1,3-
dioxolane 34cA). White solid, mp 144±1468C )Et2O):
[Found: C, 48.09;H, 5.17;N, 4.86. C 12H15NO6S requires
C, 47.83;H, 5.02;N, 4.65%]; nmax )KBr) 3097, 2896, 2876,
1539, 1362, 1297, 1161, 1104, 738, 689, 608 cm21; dH
)200 MHz, CDCl3) 8.36±8.31, 8.12±8.08 )4H, series of m,
AA0BB0 system, Ar), 5.12 )1H, s), 3.86±3.76 )4H, m), 1.36
)6H, s); dC )50 MHz, CDCl3) 150.8, 143.3, 132.2, 123.2,
103.4, 66.9, 65.5, 16.5.
Et2O): [Found: C, 74.90;H, 4.83. C 29H22O4S requires C,
74.66;H, 4.75%]; nmax )KBr) 3061, 2928, 2832, 1620,
1306, 1250, 1150, 1084, 814, 754, 730, 689 cm21; dH
)200 MHz, CDCl3) 8.15±7.83, 7.76±7.12, 7.10±6.93
)18H, series of m, Ar and vinylic), 5.66 )1H, d,
Jˆ12.0 Hz, vinylic), 3.68 )3H, s, OMe); dC )50 MHz,
CDCl3) 159.6, 154.8, 142.1, 132.7, 131.8, 130.44, 130.2,
129.4, 129.3, 129.0, 128.8, 128.2, 128.0, 127.0 )3C),
126.3, 126.1, 125.9, 124.5, 123.7, 119.4, 113.0, 109.7, 56.1.
3.3.5. 2-[10-34-Methyl-phenylsulfonyl)cyclopentyl]-1,3-
dioxolane 35). Pale yellow oil: [Found: C, 59.91;H, 5.97;
N, 4.88. C14H17NO4S requires C, 59.63;H, 5.80;N, 4.74%];
Acknowledgements
We are grateful to Mr A. Canu of the Dipartimento di
Á
n
max )neat, NaCl) 3096, 2880, 1532,1360, 1298, 1105, 737,
690, 610 cm21; dH )200 MHz, CDCl3) 8.34 )2H, d, 1/2 AB
system, Jˆ9.0 Hz, Ar), 8.13 )2H, d, 1/2 AB system,
Jˆ9.0 Hz, Ar), 5.18 )1H, s), 3.82 )4H, bs), 2.40±1.75 )8H,
series of m); dC )50 MHz, CDCl3) 150.6, 141.5, 131.4,
123.1, 96.5, 68.2, 66.7, 27.3, 22.5.
Chimica dell'Universita di Sassari for the microanalytical
determinations. This work was co-funded by MURST
)Rome) within the national project `Stereoselezione in
Sintesi Organica. Metodologie ed Applicazioni'.
References
3.3.6. 2-[10-34-Methyl-phenylsulfonyl)propyl]-1,3-dioxo-
lane 36). Yield, 90%. White solid, mp 68±698C )Et2O±
petrol. ether): [Found: C, 57.50;H, 6.87. C 13H18O4S
requires C, 57.76;H, 6.71%]; nmax )KBr) 2973, 2944,
2884, 1595, 1451, 1390, 1378, 13340, 1320, 1144, 1076,
822, 718, 681 cm21; dH )200 MHz, CDCl3) 7.85±7.74,
7.40±7.30 )4H, series of m, Ar), 5.27 )1H,d, Jˆ2.3 Hz,),
4.00±3.80 )4H, m), 3.21 )1H, td, Jˆ4.0, 2.3 Hz), 2.43
)3H, s), 1.80 )2H, dq, Jˆ8.1, 4.0 Hz), 1.05 )3H, t,
Jˆ8.1 Hz); dC )50 MHz, CDCl3) 144.5, 129.5, 129.4,
129.0, 101.1, 68.5, 65.4, 64.6, 21.6, 17.2, 12.6.
1. )a) Alexakis, A.;Mangeney, P. Tetrahedron: Asymmetry 1990,
1, 477±511. )b) Sakai, K.;Suemune, H.
Asymmetry 1993, 4, 2109±2118.
