C-C bond activation by octacarbonyldicobalt: [3+1] Cocyclizations of methylenecyclopropanes with carbon monoxide

Article abstract of DOI:10.1002/anie.200502596

(Chemical Equation Presented) Activation of C-C bonds in cyclopropanes with a cobalt complex: Methylenecyclopropanes react with one equivalent of [Co ₂(CO)₈] under mild conditions to give 2- methylenecyclobutanones in moderate to goo

Full text of DOI:10.1002/anie.200502596

Angewandte
Chemie
À
C C Activation
DOI: 10.1002/anie.200502596
À
C C Bond Activation by Octacarbonyldicobalt:
[3+1] Cocyclizations of Methylenecyclopropanes
with Carbon Monoxide**
Takuya Kurahashi and Armin de Meijere*
The activation of carbon–carbon s bonds under the influence
of transition metals remains a fundamental challenge in
organometallic chemistry.[1] Methylenecyclopropane and its
derivatives were among the first substrates for which involve-
À
ment of C C single bonds in transition-metal-catalyzed
cycloaddition reactions was observed.[2] In particular, the
cycloadditions of methylenecyclopropanes as a C3 component
À
across C C multiple bonds have been thoroughly investi-
gated.[3] Surprisingly, only a limited number of transition
metals such as Ni, Pd, and Pt have been explored. In recent
years, cobalt complexes have been demonstrated to facilitate
new types of C H and C C bond activation.[4,5] Alper et al. as
well as other groups have shown that cobalt-catalyzed
carbonylative ring expansions of epoxides and aziridines are
useful and efficient procedures for the synthesis of b-lactones
and b-lactams, respectively.[6]
À
À
In connection with our recently reported cobalt-catalyzed
[5+1] cocyclization of vinylcyclopropanes with carbon mon-
oxide leading to cyclohexenones, we found carbonylcobalt
complexes to show the highest activity among the transition-
metal complexes examined.[7] In view of the observed unique
reactivity of the octacarbonyldicobalt complex, we have set
out to further explore carbonylative ring-expansion reactions,
and here we report a novel [3+1] cocyclization of methyl-
enecyclopropanes with carbon monoxide under cobalt catal-
ysis.
Initially, heptylidenecyclopropane (1a) was treated with
one equivalent of octacarbonyldicobalt in THF at 508C for
12h, and this led to a mixture of (2 E)- and (2Z)-2-
heptylidenecyclobutanone (2a) in 85% yield (Table 1).[8] In
other solvents such as toluene, dichloroethane, hexane, and
acetonitrile the yields were lower. Among the carbonylmetal
complexes examined, octacarbonyldicobalt gave the best
[*] Dr. T. Kurahashi, Prof. Dr. A. de Meijere
Institut für Organische und Biomolekulare Chemie
Georg-August-Universität Göttingen
Tammannstrasse 2, 37077 Göttingen (Germany)
Fax: (+49)551-399-475
E-mail: armin.demeijere@chemie.uni-goettingen.de
[**] Cyclopropyl Building Blocks for Organic Synthesis, Part 121. This
work was supported by the State of Lower Saxony and the Fonds der
Chemischen Industrie. T.K. is indebted to the Alexander von
Humboldt Foundation for a research fellowship. The authors are
grateful to Dr. Burkhard Knieriem, Göttingen, for his careful
proofreading of the final manuscript. For Part 120 see: T. Kurahashi,
A. de Meijere, Synlett 2005, 2619–2622. Part 119: S. Dalai, M.
Limbach, L. Zhao, M. Tamm, M. Sevvana, A. de Meijere, Synthesis
2005, in press.
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Table 1: [Co2(CO)8]-mediated and -catalyzed [3+1] cocyclization of 1’-substituted methylenecyclopro-
panes with carbon monoxide.[8]
[Co2(CO)8] even at 258C, yet no
low-molecular-weight
could be isolated.
products
Methylenecyclopropanes 3 with
substituents at the 2- and 3-posi-
tions were also tested (Table 2).
Indeed, 2-hexyl- (3 f) and 2-phenyl-
Substrate
R1
R2
T [8C]
t [h]
Prod.
Yield [%]
E/Z[a]
1a
1a
1b
1b
1c
1d
1d
n-C6H13
n-C6H13
Ph
H
H
H
H
50
60
100
60
50
M
12
12
12
12
24
e
2a
2a
2b
2b
2c
25d0
26d0
85
88[b]
80
73:27
71:29
98:2
methylenecyclopropane
(3g)
reacted with [Co2(CO)8] to give
the corresponding 3- and 4-substi-
tuted 2-methylenecyclobutanones
4 f/5 f and 4g/5g in 84 and 71%
yield, respectively. In both cases, the
regioisomer of type 4 predominated
by a factor of about four. 2-Methyl-
2-phenyl- (3h) and (2,2,3,3-tetrame-
thyl)methylenecyclopropane (3i)
