A stereochemical study of the isomerization of cyclopropyl ethers to allyl ethers catalyzed with zinc iodide

Article abstract of DOI:10.1021/jo960448b

Optically active 1-alkoxybicyclo[4.1.0]heptane was converted using zinc iodide as a catalyst to 2-alkoxymethylidenecyclohexane without loss of optical purity. The mechanism of the isomerization was studied using a stereochemical analysis of the product and deuterium labeling experiments. The results indicated that the isomerization takes place through a stepwise mechanism that involves an attack of zinc iodide on the cyclopropane ring to cause ring opening, followed by an intramolecular 1,2-hydride shift with liberation of the zinc iodide.

Full text of DOI:10.1021/jo960448b

6100
J . Org. Chem. 1996, 61, 6100-6103
Articles
A Ster eoch em ica l Stu d y of th e Isom er iza tion of Cyclop r op yl
Eth er s to Allyl Eth er s Ca ta lyzed w ith Zin c Iod id e
Takashi Sugimura,* Tohru Futagawa, Atsushi Mori, Ilhyong Ryu,† Noboru Sonoda,† and
Akira Tai*
Faculty of Science, Himeji Institute of Technology, Kanaji, Kamigori, Ako-gun 678-12, J apan, and
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565 J apan
Received March 5, 1996X
Optically active 1-alkoxybicyclo[4.1.0]heptane was converted using zinc iodide as a catalyst to
2-alkoxymethylidenecyclohexane without loss of optical purity. The mechanism of the isomerization
was studied using a stereochemical analysis of the product and deuterium labeling experiments.
The results indicated that the isomerization takes place through a stepwise mechanism that involves
an attack of zinc iodide on the cyclopropane ring to cause ring opening, followed by an intramolecular
1,2-hydride shift with liberation of the zinc iodide.
Sch em e 1
In tr od u ction
We have recently developed a novel and convenient
method for the preparation of optically active cyclopropyl
ethers by using 1,3-diols as a chiral linking bridge
between a prochiral olefin and a zinc carbenoid.1 The
cyclopropyl ether function is a highly reactive site,
because the strained C-C bond is activated by electron
donation from the ether oxygen. The known reactions
of a typical cyclopropyl ether 1 with inorganic salts as
reagents or catalysts can be classified into three types.2
The first group is the reaction through C1-C7 bond
cleavage with desilylation giving the â-metallo ketone as
a product or an intermediate (Scheme 1, type 1). The
reactions with the salts of Cu(II),3 Ag(I),4 Hg(II),5 Sn(IV),6
Au(I),7 Pd(II),8 Pt(II),9 etc. are in this category. The
reactions in the second group are characterized by the
oxidative cleavage of the Si-O bond using the salts of
Fe(III)10 followed by a C1-C6 bond cleavage to give the
3-cycloheptanoyl radical as an intermediate (type 2). The
third group involving the isomerization via cleavage of
the C1-C7 bond without the Si-O bond fission yielding
2 is catalyzed by Zn(II),11 Rh(I),12 or Pt(II)13 (type 3). The
desilylation during the reactions of types 1 and 2 are
easily understood by the nature of the weak Si-O bond,
while the reaction of type 3 is highly unusual. For zinc
iodide-promoted isomerization reactions, the synthetic
scope has been thoroughly investigated, but the detailed
mechanism of this type of reaction has not been clarified.
The main questions include (1) the source of the hydrogen
at the 1-position of 2 and whether it comes from a 1,2-
hydrogen shift or an intermolecular reaction and (2) the
role of zinc iodide and whether or not it adds to the C1-
C7 bond giving an intermediate the same as in the
reaction of type 1. Alkyl cyclopropyl ethers also undergo
† Osaka University.
X Abstract published in Advance ACS Abstracts, August 15, 1996.
(1) (a) Sugimura, T.; Futagawa, T.; Tai, A. Tetrahedron Lett. 1988,
29, 5775. (b) Sugimura, T.; Futagawa, T.; Yoshikawa, M.; Tai, A.
Tetrahedron Lett. 1989, 30, 3807. (c) Sugimura, T.; Yoshikawa, M.;
Futagawa, T.; Tai, A. Tetrahedron, 1990, 46, 5955.
(2) For reviews, see: (a) Ryu, I.; Sonoda, N. J . Syn. Org. Chem. J pn.
