γ-lactone formation in the addition of benzenesulfonyl bromide to diene and enyne esters

Article abstract of DOI:10.1021/jo982388a

The gem-dialkyl effect has been used to promote the formation of functionalized γ-lactones in the addition of benzenesulfonyl bromide to diene and enyne esters. Introduction of 3 tool % of pyridine into the reactions increases the yields of lactones produced from tertiary esters. Formation of the C(α)-C(β) bond of γ-lactones has been achieved in both C(α)→C(β) and Cβ→C(α) radical cyclization directions.

Full text of DOI:10.1021/jo982388a

2066
J . Org. Chem. 1999, 64, 2066-2069
γ-La cton e F or m a tion in th e Ad d ition of Ben zen esu lfon yl Br om id e
to Dien e a n d En yn e Ester s
Chen Wang* and Glen A. Russell†
Department of Chemistry, Iowa State University, Ames, Iowa 50011-3111
Received December 7, 1998
The gem-dialkyl effect has been used to promote the formation of functionalized γ-lactones in the
addition of benzenesulfonyl bromide to diene and enyne esters. Introduction of 3 mol % of pyridine
into the reactions increases the yields of lactones produced from tertiary esters. Formation of the
CR-Câ bond of γ-lactones has been achieved in both CRfCâ and CâfCR radical cyclization directions.
In tr od u ction
The use of diene or enyne esters, such as allyl acry-
lates, as precusors to functionalized lactones is a promis-
ing route. However, the radical adduct of a diene ester
(1, Y ) CO) has a much slower rate of cyclization than
that of a diene ether (1, Y ) CH2).7 In fact, the addition
of tosyl bromide to allyl acrylate affords only a low yield
of acrylic CdC monoadduct along with other telomers or
polymer (Scheme 1). This is partially because ester 1 (Y
) CO) exists primarily in an s-trans conformation at
room temperature, while the cyclization process requires
an s-cis conformer.
It has been found that the addition of an arylsulfonyl
halide to N-allyl acrylamides leads to lactams as long as
the second alkyl substituent on the amide N is bulky
enough to ensure the cyclization-required s-cis con-
former.8 Conformer population of diene esters can be
influenced by the gem-dialkyl or Thorpe-Ingold effect.9
Gem-dialkyl groups can increase the population of the
s-cis conformer (2 as R1, R2 are alkyl groups) and reduce
the barrier for s-trans to s-cis interconversion.
The lactone skeleton exists in many bioactive natural
products.1 Functionalized lactones are important inter-
mediates for the synthesis of stereo-defined acyclic and
other natural products.2 The synthesis of γ-lactones can
be achieved by the lactonization of hydroxy acids, Baeyer-
Villiger oxidation, the insertion of a carbonyl group by
transition metals, etc.3 In recent years, assembly of
γ-lactones by formation of the CR-Câ (or C3-C4) bond has
drawn attention. Lu reported the Pd-catalyzed enyne
cyclization as a convenient method to make R-alkylidene-
γ-butyrolactone derivatives.4 Also, radical cyclization
methodology has been explored in this field. In most
radical cyclization reports, a carbamoyl radical, generated
from its R-derivative precursor, intramolecularly adds to
a CdC or CtC bond in a 5-exo mode.5 However, the
reactions generally proceed either in very low concentra-
tion or at high temperatures,6 and functional groups are
often lost.
* Corresponding author. Phone: 515-294-7050. Fax: 515-294-0105.
E-mail: ycwang@iastate.edu.
† Deceased.
We have explored the possibility of using the gem-
dialkyl effect to promote γ-lactone formation from diene
and enyne esters. Since the sulfonyl group is a very
versatile group in organic synthesis,10 we have chosen
PhSO2Br to initiate cyclization and thus incorporate
sulfonyl and halide groups into the final lactones.
