Short and versatile two-carbon ring expansion reactions by thermo-isomerization: Novel straightforward synthesis of (±)-muscone, nor- and homomuscones, and further macrocyclic ketones

Article abstract of DOI:10.1055/s-2002-19759

Thermo-isomerization of 1-vinyl substituted medium-and large-ring cycloalkanol derivatives in a flow reactor system at temperatures of 600°C to about 650°C leads directly to the ring-expanded macrocyclic ketones. Alkyl substituents at the vinylic moiety are transferred locospecifically to the ring-expanded ketone as corresponding α-, and β-substituents, respectively. This novel thermal 1,3-C shift reaction therefore provides a new access to short syntheses of many alkyl-substituted macrocyclic ketone derivatives [e.g. (±)-muscone and analogues] in a systematic manner.

Full text of DOI:10.1055/s-2002-19759

280
LETTER
Short and Versatile Two-Carbon Ring Expansion Reactions by Thermo-
Isomerization: Novel Straightforward Synthesis of ( )-Muscone, Nor- and
Homomuscones, and Further Macrocyclic Ketones
S
hor
t
and
V
ersatile Tw
a
o-Carbon R
t
ing Ex
t
pansio
h
n Reactions b
i
y The
a
r
mo-Isomer
s
ization Nagel,*a Hans-Jürgen Hansen,a Georg Fráterb
a
Organisch-chemisches Institut der Universität, Winterthurerstr. 190, CH 8057- Zürich, Switzerland
Fax +41(1)635 68 12; E-mail: mnagel@access.unizh.ch
b
Givaudan Research Ltd, Überlandstr. 138, CH-8600 Dübendorf, Switzerland
Fax +41(1)824 29 26; E-mail: georg.frater@givaudan.com
Received 3 September 2001
O
O
Abstract: Thermo-isomerization of 1-vinyl substituted medium-
and large-ring cycloalkanol derivatives in a flow reactor system at
temperatures of 600 °C to about 650 °C leads directly to the ring-
expanded macrocyclic ketones. Alkyl substituents at the vinylic
moiety are transferred locospecifically to the ring-expanded ketone
as corresponding -, and -substituents, respectively. This novel
thermal 1,3-C shift reaction therefore provides a new access to short
syntheses of many alkyl-substituted macrocyclic ketone derivatives
[e.g. ( )-muscone and analogues] in a systematic manner.
(CH2)n
+
(CH2)n
a)
CH3
(65 - 75%)
2a: n = 8
(2 - 10%)
3a: n = 8
3b: n = 7
OH
c)
2b: n = 7
b)
(CH2)n
(±)-7c
d)
O
O
1a: n = 8
1b: n = 7
Key words: ring expansions, macrocyclic ketones, dynamic gas
phase thermo-isomerization, two- carbon ring insertion reactions,
( )-muscone syntheses
O
(CH2)n
(CH2)n
5a: n = 8
5b: n = 7
4a: n = 8
4b: n = 7
In the preceding communication1 we described a novel
thermo-isomerization process under flash vacuum pyroly-
sis conditions, in which 1-vinylcycloalkanols (or their
corresponding ethynyl forms) can directly be transformed
into the isomeric macrocyclic ketones (or their , -unsat-
urated forms) expanded by two C-atoms.2 In order to get
more insight into the general applicability of this two-car-
bon ring expansion procedure, we investigated systemati-
cally the influence of alkyl substituents at the vinyl moiety
of the cycloalkanols.
Thermo-isomerization of the allylic alcohols3 1 with a 1-
methylethen-1-yl substituent (Scheme 1) in the same
manner as described2 gave the known 2-methyl-
cycloalkanones4,7 2 in yields of 65-75%, as well as about
2-10% of the open-chained alkenone isomers 3.8a
Scheme 1 Reaction conditions: a) Dynamic gas phase thermo-iso-
merization (FVP conditions, ~ 650 °C, 1-4 mbar, N2 flow). b) Trans-
formation of 2a into ( )-7c: ref.7 (one-carbon homologation). c)
Baeyer-Villiger oxidation, see refs.5,6. d) Alumina (Alox basic), 160
°C, 15-30 min.
mina which led to the isomeric ketone 2,2-
dimethylcyclotridecanone8b (5a).4f,9 Both ketones 5 can
easily be prepared in about 60% isolated yield by heating
the corresponding allylic alcohols 1 adsorbed on basic
alumina in a kugelrohr oven to 160 °C for 15-30 min un-
der an inert atmosphere at normal pressure. This remark-
able [1,2]C shift reaction10 with formation of the geminal
-alkylated ketones11 5 represents a new type of a solvent-
free (“dry”), surface-catalyzed12 thermo-isomerization
process.
