A short synthesis of α-allenic alcohols from α,β-unsaturated carbonyl compounds with dichloromethyl p-tolyl sulfoxide

Article abstract of DOI:10.1016/j.tetlet.2008.07.093

The reaction of the α-sulfinyl carbanion of dichloromethyl p-tolyl sulfoxide with α,β-unsaturated carbonyl compounds gave 1-chlorocyclopropyl p-tolyl sulfoxides having a carbonyl group in good to high yields. The carbonyl groups in the products were reduced or treated with alkylmetals to give alcohols. Finally, the alcohols were treated with Grignard reagent to give α-allenic alcohols via the rearrangement of the cyclopropylmagnesium carbenoid intermediates, which were generated by the sulfoxide-magnesium exchange reaction, in good to high yields. This procedure provides a new method for a short synthesis of various α-allenic alcohols in two or three steps from relatively easily available α,β-unsaturated carbonyl compounds.

Full text of DOI:10.1016/j.tetlet.2008.07.093

Tetrahedron Letters 49 (2008) 5689–5692
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Tetrahedron Letters
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A short synthesis of a-allenic alcohols from a,b-unsaturated
carbonyl compounds with dichloromethyl p-tolyl sulfoxide
*
Tsuyoshi Satoh , Takafumi Noguchi, Toshifumi Miyagawa
Department of Chemistry, Faculty of Science, Tokyo University of Science, Ichigaya-funagawara-machi 12, Shinjuku-ku, Tokyo 162-0826, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of the
a-sulfinyl carbanion of dichloromethyl p-tolyl sulfoxide with a,b-unsaturated car-
Received 26 June 2008
Revised 15 July 2008
Accepted 17 July 2008
Available online 22 July 2008
bonyl compounds gave 1-chlorocyclopropyl p-tolyl sulfoxides having a carbonyl group in good to high
yields. The carbonyl groups in the products were reduced or treated with alkylmetals to give alcohols.
Finally, the alcohols were treated with Grignard reagent to give a-allenic alcohols via the rearrangement
of the cyclopropylmagnesium carbenoid intermediates, which were generated by the sulfoxide-
magnesium exchange reaction, in good to high yields. This procedure provides a new method for a short
Keywords:
Allene
synthesis of various
a
-allenic alcohols in two or three steps from relatively easily available
a,b-unsatu-
rated carbonyl compounds.
a-Allenic alcohol
Ó 2008 Elsevier Ltd. All rights reserved.
Magnesium carbenoid
Cyclopropylmagnesium carbenoid
Doering–LaFlamme allene synthesis
1. Introduction
describe a short synthesis of various a-allenic alcohols from a,b-
unsaturated carbonyl compounds with dichloromethyl p-tolyl sulf-
Allenes, characterized by a 1,2-diene structure, are quite inter-
esting and important compounds in organic and synthetic organic
chemistry, and a large number of studies have been reported on
their chemistry, synthesis, and synthetic uses.1 Allenes having a
hydroxyl group on the carbon adjacent to the allene system are
oxide in up to three steps (Scheme 1). Thus, conjugate addition of
the
a-carbanion of dichloromethyl p-tolyl sulfoxide with a,b-
unsaturated carbonyl compounds 1 afforded 1-chlorocyclopropyl
p-tolyl sulfoxides having a carbonyl group 2 in high yields.17 The
carbonyl group was reduced or reacted with alkylmetals to give
alcohols, which were treated with Grignard reagent to give cyclo-
propylmagnesium carbenoids. Doering–LaFlamme-type rearrange-
ment18 of the generated cyclopropylmagnesium carbenoids
called
a-allenic alcohols. a-Allenic alcohol moiety is frequently
found in allenic natural products and pharmaceuticals, such as
grasshopper ketone, fucoxanthin, and allenic nucleoside ana-
logues.2 Furthermore,
a
-allenic alcohols are used as versatile
afforded a-allenic alcohols 3 in good to high yields.