(1) (a) Drioli, S.; Felluga, F.; Forzato, C.; Nitti, P.; Pitacco, G.;
Valentin, E. J . Org. Chem. 1998, 63, 2385. (b) Rossi, R.; Bellina, F.;
Mannina, F. Tetrahedron Lett. 1998, 39, 3017. (c) J acobi, P. A.;
Herradura, P. Tetrahedron Lett. 1996, 37, 8297. (d) Rodriguez, C. M.;
Martin, T.; Martin, V. S. J . Org. Chem. 1996, 61, 8448. (e) MacRae,
W. D.; Towers, G. H. N. Phytochemistry 1984, 23, 1207.
(2) (a) Robin, S.; Huet, F.; Fuvw, A.; Veschambre, H. Tetrahedron
Asymmetry 1993, 4, 239. (b) Hanessian, S.; Murray, P. J .; Sahoo, S. P.
Tetrahedron Lett. 1985, 26, 5623. (c) Cossy, J .; Ranaivosata, J . L.;
Bellosa, V. Tetrahedron Lett. 1994, 35, 1205. (d) Rojo, J .; Oarcia, M.;
Carretero, J . C. Tetrahedron 1993, 49, 9787. (e) Koch, S. C.; Cham-
berlin, A. R. J . Org. Chem. 1993, 58, 2725. (f) Ribbons, D. W.;
Sutherland, A. G. Tetrahedron 1994, 50, 3587. (g) Brown, H. C.;
Kulkstni, S. V.; Rscherla, U. S. J . Org. Chem. 1994, 59, 365.
(3) Ogliaruso, M. A.; Wolfe, J . F. Synthesis of Lactones and Lactams;
J ohn Wiley & Sons: New York, 1993.
(4) (a) Lu, X.; Zhu, G.; Wang, Z.; Ma, S.; J i, J .; Zhang, Z. Pure Appl.
Chem. 1997, 69, 553. (b) Lu, X.; Zhu, G.; Wang, Z. Synlett 1998, 117.
(5) (a) Clough, J . M.; Pattenden, G.; Wright, P. G. Tetrahedron Lett.
1989, 30, 7469. (b) Nagashima, H.; Seki, K.; Ozaki, N.; Wakamatsu,
H.; Itoh, K.; Tomo, Y.; Tsuji, J . J . Org. Chem. 1990, 55, 985. (c) Russell,
G. A.; Li, C.; Chen, P. J . Am. Chem. Soc. 1996, 118, 9831.
(6) (a) Hanessian, S.; Di Fabio, R.; Marcoux, J .-F.; Prud’homme, M.
J . Org. Chem. 1990, 55, 3436. (b) Curran, D. P.; Tamine, J . J . Org.
Chem. 1991, 56, 2746.
Resu lts a n d Discu ssion
1. Ad d ition of P h SO2Br to Acr yla tes. Table 1
summarizes the results of the addition of PhSO2Br to
(7) Serra, A. C.; da Silva Correa, C. M. M.; do Vale, M. L. C.
Tetrahedron Lett. 1991, 47, 9463.
(8) Riggi, I. D.; Gastaldi, S.; J urzur, J .-M.; Bertrand, M. P. J . Org.
Chem. 1992, 57, 6118.
(9) (a) J ung, M. E.; Gervoy, J . J . Am. Chem. Soc. 1991, 113, 224.
(b) J ung, M. E.; Trifunovich, I. D.; Lensen, N. Tetrahedron Lett. 1992,
33, 6719.
(10) Chatgilialoglu, C. The Chemistry of Sulphones and Sulphoxides;
Patai, S., Rappoport, Z., Stirling, C. J . M., Eds.; J ohn Wiley & Sons
Ltd.: New York, 1988; p 1089.
10.1021/jo982388a CCC: $18.00 © 1999 American Chemical Society
Published on Web 02/25/1999

γ-Lactone Formation
J . Org. Chem., Vol. 64, No. 6, 1999 2067
Sch em e 1
two methine H’s (Ha and Hb) cannot be used as a
criterion, because of their close distance in both cis and
trans configurations. Another possible structure with the
groups PhSO2 and Br reversed in 3c was excluded by
HMBC (heteronuclear multiple bond correlation) 2D
spectroscopy. In the HMBC spectrum, Ha correlates to
CdO (δ 173.00 ppm) and PhSO2CH2 (δ 56.63 ppm), while
Hb correlates to -CMe2 (δ 85.85 ppm) and BrCH2 (δ 29.38
ppm).