1985, 43, 112. (b) Nakamura, E. J . Syn. Org. Chem. J pn. 1989, 47,
931. Kuwajima, I.; Nakamura, E. Top. Curr. Chem. 1990, 133, 1. (c)
Kuwajima, I.; Nakamura, E. In Comprehensive Organic Synthesis;
Trost, B. M., Ed., Pergamon Press, Oxford, UK, 1991, Vol. 2, pp 441-
454.
(3) Ryu, I.; Matsumoto, K.; Kameyama, Y.; Ando, M.; Kusumoto,
N.; Ogawa, A.; Kambe, N.; Murai, S.; Sonoda, N. J . Am. Chem. Soc.
1993, 115, 12330.
(4) (a) Ryu, I.; Ando, M.; Ogawa, A.; Murai, S.; Sonoda, N. J . Am.
Chem. Soc. 1983, 105, 7192. (b) Ryu, I.; Suzuki, H.; Ogawa, A.; Kambe,
N.; Sonoda, N; Tetrahedron Lett. 1988, 29, 6137.
(5) Ryu, I; Matsumoto, K.; Ando, M.; Murai, S.; Sonoda, N. Tetra-
hedron Lett. 1980, 21, 4283.
(6) Nakahira, H.; Ryu, I.; Ikebe, M.; Oku, Y.; Ogawa, A.; Kambe,
N.; Sonoda, N.; Murai, S. J . Org. Chem. 1992, 57, 17.
(7) Ito, Y.; Inouye, M.; Suginome, M.; Murakami, M. J . Organomet.
Chem. 1988, 342, C41.
(10) (a) Ito, Y.; Fujii, S.; Saegusa, T. J . Org. Chem. 1976, 41, 2073.
(b) Ito, Y.; Saegusa, T. J . Org. Chem. 1977, 42, 2326. (c) Ito, Y.; Fujii,
S.; Nakatsuka, M.; Kawamoto, F.; Saegusa, T. Organic Synthesis,
Norland, W. E., Ed.; Wiley: New York, 1988; Collect. Vol. 6, p 327. (d)
Booker-Milburn, K. I.; Thompson, D. F. J . Chem. Soc. Perkin Trans. 1
1995, 2315.
(11) (a) Murai, S.; Aya, T.; Renge, T.; Ryu, I.; Sonoda, N. J . Org.
Chem. 1974, 39, 858. (b) Ryu, I.; Murai, S.; Sonoda, N. Chem. Lett.
1976, 1049. (c) Ryu, I.; Murai, S.; Otani, S.; Sonoda, N. Tetrahedron
Lett. 1977, 1995. (d) Ryu, I.; Aya, T.; Otani, S.; Murai, S.; Sonoda, N.
J . Organomet. Chem. 1987, 321, 279. (e) Scho¨llkopf, U.; Mittendorf,
Angew. Chem., Int. Ed. Engl. 1989, 28, 613.
(8) Aoki, S.; Fujimura, T.; Nakamura, E.; Kuwajima, I. J . Am. Chem.
Soc. 1988, 110, 3296.
(9) Ikura, K.; Ryu, I.; Ogawa, A; Sonoda, N.; Harada, S.; Kasai, N.
Organometallics 1991, 10, 528.
(12) Ikura, K.; Ryu, I.; Ogawa, A.; Kambe, N.; Sonoda, N. Tetrahe-
dron Lett. 1989, 30, 6887.
(13) Ikura, K.; Ryu, I.; Kambe, N.; Sonoda, N. J . Am. Chem. Soc.
1992, 114, 1520.
S0022-3263(96)00448-3 CCC: $12.00 © 1996 American Chemical Society

Isomerization of Cyclopropyl Ethers
J . Org. Chem., Vol. 61, No. 18, 1996 6101
Sch em e 2
Sch em e 3
Sch em e 4
the type 3 reaction under similar conditions.11 In this
study, by using an optically active alkyl cyclopropyl ether
and its deuterated analogs, the stereochemistry of the
reaction with zinc iodide was studied to clarify the
isomerization mechanism.14
Resu lts a n d Discu ssion
The optically active cyclopropyl ether 3 (>99% enantio-
and diastereoisomeric purity) was prepared from cyclo-
hexanone in three steps using our established method.1
isomerization of 9 under the same reaction conditions as
those used for 3 afforded 10. The deuterium distribution
in 10 was, as expected, at only the 1 and 6 positions.
During the isomerization, the ratio of [6-2H]-9 and [6-1H]-
9 monitored by 1H-NMR did not changed. The regio-
selective deuterium shift with rigorous stereocontrol
clearly showed that the isomerization of the cyclopropyl
ether proceeded through an intramolecular 1,2-hydride
shift (Scheme 3).