intermediates in the synthesis of a variety of 2,5-dihydrofurans,3
1,4-dienes, and cross-conjugated trienes.4
2. Results and discussion
General method for the synthesis of a-allenic alcohols is classi-
fied into two categories as follows. One is the reaction of carbonyl
compounds with propargylic titanium,5 propargylic bromides,6
propargylic acetate,7 or propargylic phosphates.8 The other is the
reactions of propargylic epoxides with several reagents, such as
organo copper,9 Grignard reagents,10 dialkylzinc,11 arylboronic
acids,12 summarium diiodide with ketones,13 and palladium-cata-
lyzed carbonylation.14 Recently, some enantioselective syntheses
Representative example of the presented procedure is described
as follows (Scheme 2).
a,b-Unsaturated ester 4 was treated with
the sodium
a
-carbanion of dichloromethyl p-tolyl sulfoxide17 to
give 1-chlorocyclopropyl p-tolyl sulfoxide 5 having ethoxycarbonyl
group at the 2-position in 84% yield. A solution of cyclopropane 5
in toluene was added to a solution of excess i-PrMgCl in toluene
at 0 °C and after 10 min, the reaction was quenched with satd aq
NH4Cl. At first, we expected that Doering–LaFlamme-type rear-
rangement will occur and allene having an ethoxycarbonyl group
will be the product. Instead of the expected allene, we obtained
desulfinylated product 7 in good yield as the product. Obviously,
the intermediate of this reaction was cyclopropylmagnesium carb-
enoid 6; however, the expected Doering–LaFlamme-type rear-
rangement did not take place at all.
of
a
-allenic alcohols were reported.15
We are also interested in the synthesis of allenes by using our
original chemistry of sulfoxide-metal exchange reaction and some
new synthetic methods were reported.16 In continuation of our
studies for the development of new synthesis of allenes, here, we
* Corresponding author. Tel.: +81 3 5228 8272; fax: +81 3 5261 4631.
E-mail address: tsatoh@rs.kagu.tus.ac.jp (T. Satoh).
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.07.093

5690
T. Satoh et al. / Tetrahedron Letters 49 (2008) 5689–5692
O
O
O
H
R'
R''
R2
R1
HO
R2
R3
R3
Cl
TolSCHCl2
Base
H
R1
R2
R1
1 or 2 steps
H
S(O)Tol
1
3
2
R1 = H, alkyl, aryl R2 = alkyl
R3 = alkyl, aryl, OR
R', R'' = H, alkyl, aryl
Scheme 1.
TolS(O)CHCl2
COOEt
PhCH2CH2 COOEt
PhCH2CH2 COOEt
PhCH2CH2
i
-PrMgCl (5 eq)
NaHMDS (1.2 eq)
H
Cl
H
Cl
Toluene, 0 ˚C, 10 min
H
H
THF, -78 ˚C ~ r.t., 3 h
84%
H
MgCl
H
S(O)Tol
4
6
5
PhCH2CH2 COOEt
H2O
82%
H
Cl
H
H
7
PhCH2CH2 CH2OMgCl
PhCH2CH2 CH2OH
i-PrMgCl (5 eq)
NaBH4 (2.5 eq)
H
Cl
H
Cl
5
Toluene, 0 ˚C, 10 min
THF, MeOH, reflux, 2 h
95%
H
MgCl
H
S(O)Tol
9
8
H2O
77%
H
H
CH2OH
CH2CH2Ph
10
Scheme 2.
Next, the ester moiety was reduced to a hydroxylmethyl group
by treatment with NaBH419 to give alcohol 8 in a quantitative yield.
Alcohol 8 was treated with i-PrMgCl under the same conditions as
described above. Quite interestingly, the treatment gave the de-
13 in a quantitative yield. As the reaction of an ester with excess
Grignard reagent is expected to give a tertiary alcohol, 14 was trea-
ted with ten equivalents of PhMgBr in toluene at 0 °C for 30 min.
sired primary a
-allenic alcohol 10 in 77% yield.20 The intermediate
Table 1
of this reaction was obviously cyclopropylmagnesium carbenoid
having a magnesium alkoxide moiety 9. From this magnesium
carbenoid the expected Doering–LaFlamme-type rearrangement
took place quickly at 0 °C. From these two results described above,
though the real reason is obscure at present, it is anticipated that
the Doering–LaFlamme-type rearrangement is prevented by the
presence of an ethoxycarbonyl group.
