Generation of a silylethylene-titanium alkoxide complex. A versatile reagent for silylethylation and silylethylidenation of unsaturated compounds

Article abstract of DOI:10.1021/jo000925x

(Trimethylsilyl)ethylene-titanium alkoxide complex (1) was generated from trimethyl(vinyl)silane, Ti(O-i-Pr)₄, and i-PrMgCl as a preformed alkene-titanium complex and reacted with several unsaturated compounds such as aldehyde, imine, other vin

Full text of DOI:10.1021/jo000925x

J . Org. Chem. 2000, 65, 6217-6222
6217
Gen er a tion of a Silyleth ylen e-Tita n iu m Alk oxid e Com p lex. A
Ver sa tile Rea gen t for Silyleth yla tion a n d Silyleth ylid en a tion of
Un sa tu r a ted Com p ou n d s
Ryo Mizojiri, Hirokazu Urabe, and Fumie Sato*
Department of Biomolecular Engineering, Tokyo Institute of Technology,
4
259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, J apan
fsato@bio.titech.ac.jp
Received J une 19, 2000
(
Trimethylsilyl)ethylene-titanium alkoxide complex (1) was generated from trimethyl(vinyl)silane,
Ti(O-i-Pr) , and i-PrMgCl as a preformed alkene-titanium complex and reacted with several
4
unsaturated compounds such as aldehyde, imine, other vinylsilane, and acetylene to give the
corresponding coupling products 4a -f, 6, 8, and 10a -d in a regioselective manner. Both of the
two carbon-titanium bonds of the complex 1 reacted successively with esters to afford silylcyclo-
propanols 11a -j, 13, and 15, some synthetic applications of which were illustrated in the preparation
of â-silyl ketones 16 and cyclopropenes 17. Asymmetric addition of 1 to a chiral acyloxazolidinone
1
9 gave optically active cyclopropanol (+)-11a of 50% ee.
In tr od u ction
reagent, are basically under equilibrium. It should be
noted that, in both methods, complex A has been always
generated as a transient species in the presence of the
acceptor (esters). However, the coupling reaction with
other substrates that are not compatible with the condi-
tions for the concomitant generation of A should require
the preformed complex prior to their reaction.
Alkene-titanium alkoxide complex A, originally re-
ported by Kulinkovich et al. in 1989,1 has attracted
much attention recently, because it has realized a unique
-3
preparation of cyclopropanols from carboxylic esters as
shown in eq 1.1
,4-6
While complex A was initially gener-
ated from a titanium alkoxide and 2 equiv of an ap-
propriate Grignard reagent according to eq 1,1
a,b,4a-c
later,
it was generated via the olefin exchange reaction as
shown in eq 2,1
c,4d,6
in which two alkene-titanium
complexes, A and another one derived from the Grignard
(1) (a) Kulinkovich, O. G.; Sviridov, S. V.; Vasilevskii, D. A.;
Pritytskaya, T. S. Zh. Org. Khim. 1989, 25, 2244-2245. (b) Kulink-
ovich, O. G.; Sviridov, S. V.; Vasilevski, D. A. Synthesis 1991, 234. (c)
Kulinkovich, O. G.; Savchenko, A. I.; Sviridov, S. V.; Vasilevskii, D.
A. Mendeleev Commun. 1993, 230-231.
(
2) Sato, F.; Urabe, H.; Okamoto, S. Pure Appl. Chem. 1999, 71,
511-1519. Sato, F.; Urabe, H.; Okamoto, S. Synlett 2000, 753-775.
