Aluminum carbenoids in allene cyclopropanation

Article abstract of DOI:10.1016/j.tetlet.2010.09.093

The reactions of aluminum carbenoids with alkyl- and phenyl-substituted allenes and cyclic allenes are studied. An efficient method for the synthesis of substituted spiropentanes was developed. 1,2-Cyclononadiene was selectively converted into bicyclo[7.1.0]dec-1-ene. An unusual transformation of α-methylphenylallene into a spiroindane derivative under the action of Et₃Al-CH₂I₂ was found.

Full text of DOI:10.1016/j.tetlet.2010.09.093

Tetrahedron Letters 51 (2010) 6268–6269
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Tetrahedron Letters
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Aluminum carbenoids in allene cyclopropanation
Ilfir R. Ramazanov a, , Alsu V. Yaroslavova a, Usein M. Dzhemilev a, Oleg M. Nefedov b
⇑
a Institute of Petrochemistry and Catalysis of Russian Academy of Sciences, 141 Prospekt Oktyabrya, Ufa 450075, Russian Federation
b N. D. Zelinskii Institute of Organic Chemistry of Russian Academy of Sciences, 47 Lenin prosp., Moscow 117913, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 July 2010
Revised 25 August 2010
Accepted 20 September 2010
Available online 25 September 2010
The reactions of aluminum carbenoids with alkyl- and phenyl-substituted allenes and cyclic allenes are
studied. An efficient method for the synthesis of substituted spiropentanes was developed. 1,2-Cyclono-
nadiene was selectively converted into bicyclo[7.1.0]dec-1-ene. An unusual transformation of
ylphenylallene into a spiroindane derivative under the action of Et3Al–CH2I2 was found.
a-meth-
Ó 2010 Elsevier Ltd. All rights reserved.
Earlier, we reported that alkynes react with CH2I2 and trialkyl-
aluminums (Me3Al, Et3Al, and i-Bu3Al) to give substituted cyclo-
propanes.1 It was found that the structures of the products and
the mechanism of their formation depended strongly on the nature
of the multiple bonds. In the case of alkenes, the reaction proceeds
as a one-stage methylene transfer process to afford the product of
cyclopropanation.2 Contrary to this, the reaction of alkynes with
CH2I2–R3Al (R = Me, Et and i-Bu) proceeds via a sequence of rear-
rangements. According to the scheme proposed for the reaction,
carboalumination of the triple bond by aluminum carbenoids oc-
curs in the first stage. Thus, alkenes and alkynes show a curious
difference in behavior toward aluminum carbenoids. This
prompted us to investigate the reaction of aluminum carbenoids
with allenes which contain both sp2- and sp-hybridized carbon
atoms. In order to develop a general method for the selective prep-
aration of alkylidenecyclopropanes and spiropentanes, the influ-
ence of the nature of the substituent on the allene moiety, the
degree of substitution, and the structure of allene have been stud-
ied. It should be noted that in the literature there is a single exam-
ple of the exhaustive cyclopropanation of 3,4-pentadien-1-ol using
Me3Al–CH2I2.3
CH2I2 (3 eq)
Et3Al (3 eq)
H
R
H
1a R= n-Hex (82%)
1b R= PhCH2 (85%)
1c R= Ph (73%)
CH2Cl2, rt, 8 h
R
1a-c
CH2I2 (1 eq)
Et3Al (1 eq)
CH2I2 (3 eq)
Et3Al (3 eq)
C
CH2Cl2, rt, 12 h
CH2Cl2, rt, 8 h
( )n
( )n
( )n
3a 95% (n=1)
3b 92% (n=4)
2a 88% (n=1)
CH2I2 (3 eq)
Et3Al (3 eq)
83%
CH2Cl2, rt, 8 h
Me
Me
4
Scheme 1. Cyclopropanation of allenes.
It was found that the monosubstituted allenes (n-hexylallene,
benzylallene, and phenylallene) reacted with CH2I2 and Et3Al (in
a molar ratio of 1:3:3) in CH2Cl2 at room temperature for eight
hours to give the substituted spiropentanes 1a–c in high yields
(GC) (Scheme 1).4 When using one equivalent of CH2I2 and Et3Al,
(bicyclo[7.1.0]dec-1-ene) (2a) was obtained in high yield when
using an equimolar ratio of reagents, apparently due to steric hin-
drance of the second cyclopropanation. The reaction with three
equivalents of CH2I2 and Et3Al gave tricyclo[8.1.0.01,3]undecane
(3a) with the R R configuration at the chiral centers. Due to molec-
ular symmetry, the two cyclopropyl methylene groups are magnet-
ically equivalent. The cyclopropanation of 1,2-cyclotridecadiene
using equimolar amounts of CH2I2 and Et3Al lacked selectivity with
the preferential formation of the exhaustive cyclopropanation prod-
uct 3b.
6
* *
a
mixture of mono- and bis-cyclopropanation products was
formed. The yield of 1a did not change significantly when i-Bu3Al
was used instead of Et3Al. In contrast to this, the reaction was slug-
gish with Me3Al–CH2I2. The structures of spiropentanes 1a–c were
established by 1D and 2D NMR spectroscopy.5
The cyclopropanation of cyclic allenes (1,2-cyclononadiene, 1,2-
cyclotridecadiene) proceeded in the same way (Scheme 2). In the
case of 1,2-cyclononadiene, the product of mono-cyclopropanation
The reaction of a-methylphenylallene with three equivalents of
CH2I2 and Et3Al in CH2Cl2 at room temperature for eight hours gave
10-methylspiro(cyclopropane-1,20-indane) (4) in 83% yield.7 Deu-
terolysis of the reaction mixture did not result in the formation
of a deutero-substituted compound.
⇑
Corresponding author. Tel./fax: +7 347 284 2750.
E-mail address: iramazan@inbox.ru (I.R. Ramazanov).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.09.093