Synthesis of
aldehyde 11 with Grignard reagents
a-allenic alcohols 12 from 1-chlorocyclopropyl p-tolyl sulfoxide 5 via
O
O
PhCH2CH2
OEt
PhCH2CH2
H
LDBBA (1.5 eq)
H
Cl
H
H
Cl
THF, 0 °C, 1 h
H
S(O)Tol
S(O)Tol
As we recognized that this is a quite interesting and novel meth-
od for a short synthesis of a-allenic alcohols from a,b-unsaturated
88%
5
11
HO
carbonyl compounds, scope and limitation of this procedure were
investigated. At first, ester 5 was reduced directly to aldehyde 11
with lithium diisobutyl-tert-butoxyaluminum hydride (LDBBA)21
in good yield (Table 1). Aldehyde 11 was treated with excess Grig-
nard reagents (MeMgBr, EtMgBr and PhMgBr) in toluene at 0 °C for
H
RMgX (10 eq)
R
Toluene, 0 °C, 30 min
H
CH2CH2Ph
12
30 min. We obtained the desired secondary a-allenic alcohols 12 in
Entry
RMgX
12
Yield (%)
variable yields directly from aldehyde 11. Reducing the amount of
the Grignard reagent resulted in the lowering of the yields of the
product.
1
2
3
CH3MgBr
CH3CH2MgBr
PhMgBr
12a
12b
12c
52
70
35
Finally, 1-chlorocyclopropyl p-tolyl sulfoxide 14, having a benz-
yloxycarbonyl group, was synthesized from
a,b-unsaturated ester

T. Satoh et al. / Tetrahedron Letters 49 (2008) 5689–5692
5691
Fortunately, both formation of tertiary alcohol and sulfoxide-mag-
nesium exchange reaction took place simultaneously to give the
O
TolS(O)CHCl2
O
H
H3C
H
NaHMDS (1.2 eq)
OBn
Cl
S(O)Tol
H3C
H
desired tertiary
The procedure for the synthesis of
herein was found to be quite effective even when
a
-allenic alcohol 15 in good yield (Scheme 3).
-allenic alcohols presented
,b-unsaturated
OBn
a
THF, -78 ~ 0 °C, 2 h
H
a
99%
ketones were used as the starting materials. For example, 1-chloro-
13
14
cyclopropyl p-tolyl sulfoxide having a benzoyl group 17 was syn-
a
,b-unsaturated ketone 16 in high yield.17 The
Ph
Ph
CH3
thesized from
HO
H
H
PhMgBr (10 eq)
benzoyl group was reduced with NaBH4 to give alcohol 18 in a
quantitative yield. Finally, 18 was treated with excess i-PrMgCl in
Toluene, 0 °C, 30 min
toluene at 0 °C to give the desired secondary
a-allenic alcohol 19 in
67% yield (Scheme 4).
77%
15
Other examples of the synthesis of secondary
a
-allenic alcohols,
starting from the corresponding 1-chlorocyclopropyl p-tolyl
Scheme 3.
sulfoxides 20 via alcohols 21, are summarized in Table 2. 1,1-
Disubstituted
tuted -allenic alcohols (22c, 22d, and 22e) were synthesized from
corresponding 20 in good to high overall yields in two steps. Cyclic
-allenic alcohol 22f was also synthesized from 20f, which was
a-allenic alcohols (22a and 22b) and 1,1,3-trisubsti-
a
O
O
a
H3C
Ph
Cl
S(O)Tol
H3C
synthesized from 2-(3-phenylpropylidene)cyclohexanone in 90%
NaBH4 (3 eq)
Ph
Ph
H
yield,17 in good overall yield (entry 6).
EtOH, 0 °C, 30 min
H
Finally, synthesis of tertiary a-allenic alcohols was investigated
H
H
99%
by combination of ketone 20b with some carbon nucleophiles and
the results are summarized in Table 3. Thus, lithium carbanion of
phenylacetylene was treated with 20b in THF at À78 °C for 1 h.
