Benzotriazole-mediated synthesis of 2,3-disubstituted allylic alcohols

Full text of DOI:10.1021/jo000469c

J . Org. Chem. 2001, 66, 2149-2153
2149
Sch em e 1
Ben zotr ia zole-Med ia ted Syn th esis of
2,3-Disu bstitu ted Allylic Alcoh ols
Yoon Ho Kang, Chang J ae Lee, and Kyongtae Kim*
Department of Chemistry, Seoul National University,
Seoul 151-742, Korea
kkim@plaza.snu.ac.kr
Received March 28, 2000
using diverse bases such as diethylaluminum 2,2,6,6-
tetramethylpiperidide (DATMP),8 a mixture of lithium
diisopropylamide, and t-BuOK (LIDAKOR reagent),9 and
methylmagnesium N-cyclohexylisopropylamide.10 The re-
sulting double bonds prefer (E)-configuration. However,
treatment of 1-methyl-1-vinyloxirane with alkyllithium
in the presence of tertiary amine or lithium alkoxide gave
allylic alcohols with (Z)-configuration predominant.11 The
third method involves alkylation of allylic sulfones,
followed by the reductive elimination of the derived
diastereomeric epoxysulfones, which results in predomi-
nant (E)-isomers.12 The latter two methods are concerned
with 2- and/or 3-aryl-substituted allylic alcohols. Besides,
regioselective reduction of R,â-unsaturated carbonyl com-
pounds by vapor phase hydrogen-transfer over an MgO-
B2O3 (Mg/B ) 100/2) catalyst using secondary alcohols
as a hydrogen donor,13 and oxidation of allylselenides
with 15%-H2O2 in the presence of pyridine in CH2Cl2 at
0 °C14 are reported to give 2- and/or 3-substituted allylic
alcohols. However, the former yields saturated alcohols
and saturated aldehydes as byproducts depending on the
substituents at R and â positions of the carbonyl com-
pounds, whereas the latter appears to be preferable to
the preparation of allylic alcohols without a substituent
at the terminal olefinic carbon atom. In addition, oxida-
tion of allylic phenyl tellurides may be utilized for the
preparation of 1-phenylallylic alcohols.15 However, it is
uncertain whether the method serves our purpose or not.
Therefore, it may be worthwhile to exploit a new method
for the synthesis of allylic alcohols with specific substit-
uents at C-2 and C-3. With this in mind, the reactions of
1 with a base have been studied. The results are
described herein.
In tr od u ction
During the past decade, benzotriazole was widely used
as a synthetic auxiliary for introducing diverse organic
functionality.1 A survey of the literature inter alia shows
that benzotriazole-mediated reactions with acyl or aroyl
halides initially undergo two types of reaction: nucleo-
philic displacement of halides,2-4 and nucleophilic attack
on the carbonyl carbon, followed by displacement of
halides concomitant with the formation of oxiranes.5
Since treatment of 1-(arylmethyl)benzotriazoles 1 with
strong bases such as LDA and n-BuLi in THF generates
a carbanion at R-carbon bonded to N-1,1 it is expected
that reactions of the carbanion with R-monohalo ketones
would give a mixture of diastereomers (R,S)- and (S,R)-,
and (R,R)- and (S,S)-1-alkyl (or aryl)-1-[(aryl)(benzotria-
zol-1-yl)methyl]oxiranes 2 (Scheme 1). These may be
utilized as precursors for allylic alcohols having specific
substituents at C-2 and C-3 by introducing a radical or
a carbanion at R-carbon bonded to N-1 upon removal of
a benzotriazole moiety.
Synthesis of 2,3-disubstituted allylic alcohols has been
mainly achieved by three methods: The first method
involves regio- and stereospecific anti additions of Grig-
nard reagents in the presence of cuprous iodide into
propargyl alcohols, giving γ-functionally substituted vi-
nylmagnesium compounds, which subsequently reacts
with alkyl halides to give 2,3-dialkyl-substituted allylic
alcohols with (E)-configuration.6 Alternatively, iodination
of the vinylmagnesium compounds followed by addition
of Grignard reagents in the presence of (PPh3)2NiCl2 gives
allylic alcohols.7 This is the only method to give 2,3-
diaryl-, 2,3-dialkyl-, 2-alkyl-3-aryl-, and 2-aryl-3-alkyl-
substituted allylic alcohols, and the reaction proceeds
with high stereoselectivity. The second method involves
isomerization of substituted oxiranes into allylic alcohols
Resu lts a n d Discu ssion
Compounds 1 were prepared by a documented proce-
dure,16 and treatment of 1 with LDA in THF at -78 °C
for 5 min, followed by addition of 1-chloro-3,3-dimethyl-
2-butanone, gave a mixture of diastereomers 2 (R ) t-Bu)
(1) (a) Katritzky, A. R.; Lan, X.; Yang, J . Z.; Denisko, O. V. Chem.