Products 6, 7, and 8 come from the addition of PhSO2-
Br to dienes liberated from the corresponding tertiary
esters. Since the PhSO2Br sample inevitably contains a
trace of acid, the R1 and R2 groups facilitate the acid-
catalyzed hydrolysis and dehydration of the tertiary
esters. We have found that the addition of 3 mol % of
pyridine to the reaction mixture increases the yields of
3c-e to 74%, 56%, and 55%, respectively, with the
decreased yields of 6, 7, and 8. We have also confirmed
that isoprene was generated when 2c was mixed with
PhSO2Br and kept in the dark at 40 °C for 1 h. The
addition of PhSO2Br to an authentic isoprene sample
under the same reaction conditions yielded 93% of 6 with
the same ratio of 6a /6b. Similarly, 7 and 8 come from
the addition of PhSO2Br to olefin 9, which was liberated
from 2e (eq 2). Since 10 and 3e are inseparable on TLC,
the mixture was treated with triethylamine for 1 h at
room temperature, and then 8 and 3e could be separated.
Ta ble 1. Ad d ition of P h SO2Br to Allyl Acr yla tes (2)
u n d er Su n la m p Ir r a d ia tion in CH3CN
2
R1
R2
products (yield %)
5a (15)
2a
2b
2c
2d
2e
2f
H
H
H
Me
i-Pr
Me
Me
i-Pr
5b (23)
3c (54, 74a) 6b(31)
3d (30, 56a)
-(CH2)5-
3e (26, 55a) 7 (24) 8 (10)
3f (18, 41c) 5f (53, 15c)
5g (23)
t-Bu
H
H
2g
-CHdCH2
a
b
Yields of the reactions with 3 mol % of pyridine. Compound
6 is an inseparable mixture of 6a and 6b in a ratio of 1/4.11 c Yields
of the reaction diluted to 1/4 of the typical concentration.
F igu r e 1. 1H-1H NOE of 3c.
allyl acrylates 2 (eq 1). All reactions were conducted in
acetonitrile under sunlamp irradiation at room temper-
ature.
One interesting product is lactone 3f from ester 2f.
Only one stereoisomer was found with the t-Bu group
trans to -CH2Br and cis to -CH2SO2Ph. The chiral
center at the γ-position induces the configurations of both
R and â chiral centers in one step. Though the yield of 3f
was only 18%, it could be increased to 41% when the
concentration of the reaction mixture was diluted to one-
fourth of that used in Table 1, and the yield of 5f was
decreased to 15%. Obviously, a reaction conducted at low
concentration favors intramolecular cyclization.
The addition of PhSO2Br to acrylate 11 yielded lactone
12 in 40%. The gem-dimethyl groups were found essential
for the formation of lactone 12, and an isomerization step
of the CdC bond was involved.5a
Uncyclized monoadducts 4 partially dehydrobromi-
nated during TLC separation. Treatment of 4 with
triethylamine at room temperature yielded sulfone 5
quantitatively.
The results in Table 1 show that, with gem-dialkyl
groups R1 and R2, γ-lactones can be formed stereoselec-
tively from the diene esters. Only trans cyclized lactones
3c-f were isolated. The configurations of the lactones
were determined by 2D COSY and NOESY spectroscopy.
Taking 3c as an example, the assignment of its trans
configuration is based on the observed NOE coupling
shown in Figure 1. No NOE was observed between
PhSO2CH2 and BrCH2. The NOE coupling between the
It is interesting to note that all of the lactones
mentioned thus far are formed by radical cyclizations
proceeding from CR to Câ. The sulfonyl radical always
adds preferentially to the acrylic CdC bond than the allyl
CdC bond or propargyl CtC bond, even though it is an
electrophilic radical12 and the acrylic CdC bond is more
electrophilic. Another electrophilic radical Cl3C•, gener-
(11) Zakharkin, L. I.; Zhigareva, G. G. J . Org. Chem. USSR 1973,
918.