I. R. Ramazanov et al. / Tetrahedron Letters 51 (2010) 6268–6269
6269
CH2I2 + Et3Al
Et2AlCH2I + Et2AlI
Et2AlCH2I
Me
HI
Et2AlCH2I
-Et2AlI
C
I
Me
Et2Al
Me
Et2Al
Me
Me
I
Et2AlCH2I
Et2Al
Me
Scheme 2. The reaction of a-methylphenylallene with CH2I2–Et3Al.
3. Russo, J. M.; Price, W. A. J. Org. Chem. 1993, 58, 3589.
4. Synthesis of 1-hexylspiro[2.2]pentane (1a): To solution of n-hexylallene
Scheme 2 shows two possible routes for the formation of com-
pound 4. Investigation of the mechanism of this unusual transfor-
mation and its scope is the subject of further research.
a
(3 mmol) and diiodomethane (0.73 mL, 9 mmol) in CH2Cl2 (15 mL), Et3Al
(9 mmol) (Caution: organoaluminums are pyrophoric and can ignite on contact
with air, water, or any oxidant) was added at 0 °C under an argon atmosphere.
The mixture was stirred at room temperature for 8 h. The reaction was
terminated by dilution with CH2Cl2 (10 mL) followed by treatment with an aq
solution of HCl (7 wt %). The aqueous layer was extracted with CH2Cl2
(3 ꢀ 10 mL). The combined organic layers were then washed with satd
NaHCO3 and dried over anhydrous CaCl2. The solvent was removed under
reduced pressure and the residue was distilled to give 0.34 g (74% isolated
yield) of 1a. Bp 87–90 °C (15 Torr).
Earlier, Me3Al–CH2I2 was preferably used for the cyclopropana-
tion of 3,4-pentadien-1-ol.3 It was noted that the use of Et3Al and
i-Bu3Al instead of Me3Al led to the rapid decomposition of alumi-
num carbenoids formed in situ. Contrary to this, in the case of
alkyl- and phenyl-substituted and cyclic allenes, we obtained
cyclopropanation products in high yield using only CH2I2–Et3Al
and CH2I2–i-Bu3Al, whereas the reaction with CH2I2–Me3Al was
slow. We observed the same difference between trialkylalumi-
nums earlier in the reactions with propargyl alcohols.1b The low
activity of Me3Al may be the result of its greater tendency to form
stable complexes.8 In addition, the importance of the procedure
should be emphasized.9
5. 1H and 13C NMR spectra were recorded as CDCl3 solutions on a Bruker Avance
400 (400.13 MHz for 1H and 100.62 MHz for 13C) spectrometer.
6. 1H NMR spectral parameters of compounds 2a were identical to published
data.11a 13C NMR of 3a (d, ppm): 12.45 (2C, C(2, 11)), 19.36 (2C, C(3, 10)), 19.75
(C(1)), 25.10 (2C, C(6, 7)), 27.33 (2C, C(5, 8)), 29.21 (2C, C(4, 9)). 1H NMR of 3a
(d, ppm): 0.45–0.5 (m, 2H, C(2, 11)Ha), 0.7–0.8 (m, 2H, C(2, 11)Hb), 1.15–1.3 (m,
4H, C(4, 9)Ha, C(3, 10)H), 1.3–1.45 (m, 4H, C(5–8)Ha), 1.45–1.7 (m, 4H, C(5–
8)Hb), 2.15–2.25 (m, 2H, C(4–9)Hb).
4
5
Despite the fact that the cyclopropanation of allenes with metal
carbenoids and CH2N2 is a well known method to prepare spir-
opentanes and methylenecyclopropanes, we have revealed herein
some features of the reactions of aluminum carbenoids with alkyl-
and aryl-substituted allenes and cyclic allenes. Unlike zinc carbe-
noids,10 aluminum carbenoids reacted not only with alkyl-substi-
tuted allenes, but also with phenylallene. It should be noted that
the reaction of phenylallene with CH2N2/Pd(acac)2 gave only the
mono-cyclopropanation product, benzylidenecyclopropane, in
49% yield.11a Interestingly, according to the published data,11a,b