Rev. 1998, 98, 409. (b) Katritzky, A. R.; Gordeev, M. F.; Greenhill, J .
V.; Steel, P. J . J . Chem. Soc., Perkin Trans. 1 1992, 1111. (c) Katritzky,
A. R.; Gordeev, M. F. J . Chem. Soc., Perkin Trans. 1 1992, 1295. (d)
Katritzky, A. R.; Gupta, V.; Gordeev, M. F. J . Heterocycl. Chem. 1993,
30, 1073.
(2) Katritzky, A. R.; Kuzmierkiewicz, W. J . Chem. Soc., Perkin
Trans. 1 1987, 819.
(3) Katritzky, A. R.; Shcherbakova, I. V. J . Heterocycl. Chem. 1996,
33, 2031.
(4) Katritzky, A. R.; Soleiman, M.; Yang, B. Heteroatom Chem. 1996,
7, 365.
(5) (a) Katritzky, A. R.; Fali, C. N.; Li, J . J . Org. Chem. 1997, 62,
8205. (b) Katritzky, A. R.; Li, J . J . Org. Chem. 1995, 60, 638.
(6) (a) Negishi, E.; Zhang, Y.; Cederbaum, F. E.; Webb, M. B. J . Org.
Chem. 1986, 51, 4080. (b) Duboudin, J . G.; J ousseaume, B. J .
Organomet. Chem. 1979, 168, 1.
(8) Yamamoto, H.; Nozaki, H. Angew. Chem., Int. Ed. Engl. 1978,
17, 169.
(9) Mordini, A.; Ben Rayana, E.; Margot, C. Tetrahedron 1990, 46,
2401.
(10) Mosset, P.; Manna, S.; Viale, J .; Falck, J . R. Tetrahedron Lett.
1986, 27, 299.
(11) Tamura, M.; Suzukamo, G. Tetrahedron Lett. 1981, 22, 577.
(12) Kocienski, P. J . Tetrahedron Lett. 1979, 441.
(13) Ueshima, M.; Shimasaki, Y. Chem. Lett. 1992, 1345.
(14) Nishiyama, H.; Itagaki, K.; Sakuta, K.; Itoh, K. Tetrahedron
Lett. 1981, 22, 5285.
(15) Uemura, S.; Fukuzawa, S.-i.; Ohe, K. Tetrahedron Lett. 1985,
26, 921.
(16) Kang, Y. H.; Kim, K. J . Heterocycl. Chem. 1997, 34, 1741.
(7) Duboudin, J . G.; J ousseaume, B.; Bonakdar, A. J . Organomet.
Chem. 1979, 168, 227.