3) For review on relevant Group 4 metalocene-olefin complexes,
see: Yasuda, H.; Nakamura, A. Angew. Chem., Int. Ed. Engl. 1987,
1
(
2
1
6, 723-742. Buchwald, S. L.; Nielsen, R. B. Chem. Rev. 1988, 88,
047-1058. Negishi, E. In Comprehensive Organic Synthesis; Trost,
B. M., Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 5, pp
1
1
163-1184. Broene, R. D.; Buchwald, S. L. Science 1993, 261, 1696-
701. Negishi, E.; Takahashi, T. Acc. Chem. Res. 1994, 27, 124-130.
This time, we found that silylethylene complex 1 can
be generated as a preformed species, satisfying the above
argument, to enable reactions with a variety of coupling
Maier, M. In Organic Synthesis Highlights II; Waldmann, H., Ed.;
VCH: Weinheim, 1995; pp 99-113. Ohff, A.; Pulst, S.; Lefeber, C.;
Peulecke, N.; Arndt, P.; Burlakov, V. V.; Rosenthal, U. Synlett 1996,
1
7
11-118. Negishi, E.; Takahashi, T. Bull. Chem. Soc. J pn. 1998, 71,
55-769. Rosenthal, U.; Pellny, P.-M.; Kirchbauer, F. G.; Burlakov,
7
partners other than esters (eq 3 in Scheme 1). In
addition, this complex underwent the aforementioned
Kulinkovich cyclopropanol formation as efficiently as
other nonsilylated alkene-titanium alkoxide complexes
V. V. Acc. Chem. Res. 2000, 33, 119-129.
(4) For earlier reports, see: (a) de Meijere, A.; Kozhushkov, S. I.;
Spaeth, T.; Zefirov, N. S. J . Org. Chem. 1993, 58, 502-505. (b) Corey,
E. J .; Rao, A.; Noe, M. C. J . Am. Chem. Soc. 1994, 116, 9345-9346. (c)
Lee, J .; Kim, H.; Cha, J . K. J . Am. Chem. Soc. 1995, 117, 9919-9920.
(d) Lee, J .; Kang, C. H.; Kim, H.; Cha, J . K. J . Am. Chem. Soc. 1996,
(6) For the contribution from our group, see: (a) Kasatkin, A.; Sato,
F. Tetrahedron Lett. 1995, 36, 6079-6082. (b) Kasatkin, A.; Kobayashi,
K.; Okamoto, S.; Sato, F. Tetrahedron Lett. 1996, 37, 1849-1852. (c)
Okamoto, S.; Iwakubo, M.; Kobayashi, K.; Sato, F. J . Am. Chem. Soc.
1997, 119, 6984-6990. (d) Hikichi, S.; Hareau, G. P-J .; Sato, F.
Tetrahedron Lett. 1997, 38, 8299-8302. (e) Mizojiri, R.; Urabe, H.; Sato,
F. Angew. Chem., Int. Ed. 1998, 37, 2666-2669; Angew. Chem. 1998,
110, 2811-2814. (f) Mizojiri, R.; Urabe, H.; Sato, F. Tetrahedron Lett.
1999, 40, 2557-2560.
1
18, 291-292.
(5) For latest reports, see: (a) Epstein, O. L., Kulinkovich, O. G.
Tetrahedron Lett. 1998, 39, 1823-1826. (b) Williams, C. M.; Chaplin-
ski, V.; Schreiner, P. R.; de Meijere, A. Tetrahedron Lett. 1998, 39,
7
6
5
Tetrahedron Lett. 1999, 40, 5935-5938. (f) Chevtchouk, T. A.; Isakov,
V. E.; Kulinkovich, O. G. Tetrahedron 1999, 55, 13205-13210. (g) Park,
S.-B.; Cha, J . K. Org. Lett. 2000, 2, 147-149. (h) Cho, S. Y.; Cha, J . K.
Org. Lett. 2000, 2, 1337-1339.
695-7698. (c) Lee, K. L.; Kim, S.-I.; Cha, J . K. J . Org. Chem. 1998,
3, 9135-9138. (d) Sung, M. J .; Lee, C.-W.; Cha, J . K. Synlett 1999,
61-562. (e) Epstein, O. L.; Savchenko, A. I.; Kulinkovich, O. G.