(12) (a) Takahara, Y.; Lino, M.; Matsuda, M. Bull. Chem. Soc. J pn.
1976, 49, 2268. (b) da Silva Correa, C. M. M.; Waters, W. A. J . Chem.
Soc., Perkins Trans. 2 1972, 1575.

2068 J . Org. Chem., Vol. 64, No. 6, 1999
Wang and Russell
Sch em e 2
Sch em e 3
ated from Cl3CBr under photolysis, also gave the CRfCâ
cyclized lactone 13 (eq 3). This shows that polar effects
do not control the chemoselectivity of the radical addition
step here.
24 were isolated as only one stereoisomer, whose con-
figurations were determined by 2D NOESY spectroscopy.
So far, both CRfCâ and CâfCR cyclizations have been
observed separately. They can proceed in sequence as in
the addition of PhSO2Br to fumarate 25. Compound 26
was isolated as a mixture of stereoisomers in a yield of
33%, and its yield was increased to 55% when 3 mol %
pyridine was added before photolysis (eq 4).
(3)
2. Ad d ition of P h SO2Br to â-Su bstitu ted Acr yla tes
a n d P r op iola tes. Assembling the lactone skeleton with
different functionality by a CâfCR cyclization process can
be achieved with â-substituted acrylates and propiolates.
The addition of PhSO2Br to diene esters 14a and 14b
yielded uncyclized 15 (68%) and 16 (65%), respectively.
The addition of PhSO2Br to ester 14c yielded lactone 17
(65%) and 6 (10%), which also shows the gem-dimethyl
effect in the CâfCR radical cyclization process. However,
no significant reactions were observed for esters 14d -f
even after prolonged reaction times. This suggests that
a bulky R1 or R2 group strongly inhibits the addition of
PhSO2• to the allyl CdC bond or the bromo-transfer from
PhSO2Br to the adduct radicals. The reversibility of this
addition step is predominant when the rate of the CâfCR
cyclization step is slow. This inhibition effect is similar
to the steric effect introduced by remotely positioned
groups13 and can explain the chemoselectivity shown in
Table 1. The reversible addition of sulfonyl radicals to
CdC bonds has been observed in many cases.14
Con clu sion
Our work shows that the gem-dialkyl effect can be used
to promote γ-lactone formation in the addition of PhSO2-
Br to diene and enyne esters. This effect is more
significant for diene esters than for enyne esters. Also,
gem-dialkyl groups strongly inhibit the addition of Ph-
•
SO2 to the allyl CdC bond of allyl acrylates or allyl
propiolates and facilitate the hydrolysis and dehydration
of tertiary esters. Introduction of 3 mol % of pyridine as
a base into the reactions increases the yields of lactones
produced from tertiary esters.
Exp er im en ta l Section
NMR spectra were recorded in CDCl3 unless stated other-
wise (1H at 400 MHz and 13C at 100 MHz). IR spectra were
measured as thin films on a NaCl plate. All melting points
were determined without correction. Photostimulated reactions
utilized a 275 W fluorescent sunlamp. Yields are based on the
starting esters. PhSO2Br was prepared according to a litera-
ture procedure.15 Esters 2a ,b, 2f,g, 14a ,b, 14d -f, 18 (R ) H),
and 22 (R ) H) were prepared from the appropriate acyl
chlorides and alcohols with triethylamine at room temperature
in anhydrous ethyl ether. Esters 2c-e, 11, 14c, 18 (R ) Me),
22 (R ) Me), and 25 were prepared from the appropriate acyl
chlorides and deprotonated alcohols (by n-BuLi) at 0 °C in
anhydrous ethyl ether.