10.1021/jo000469c CCC: $20.00 © 2001 American Chemical Society
Published on Web 02/22/2001

2150 J . Org. Chem., Vol. 66, No. 6, 2001
Ta ble 1. Qu a n tities of Rea cta n ts a n d Yield s a n d Meltin g P oin ts of 2
Notes
BtCH2Ar
Ar
RCOCH2Cl
(R,S)-2
yielda (%)
(R,R)-2
yielda (%)
mp (°C)
time
(min)
compd
mmol
R
mmol
mp (°C)
a
Ph
2.69
1.43
2.58
0.730
1.34
1.27
1.48
1.18
1.62
0.866
2.20
2.75
2.61
2.60
1.43
2.64
4.48
1.88
t-Bu
3.23
1.50
2.58
0.730
1.41
1.27
1.55
1.18
1.62
0.866
2.20
2.75
2.61
2.60
1.51
2.64
4.93
1.88
5
15
5
5
15
5
15
5
5
5
5
5
8
3
4
5
198-200b
25
23
20
18
27
23
20
45
57
24
55
31
29
27
35
14
26
45
133-134c
b
c
3-MeOC6H4
3-MeC6H4
t-Bu
t-Bu
204-206b
182-184c
122-123e
liquid
d
3,4-Me2C6H3
liquid
e
f
g
h
i
3-PhOC6H4
2-Pyridyl
3-Pyridyl
6-Me-2-pyridyl
Ph
t-Bu
t-Bu
t-Bu
t-Bu
Ph
11
30
22
42
10
19
8
10
9
37
6
170-171b
197-198b
204-206b
181-182b
166-167b
liquid
104-106c
105-106c
171-172c
121-122d
172-173b
192-194b
97-98c
5
5
j
k
Ph
Ph
3-MeC6H4
2,5-Me2C6H3
10
15
10
15
10
114-115d
l
3-MeC6H4
2,5-Me2C6H3
2,5-Me2C6H3
163-164b
126-128c
99-111c
m
3-MeOC6H4
110-111c
a
b
d
Isolated yields. MeOH was used for recrystallization. c n-Hexane was used for recrystallization. A mixture of n-hexane and CH2Cl2
was used for recrystallization. e A mixture of n-hexane and EtOAc was used for recrystallization.
Sch em e 2
(Rf ) 0.5 and 0.4, n-hexane and EtOAc ) 5:1). The
diastereomers 2 were separated by chromatography on
a silica gel column. The former with a higher Rf value
was assigned to be an enantiomeric mixture [abbreviated
as (R,R)] with R and R configurations. The latter with a
lower Rf value was an enantiomeric mixture [abbreviated
as (R,S)] with R and S configurations. Selected com-
pounds 1 (1a ,c-d ,k -l) were treated with LDA for 15
min, and then the mixtures were subjected under the
same conditions as mentioned above. However, the yields
of 2 were not much different. The quantities of reactants,
the yields, and melting points of diastereomers (R,S)-
2a -h and (R,R)-2a -h are summarized in Table 1.
The structures of the diastereomers of 2a -h were
determined on the basis of the spectroscopic (1H NMR,
IR, and MS) data and elemental analyses. The 13C NMR
(75 MHz, CDCl3) spectrum of 2a exhibited absorption at
146.1, 136.4, 134.3, 129.7, 129.3, 129.1, 127.8, 124.2,
120.4, 111.1, 64.0, 63.3, 49.0, 34.7, 27.5 ppm, which can
be identified with the structure 2a . The stereochemistry
of diastereomers 2a -h was assigned based on the X-ray
crystallographic analysis of the major product 2a (Sup-
porting Information). The figure in the Supporting In-
formation clearly shows that the bulky benzotriazole
moiety and tert-butyl group are anti. Consequently the
major compound 2a is an enantiomeric mixture of (R,R)-
and (S,S)-configurations. J udging from this, the minor
compound should be an enantiomeric mixture having
(R,S)- and (S,R)- configurations. By analogy with 2a ,
compounds 2b-h , which are major products, would be
enantiomeric mixtures with (R,R)- and (S,S)- configura-
tions and the minor compounds 2b-h would be enan-
tiomeric mixtures with (R,S)- and (S,R)-configurations.
To remove a benzotriazole moiety,17 concomitant with
generation of a radical center at the R-carbon bonded to
N-1, lithium naphthalenide 3, which is a well-known one-
electron donor18 was added to a solution of (R,R)-2a -h
in THF until the dark color of 3 prevailed. The reaction
proceeded smoothly to give (Z)-3-aryl-2-(tert-butyl)-2-
propenol 4a -h together with a minute amount of the (E)-
isomers (E)-4a -d , benzotriazole 5, naphthalene, and an
unknown mixture (Scheme 2). However, no (E)-isomers
were obtained from the reactions with 2f-h . Similarly,
treatment of (R,S)-2a (0.0651 mmol) with 3 (0.112 mmol)
under the same conditions gave (Z)- 4a (65%), (E)-4a
(5%), and 5 (77%). Unexpectedly, it was found that the
reaction of (R,R)-2e under the same conditions gave (Z)-
and (E)-4a instead of the corresponding (Z)-and (E)-2-
(tert-butyl)-3-(3-phenoxyphenyl)-2-propenols 4 (Ar )
3-PhOC6H4). Since we were unaware of the dephenoxyl-
ation of aryl phenyl ether by 3, diphenyl ether (1.257
mmol) was treated with 3 (2.011 mmol) in THF (5 mL)
under the same foregoing condition. From the reaction
mixture were isolated phenol (45%), unreacted ether
(13%), and unknown mixtures. This result indicates that
(Z)-4a can be formed from (R,R)-2e. However, the mech-
anism for the dephenoxylation of 2e is uncertain. Quan-
tities of reactants, (R,R)-2a -h and 3, and yields of (Z)-
4a -h and (E)-4a -d are summarized in Table 2.