1,2-cyclononadiene reacted with CH2N2 in the presence of a palla-
dium catalyst with the formation of 2a in 85% yield. Further reac-
tion of the latter with CH2N2 gave 3a in only 15% yield.
3
2
6
1
7
11
10
8
9
7. The 1H NMR spectrum of 4 in CDCl3 solution shows four multiplets for the
cyclopropyl hydrogen atoms at 0.4–0.8 ppm. The doublet signal of the methyl
group has a cross-peak with the quartet for the hydrogen atom at C(1) in the
COSY spectrum. The quaternary carbon atoms of the benzene moiety are
magnetically non-equivalent due to the lack of symmetry in the molecule. The
HMBC spectrum shows the interaction between the carbon atom at
148.92 ppm and the doublet assigned to the methyl group. 13C NMR (d,
ppm): 8.75 (C(11)), 12.52 (C(12)), 16.82 (C(10)), 26.92 (C(2)), 41.70 (C(3)),
44.45 (C(1)), 123.40 and 124.15 (C(5, 8)), 126.20 (2C, C(6, 7)), 142.42 (C(4)),
148.92 (C(9)). 1H NMR (d, ppm): 0.4–0.5 (m, 1H, C(11)Ha), 0.55–0.6 (m, 1H,
C(12)Ha), 0.6–0.7 (m, 1H, C(12)Hb), 0.75–0.8 (m, 1H, C(11)Hb), 1.12 (d, 3H,
J = 6.8 Hz, C(10)H3), 2.85–3.05 (m, 3H, C(1)H, C(3)H2), 7.1–7.35 (m, 4H, Ar). MS
(m/z, %): 158 (5) [M]+, 143 (5) [MꢁCH3]+, 141 (6), 131 (13), 130 (100), 129 (40),
128 (27), 115 (40). Anal. Calcd for C12H14: C, 91.08; H, 8.92. Found: C, 90.7; H,
8.6.
Thus, compared to other cyclopropanation agents, aluminum
carbenoids show useful activity toward allenes.
5
3
Acknowledgments
12
4
6
2
7
1
11
9
This work was supported by the Department of Chemistry and
Material Sciences of the Russian Academy of Sciences (program No.
1-OKhNM) and Russian Federation President’s Council on Grants
(grant NSc 4105.2010.3).
8
10
8. Smith, M. B. J. Organomet. Chem. 1972, 46, 31.
9. Slow addition of R3Al to a solution of CH2I2 may lead to the formation of
compounds such as RAl(CH2I)2 and Al(CH2I)3 which are more electrophilic and
are stronger Lewis acids and which may contribute to oligomerization of the
allene. This is especially true for Et3Al and i-Bu3Al, which react with CH2I2 at a
far greater rate than Me3Al. Treatment of CH2I2 with Et3Al or i-Bu3Al (1:1 molar
ratio) in CH2Cl2 at room temperature resulted in the disappearance of CH2I2 in
5 min due to aluminum carbenoid formation. In the case of Me3Al, the
conversion of CH2I2 was 73% over 2 h.
10. (a) Battioni, P.; Vo-Quang, L.; Vo-Quang, Y. Bull. Soc. Chim. Fr. 1970, 3942; (b)
Rahman, W.; Kuivila, H. G. J. Org. Chem. 1966, 31, 772.
11. (a) Zefirov, N. S.; Lukin, K. A.; Timofeeva, A. Yu. J. Org. Chem. USSR 1987, 23,
2246; (b) Zimmer, R.; Dinesh, C. U.; Nandanan, E.; Khan, F. A. Chem. Rev. 2000,
100, 3067.
References and notes
1. (a) Ramazanov, I. R.; Dil’mukhametova, L. K.; Khalilov, L. M.; Dzhemilev, U. M.;
Nefedov, O. M. Tetrahedron Lett. 2008, 49, 6058; (b) Ramazanov, I. R.;
Yumagulova, A. V.; Dzhemilev, U. M.; Nefedov, O. M. Tetrahedron Lett. 2009,
50, 4233; (c) Ramazanov, I. R.; Dil’mukhametova, L. K.; Dzhemilev, U. M.;
Nefedov, O. M. Russ. Chem. Bull., Int. Ed. 2009, 58, 1349; (d) Ramazanov, I. R.;
Dil’mukhametova, L. K.; Dzhemilev, U. M.; Nefedov, O. M. J. Organomet. Chem.
2010, 695, 1761.
2. (a) Li, Z.-H.; Ke, Z.; Zhao, C.; Geng, Z.-Y.; Wang, Y.-C.; Phillips, D. L.
Organometallics 2006, 25, 3735; (b) Maruoka, K.; Fukutani, Y.; Yamamoto, H.
J. Org. Chem. 1985, 50, 4412.