(7) Although the reactivity of various alkene complexes of Group 4
metals has been investigated, that of silylalkene complexes has not
been studied (see ref 3).
1
0.1021/jo000925x CCC: $19.00 © 2000 American Chemical Society
Published on Web 09/15/2000

6
218 J . Org. Chem., Vol. 65, No. 19, 2000
Mizojiri et al.
Sch em e 1. Gen er a tion a n d Rea ction s of
Silyleth ylen e-Tita n iu m Alk oxid e Com p lex
of the propene unit, was not formed, as evidenced by the
detection of only a negligible amount of trimethyl(pentyl)-
silanes upon hydrolysis of the reaction mixture.
The preformed complex 1 reacted with cyclohexanecarb-
1
1,12
aldehyde to give γ-silyl alcohol 4b in good yield (eq 5).
Propylation of the aldehyde with remaining i-PrMgCl
and/or 213 was not observed at all, confirming the
complete exchange of the ligating propene of 2 with the
added vinylsilane to give cleanly 1. As far as the regio-
selectivity is concerned, the γ-silyl alcohol was exclusively
produced with >99% selectivity. The reaction with other
aldehydes gave the corresponding alcohols 4a -f in a
similar manner as shown in eq 5. The presence of the
intermediate oxatitanacycles was verified by deuteriolysis
and iodinolysis (to give 4c and 4d ), which, at the same
time, demonstrated the successive introduction of two
different electrophiles to 1. Although chiral imine 5
shown in eq 6 seemed to be less reactive than aldehydes
and required a higher reaction temperature, it behaved
like an aldehyde to afford γ-silylamine 6. The coupling
reaction again proceeded with virtually complete regio-
selection and with an appreciable diastereoselectivity of
around 3:1.
Sch em e 2. Gen er a tion of Silyleth ylen e-Tita n iu m
Alk oxid e Com p lex
to give silylcyclopropanols, which are otherwise tedious
8
to prepare, in good yields (eq 4 in Scheme 1). From the
synthetic point of view, complex 1 should become a
convenient reagent to impart a silylated moiety to organic
molecules, based on the fact that organosilicon com-
pounds are versatile intermediates in organic synthesis.9
Herein, we disclose our findings on the generation of the
silylethylene-titanium alkoxide complex 1 and its be-
havior toward unsaturated compounds that has not been
previously reported.
Resu lts a n d Discu ssion
(
Trimethylsilyl)ethylene-titanium alkoxide complex 1
can be readily generated via the ligand exchange reaction
between the added vinylsilane and (η -propene)Ti(O-i-
Pr)
Scheme 2). All steps are carried out in situ and in one
pot. Thus, in practice, i-PrMgCl (2.0 equiv) was added
to a mixture of vinylsilane (1.0 equiv) and Ti(O-i-Pr) (1.0
2
2 4
(2) that is generated from Ti(O-i-Pr)
and i-PrMgCl2
(
Treatment of complex 1 with a different vinylsilane 7
gave 1,4-disilylbutane 8 as the cross-coupling product
after hydrolysis (eq 7). Neither the homo-coupling prod-
ucts nor the regioisomers were detected in this reaction.
This result illustrates a successful example of cross-
coupling reaction of two olefins mediated by the titanium
alkoxide species, even though the attempted coupling of
4
equiv) in ether at -78 °C, and the mixture was stirred
at -50 °C for 2 h to give 1 ready for a subsequent
reaction. Two points are noteworthy in this process. (i)
This method enables the clean generation of olefin
complex 1 as a preformed species before the subsequent
reaction; that is, the equilibration exclusively shifted from
(
11) The same reaction, silylethylation of aldehydes, was previously
carried out with Me SiCH CH Li or -MgBr generated via unstable Me
SiCH CH Br prepared from vinylsilane and HBr. Wilson, S. R.;
Shedrinsky, A. J . Org. Chem. 1982, 47, 1983-1984.