The stereochemistry of 4 was determined based on a
NOESY spectrum of (Z)-4b (Ar ) 3-MeOC6H4) (Figure
1), which shows interactions between the vinyl proton
and the protons of the tert-butyl group, and between the
methoxy protons and the methylene protons. Further-
more, the NOESY spectrum shows an interaction be-
tween the methylene protons and the protons at C-2 and
C-6 of the 3-anisyl group, indicating a trans relationship
between the two bulky groups, i.e., tert-butyl and 3-anisyl
groups.
(17) Benzotriazole has been reported to accept at least four elec-
trons: Refer to Wamhoff, H. Comprehensive Heterocyclic Chemistry;
Katritzky, A. R., Rees, C. W. Eds.; Pergamon Press: Oxford, 1984; Vol.
5, 4. 11, p 689.
(18) (a) Garst, J . F. Acc. Chem. Res. 1971, 4, 400. (b) Garst, J . F.
Free Radical; Kochi, J . K., Ed.; Wiley and Sons: New York, 1973; Vol.
1, Chapter 9, pp 503-546.
The stereoselective formation of (Z)-4a -h may be
understood by examination of the transition state in a
Newman projection (Scheme 3). One electron-transfer
from 3 to 2 would form an anion radical of 2. The most

Notes
J . Org. Chem., Vol. 66, No. 6, 2001 2151
Ta ble 2. Qu a n tities of Rea cta n ts 2 a n d 3, a n d Yield s of 4 a n d 5
(R,R) and (S,S)-2
3
entry
compd
Ar
R
mmol
mmol
compd
(·)-4
(Ε)-4
5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
a
b
c
d
e
f
g
h
i
j
k
l
m
n
Ph
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
0.345
0.267
0.261
0.280
0.315
0.318
0.295
0.344
0.391
0.492
0.287
0.492
0.322
0.452
0.569
0.427
0.417
0.462
0.519
0.525
0.487
0.567
0.635
0.597
0.597
0.597
0.597
0.678
a
b
c
d
e
f
g
h
i
j
k
l
m
n
59
54
43
54
40
53
67
47
28
21
54
47
47
39
6
7
6
7
5
3-MeOC6H4
3-MeC6H4
3,4-Me2C6H3
3-PhOC6H4
2-Pyridyl
3-Pyridyl
6-Me-2-pyridyl
Ph
Ph
32
13
20
32
14
40
77
51
74
81
83
61
Ph
Ph
3-MeC6H4
2,5-Me2C6H3
2,5-Me2C6H3
2,5-Me2C6H3
Me
3-MeC6H4
3-MeOC6H4
Ph
a
Isolated yields. (E)- and (Z)-4 are all liquids.
F igu r e 1. NOESY spectrum of (Z)-3-(3-anisyl)-2-(tert-butyl)-2-propenol (Z)-4b.
favorable conformation around R-C of an anion radical
of 2 is shown in the intermediate 6 in which the two
bulky groups, i.e., the tert-butyl and benzotrizole moi-
eties, are anti. The interaction of Li+ ions with nonbond-
ing electrons on the oxygen and N-1 atoms would be
expected to facilitate the formation of such a gauche type
arrangement.19 The rapid extrusion of the stable benzo-
triazolate ion 7 from the anion radical 6 initially gener-
ates the benzylic radical 8a whose unpaired electrons
should push the other two bonding orbitals (C-Ar and
C-H) away so that the steric hindrance between Ar and
R groups in 8a will be much more important than that
in the conformational isomer 8b. Severe steric repulsion
due to the close proximity between tert-butyl and aryl
groups in the transition state would cause the C-C bond
rotation to select the conformer 8b as a preferable
conformer. Since the opening of epoxides to a radical
center is a common reaction,20 the formation of â,γ-
unsaturated alkoxy radicals 9 and 10 from 8b and 8c,
respectively, is conceivable. Intermolecular hydrogen
abstraction of 9 would give (Z)-4. Since small amounts
of (E)-4 were isolated, the transition state leading to 10
would be highly energetic, presumably due to severe
(19) We have proposed the involvement of Li+ in the formation of
2-(2-arylethyl)-5-methyltetrahydrofurans from 2-[2-aryl-2-(benzotria-
zol-1-yl)ethyl]-5-(methyl)tetrahydrofurans and 7: Refer to Kang, Y. H.;
Kim, K. Tetrahedron 1999, 55, 4271.