The lithium acetylide was found to be reactive only with the
carbonyl carbon at À78 °C and the sulfinyl group was found to
be intact with the lithium acetylide to afford the adduct, tertiary
alcohol 23a, in 75% yield. Finally, alcohol 23a was treated with
17
16
HO
HO
H3C
H
H
i
-PrMgCl (5 eq)
Ph
Cl
S(O)Tol
Toluene, 0 °C, 30 min
H
CH3
H
excess of i-PrMgCl to give the desired tertiary
a-allenic alcohol
67%
19
18
24a in 81% yield. Reducing the amount of the Grignard reagent
resulted in incomplete reaction. The procedure with 2-furyllithium
and 2-thienyllithium resulted in the formation of the desired
Diastereomeric ratio
2 : 1
tertiary
a-allenic alcohols 24b and 24c in good overall yields
Scheme 4.
(entries 2 and 3).
Table 2
Synthesis of various
a-allenic alcohols 22 starting from 1-chlorocyclopropyl p-tolyl sulfoxides 20, synthesized from
a, b-unsaturated ketones, through alcohols 21
O
HO
R2
R1
HO
R2
R1
R3
Cl
S(O)Tol
20
R3
Cl
S(O)Tol
21
R3
H
i
-PrMgCl (5 eq)
NaBH4 (3 eq)
R1
R2
EtOH, 0 ˚C, 30 min
Toluene, 0 ˚C, 30 min
H
H
22
Entry
20
21
22
R1
R2
R3
Ph
Yield (%)
Diastereomeric ratio
Yield (%)
1
2
3
4
5
20a
20b
20c
20d
20e
H
H
CH3
Ph
CH2CH2CH3
CH3
CH3
CH3
CH3
21aa
93
80
88
99
99
1:1
4:1
5:1
10:1
22a
22b
79
88
68
72
79
CH2CH2CH2Ph
Ph
CH2CH3
CH2CH3
21ba
21ca
21da
21e
22cb
22db
22eb
CH2CH2Ph
Single isomer
H
CH2CH2Ph
Cl
O
6
20f
21f
96
Single isomer
22fb,c
76
S(O)Tol
a
b
c
A mixture of two diastereomers was used in the next reaction.
A single isomer was obtained.
The structure of 22f is shown in the below.
OH
H
CH2CH2Ph
22f

5692
T. Satoh et al. / Tetrahedron Letters 49 (2008) 5689–5692
3. (a) Aurrecoechea, J. M.; Solay, M. Tetrahedron 1998, 54, 3851; (b) Ma, S.; Gao, W.
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2001, 3, 2537; (d) Krause, N.; Hoffmann-Roder, A.; Canisius, J. Synthesis 2002,
1759.
Synthesis of tertiay
a-allenic alcohols 24 from 1-chlorocyclopropyl p-tolyl sulfoxide
20b through the adduct with alkynyllithium, furyllithium, and thienyllithium (23)
O
4. Shimp, H. L.; Hare, A.; McLaughlin, M.; Micalizio, G. C. Tetrahedron 2008, 64,
3437.
5. Furuta, K.; Ishiguro, M.; Haruta, R.; Ikeda, N.; Yamamoto, H. Bull. Chem. Soc. Jpn.
1984, 57, 2768.
6. (a) Iyoda, M.; Kano, Y.; Nishizaki, M.; Oda, M. Bull. Chem. Soc. Jpn. 1989, 62,
3380; (b) Yi, X.-H.; Meng, Y.; Hua, X.-G.; Li, C.-J. J. Org. Chem. 1998, 63, 7472.
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2387.
10. Kar, A.; Argade, N. P. Synthesis 2005, 2995.
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Tetrahedron Lett. 1999, 40, 4893.
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2007, 46, 7101.