Gem-dialkyl groups can also promote CâfCR cycliza-
tion in the addition of PhSO2Br to enyne esters 18 and
19 (Schemes 2 and 3). It is unexpected that both 21 and
Gen er a l P r oced u r e for th e Ad d ition of P h SO2Br to
Dien e or En yn e Ester s. A mixture of the ester (0.20 mmol)
and PhSO2Br (0.22 mmol) with or without 3 mol % of pyridine
in CH3CN (1.0 mL) was irradiated in a 5 mm NMR tube at
(13) (a) Huyser, E. S.; Taliaferro, J . O. J . Org. Chem. 1963, 28, 1676.
(b) Bridger, R. F.; Russell, G. A. J . Am. Chem. Soc. 1963, 85, 3754.
(14) (a) Kuehne, M. E.; Pamon, R. E. J . Org. Chem. 1977, 42, 1825.
(b) Edwards, J . E.; McQuillin, F. J .; Wood, M. J . Org. Chem. 1978, 43,
438. (c) Stork, G.; Mook, R. J . Am. Chem. Soc. 1987, 109, 2829. (d)
Smith, T. A. K.; Whitham, G. H.; J . Chem. Soc., Chem. Commun. 1985,
897.
(15) Poshkus, A. C.; Herweh, J . E.; Magnotta, F. A. J . Org. Chem.
1963, 28, 2766.

γ-Lactone Formation
J . Org. Chem., Vol. 64, No. 6, 1999 2069
room temperature until the starting ester disappeared as
indicated by TLC analysis. The products were obtained by TLC
separation on 20 × 10 cm silica gel plates with hexanes-ethyl
acetate as the eluent.
4.25 (s, 2H), 4.38 (s, 2H), 7.50-7.90 (m, 5H); 13C NMR δ 18.87,
25.46, 51.48, 86.92, 119.59, 128.62, 129.60, 134.83, 138.06,
168.87, 169.59; HREIMS m/z (relative intensity) 279.0687 [75,
calcd for C14H15SO4 (M - Br) 279.0691), 215 (48), 125 (18),
123 (64), 121 (47), 95 (20), 77 (82), 67 (20), 51 (41), 42 (100).
tr a n s-3-Ben zen esu lfon ylm et h yl-4-b r om om et h yl-5,5-
d im eth yld ih yd r o-2(3H)-fu r a n on e (3c) was isolated as a
tr a n s-4-Br om om eth yl-3-(2,2,2-tr ich lor oeth yl)-5,5-d iiso-
p r op yld ih yd r o-2(3H)-fu r a n on e (13) was isolated as a white
solid, mp 119-121 °C: IR (cm-1) 1770; 1H NMR δ 1.49 (s, 3H),
1.68 (s, 3H), 2.62 (dt, J ) 4.0, 11.2 Hz, 1H), 2.80 (dt, J ) 11.2,
4.4 Hz, 1H), 2.91 (dd, J ) 4.4, 15.2 Hz, 1H), 3.42 (t, J ) 11.2
Hz, 1H), 3.50 (dd, J ) 4.4, 15.2 Hz, 1H), 3.87 (dd, J ) 4.0,
11.2 Hz, 1H); 13C NMR δ 21.60, 28.53, 29.58, 43.93, 52.72.
54.42, 85.13, 97.84, 173.95; HREIMS m/z (relative intensity)
320.8843 [7, calcd for C8H979Br35Cl3O2S (M - CH3) 320.8852),
267 (5), 201 (26), 199 (28), 135 (39), 117 (100), 75 (45); CIMS
m/z 360/358/356/354 (M + NH4+).