(20) Fossey, J .; Lefort, D.; Sorba, J . Free radicals in Organic
Chemistry; J ohn Wiley and Sons: New York, 1995; Chapter 13, pp
151-165.

2152 J . Org. Chem., Vol. 66, No. 6, 2001
Notes
Sch em e 3
2,5-Me2C6H3), which was prepared by treatment of 2l
with TMSOTf in CH2Cl2 at room temperature. The
stereochemistry of 12l was assigned based on that of the
known 12i (Ar ) R ) Ph),21 whose mp (94 °C) and
spectroscopic (1H NMR, IR, MS) data were in good
agreement with those of 12i (mp, 92-93 °C) prepared
according to the procedure for 12l.
The spectroscopic data coupled with the failure to
isolate unreacted 2l support the formation of compounds
(E)- and (Z)-4 via a radical mechanism. Stabilization of
conjugated aldehydes 11 and 12 may be the driving force
for oxidation of 8b and/or 8c. Based on this result, a
possible SET reaction of 8 to generate carbanions 13 and
14, followed by heterolytic cleavage of C-O bond to give
eventually (E)- and (Z)-4, is unlikely.
Similarly a mixture of diastereomers (R ) aryl) (Rf )
0.5 and 0.4, n-hexane and EtOAc ) 8:1) was separated
by chromatography on a silical gel using a mixture of
n-hexane and EtOAc (20:1). The former with a higher Rf
value and the latter with a lower Rf value were assigned
to be enantiomeric mixtures with (R,R)- and (R,S)-
configurations, respectively. Interestingly, treatment of
2i-m (Ar ) R ) aryl) with 3 under the same conditions
as for 2a -h gave a mixture of diastereomers (Z)-4i-m
and (E)-4i-m , which were separated by chromatography.
Yields of the diastereomers are summarized in Table 2.
The structures of (Z)-4i-m and (E)-4i-m were deter-
mined by the same method as for (Z)-4a -h . The NOESY
spectrum of (Z)-4m clearly shows the interactions be-
tween the methylene protons and the protons of the
methoxy group. Entries 9-13 show that (E)- and (Z)-
isomers are produced in the ratios of 3:1 to 1:1 when
oxiranes 2i-m have less bulkier aryl groups compared
with the tert-butyl group at C-1 of the oxirane ring. In
addition, Table 2 shows that the ratio of (E)- to (Z)-
isomers decreases with further steric interactions be-
tween Ar and R groups (in the order of entries 9 > 10 >
11 > 12 > 13 > 1-8), which manifests the decrease of
the population of the conformer 8c, the inversion isomer
of 8a , in equilibrium with the conformer 8b.
Sch em e 4
steric repulsion between tert-butyl and Ar groups which
are cis each other. On the other hand, when R is an aryl
group, which is less bulky than tert-butyl, conformers 8b
and 8c would be in equilibrium, from which geometric
isomers (E)- and (Z)-4 would result (vide infra). In fact,
when R ) Me, the corresponding (E)- and (Z)-4n (Ar )
Ph, R ) Me) were isolated in 40% and 39% yields,
respectively.
In conclusion, a method for the synthesis of 2-substi-
tuted 3-aryl-2-propen-1-ols has been developed by treat-
ment of 1-alkyl (or aryl)-1-[(aryl)(benzotriazol-1-yl)methyl]-
oxiranes with lithium naphthalenide in THF at room
temperature. The stereochemistry around the CdC double
bond depends on the bulkiness of the alkyl (or aryl)
groups at C-1 of oxiranes, which originate from 1-alkyl
(or aryl)-2-chloroethanones. The merit of the method lies
in the chemoselective introduction of an alkyl or aryl
group at C-2 and an aryl group at C-3 of allylic alcohols,
which has been seldom explored hitherto.