The macrocyclic 2-methylketones 2 were used previously
as the precursors for the synthesis of the naturally occur-
ring vegetable macrolides 4 (compounds with musky
odor)5a which were synthesized from 2 by employing a
Baeyer-Villiger oxidation (60-70% yield) as final trans-
formation in multistep ring-enlargement procedures.4a,f
Ketone 2a was also the intermediate in an earlier synthesis
of ( )-muscone (7c) by a two-step regioselective one-car-
bon ring homologation sequence.7
The ring-expanded 13- to 17-membered 3-methylcycloal-
kanones 7a–e were easily obtained by the dynamic gas
phase thermo-isomerization procedure from both isomers
of the corresponding 1-(propen-1-yl)cycloalkanols 6a-e
in about 45-55% yields (Scheme 2). With (E/Z)-1-(pro-
pen-1-yl)cyclotridecanol 6c as starting material, the valu-
able musk odorant13 ( )-musone 7c (3-methyl-
cyclopentadecanone)14 is directly formed (45-55%). The
homologous 16-membered macrocyclic 3-methylketones
7d (“homomuscone”),15 as well as the 17-membered 7e
(“dihomomuscone”),13g,15c were easily obtained in the
same manner. The corresponding lower muscone homo-
logues, cyclotetradecanone derivative 7b (“normus-
cone”),14k,15c,16 as well as the cyclotridecanone derivative
7a (“dinormuscone”),7,15b,c,17 are each accessible analo-
gously from the alcohols 6a and 6b, respectively. In all
A novel one-carbon insertion reaction was also observed,
when alcohol 1a was heated in the presence of basic alu-
Synlett 2002, No. 2, 01 02 2002. Article Identifier:
1437-2096,E;2002,0,02,0280,0284,ftx,en;G19401ST.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0936-5214

LETTER
Short and Versatile Two-Carbon Ring Expansion Reactions by Thermo-Isomerization
281
cases, the open-chained enone-isomers 8a–e (Scheme 2) boiling t-BuOMe instead of Et2O), which also made the
were also formed as side-products [predominantly the work-up procedure more efficient.20d When aminoalcohol
(E)-isomer] in average yields of 5-15%.18
14 was treated with sodium nitrite and acetic acid accord-
ing to the literature procedures for Tiffeneau-Demjanov
ring expansion reactions,19b–19d ketone 11 was formed in
about 50-60% yield, but the isomeric oxirane 15 (about
30%) and the starting ketone 12 (about 5-10%) were also
found and could not be separated efficiently from 11.
Since these unsatisfactory results could not be circum-
vented by systematic variations of the experimental con-
ditions, a method for the separation of the spirooxirane 15
from ketone 11 was developed by selective chemical
modification to form a more polar derivative. A straight-
forward method for directly recovering the aminoalcohol
14 from the reaction mixtures of the Tiffeneau-Demjanov
procedure involves reaction with ammonia.21 By heating
the raw reaction mixtures, which contained the ketone 11
and oxirane 15 (besides minor amounts of 12), in concd.
aqueous ammonia solution (excess) and i-PrOH in an au-
toclave at 140-160 °C for 2-4 h, the by-product 15 was
transformed back into starting material 14 almost quanti-
tatively. The -aminoalcohol 14 could now easily be sep-
arated from the ketones, either by crystallization in non-
polar solvents, or by filtration after transformation into its
hydrochloride by bubbling gaseous HCl into a stirred an-
hydrous t-BuOMe solution of the components. Finally,
cyclotridecanone (11) can be separated from homologous
ketone 12 by distillation over a Vigreux column under re-
duced pressure (GC purity > 98%). Since aminoalcohol
O
O
OH
a)
(CH2)n
(CH2)n
+
H3C
(CH2)n
(E/Z)
7a-e
(45 - 55%)
(E/Z)-8a-e
6a-e
(5 - 15%)
a: n = 7; b: n = 8; c: = 9; d: n = 10; e: n = 11.
Scheme 2 Reaction conditions: a) Dynamic gas phase thermo-iso-
merization (FVP conditions, ~ 650 °C, 1-4 mbar, N2 flow).