1
white solid, mp 123-125 °C: IR (cm-1) 1770, 1308, 1146; H
NMR δ 1.46 (s, 3H), 1.68 (s, 3H), 2.76 (ddd, J ) 4.0, 11.0, 11.7
Hz, 1H), 3.09 (ddd, J ) 3.0, 7.8, 11.7 Hz, 1H), 3.28 (dd, J )
7.8, 14.4 Hz, 1H), 3.45 (t, J ) 11.0 Hz, 1H), 3.79 (dd, J ) 3.0,
14.4 Hz, 1H), 4.18 (dd, J ) 4.0, 11.0 Hz, 1H), 7.60-8.00 (m,
5H); 13C NMR δ 21.93, 28.60, 29.55, 40.76, 52.37. 56.81, 86.03,
128.15, 129.82, 134.60, 139.24, 173.18; HREIMS m/z (relative
intensity) 281.0848 [8, calcd for C14H17O2S (M - Br) 281.0848],
263 (27), 223 (19), 148 (100), 139 (34), 125 (59), 123 (46), 95
(93), 77 (49); CIMS m/z 380/378 (M + NH4+).
tr a n s-3-Ben zen esu lfon ylm eth yl-4-br om om eth yl-5,5-d i-
isop r op yld ih yd r o-2(3H)-fu r a n on e (3d ) was isolated as a
colorless oil: IR (cm-1) 1770, 1319, 1152; 1H NMR δ 0.97 (d, J
) 6.8 Hz, 3H), 1.00 (d, J ) 6.8 Hz, 3H), 1.04 (d, J ) 6.8 Hz,
3H), 1.06 (d, J ) 6.8 Hz, 3H), 2.22 (septet, J ) 6.8 Hz, 1H),
2.38 (septet, J ) 6.8 Hz, 1H), 3.16 (ddd, J ) 5.2, 6.0, 7.2 Hz,
1H), 3.23 (ddd, J ) 4.8, 5.2, 6.0 Hz, 1H), 3.52 (dd, J ) 5.2,
14.4 Hz, 1H), 3.68 (dd, J ) 5.2, 10.8 Hz, 1H), 3.80 (dd, J )
4.8, 14.4 Hz, 1H), 3.90 (dd, J ) 7.2, 10.8 Hz, 1H), 7.50-8.10
(m, 5H); 13C NMR δ 17.10, 17.12, 17.77, 19.44, 30.83, 31.17,
33.23, 43.71, 44.98, 57.06, 93.25, 128.22, 129.63, 134.31,
139.91, 174.41; HREIMS m/z (relative intensity) 373.0117 [8,
calcd for C15H1879BrO4S (M - C3H7) 373.0109], 293 (100), 275
(19), 223 (13), 151 (83), 125 (24), 77 (30), 41 (48); CIMS m/z
436/334 (M + NH4+).
4-Be n ze n e su lfon ylm e t h yl-3-isop r op ylid e n e -5,5-d i-
m eth yld ih yd r o-2(3H)-fu r a n on e (17) was isolated as a white
solid, mp 143-144 °C: IR (cm-1) 1743, 1308, 1150; 1H NMR δ
(CD3CN) 1.32 (s, 3H), 1.43 (s, 3H), 1.73 (s, 3H), 2.10 (s, 3H),
3.14 (dd, J ) 3.2, 15.2 Hz, 3H), 3.38-3.41 (m, 1H), 3.63 (dd, J
) 8.0, 15.2 Hz, 1H), 7.60-7.90 (m, 5H); 13C NMR δ 20.76,
23.71, 24.01, 29.75, 43.11, 57.79, 81.78, 124.56, 128.02, 129.83,
134.34, 140.03, 153.66, 168.51; HREIMS m/z (relative inten-
sity) 308.1080 (36, calcd for C16H20SO4 308.1082), 290 (9), 225
(7), 166 (63), 149 (62), 121 (80), 81 (100), 43 (35).