To confirm the involvement of the cleavage of the C-O
bond of epoxides 8b and 8c in a radical mechanism, 2l
(0.244 mmol) was treated with 3 (1 equiv) for 5 min under
the same conditions as described. From the reaction
mixture were isolated (Z)- (46%) and (E)-4l (32%), 5
(66%), and unknown mixtures (27 mg) showing many
spots on TLC (Rf ) 0.8, 0.7, 0.6, 0.5, EtOAc: n-hexane )
1:10). No unreacted 2l was recovered. The GC-MS
spectrum (retention time ) 11.4 min, HP-Ultra 1
column, 0.2 mm × 30 m, EI) of one (Rf ) 0.5) of the
unknown fractions exhibited a mass number, m/z ) 250,
corresponding to the molecular weight of (E)-2-(2,5-
dimethylphenyl)-3-(3-tolyl)acrolein 12l. The IR (neat)
spectrum of the fraction exhibited a carbonyl absorption
Exp er im en ta l Section
Gen er a l Meth od s. The 1H and 13C NMR spectra were
recorded at 300 and 75 MHz in CDCl3 solution containing Me4Si
as an internal standard, respectively. IR spectra were obtained
in KBr or as thin films on KBr plates. GC-MS spectra were
obtained by electron impact at 70 eV. Elemental analyses were
carried out by the Korea Basic Science Institute. Column
chromatography was performed using silica gel (70-230 mesh).
Chromatograms were visualized by a mineral UV lamp. Melting
points are uncorrected.
at 1673 cm-1. The H NMR (300 MHz, CDCl3) spectrum
1
showed a singlet at 9.76 ppm, indicating the existence
of a formyl group. All of these data were consistent with
those of the authentic sample 12l (Ar ) 3-MeC6H4, R )
(21) (a) Gupton, J . T.; Polaski, C. M. Synth. Commun. 1981, 11, 561.
(b) Payne, G. B.; Williams, P. H. J . Org. Chem. 1961, 26, 651.

Notes
Gen er a l P r oced u r e for th e Syn th esis of 1-Alk yl (or
J . Org. Chem., Vol. 66, No. 6, 2001 2153
(48 mg, 0.217 mmol). The mixture was stirred for 5 h at room
temperature, by the time no spot corresponding to 2l (Rf ) 0.5,
EtOAc: n-hexane ) 1:10) was observed on TLC. The mixture
was quenched by the addition of water (5 mL), followed by
extraction with CH2Cl2 (40 mL × 3). The combined extracts were
dried over MgSO4 and chromatographed on a silica gel column
(3 × 10 cm). Elution with a mixture of EtOAc and n-hexane
(1:7) gave 12l (17 mg, 36%): yellow liquid; 1H NMR δ 2.01 (s,
3H), 2.27 (s, 3H), 2.30 (s, 3H), 6.83 (s, 1H), 6.89 (d, J ) 1.4 Hz,
1H), 7.00 (s, 1H), 7.08-7.22 (m, 5H), 7.40 (s, 1H), 9.80 (s, 1H);
13C NMR δ 19.0, 21.0, 21.3, 127.4, 128.6, 129.3, 129.4, 130.4,
131.3, 131.7, 132.9, 133.3, 134.2, 135.9, 138.3, 141.8, 150.9, 194.2;
IR (neat) 3024, 2928, 2704, 1677, 1610, 1446, 1168 cm-1; MS
m/z 250 (M+, 100 ), 235 (31.4), 192 (30.0), 130 (57.4). Anal. Calcd
for C18H18O: C, 86.36; H, 7.25. Found: C, 86.42; H, 7.21.
X-r a y Str u ctu r e An a lysis of Com p ou n d 2a . A single
crystal of 2a was obtained from CH2Cl2. The data were collected
on an Enraf-Nomius CAD 4 diffractometer using graphite-
monochromated Mo KR radiation. The structure was inferred
by direct methods and subsequent Fourier maps. Refinements
were carried out by full-matrix least-squares techniques. Non-
hydrogen atoms were anisotropically refined. Atomic scattering
factors were taken from International Tables for X-ray Crystal-
lography, Vol IV, 1974. All calculations and drawings were
performed using a Micro VAX II Computer with an SDP system.