Tetrahedron:
2. )a) Greeen, T. W.;Wuts, P. G. M. Protective Groups in Organic
Synthesis, Wiley-Interscience: New York, 1991. )b) Kocienski,
P. J. Protecting Groups, Georg Thieme Verlag: Stuttgart, 1994.
3. Omura, S.;Tanaka, H. In Macrolide Antibiotics: Chemistry,
Biology and Practice, Omura, S., Ed.;Academic Press: New
York, 1984;pp 351±404.
4. Andrus, M. B.;Lepore, S. D. Tetrahedron Lett. 1995, 36, 9149±
9152 and references cited therein.
3.3.7. 2-[10-Methyl-10-34-methyl-phenylsulfonyl)propyl]-
1,3-dioxolane 37). Slurry: [Found: C, 59.32;H, 7.25.
C14H20O4S requires C, 59.13;H, 7.09%]; nmax )NaCl)
2996, 2932, 2884, 1640, 1446, 1398, 1289, 1157, 1124,
734, 657 cm21; dH )200 MHz, CDCl3) 7.85±7.74, 7.40±
7.30 )4H, series of m, Ar), 5.12 )1H, s), 3.92±3.75 )4H,
m), 2.40 )3H, s), 1.90 )2H, dq, Jˆ7.8, 2.0, Hz), 1.28 )3H,
s, CH3), 1.08 )3H, t, Jˆ7.8 Hz); dC )50 MHz, CDCl3) 143.3,
130.4, 128.8, 127.4, 103.5, 73.7, 65.2, 64.9, 23.8, 21.3, 17.8,
12.6.
5. Kunz, H.;Waldmann, H. Comprehensive Organic Synthesis,
Trost, B. M., Fleming, I., Eds.;Pergamon Press: New York,
1991;6, pp 659.
6. )a) Cossu, S.;De Lucchi, O.;Fabris, F.;Ballini, R.;Bosica, G.
Synthesis 1996, 1481±1484. )b) Evans, P. A.;Garber, L. T.
Tetrahedron Lett. 1996, 37, 2927±2930.
7. Acetals substituted with electron-withdrawing groups at the
g-position have been studied extensively: )a) Simpkins, N. S.
Sulphones in Organic Synthesis, Pergamon Press: Oxford,
1993. )b) Patai, S. In The Chemistry of Sulphones and
Sulphoxide, Patai, S., Rappoporta, Z., Stirling, C. J. M., Eds.;
John Wiley & Sons: New York, 1988. )c) Caballero, M.;
Garcia-Valverde, M.;Pedrosa, R.;Vicente, M. Tetrahedron:
Asymmetry 1996, 7, 219±226. )d) Kato, K.;Suemune, H.;
Sakai, K. Tetrahedron Lett. 1992, 33, 247±250.
3.3.8. 3E)-1-Phenylsulfonyl-2-320-methylthiophenylthio)-
ethylene 38). White solid, mp 105±1078C )Et2O): [Found:
C, 55.35;H, 5.71. C 15H18O2S3 requires C, 55.18;H, 5.56%];
n
max )KBr) 3029, 2920, 2848, 1551, 1430, 1348, 1306, 1144,
1076, 835, 750 cm21; dH )200 MHz, CDCl3) 7.97±7.78
)2H, m, Ar), 7.72 )1H, d, Jˆ14.6 Hz), 7.65±7.36, 7.29±
7.09 )7H, series of m, Ar), 5.91 )1H, d, Jˆ14.6 Hz), 2.39
)3H, s); dC )50 MHz, CDCl3) 144.9, 144.2, 141.00, 135.5,
133.0, 130.9, 129.1, 127.3 )2C), 125.5, 125.4, 123.2, 15.4.
8. )a) Godebout, V.;Lecomte, S.;Levasseur, F.;Duhamel, L.
Tetrahedron Lett. 1996, 37, 7255±7258. )b) Maezaki, N.;
Soejima, M.;Takeda, M.;Sakamoto, A.;Matsumori, Y.;
Tanaka, T.;Iwata, C. Tetrahedron 1996, 52, 6527±6546.
)c) Maier, P.;Redlich, H. Synlett 2000, 257±259.
9. Pine, S. H.;Shen, G.;Bautista, J.;Sutton, Jr., C.;Yamada, W.;
Apodaca, L. J. Org. Chem. 1990, 55, 2234±2237.
3.3.9. 2-[3E)-2-Phenylsulfonylethenyl]-20-methoxy-1,10-
binaphthalene 39). White solid, mp 115±1178C )CH2Cl2±