4-(E)-Ben zen esu lfon ylm eth ylen e-3-isop r op ylid en e-5,5-
d im eth yld ih yd r o-2-(3H)-fu r a n on e (21) was isolated as a
1
white solid, mp 135-137 °C: IR (cm-1) 1756, 1307, 1150; H
t r a n s-3-Be n ze n e su lfon ylm e t h yl-4-b r om om e t h yl-1-
oxa sp ir o[4,5]-2-d eca n on e (3e) was isolated as a white solid,
mp 205-207 °C: IR (cm-1) 1761, 1310, 1148; 1H NMR δ 1.20-
1.30 (m, 2H), 1.55-1.90 (m, 7H), 2.10-2.20 (m, 1H), 2.68 (ddd,
J ) 4.0, 10.0, 11.6 Hz, 1H), 3.11 (ddd, J ) 3.2, 7.6, 11.6 Hz,
1H), 3.31 (dd, J ) 7.6, 14.4 Hz, 1H), 3.52 (dd, J ) 10.0, 11.2
Hz, 1H), 3.78 (dd, J ) 3.2, 14.4 Hz, 1H), 4.09 (dd, J ) 4.0,
11.2 Hz, 1H), 7.60-8.00 (m, 5H); 13C NMR δ 21.55, 22.72,
25.16, 28.75, 30.80, 38.21, 40.55, 52.41, 56.90, 87.25, 128.17,
129.79, 134.55, 139.30, 173.49; HREIMS m/z (relative inten-
sity) 321.1168 [58, calcd for C17H21O4S (M - Br) 321.1161],
303(18), 259 (17), 223 (41), 179(100), 125 (51), 77 (69), 69 (81),
55 (43), 53 (46); CIMS m/z 420/418 (M + NH4+).
NMR δ 1.40 (s, 6H), 2.37 (s, 3H), 2.51 (s, 3H), 6.04 (s, 1H),
7.50-7.90 (m, 5H); 13C NMR δ 22.67, 26.60, 28.40, 82.84,
121.43, 127.50, 129.52, 131.59, 133.78, 141.26, 152.63, 165.88,
167.80; HREIMS m/z (relative intensity) 306.0923 [24, calcd
for C16H18SO4 306.0926), 288 (14), 165 (100), 147 (15), 119 (23),
77 (59), 43 (36).
4-Ben zen esu lfon ylm eth yl-3-(E)-(1-br om o)eth ylid en e-
5,5-d im eth yld ih yd r o-2(3H)-fu r a n on e (24) was isolated as
an inseparable mixture with 6: 1H NMR δ 1.50 (s, 3H), 1.70
(s, 3H), 2.80 (s, 3H), 3.31 (dd, J ) 1.0, 14.8 Hz, 1H), 3.51 (d, J
) 10.0 Hz, 1H), 3.59 (dd, J ) 10.0, 14.8 Hz, 1H), 7.60-7.90
(m, 5H); 13C NMR δ 24.13, 26.20, 30.22, 48.38, 56.22, 82.76,
128.35, 129.70, 129.73, 134.30, 142.00, 142.76, 165.21; HRE-
(3r, 4â, 5r)-(()-3-Ben zen esu lfon ylm et h yl-4-b r om o-
m eth yl-5-ter t-bu tyld ih yd r o-2(3H)-fu r a n on e (3f) was iso-
lated as a white solid, mp 103-105 °C: IR (cm-1) 1771, 1309,
IMS m/z (relative intensity) 293.0845 [100, calcd for C15H17
-
SO4 (M - Br) 293.0848], 209 (3), 175 (14), 125 (17), 107 (17),
1
1154; H NMR δ 1.01 (s, 9H), 2.81-2.86 (m, 1H), 3.23 (dd, J
77 (23); CIMS m/z 392/390 (M + NH4+).
) 10.8, 14.0 Hz, 1H), 3.37 (ddd, J ) 2.4, 7.2, 10.8 Hz, 1H),
3.62 (dd, J ) 2.8, 10.2 Hz, 1H), 3.72 (dd, J ) 2.4, 14.0 Hz,
1H), 4.21 (dd, J ) 2.8, 10.2 Hz, 1H), 4.25 (d, J ) 6.4 Hz, 1H),
3.90 (dd, J ) 7.2, 10.8 Hz, 1H), 7.60-8.00 (m, 5H); 13C NMR
δ 25.40, 34.78, 37.57, 39.69, 41.36, 56.99, 89.51, 128.26, 129.89,
134.68, 138.60, 174.95; HREIMS m/z (relative intensity)
331.9726 [62, calcd for C12H1379BrO4S (M - C4H8) 331.9718],
225 (10), 197 (16), 151 (15), 143 (78), 125 (84), 109 (46), 77
(49), 57 (100); CIMS m/z 408/406 (M + NH4+).