Atomic coordinates, bond lengths, angles, and thermal param-
eters have been deposited at the Cambridge Crystallographic
Data Centre.
Ar yl)-1-[(a r yl)(ben zotr ia zol-1-yl)m eth yl]oxir a n es (2). To a
solution of 1 (0.7-2.8 mmol) in THF (15 mL) at -78 °C was
added LDA (1.1-4.0 mmol). The mixture was stirred for 5 min,
followed by addition of 1-chloro-3,3-dimethyl-2-butanone (0.7-
3.2 mmol). The mixture was additionally stirred for 10 min,
followed by addition of water (50 mL), which was extracted with
CH2Cl2 (50 mL × 3). The extracts were dried over MgSO4.
Removal of the solvent in vacuo gave a residue, which was
chromatographed (3 × 13 cm), with a mixture of n-hexane and
EtOAc (10:1) as eluent to give an enantiomeric mixture of (R,R)
and (S,S)-1-[(aryl)(benzotriazol-1-yl)methyl]-1-(tert-butyl)oxi-
ranes (2) [(R,R)-2] and an enantiomeric mixture of (R,S) and
(S,R)-1-[(aryl)(benzotriazol-1-yl)methyl]-1-(tert-butyl)oxiranes (2)
[(R,S)-2]. However, when 1-aryl-2-chloroethanones (1.2-2.8
mmol) were employed, the reaction mixture was eluted with the
same solvent mixture (20:1) to give enantiomeric mixtures of
(R,R)- and (S,S)-, and (R,S)- and (S,R)-1-aryl-1-[(aryl)(benzotria-
zol-1-yl)methyl]oxiranes (2). Quantities of reactants, and yields
and melting points of (R,R)-2, and (R,S)-2 are summarized in
Table 1.
Gen er a l P r oced u r e for th e Rea ction s of (R,R)-2 w ith
Lith iu m Na p h th a len id e (3). To a solution of 2 (0.09-0.49
mmol) in THF (8 mL) was dropwise added 3 (0.19-0.64 mmol),
prepared in situ by addition of lithium lump (76 mg, 10.9 mmol)
to the stirred solution of naphthalene (866 mg, 6.76 mmol) in
THF (30 mL) for 40 min at room temperature, using a hypo-
dermic syringe. The mixture was stirred for an additional 5 min,
followed by addition of water (50 mL), which was extracted with
CH2Cl2 (50 mL × 3). The extracts were dried over MgSO4 and
worked up as usual. Chromatography (2 × 13 cm) of the reaction
mixture using n-hexane gave naphthalene. Elution with a
mixture of n-hexane and EtOAc (9:1) gave (Z)-3-aryl-2-(tert-
butyl)-2-propenol (Z)-4a -h . Subsequent elution with the same
solvent mixture gave (E)-4a -d . However, when 2i-m were
treated with 3, (E)-4i-m , followed by (Z)-4i-m were eluted with
a mixture of n-hexane and EtOAc (10:1). The aqueous layer was
treated with concentrated HCl to give benzotriazole 5, which
was extracted with CH2Cl2. Consult Table 2 for quantities of
the reactants, and yields of 4 and 5.
Ack n ow led gm en t. The authors are grateful to the
S.N.U. Daewoo Research Fund (Grant No. 96-05-2066)
for financial support.
Su p p or tin g In for m a tion Ava ila ble: Copies of 1H NMR,
IR, elemental analyses of (R,R)-2a -m , (R,S)-2a -m , and (Z)-
4a -n , (E)-4i-n ; X-ray crystallographic data of 2a ; and an
ORTEP drawing of an enantiomeric mixture of (R,R)-1-
[(benzotriazol-1-yl)(phenyl)methyl]-1-(tert-butyl)oxiranes (2a ).
This material is available free of charge via the Internet at
http://pubs.acs.org.
P r ep a r a tion of (E)-2-(2,5-Dim eth ylp h en yl)-3-(3-tolyl)-
a cr olein (12l). To a solution of 2l (80 mg, 0.217 mmol) in CH2-
Cl2 (5 mL) was added trimethylsilyl trifluoromethanesulfonate
J O000469C