Cyclotridecanone (11) is the essential precursor for the
synthesis of 15-membered cyclic ketones by the two-car-
bon insertion procedure.1 In consideration of the prohibi-
tively high prices of the odd-membered homologous
ketones 11 and also 9, compared with the much lower
price of 12, a one-carbon ring-expansion method starting
from 12 was thought to be a more attractive approach for
the synthesis of larger amounts (200-500 g) of 11 under
economical aspects. We tried to use the known Tiffeneau-
Demjanov homologation procedure19 for this purpose
(Scheme 3), via the protected cyanohydrin 13 and subse-
quent reduction with LiAlH4.20 The yields of aminoalco-
hol 14 could be raised by changing the solvent (higher
O
TMSO CN
O
HO
Me3SOI
aq NH3, i-PrOH
NH2
LiAlH4
MTBE
t-BuOK/KOH
TMSCN
cat. ZnI
140 - 160°C
autoclave
(t-BuOH)
12
12
12
12
12
(~ quant.)
(~ quant.)
60°C, 3 h
(> 70%)
(80 - 90 %)
12
13
14
recycling procedure
15
Tiffeneau-Demjanov
one-carbon insertion
a)
(ca. 30%)
MgBr
– N2
HO
R
NaNO2/H2O, HOAc
O
R
(ca. 50 - 60%)
O
HO
a)
b)
H2,
Pd/C
13
15
O
R
MgBr
b)
7b
R = H, Me
14
12
(ca. 650°C)
18: R = H
20: R = Me
(E)-19: R = H
13
(ca. 650°C)
(E/Z)-21*: R = Me
16
(E/Z)-17*
(20 - 45%)
R = H:
c)
R = Me:
H2, Pd/C
a)
b)
11
HO
MgBr
O
(ca. 650°C)
a)
HO
b)
O
15
MgBr
13
11
11
(ca. 650°C)
9
10
(E/Z)-6c
(±)-7c
Scheme 3 Reaction conditions: a) 1. Anhyd CeCl3 (0.1-0.4 mol-equiv), THF, r.t. 0.5-1 h (precomplexation of the ketone); 2. Grignard reagent
(THF solution), r.t., 0.5 h. b) Dynamic gas phase thermo-isomerization (FVP conditions, ~ 650 °C, 1-4 mbar, N2 flow). c) See ref. 4 and litera-
ture therein. 17* and 21*: (E)/(Z)-Isomers not separated.
Synlett 2002, No. 2, 280–284 ISSN 0936-5214 © Thieme Stuttgart · New York

282
M. Nagel et al.
LETTER
14 could be obtained very efficiently from the spiroep-
oxide 15, we tried to use the latter as a main precursor of
14. The methylene transfer reaction to ketone 12 from the
ylide obtained from trimethylsulfoxonium iodide
(Me3SOI) under basic conditions22 takes place in one step
and in excellent yields to 15. Encouraged by similar liter-
ature procedures,23 this step could be improved further to
nearly solvent-free conditions, so that the use of DMSO as
solvent was not longer necessary.24
CH3
O
(H2C)n
O
OH
R1
R1
R2
a)
R1
R2
(CH2)n
(CH2)n
R2
+
R3
R3
R3
n = 8
R1= H, R2, R3 = Me
23
22
24
R1= Me, R2 = H, R3 = Me
R1= Me, R2 = Me, R3 = H
(Z)-27
(E)-27
(E)-25
(Z)-25
26 (cis/trans)
29 (cis/trans)
A further approach to the synthesis of ( )-muscone 7 from
cycloalkanone 11 via the 3-methyl-2-cyclopentadecenone
(“2-muscenone”) intermediate 21 is also outlined in
Scheme 3. The thermo-isomerization of 1-prop-1-ynyl-
cyclotridecanol 20 gave the ring-enlarged cycloalkenone
isomers 21 in a complex mixture,25 together with open-
chained isomers, starting ketone 11, and dehydration
products. Hydrogenation of the raw thermolysate resulted
in the formation of three main compounds which were
separable by column chromatography (SiO2, hexane–t-
BuOMe, 97:3): ( )-muscone 7c (about 20% isolated
yield), 4-hexadecanone (about 15%), and cyclic ketone 11
R1/R2 = -(CH2)4-, R3 = H
28
30
Scheme 4 Reaction conditions: a) Dynamic gas phase thermo-iso-
merization (FVP conditions, ~ 650 °C, 1-4 mbar, N2 flow).
procedure by dynamic gas phase thermo-isomerization
for the synthesis of macrocyclic musk compounds are un-
der investigation and will be published elsewhere.