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15. (a) Corey, E. J.; Yu, C.-M. ; Lee, D.-H. J. Am. Chem. Soc. 1990, 112, 878; (b)
Iseki, K.; Kuroki, Y.; Kobayashi, Y. Tetrahedron: Asymmetry 1998, 9, 2889; (c) Yu,
C.-M.; Yoon, S.-Y.; Baek, K.; Lee, J.-Y. Angew. Chem., Int. Ed 1998, 37, 2392; (d)
Nakajima, M.; Saito, M.; Hashimoto, S. Tetrahedron: Asymmetry 2002, 13, 2449;
(e) Otte, R.; Wibbeling, B.; Frohlich, R.; Nakamura, S.; Shibata, N.; Toru, T.;
Hoppe, D. Tetrahedron Lett. 2007, 48, 8636.
16. (a) Satoh, T.; Itoh, N.; Watanabe, S.; Koike, H.; Matsuno, H.; Matsuda, K.;
Yamakawa, K. Tetrahedron 1995, 51, 9327; (b) Satoh, T.; Kuramochi, Y.; Inoue,
Y. Tetrahedron Lett. 1999, 40, 8815; (c) Satoh, T.; Sakamoto, T.; Watanabe, M.
Tetrahedron Lett. 2000, 43, 2043; (d) Satoh, T.; Kurihara, T.; Fujita, K.
Tetrahedron 2001, 57, 5369; (e) Satoh, T.; Hanaki, N.; Kuramochi, Y.; Inoue,
Y.; Hosoya, K.; Sakai, K. Tetrahedron 2002, 58, 2533; (f) Satoh, T.; Sakamoto, T.;
Watanabe, M.; Takano, K. Chem. Pharm. Bull. 2003, 51, 966; (g) Satoh, T.; Gouda,
Y. Tetrahedron Lett. 2006, 47, 2835.
HO
H3C
R
R1
R1Li
H3C
H
R
Cl
H
Cl
THF, -78 °C, 1 h
H
S(O)Tol
H
S(O)Tol
20b
23 (single isomer)
R = CH2CH2CH2Ph
R
HO
i-PrMgCl (10 eq)
H
H
R1
CH3
Toluene, 0 °C, 30 min
24
Entry
R1Li
23
Yield (%)
24
Yield (%)
1
2
23a
23b
75
24a
81
73
(2 eq)
(3 eq)
Ph
Li
O
67a
24b
24c
Li
Li
S
3
23c
82
65b
(3 eq)
a
Starting material 20b was recovered in 12%.
The reaction mixture was stirred at 0 °C for overnight. Starting material 23c was
b
recovered in 7%.
17. Miyagawa, T.; Tatenuma, T.; Tadokoro, M.; Satoh, T. Tetrahedron 2008, 64,
5279.
18. (a) Doering, W. von E. ; LaFlamme, P. M. Tetrahedron 1958, 2, 75; (b) Li, J. J.
Name Reactions; Springer: Berlin, 2002; (c) Hassner, A.; Stumer, C. Organic
Synthesis Based on Name Reactions; Pergamon: Amsterdam, 2002.
19. Soai, K.; Oyamada, H.; Takase, M.; Ookawa, A. Bull. Chem. Soc. Jpn. 1984, 57,
1948.
In conclusion, a procedure for the short synthesis of
a-allenic
alcohols from
a,b-unsaturated carbonyl compounds with dichlo-
romethyl p-tolyl sulfoxide in up to three steps via the rearrange-
ment of cyclopropylmagnesium carbenoids as the key reaction
was established. Various kinds of primary, secondary, and tertiary
-allenic alcohols can be synthesized from a,b-unsaturated car-
bonyl compounds with reducing agents and carbon nucleophiles.
The results presented herein will contribute greatly to the synthe-
sis of a-allenic alcohols.
20. The experimental procedure for the synthesis of
a-allenic alcohol 10 is as
follows. To a solution of 2-(2-phenylethyl)acrylic acid ethyl ester 4 (245 mg;
1.2 mmol) and dichloromethyl p-tolyl sulfoxide (223 mg; 1.0 mmol) in 10 mL
of dry THF at À78 °C was added a solution of sodium hexamethyldisilazide
(1.9 M solution in THF, 0.63 mL; 1.2 mmol) dropwise with stirring.