12) Addition of other types of nonsilylated alkene-Group 4 metal
2
to 1.10 (ii) The titanacycle 3, which may act as an
equivalent of the olefin complex 1 with the dissociation
3
2
2
3
-
2
2
(
(
8) This part has appeared in a preliminary form. See ref 6f.
complexes to aldehydes, ketones, and imines is known. Cohen S. A.;
Bercaw, J . E. Organometallics 1985, 4, 1006-1014. Mashima, K.;
Haraguchi, H.; Ohyoshi, A.; Sakai, N.; Takaya, H. Organometallics
1991, 10, 2731-2736. Takahashi, T.; Suzuki, N.; Hasegawa, M.; Nitto,
Y.; Aoyagi, K.; Saburi, M. Chem. Lett. 1992, 331-334. Hill, J . E.;
Fanwick, P. E.; Rothwell, I. P. Organometallics 1992, 11, 1771-1773.
Thorn, M. G.; Hill, J . E.; Waratuke, S. A.; J ohnson, E. S.; Fanwick, P.
E.; Rothwell, I. P. J . Am. Chem. Soc. 1997, 119, 8630-8641.
(9) (a) Weber, W. P. In Silicon Reagents for Organic Synthesis;
Springer-Verlag: Berlin, 1983. (b) Colvin, E. W. In Silicon in Organic
Synthesis; Butterworth: London, 1981. (c) Fleming, I.; Dunogu e´ s, J .;
Smithers, R. In Organic Reactions; Kende, A. S., Ed.; Wiley: New York,
1
989; Vol. 37, pp 57-575. (d) Fleming, I.; Barbero, A.; Walter, D. Chem.
Rev. 1997, 97, 2063-2192.
10) To investigate the coupling reaction of 1 with aldehydes or
(
imines (vide infra), the generation of 1 as a preformed species is critical;
otherwise, the added aldehyde or imine is consumed by the remaining
i-PrMgCl or 2.
4
(13) For control, complex 2 generated from Ti(O-i-Pr) and i-PrMgCl
(-50 °C, 2 h) (ref 2) undergoes the smooth coupling reaction with
aldehyde to give propyl carbinol.

Silylethylene-Titanium Alkoxide Complex
with other terminal alkenes such as styrene, ethyl
acrylate, or ethyl vinyl ether only resulted in the forma-
tion of a product mixture.
J . Org. Chem., Vol. 65, No. 19, 2000 6219
1
selection of the product favored the trans relationship
between the silyl and hydroxy groups.
Although the reaction of eq 9 started with preformed
olefin complex 1, an alternative method where complex
1
was generated as a transient species and was trapped
The coupling of 1 with 4-octyne proceeded also in a
highly regioselective manner to give stereodefined (â-
silylethyl)alkene (10a ), a homoallylsilane, in good yield
8
by the ester as it formed was possible. In fact, this
transformation could be carried out just by the addition
of a mixture of an ester and vinylsilane to 2. The latter
method appears to attain somewhat higher product yields
than the former one (cf. the yields of 11a in eq 9 and
entry 1 of Table 1). Table 1 displays the preparation of a
variety of cyclopropanols by the latter method. In all
cases, the corresponding silylated cyclopropanols were
obtained without any complications. Both aromatic and
aliphatic esters gave the desired products. The presence
of an additional functional group in the esters such as
olefin, alkyl bromide, and phenyl ether does not interfere
with the reaction at all. To our surprise, methyl 6-hep-
tenoate did undergo the intermolecular reaction to give
the corresponding silylcyclopropanol without any com-
plication, even though it was reported that this unsatur-
ated ester gave a bicyclic cyclopropanol in the intramo-
1
4
after hydrolysis as shown in eq 8.1
5,16
The presence of the
1
2
intermediate titanacyclopentene 9 (R ) R ) Pr) was
verified by deuteriolysis that shows a high degree of
deuterium incorporation. A few terminal acetylenes
afforded the expected products as well, but a mixture of
regioisomers with respect to the reacting acetylene was
3
obtained. Sterically demanding Me Si and t-Bu substit-
uents decreased the product yields and increased the
proportion of the regioisomer in which they are placed
at the R position of the titanacycle.