Acknowledgement
(about 10%) as well as non-polar hydrocarbon fractions. Financial support of this work by a grant from the Givaudan Rese-
arch Ltd., Dübendorf (Switzerland) to MN is gratefully acknowled-
ged. MN also thanks Dr. A. Linden for his assistance with proof-
reading this manuscript and Dr. Ch. Weymuth for helpful discussi-
ons.
In the same manner, the homologous (E/Z)-3-methyl-2-
cyclotetradecenone isomers25a 17 (20-45%, based on
NMR spectra) were obtained under equivalent conditions
from 1-prop-1-ynylcyclododecanol (16), and gave, also
after hydrogenation of the product mixture, the cyclic ke-
References
tone 3-methylcyclotetradecanone 7b (about 25%) as well
as the open-chained isomer 4-pentadecanone (about 25%)
as the main products of the isomerization process.
(1) Nagel, M.; Hansen, H.-J.; Fráter, G. Synlett 2002, 275.
(2) For a description of the thermo-izomerization procedure and
the experimental setup, see ref.1 and references therein.
(3) All mentioned cycloalkanols were synthesized by addition
of the corresponding commercially available vinylic halides
(normally the bromide) to the ketone by using a Grignard
reaction. The yields could be improved significantly by pre-
complexation of the ketone with CeCl3, according to the
analogous procedure described in ref. 1 for the simple 1-
vinylcycloalkanols. The propynyl substituted alcohol
derivatives 16 and 20 were obtained in a similar manner by
addition of propynyl magnesium bromide to the parent
ketone. The 1-cyclohexen-1-yl-cyclododecanol 28 was
obtained via addition of the lithio cyclohexenyl intermediate
according to ref.27
(4) (a) Kaiser, R.; Lamparsky, D. Helv. Chim. Acta 1978, 61,
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yield to almost 1:2 mixtures of 3,3-dimethylcyclotetrade-
canone 23 and its open-chain isomer 24. A similar behav-
ior was observed with the (E/Z)-2-buten-2-yl-substituted
isomers 25 as starting material. Both isomers gave mix-
tures of the two racemic cis/trans-isomers 26 (ca. 30%)
and the open-chain (E/Z)-isomers 27 (ca. 20%). With the
cyclohexen-1-yl substituent26 in 28, the ring expansion
process led to mixtures (about 1:1:4, 45-55% average
yields) of the known cis/trans isomers of bicyc-
lo[12.4.0]hexadecan-2-one (29)27 and also the cylohexen-
1-yl undecyl ketone (30)28 which were not fully separable
by column chromatography.
During the past 75 years, since Ruzicka had established
the molecular structure of naturally occurring muscone, a
huge number of syntheses of either ( )-muscone 7c or also
its enantiomers have been published,14 but ring expansion
procedures by two carbon atoms are rare among them.
Only limited examples have been described in earlier re-
ports, where 7c was synthesized in multistep protocols via
[1,3]C shift reactions from more complex 13-membered
cyclic precursor systems by two-carbon insertion reac-
tions.29
Effects of substituents at C(2) as well as further applica-
tions and extensions of this versatile bis-homologation
Synlett 2002, No. 2, 280–284 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Short and Versatile Two-Carbon Ring Expansion Reactions by Thermo-Isomerization
283
(6) For further syntheses of 8a and 8b: (a) See ref.4e
(b) Hinkamp, L.; Schäfer, H. J.; Wippich, B.; Luftmann, H.
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Chim. Acta 1983, 66, 2294.
T., Ed.; Academic Press: New York, 1982, Chap. 12, 433–
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1980, Chap. 14, 155–166.
(14) Syntheses of muscone (7c): (a) For leading references cf.
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May/June 1-4; and references therein. (c) Alexakis, A.;
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(k) Karpf, M.; Dreiding, A. S. Helv. Chim. Acta 1975, 58,
2409.
(15) Syntheses of 3-methylcyclohexadecanone (7d): (a) Weiper-
Idelmann, A.; a. d. Kamen, M.; Schäfer, H. J.; Gockeln, M.