4-Ben zen esu lfon ylm et h yl-3-[4′-b r om om et h yl-5′,5′-d i-
m eth yld ih yd r o-2′(3′H)-fu r a n on e-3′-yl)]-5,5-d im eth yld ih y-
d r o-2(3H)-fu r a n on e (26) was isolated as a mixture of ste-
reoisomers. Only one isomer can be isolated partially pure as
a white solid, mp 165-167 °C: IR (cm-1) 1766, 1307, 1109.
1H NMR δ 1.29 (s, 3H), 1.40 (s, 3H), 1.46 (s, 3H), 1.68 (s, 3H),
3.14-3.58 (m, 8H), 7.60-8.00 (m, 5H); 13C NMR δ 21.90, 23.09,
27.13, 28.34, 29.56, 41.19, 44.51, 44.62, 48.73, 56.40, 84.49,
85.49, 128.35, 129.92, 134.69, 138.70, 174.53, 174.63; HREIMS
m/z (relative intensity) 472.0554 [8, calcd for C20H25SO679Br
472.0555], 393 (100), 251 (40), 233 (32), 193 (17), 125 (20), 77
(60), 69 (75), 43 (65); CIMS m/z 490 (M + NH4+).
(E)-1-Ben zen esu lfon yl-2-m eth yl-4-br om o-2-bu ten e (6a )
a n d (E)-1-Ben zen esu lfon yl-3-m eth yl-4-br om o-2-bu ten e
(6b). Compound 6 was isolated as an inseparable white solid
1
mixture of 6a and 6b in a ratio of 1/4 (from H NMR), mp 70-
72 °C (lit.11 73-74 °C). The NMR data were obtained from
mixture of sulfone 6. 6a : 1H NMR δ 1.86 (s, 3H), 3.77 (s, 2H),
3.85 (d, J ) 8.4 Hz, 2H), 5.39 (t, J ) 8.4 Hz, 1H), 7.27-7.87
(m, 5H); 13C NMR δ 16.92, 26.96, 65.74, 128.71, 129.38, 130.39,
130.65, 134.05, 138.24; 6b: 1H NMR δ 1.43 (s, 3H), 3.82 (d, J
) 8.0 Hz, 2H), 3.88 (s, 2H), 5.62 (t, J ) 8.4 Hz, 1H), 7.27-
7.87 (m, 5H); 13C NMR δ 14.94, 38.92, 56.18, 116.46, 128.67,
129.47, 134.05, 138.46, 141.89; HREIMS of 6 m/z (relative
Ack n ow led gm en t. This work was supported by a
grant from the National Science Foundation.
Su p p or tin g In for m a tion Ava ila ble: Characterization
data for compounds 5a , 5b, 5f, 5g, 7, 8, 15, 16, 19, 20, and
1
1
23; H, 13C NMR and 2D H-1H NOE spectra for compounds
intensity) 209.0639 [100, calcd for
C11H13O2S (M - Br)
3c-f, 13, and 21; H and 13C spectra for compounds 5b, 5f,
6-8, 12, 15-17, 19, 20, and 26. This material is available free
of charge via the Internet at http://pubs.acs.org.
1
209.0636], 145 (14), 125 (24), 77 (66), 53 (15); CIMS m/z 308/
306 (M + NH4+).
3-Ben zen esu lfon ylm eth yl-4-br om om eth yl-5,5-dim eth yl-
2(5H)-fu r a n on e (12) was isolated as a white solid, mp 162-
164 °C: IR (cm-1) 1758, 1310, 1144; H NMR δ 1.56 (s, 6H),
J O982388A
1