lecular reaction promoted by an olefin-titanium alkoxide
complex.4
d,6a
As far as the diastereoselectivity of the
reaction is concerned, the selectivity generally falls
within a good range, favoring trans relationship between
the silyl and hydroxy groups in most cases where the
alkyl side chain is not sterically demanding (all entries
except entry 6) and, contrarily, cis for a sterically
encumbered tert-butyl substituent (entry 6) (vide infra).
Besides trimethyl(vinyl)silane, chloro- and alkoxy-
silanes 12 or 14 gave the corresponding (alkoxysilyl)-
cyclopropanols 13 or 1517 as shown in eqs 10 and 11. If
the chlorosilane was used, the chloride was most likely
displaced by the isopropoxide anion in situ to give the
observed product (eq 10).
The above results are the first examples of the cross-
coupling reaction of titanium alkoxide complex 1 with a
variety of unsaturated compounds such as aldehyde,
imine, vinlysilane, and acetylene. As one of the most
unique reactions of alkene-titanium alkoxide complexes
should be the formation of cyclopropanols upon reaction
with esters as mentioned in the introductory part (see
Scheme 1), we next turned our attention to the feasibility
of this reaction starting with 1. Gratifyingly, the silylated
olefin complex 1 was found to participate in the coupling
reaction with ethyl benzoate as well to afford the corre-
sponding silylcyclopropanol 11a (eq 9). The diastereo-
(
14) For synthetic utility of homoallylsilanes, see: (a) ref 9a, p 178.
(
b) Sarkar, T. K.; Ghorai, B. K.; Das, S. K.; Gangopadhyay, P.; Rao, P.
S. V. S. Tetrahedron Lett. 1996, 37, 6607-6610. For the basis of the
reactivity of homoallylsilanes, see: (c) Lambert, J . B. Tetrahedron
1
990, 46, 2677-2689.
15) The unsuccessful coupling of nonsilylated alkene complex 2 with
(
acetylenes has been reported. Harada, K.; Urabe, H.; Sato, F. Tetra-
hedron Lett. 1995, 36, 3203-3206.
(
16) For the coupling of an acetylene-titanium alkoxide complex
with vinylsilane, that is, a reversal combination of eq 8, see: Urabe,
H. J . Synth. Org. Chem. J pn. 1999, 57, 492-502. Alternatively, that
2
a mixture of an internal alkyne and vinylsilane was treated with Cp -
The relative stereochemistry of a few silylcyclopro-
panols shown in Figure 1 has been unambiguously
ZrBu
2
to give a coupling product was reported. Takahashi, T.; Xi, Z.;
Rousset, C. J .; Suzuki, N. Chem. Lett. 1993, 1001-1004.

6
220 J . Org. Chem., Vol. 65, No. 19, 2000
Mizojiri et al.
Ta ble 1. Syn th esis of Silylcyclop r op a n ols via Tita n iu m (II)-Med ia ted Cou p lin g of Tr im eth yl(vin yl)sila n e a n d Ester sa
a
See text and Experimental Section. b Determined by H NMR spectroscopy. Trans/cis refers to the relationship between the silyl and
1
hydroxy groups.
Sch em e 3. Syn th etic Ap p lica tion of
Silylcyclop r op a n ol
F igu r e 1. Values in % refer NOE enhancements.
determined by measurements of the nuclear Overhauser
1
effects in the H NMR spectra. As the major isomers
1
1b-e,g,i-j and 13 (Table 1 and eq 10) as well as 11a ,h
and 15 (eq 9 and Figure 1) of the established structures
always behaved as the more polar component upon silica
gel chromatography (TLC or preparative) than the minor
isomers (as readily expected based on the degree of steric
shielding of the hydroxy group), the stereochemical
assignments for the major and minor isomers of the
former products were made as shown in Table 1 by
analogy. This fact also indicates that the stereoisomers
were successfully separated by flash chromatography on
silica gel to yield pure fractions (of the major isomers).