Acta Chem. Scand. 1998, 52, 672. (b) Mash, E. A.; Gregg,
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(16) Syntheses of 3-methylcyclotetradecanone (7b): (a) Yoshii,
E.; Kimoto, S. Chem. Pharm. Bull. 1969, 17, 629. (b) See
ref.14j (c) See ref.14k
(7) Taguchi, H.; Yamamoto, H.; Nozaki, H. Tetrahedron Lett.
1976, 2617.
(8) Selected characteristic spectroscopic data of (a) 3a: 1H
NMR (300 MHz, CDCl3): 5.94 and 5.74 [br s, H2-C(1)], 1.86
[br s, Me-C(2)], 0.87 [t-type m, H3C( )]. 13C NMR (75
MHz, CDCl3): 202.3 [s, C(3)], 144.6 [s, C(2)], 124.1 [t,
C(1)], 17.7 [q, Me-C(2)], 13.5 [q, C( )]. (b) 5a: 1H NMR
(300 MHz, CDCl3): 2.52 [t-type m, 2 H, H2-C(13)], 1.68-
1.63 (m, 2 H), 1.54-1.49 (m, 2 H), 1.33-1.15 (m, 16 H), 1.12
[s, 6 H, Me2-C(2)]. 13C NMR (75 MHz, CDCl3): 216.0 (s),
47.84 (s), 40.83, 35.68, 26.96, 26.69, 26.63, 25.45, 25.26 (7
t), 24.70 (q, 2), 24.56, 24.48, 22.27, 21.86 (4 t).
(9) Casanova, J.; Waegell, B. Bull. Soc. Chim. Fr. 1971, 1289.
(10) For examples of analogous one-carbon insertion reactions
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(b) Johnson, C. R.; Cheer, C. J.; Goldsmith, D. J. J. Org.
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CDCl3): (E)-8a: 6.84 [dq, J = 15.5, 7 Hz, H-C(2)], 6.12 [dq,
J = 15.5, 1.7 Hz, H-C(3)], 1.87 (dd, J = 7, 1.5 Hz). (Z)-8a:
6.19 [m, 2 H, H-C(2,3)], 2.11 (d, J = 7 Hz). 13C NMR (75
MHz, CDCl3): 200.4 [s, C(4)], (E)-8a: 141.9 [d, C(2)], 131.9
[d, C(3)], 18.0 [q, C(1)]. (Z)-8a: 142.2 [d, C(2)], 127.6 [d,
C(3)], 15.9 [q, C(1)].
(19) For a survey: (a) Hesse, M. Ring Enlargement in Organic
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Chem. Soc. 1987, 7797.
E+
+ E+B–
B:–
O
H
H
E
O
E
O
n+1
n
n
– B-H
Scheme 5
(11) Examples for the synthesis of geminal , -dialkylated cyclic
ketones by one-carbon expansion reactions: (a) Krief, A.;
Laboureur, J. L. Tetrahedron Lett. 1987, 28, 1549.
(b) Krief, A.; Laboureur, J. L. J. Chem. Soc., Chem.
Commun. 1986, 702. See also: (c) Hesse, M. Ring
Enlargement in Organic Chemistry; VCH: Weinheim,
Germany, 1991, Chap. 2, 5–37; and references therein.
(12) For surface supported reactions on aluminium oxide see:
Posner, G. H. Angew. Chem.; 1978, 90, 527.
(13) For leading references see: (a) Hesse, M. Ring Enlargement
in Organic Chemistry; VCH: Weinheim, Germany, 1991.
(b) Williams, A. S. Synthesis 1999, 1707. (c) Fráter, G.;
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(d) Fráter, G.; Lamparsky, D. In Perfumes: Art, Science and
Technology; Müller, P. M.; Lamparsky, D., Eds.; Elsevier:
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Düfte; Springer: Berlin, 1990, Chap. 9, 195–219.
(20) (a) Evans, D. A.; Carroll, G. L.; Truesdale, L. K. J. Org.
Chem. 1974, 39, 914. (b) Vincek, W. C.; Aldrich, C. S.;
Borchardt, R. T.; Grunewald, G. L. J. Med. Chem. 1981, 24,
7. (c) Choudary, B. M.; Narender, N.; Bhuma, V. Synth.
Commun. 1995, 25, 2829. (d) Modification of the work-up
procedure: To dissolve all the aminoalcohol during the
washing procedure, the white granular precipitate was
digested in a glass filter with hot t-BuOMe several times and
finally with one portion of hot THF.
(f) Mookherjee, B. D.; Wilson, R. A. In Fragrance
Chemistry: The Science of the Sense of Smell; Theimer, E.