In order to clarify whether this 1,2-hydride shift occurs
after the C1-C7 bond cleavage or if the shift and the
cleavage occur synchronously, we next studied the ster-
eochemical outcome through a rotation of the C6-C7
bond within the isomerization using the two deuterium
labeling experiments as shown in Scheme 4.
The reaction of 3 with freshly dried zinc iodide (3
equiv)15 in dry benzene under reflux afforded 4 as a single
diastereomer in 70% isolated yield. Under the same
conditions, a mixture of diastereoisomers, 3 and 5 (3/5
) 7/3), afforded a mixture of 4 and 6 in the same 7/3 ratio.
Through these studies, it was determined that both
diastereomers 3 and 5 stereospecifically afforded 4 and
6, respectively. Thus, the chiral pentanediol moiety in
the substrate did not participate in the stereocontrolled
mechanism of the rearrangement and the stereochemis-
try of the cyclopropyl ether skeleton was fully conserved
in the resulting allyl ether. The stereochemistry of 4 was
assigned to be 2S by chemical correlation with (+)-(S)-
7,16 as shown in Scheme 2. The conservation of the
stereochemistry with inversion at the ether chiral center
strongly suggests the involvement of an intramolecular
1,2-hydride shift during the isomerization.17
A mixture of (endo)-[2H]-13 and (exo)-[2H]-13 in a ratio
of 2.5/1 prepared from 1118,19 was subjected to isomer-
ization with zinc iodide and diethylzinc in dichlo-
romethane.15 The reaction was accomplished in 2 days
at room temperature without any detectable side reac-
tions. The E/Z ratio of deuterium in 17 determined by
1H-NMR was 1/1. Thus, the stereochemical purity at the
7-position of 13 was completely lost during the reaction.
When 16 (endo-[2H]/exo-[2H] ) 3.5/1) obtained from 14
was isomerized under the same conditions, the E/Z ratio
of deuterium in 18 was again 1/1. The isomerization with
no stereospecificity signifies a free rotation of the C6-
C7 bond, which indicated the existence of an intermediate
after the C1-C7 bond cleavage. Only a reasonable
intermediate we could assume from natures of cyclo-
propyl ether and zinc iodide is a zwitterionic intermediate
the same as that in type 1.
To confirm the intramolecular 1,2-hydride shift mech-
anism, a deuterium labeling experiment was carried out
with 9 (2,6-deuterated 3, 50% deuterium content at each
position) prepared from 8 by the reported method.1 The
From the present study, it can be concluded that, in
the presence of zinc iodide, cyclopropyl ether isomerizes
to allyl ether through at least the following two steps:
(1) cleavage of the C-C bond to form the adduct and (2)
1,2-hydride shift eliminating zinc iodide to produce a
double bond (Scheme 5).
(14) A part of this work has been published as a communication:
Sugimura, T.; Futagawa, T.; Ryu, I.; Tai, A. J . Chem. Soc., Chem.
Commun. 1992, 324.
(15) Zinc iodide is a highly hygroscopic reagent and absorbed water
drastically decreases the reaction rate. The problem introduced by the
use of commercially available zinc iodide was solved by using freshly
dried commercial zinc iodide or by the addition of diethylzinc.
(16) Hoffmann, R. W.; Gerlach, R.; Goldmann, S. Tetrahedron Lett.
1978, 2599.
(17) The inversion of the ether chiral center in the type 3 reaction
was also reported during the isomerization with the Pt(II) salt. See
ref 12.
(18) Miyano, S.; Matsumoto, Y.; Hashimoto, H. J . Chem. Soc., Chem.
Commun. 1975, 364.
(19) Magarian, R. A.; Benjamin, E. J . J . Pharm. Sci. 1975, 64, 1626.

6102 J . Org. Chem., Vol. 61, No. 18, 1996
Sugimura et al.
refluxed overnight with a catalytic amount of PPTS using a
Dean-Stark apparatus to collect the H2O produced. The
mixture was extracted and purified by silica gel column
chromatography (75 g, 6% ethyl acetate in hexane) to give 1.49
g of 8, which contained 50% of deuterium at the 2- and
6-positions (δ 1.64, m).