Cyclopropanols and their derivatives are useful inter-
mediates in organic synthesis.18 To disclose the synthetic
application of silylated cyclopropanols,19 their transfor-
mations are exemplified in Scheme 3. The treatment of
silylcyclopropanols 11d and 11h with potassium hydride
or sulfuric acid effected the regioselective ring-opening
of cyclopropane to give the â-silyl ketones 16a and 16b.
The silyl group appears to control the regioselective
2
0
(
17) An alkoxysilyl group could be stereospecifically converted to a
hydroxy group. J ones, G. R.; Landais, Y. Tetrahedron 1996, 52, 7599-
662.
7
cleavage of the carbon-carbon bond under both acidic

Silylethylene-Titanium Alkoxide Complex
J . Org. Chem., Vol. 65, No. 19, 2000 6221
Sch em e 4. Rea ction s of Silyleth ylen e-Tita n iu m Alk oxid e Com p lex 1
and basic reaction conditions.14c Another example is the
preparation of cyclopropenes 17a and 17b via the Peter-
son-like olefination consisting of mesylation followed by
Con clu sion
The silylethylene-titanium alkoxide complex under-
goes carbon-carbon bond formation and subsequent
functionalization with a variety of unsaturated com-
pounds as shown in Scheme 4, which should be informa-
tive regarding the behavior of Group 4 metal-alkene
2
1
treatment with a fluoride anion in good yield.
A few carboxylic acid derivatives having a chiral
auxiliary were examined in order to develop a substrate-
2
2
controlled asymmetric synthesis of silylcyclopropanols.
Oppolzer’s acylcamphorsultam 1823 afforded the desired
4
complexes. Since the reagents, vinylsilane, Ti(O-i-Pr) ,
and the Grignard reagent, are inexpensive and readily
available, this new silylethylation method with possible
introduction of an additional electrophile could find
application in organic synthesis.
cyclopropanol 11a in good yield but, unfortunately,
without any detectable chiral induction (eq 12). On the
other hand, a chiral amide 19 derived from Evans’s
oxazolidinone24 furnished optically active (+)-silylcyclo-
propanol 11a of 50% ee (eq 13). Its absolute configuration
has not yet been determined.
Exp er im en ta l Section
Gen er a tion of P r efor m ed (Tr im eth ylsilyl)eth ylen e-
Tita n iu m Com p lex 1. To a solution of Ti(O-i-Pr) (0.45 mL,
4
1
.5 mmol) and trimethyl(vinyl)silane (0.22 mL, 1.5 mmol) in
Et
2
O (10 mL) was added i-PrMgCl (2.0 mL of a 1.5 M ethereal
solution, 3.0 mmol) at -78 °C to give a yellow homogeneous
mixture. The solution was warmed to -50 °C over 30 min,
during which period its color turned brown. After stirring for
2
h at -50 °C to -55 °C, the generation of silylethylene-
titanium complex 1 was complete, and it was ready for the
next reaction without isolation.
Gen er ation of (Tr im eth ylsilyl)eth ylen e-Titan iu m Com -
p lex 1 in Situ . Typ ica l P r oced u r e for th e P r ep a r a tion
of Silylcyclop r op a n ols in Ta ble 1. (1RS,2SR)-1-P h en yl-
2
-(tr im eth ylsilyl)cyclop r op a n ol (11a ). To a stirred solution
of Ti(O-i-Pr) Cl (1.5 mL of a 1.0 M solution in hexane, 1.5
mmol) in Et O (10 mL) was added i-PrMgCl (2.2 mL of a 1.3
3
2
(
18) Murai, S.; Ryu, I.; Sonoda, N. J . Organomet. Chem. 1983, 250,
M solution in ether, 2.9 mmol) at -60 °C. Ten minutes later,
a mixture of trimethyl(vinyl)silane (0.22 mL, 1.5 mmol) and
ethyl benzoate (0.14 mL, 1.0 mmol) was added to the solution.