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LETTER
(21) (a) Gabel, G. Bull. Soc. Chim. Fr. 1934, 1006. (b) Kerwin,
J. F.; Ullyot, G. E.; Fuson, R. C.; Zirkle, C. L. J. Am. Chem.
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(e) Reddy, L. R.; Reddy, M. A.; Bhanumathi, N.; Rao, K. R.
Synlett 2000, 339. (f) Tiffeneau, M.; Weill, P.; Tchoubar, B.
C. R. Acad. Sci. 1937, 205, 54. (g) Tchoubar, B. Bull. Soc.
Chim. Fr. 1949, 164. (h) Clark, R. D.; Caroon, J. M.; Repke,
D. B.; Strosberg, A. M.; Bitter, S. M. J. Med. Chem. 1983,
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(22) (a) Corey, E. J.; Chaykovsky, M. J. Am. Chem. Soc. 1965,
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(c) Bouda, H.; Borredon, M. E.; Delmas, M.; Gaset, A.
Synth. Commun. 1987, 17, 503. (d) Blake, A. J.; Danks, J.
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20, 1193; and references therein.
(23) Toda, F.; Kanemoto, K. Heterocycles 1997, 46, 185.
(24) Cyclododecanone (12, 60 g, 0.33 mol) was melted by
keeping it at 65-70 °C, then t-BuOH (15 mL) and trimethyl
sulfoxonium iodide (117 g, 0.52 mol, 1.6 mol equiv.) were
added with stirring. The resulting pulpy suspension was kept
at 70 °C and potassium t-butoxide (56 g, 0.5 mol) were
added in several portions. After an induction period of
several minutes the insoluble precipitates slowly dissolved,
due to the formation of equimolar amounts of DMSO during
the spiroepoxide formation. After stirring for 1.5 h,
powdered KOH (2 g) was added to the mixture. The course
of the reaction was then followed by GC (conversion up to
95%). When further addition of KOH resulted in no
additional epoxide formation, the mixture was allowed to
cool to r.t. and water (100 mL) was added slowly with
stirring. The mixture was diluted with t-BuOMe and then
washed several times with water and brine. The organic
layer was dried on MgSO4 and the solvent removed. After
bulb-to-bulb distillation, oxirane 15 was obtained as a
colorless oil (61 g, containing 5-10% 12) and was used for
the transformation into 14 without further purification.
(25) The mixture of the (E/Z)-isomers 17, and 21, respectively,
was found already earlier to be difficult to separate, cf. ref.14k
For 21 see also: (a) Stoll, M.; Rouvé, A. Helv. Chim. Acta
1947, 30, 2019. (b) Ito, Y.; Saegusa, T. J. Org. Chem. 1977,
42, 2326. (c) Ref.17a (d) Flieri, H. G.; Scholz, D.; Stütz, A.
Monatsh. Chem. 1979, 110, 245. (e) Torii, S.; Inokuchi, T.;
Mizuguchi, K.; Yamazaki, M. J. Org.Chem. 1979, 44, 2303.
(f) See ref.19c (g) Tsuji, J.; Yamada, T.; Kaito, M.; Mandai,
T. Bull. Chem. Soc. Jpn. 1980, 53, 1417. (h) Rautenstrauch,
V.; Snowden, R. L.; Linder, S. M. Helv. Chim. Acta 1990,
73, 896. (i) See ref.14b
(26) (a) Marson, Ch.; Walker, A. J.; Pickering, J.; Hobson, A. D.
J. Org. Chem. 1993, 58, 5944. (b) Adam, W.; Richter, M. J.
Synthesis 1994, 176. (c) Brandsma, L.; Verkruijsse, H.
Preparative Polar Organometallic Chemistry 1; Springer:
Berlin/Heidelberg, 1987, 50–51.
(27) McMurry, J. E.; Miller, D. D. J. Am. Chem. Soc. 1983, 105,
1660.
(28) Satoh, T.; Masayuki, I.; Yamakawa, K. Chem. Lett. 1987,
1949.
(29) (a) Thies, R. W.; Daruwala, K. P. J. Org. Chem. 1987, 52,
3798; and references therein. (b) Wilson, S. R.; Misra, R.
N.; Georgiadis, G. M. J. Org. Chem. 1980, 45, 2460.
Synlett 2002, No. 2, 280–284 ISSN 0936-5214 © Thieme Stuttgart · New York