Sch em e 5
(2S,2′R,4′R)-1-([2,2′,6-2H3]Bicyclo[4.1.0]h ep tyl 2-(4-h y-
d r oxyp en tyl) eth er (9). To a solution of 8 (640 mg) in
anhydrous CH2Cl2 (36 mL) was added triisobutylaluminum
(18.1 mL, 0.94 M in hexane) at 0 °C. After stirring for 1.5 h,
the mixture was poured onto 1 N NaOH and extracted with
CH2Cl2 (3×). The combined organic layer was washed with a
1 N NaOH (2×) and dried (Na2SO4). This concentration
afforded 600 mg of 9, which contained ca. 50% of deuterium
at the 2- and 6-positions. The resulting enol ether (600 mg)
was treated with diethylzinc (16.3 mL, 0.98 M in hexane) and
diiodomethane (2.56 mL) in THF (20 mL). By using the
reported purification method,1c 360 mg of 9 was obtained as
colorless oil. The 1H-NMR and 13C-NMR of 9 indicated that
it was free from the diastereomer and contained 50% deute-
rium at the 2- and 6-positions (δ 2.12, 1.98, and 1.23).
Isom er iza tion 9 to 10 w ith Zin c Iod id e. Using 95 mg
of 9, 55 mg of 10 was obtained by the method described for
the preparation of 4. The product isolated by MPLC was
further purified by preparative GLC (NPGS, 2 m, 130 °C). The
1H-NMR of 10 was identical to that of 4 except for the peak
integration at δ 3.88 (0.5 H, H-1) and 1.77-1.33 (8 H, H-6,6′
was included). Under the same conditions, a mixture of 9 and
10 was also obtained by the shorter reaction of 24 h (50%
conversion) or 48 h (90% conversion). In both cases, 9 in the
mixture contained 50% deuterium at the 2- and 6-positions.
1-(ter t-Bu t yld im et h ylsiloxy)-7-(en d o)-b r om ob icyclo-
[4.1.0]h ep ta n e (12). To a solution of 11 (258.8 mg) in dry
ether (5 mL) was added diethylzinc (6.1 mL, 1 M solution in
hexane) at rt. After cooling to 0 °C, bromoform (1.1 mL) was
added over 2 min. The mixture was warmed to rt and allowed
to stand for 2 h. The reaction mixture was quenched with
saturated NH4Cl (30 mL) and extracted with ether (20 mL,
6×). The mixture included two diastereomeric isomers, 12 and
its exo-isomer (ratio ) 2.5/1), the stereochemistries of which
were determined by their coupling constants of H-7; J 6,7 ) 4.6
Hz for 12 and J 6,7 ) 9.5 Hz for the exo-isomer.
The rate-determining step of the isomerization is
probably the first C-C bond cleavage step, since no
isotope effect was observed in the isomerization of 9 to
10. This study is also significant from a synthetic point
of view, since optically active allyl alcohol can be easily
prepared from the prochiral ketone using the diastereo-
differentiating cyclopropanation and the present ste-
reospecific isomerization.
Exp er im en ta l Section
Gen er a l. 1H-NMR (and 13C-NMR) spectra were recorded
at 400 MHz (and 100 MHz) using CDCl3 as both a solvent and
internal standard (7.26 and 77.1 ppm for CHCl3). GLC
analysis was conducted using a TC-WAX capillary column (60
m, 0.25 mm i.d.). MPLC was carried out using a pump (10
mL/min) and a Lobar column (MERCK Si-60 type B). All
solvents were purified by distillation. All reactions were
carried out in a dry N2 atmosphere.
(2S,2′R,4′R)-2-Meth ylen ecycloh exyl 2-(4-Hyd r oxyp en t-
yl) Eth er (4). A solution of 3 (100 mg, >99% de) and
anhydrous zinc iodide (450 mg) in dioxane (5 mL, distilled from
benzophenone ketyl) was refluxed for 3 days. The mixture was
extracted with ether, washed (2×) with aqueous ammonium
chloride and ammonia, and dried (Na2SO4). The residue from
the solvent evaporation was purified by MPLC on silica gel
(30% ethyl acetate in hexane) giving 4 (70 mg) as a colorless
20
1
oil. [R]D ) -16.2° (c 0.7, MeOH); H-NMR δ 4.81 (bs, 2 H),
4.14 (m, 1 H), 3.88 (dd, J ) 4.6, 3.2 Hz, 1 H), 3.79 (m, 1 H),
3.79 (m, 1 H), 2.88 (m, 1 H), 2.07 (ddd, J ) 13.4, 4.9, 4.6 Hz,
1 H), 1.77-1.33 (m, 9H), 1.16 (d, J ) 6.1 Hz, 3 H), 1.15 (d, J
) 6.3 Hz, 3 H); 13C-NMR δ 148.4, 109.6, 76.6, 69.8, 64.6, 44.8,
34.4, 32.0, 27.9, 23.5; MS m/ z (M+) calcd for C12H22O2
198.1601, obsd 198.1600.