The reaction mixture was then warmed to -25 °C over 30 min
and was stirred at -25 °C to -20 °C for 1 h and finally at 0
1
21-133. Wong, H. N. C.; Hon, M.-Y.; Tse, C.-W.; Yip, Y.-C.; Tanko,
J .; Hudlicky, T. Chem. Rev. 1989, 89, 165-198. Kuwajima, I.; Naka-
mura, E. Top. Curr. Chem. 1990, 155, 1-39. Kuwajima, I.; Nakamura,
E. In Comprehensive Organic Synthesis; Trost, B. M.; Fleming, I., Eds.;
Pergamon Press: Oxford, 1991; Vol. 7, pp 441-454. Ryu, I.; Murai, S.
In Houben-Weyl Methods of Organic Chemistry; de Meijere, A., Ed.;
Thieme: Stuttgart, 1997; Vol. E 17c, pp 1985-2040.
°
C for 1 h. After water (0.5 mL) in THF (2.0 mL) was added at
(
19) Reactivity of silylcyclopropanols has not been elucidated. Refer-
ence 18 and Paquette, L. A. Chem. Rev. 1986, 86, 733-750.
20) For synthetic utility of â-silyl ketones, see: Tanino, K.; Sato,
K.; Kuwajima, I. Tetrahedron Lett. 1989, 30, 6551-6554.
21) For the preparation of cyclopropenes via dehalosilylation, see:
room temperature, the heterogeneous mixture was stirred for
0.5 h. The resultant suspension was filtered through a pad of
Celite, which was subsequently washed with ether. The
combined filtrate and ethereal fractions were concentrated in
(
(
1
vacuo to afford a crude oil, H NMR analysis of which showed
Chan, T. H.; Massuda, D. Tetrahedron Lett. 1975, 16, 3383-3386.
Billups, W. E.; Haley, M. M. J . Am. Chem. Soc. 1991, 113, 5084-5085.
Haley, M. M.; Biggs, B.; Looney, W. A.; Gilbertson, R. D. Tetrahedron
Lett. 1995, 36, 3457-3460. Halton, B.; Banwell, M. G. In The Chemistry
of the Cyclopropyl Group; Rappoport, Z., Ed.; Wiley: Chichester, 1987;
Vol. 2, pp 1223-1339.
the diastereomeric ratio to be 93:7. Purification by column
chromatography on silica gel (pretreated with 1% NEt in
3
(23) Oppolzer, W.; Barras, J .-P. Helv. Chim. Acta 1987, 70, 1666-
1675.
(22) For preparation of optically active cyclopropanols via substrate-
controlled synthesis, see ref 6e. For the reagent (titanium species)-
controlled asymmetric synthesis, see ref 4b.
(24) Evans, D. A.; Bartroli, J .; Shih, T. L. J . Am. Chem. Soc. 1981,
103, 2127-2129.

6
222 J . Org. Chem., Vol. 65, No. 19, 2000
Mizojiri et al.
hexane and eluted with hexane/ether 8:1) afforded pure 11a
as a colorless oil (182 mg, 88%).
Su p p or tin g In for m a tion Ava ila ble: Typical procedures
for the preparation of 4a , 4d , 6, 8, 10a , 11a (from preformed
1
), 13, 16, 17a , 19, and (+)-11a and the characterization data
for all products. This material is available free of charge via
the Internet at http://pubs.acs.org.
Ack n ow led gm en t. We thank the Ministry of Edu-
cation, Science, Sports and Culture (J apan) for financial
support.
J O000925X