Temperature of the reaction mixture was slowly allowed to rise to room
temperature for 3 h. The reaction was quenched by satd aq NH4Cl and the
whole was extracted with CHCl3. The product was purified by silica gel column
chromatography to give 5 (328 mg; 84%) as a colorless oil. IR (neat) 2998,
a
1727(CO), 1495, 1454, 1266, 1136, 1091, 1062, 811 cmÀ1 1H NMR d 1.30 (1H,
,
d, J = 7.4 Hz), 1.36 (3H, s), 1.99 (1H, dt, J = 14.0, 8.5 Hz), 2.32–2.42 (1H, m), 2.41
(3H, s), 2.58 (1H, d, J = 7.5 Hz), 2.73 (2H, d, J = 8.0 Hz), 4.28 (2H, q, J = 7.1 Hz),
7.14–7.21 (3H, m), 7.32 (2H, d, J = 8.1 Hz), 7.59 (2H, d, J = 8.1 Hz).
Acknowledgment
This work was supported by a Grant-in-Aid for Scientific
Research No. 19590018 from the Ministry of Education, Culture,
Sports, Science and Technology, Japan, which is gratefully
acknowledged.
To a solution of ester 5 (78 mg; 0.2 mmol) in 2 mL of THF was added NaBH4
(19 mg; 0.5 mmol) at room temperature. The suspension was stirred and
heated under reflux for 5 min. To the suspension was added MeOH (0.2 mL)
dropwise with stirring and the reaction mixture was refluxed for 2 h. The
reaction was quenched by adding satd aq NH4Cl and the whole was extracted
with CHCl3. The product was purified by silica gel column chromatography to
give 8 (66 mg; 95%) as colorless crystals. IR (KBr) 3325 (OH), 2901, 1499, 1438,
1074, 1030, 812 cmÀ1 1H NMR d 1.21 (1H, d, J = 7.7 Hz), 1.48 (3H, s), 1.95 (1H,
;
References and notes
d, J = 7.2 Hz), 2.42 (3H, s), 3.13 (1H, br s), 3.82 (1H, dd, J = 12.0, 5.8 Hz), 4.06
(1H, dd, J = 12.0, 3.8 Hz), 7.32 (2H, q, J = 7.7 Hz), 7.68 (2H, d, J = 8.8 Hz).
To a solution of 8 (34.9 mg; 0.1 mmol) in 2 mL of dry toluene at 0 °C was added
i-PrMgCl (2.0 M solution in Et2O, 0.25 mL; 0.5 mmol) dropwise with stirring.
After 10 min, the reaction was quenched by satd aq NH4Cl and the whole was
extracted with CHCl3. The product was purified by silica gel column
chromatography to give 2-(2-phenylethyl)buta-2,3-dien-1-ol 10 (13.4 mg;
77%) as a colorless oil. IR (neat) 3364 (OH), 2923, 1957 (allene), 1496, 1454,
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and 2; Patai, S., Ed.; John Wiley and Sons: Chichester, 1980; (b) Brandsma, L.;
Verkruijsse, H. D. Synthesis of Acetylenes, Allenes and Cumulenes, A Laboratory
Manual; Elsevier: Amsterdam, 1981; (c) Schuster, H. F.; Coppola, G. M. Allenes in
Organic Synthesis; John Wiley and Sons: New York, 1984; (d) Pasto, D. J.
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105, 2829; (j) Ma, S. Aldrichim. Acta 2007, 40, 91; (k) Brummond, K. M.;
DeForrest, J. E. Synthesis 2007, 795.
1015, 850, 741, 698 cmÀ1 1H NMR d 1.50 (1H, s), 2.27–2.35 (2H, m), 2.75–2.80
;
(2H, m), 4.06 (2H, s), 4.89 (2H, quintet, J = 3.2 Hz), 7.15–7.21 (3H, m), 7.25–7.31
(2H, m). MS (FAB) m/z (%) 197 ([M+Na]+, 35), 157 (51), 129 (38), 115 (100), 91
(89), 23 (82). Calcd for C12H14ONa: M, 197.0942. Found: m/z 197.0946.
21. Kim, M. S.; Choi, Y. M.; An, D. K. Tetrahedron Lett. 2007, 48, 5061.
2. Hoffmann-Roder, A.; Krause, N. Angew. Chem., Int. Ed 2004, 43, 1196.