Purification by MPLC on silica gel (0.5% ethyl acetate in
hexane) afforded 73.4 mg of 12 as a pale yellow oil. 1H-NMR
δ 2.62 (d, J ) 4.6 Hz, 1 H), 2.13-1.97 (m, 2 H), 1.89 (m, 1 H),
1.62-1.43 (m, 2 H), 1.26-1.18 (m, 2 H), 1.05 (m, 1 H), 0.92 (s,
9 H), 0.18 (s, 3 H), 0.14 (s, 3 H); 13C-NMR δ 57.2, 31.6, 31.4,
(2R,2′R,4′R)-2-Meth ylen ecycloh exyl 2-(4-Hyd r oxyp en t-
yl) Eth er (6). A solution of a mixture of 3 and 5 (49.6 mg,
3/5 ) 69/31, determined by capillary GLC) and anhydrous ZnI2
(200 mg) in 5 mL of dry benzene was refluxed for 2 days.
Analysis of the extract by capillary GLC indicated the ratio of
4 and 6 to be 68/28. The mixture was purified by MPLC on
silica gel (elution with 30% ethyl acetate in hexane) giving 4
30.0, 25.9, 23.9, 21.6, 21.1, 18.2, -3.0, -3.6; MS m/ z (M+
Br) calcd for C13H25OSi 225.1675, obsd 225.1654.
-
[7-2H ]-1-(t er t -B u t y ld im e t h y ls ilo x y )b ic y c lo [4.1.0]-
h ep ta n e (13). To a solution of 12 (178.1 mg) in dry ether (15
mL) was added sodium (1.17 g) followed by the addition of CH3-
OD/D2O (99% of 2H, 30/1, 5 mL) at 0 °C. After extraction and
MPLC purification on silica gel (1% ethyl acetate in hexane),
a monodeuterated product 13 (81.2 mg, 66.1%) was obtained.
The 1H-NMR spectrum was identical with the reported non-
deuterated compound except for the peak integration of H-7.
The stereochemistries were determined by the coupling con-
stants of H-7: J 6,7 ) 6.3 Hz for (endo)-[2H]-13 and J 6,7 ) 10.5
Hz for (exo)-[2H]-13. 1H-NMR δ 2.13-1.96 (m, 2 H), 1.88 (m,
1 H), 1.52-1.35 (m, 2 H), 1.32-1.19 (m, 2 H), 1.10-0.97 (m, 2
H), 0.85 (s, 9 H), 0.76 (d, J ) 10.6 Hz, 0.29 H), 0.27 (d, J ) 6.3
Hz, 0.71 H), 0.10 (s, 6 H); 13C-NMR δ 56.2, 32.53 (and 32.51
for the diastereomer), 25.9, 24.71 (24.69), 22.0, 21.5, 19.5, 18.56
(J C-D ) 23.8 Hz, and 18.51, J C-D ) 23.8 Hz), 17.8, -3.2, -3.4;
MS m/ z (M+) calcd for C13H25DOSi 227.1816, obsd 227.1837.
1-Meth oxy-7-(en d o)-br om obicyclo[4.1.0]h ep ta n e (15).
To a solution of 1-methoxycyclohexene (14, 700 mg) in dry
hexane was added diethylzinc (1 M solution in hexane, 31 mL)
followed by bromoform (5.45 mL) at 0 °C. The mixture was
allowed to stand for 30 min and was extracted and purified
by MPLC on silica gel (6% ethyl acetate in hexane), yielding
500 mg of 15 as a colorless oil. In this case, no endo product
was detected. 1H-NMR δ 3.42 (s, 3 H), 2.64 (dm J ) 4.9 Hz,
1 H), 2.09-1.91 (m, 3 H), 1.63-1.39 (m, 3 H), 1.31-1.10 (m, 3
H); 13C-NMR δ 61.7, 54.2, 30.6, 28.7, 26.3, 23.6, 21.4, 20.9; MS
20
(23 mg) and 6 (12 mg). 6: colorless oil, [R]D ) -34° (c 0.7,
1
MeOH); H-NMR δ 4.84 (s, 1 H), 4.77 (s, 1 H), 4.16 (m, 1 H),
3.88-3.84 (m, 2 H), 2.32 (m, 1 H), 2.04 (m, 1 H), 1.79-1.45
(m, 9 H), 1.20 (d, J ) 6.1 Hz, 3 H), 1.18 (d, J ) 6.1 Hz, 3 H);
13C-NMR δ 149.4, 108.0, 78.2, 71.7, 64.7, 43.2, 34.3, 32.9, 28.0,
23.7, 22.7, 20.0; MS m/ z (M+) calcd for C12H22O2 198.1601,
obsd 198.1597.
(S)-2-Meth ylen ecycloh exa n ol (7). To a solution of 4 (20
mg) in 5 mL of dry CH2Cl2 was added PCC (55 mg) at rt. The
mixture was stirred for 4 h, quenched with the addition of a
small amount of H2O, and filtered though a silica gel pad. The
filtrate was concentrated and dissolved in MeOH (3 mL) with
K2CO3 (20 mg). The mixture was stirred overnight and
extracted with CH2Cl2. After reduction of the solvent to 1/10,
the mixture was purified using preparative GLC (NPGS, 2 m,
20
90 °C) to give 7 (7 mg). [R]D ) 18° (c 0.1, ether) (lit.16 [R]D
)
12.7° for 60% ee of (S)-7). The other spectroscopic data were
identical with the reported data.
[2,2,6,6-2H4]Cycloh exan on e (2R,4R)-2,4-P en tan ediol Ac-
eta l (8). A solution of cyclohexanone (5 g) and K2CO3 (500
mg) in D2O (10 mL, 99%) and anhydrous THF (3 mL) was
stirred for 5 h at rt and then extracted with ether. The 1H-
NMR indicated that the incorporation of deuterium at the 2,6-
positions was ca. 80%. A solution of deuterated cyclohexanone
(2 g) and (R,R)-2,4-pentanediol (3 g) in benzene (80 mL) was

Isomerization of Cyclopropyl Ethers
J . Org. Chem., Vol. 61, No. 18, 1996 6103
m/ z (M+) calcd for C8H13BrO 204.0150 and 206.0130, obsd
204.0155 and 206.0136.
Isom er iza tion of 13 a n d 16. Isomerization was carried
out using the method discovered for the conversion of 1 to 2.
The product was isolated by MPLC on silica gel (hexane) for
17 (50-60% yield) and by preparative GLC (OV-101, 2 m, 90
°C) for 18 (ca. 70% yield). The spectra of 17 and 18 were fully
identical with those of the nondeuterated compounds except
for the integration of 1H-NMR peaks. Since the olefin protons
of 18 showed the same chemical shift at δ 4.82, Eu(fod)3 was
added to separate them into δ 4.87 and 4.85.
[7-2H]-1-Meth oxybicyclo[4.1.0]h ep ta n e (16). To a solu-
tion of 16 (205 mg) in dry ether (25 mL) was added sodium (2
g) was added at 0 °C. A mixture of CH3OD and D2O (30/1, 8
mL) was added over a period of 1 h at the same temperature,
extracted with pentane (2×), and washed with water. Most
of the solvent was removed under a slightly reduced pressure,
and the residue was purged on a preparative GLC (OV-101, 2
m, 90 °C). Its 1H-NMR was identical to the authentic non-
deuterated compound except for the peak integration at δ 0.83
and 0.24. The signals at the 7-position were assigned on the
basis of the coupling constants and shift reagent experiment
with Eu(fod)3; the shift values (∆δ) are cited in parentheses.
1H-NMR δ 3.24 (s, 3 H, ∆δ ) 0.27), 2.07-1.90 (m, 3 H), 1.49
(m, 2 H), 1.26 (m, 1 H), 1.94-1.08 (m, 3 H), 0.83 (d, J ) 10.7
Hz, 0.22 H, H-7 (endo), ∆δ ) 0.20), 0.24 (dd, J ) 6.4, 5.1 Hz,
0.78 H, H-7(exo), ∆δ ) 0.14); 13C-NMR δ 61.1, 53.4, 27.3, 24.6,
22.0, 21.4, 18.7, 17.0 (J C-D ) 24.2 Hz); MS m/ z (M+) calcd for
C8H13DO 127.1104, obsd 127.1089.
Su p p or tin g In for m a tion Ava ila ble: 1H-NMR spectra of
4, 6, 12, 13, 15, and 16 and 13C-NMR spectra of 12, 13, 14,
and 15 (10 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
J O960448B