also readily reacted to furnish the
di- and tetrasubstituted 2-methyle-
necyclobutanones in good yields.
À
Ph
<1[b]
5
-(CH2)5-
M
M
e
e
2427
M
e
4815[b]
1e
H
50
24
2e
53
98:2
[a] The diastereomer ratio was determined by integration of corresponding 1H NMR signals for the
crude product. [b] Reaction carried out with a catalytic amount (5 mol%) of [Co2(CO)8] under an
atmosphere of CO (balloon).
yield of this product. With [Cr(CO)6], [Mo(CO)6], [W(CO)6],
and [Fe(CO)5] the yields were very low (5, 8,
< 1, and < 1%, respectively). The reactivity of methylenecy-
clopropanes with an electron-withdrawing group in the 1’
position was lower, and the reaction of [Co2(CO)8] with
(phenylmethylene)cyclopropane (1b) at 508C gave only a
trace amount of the corresponding benzylidenecyclobuta-
none 2b. However, at elevated temperature (1008C) 1b
furnished the product 2b in 80% yield with a diastereomeric
excess of 96%. More electron-deficient methylenecyclopro-
panes such as (bromomethylene)cyclopropane and tert-butyl
methylenecyclopropane-1’-carboxylate did not react with
[Co2(CO)8] even at 1008C. Sterically encumbered 1’,1’-
disubstituted methylenecyclopropanes such as 1c and 1d
reacted sluggishly to give 2c and 2d in 5 and 27% yield,
respectively. With the alkenyl-substituted methylenecyclo-
propane 1e, [Co2(CO)8] reacted at the methylenecyclopro-
pane moiety selectively to give the corresponding cyclo-
butanone 2e in moderate yield. Unsubstituted methylenecy-
clopropane and bicyclopropylidene also reacted with
The reaction tolerates ester functionalities and other C C
double bonds as exemplified by the successful transforma-
tions of 3j and 3k to 4j/5j and 4k/5k, respectively. Even the
unprotected 4-(hydroxymethyl)methylenespiropentane (3l)
reacted with [Co2(CO)8] to give the regioisomeric
methylenespiro[2.3]hexanones 4l and 5l in a ratio of 86:14
in 66% yield (Scheme 1).
These transformations of methylenecyclopropanes to 2-
methylenecyclobutanones, which are essentially insertions of
carbon monoxide into the proximal C C single bonds of the
À
methylenecyclopropanes 1 and 3, also proceed in the presence
of only 5 mol% of [Co2(CO)8]
[9]
under an atmosphere of
Scheme 1. [Co2(CO)8]-mediated and -catalyzed [3+1] cocyclization of 3l
and carbon monoxide.
Table 2: [Co2(CO)8]-mediated and -catalyzed [3+1] cocyclization of 2- and 2,3-substituted methylenecyclopropanes and carbon monoxide.
Substrate
R3
R4
R5
R6
T [8C]
t [h]
Prod.
Yield [%]
4/5[a]
3 f
3 f
3g
3g
3h
3i
n-C6H13
n-C6H13
Ph
Ph
Ph
M
M
AcOCH2
H
H
H
H
H
H
H
H
H
H
H
H
H
H
50
60
RT
40
50
12
12
12
12
12
M
4 f + 5 f
4 f + 5 f
4g + 5g
4g + 5g
4h + 5h
84
81:19
85:15
83:17
82:18
89:11
90[b]
71
62[b]
67
81 12
75[b] 24
62
Me
e
e
M
M
e
e
M
M
e
e
e4i
e4i
4j + 5j
50
60
3i
3j
M
12
H
H
H
H
H
H
50
50
78:22
95:5
3k
24
4k + 5k
58
[a] The ratio of regioisomers 4:5 was determined by integration of corresponding 1H NMR signals for the crude product. [b] Reaction carried out with a
catalytic amount (5 mol%) of [Co2(CO)8] under an atmosphere of CO (balloon).
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À
carbon monoxide (provided by a balloon). For example, 1a
thus reacted at 608C to furnish 2a in 88% yield.[8] 1’-
Phenylmethylenecyclopropane (1b) did not yield the cyclo-
butanone 2b at 608C under these conditions. Even at elevated
temperature (1008C in dioxane) only a trace amount of the
product 2b was identified. The 1’,1’-disubstituted methylene-
cyclopropane 1d reacted sluggishly to give 2d in 15% yield.
But 2-substituted and 2,3-oligosubstituted methylenecyclo-
propanes such as 3 f and 3g did give the corresponding
products 4 f/5 f and 4g/5g, respectively, in good yields. Even
the tetrasubstituted methylenecyclopropane 3i readily pro-
vided the product 4i in 75% yield.
Mechanistically, this formation of cyclobutanones 2 from
methylenecyclopropane 1 is initiated by exchange of one or
two CO ligands of the [Co2(CO)8] complex with a methyl-
enecyclopropane ligand. The resulting alkene complex,
resembling a cobaltaspiropentane 8B,[10] can either undergo
migratory CO insertion to give the cobaltaspiro[2.3]hexanone
7 or a (cyclopropylmethyl)metal-to-homoallylmetal rear-
rangement[11] to yield an alkylidenecobaltacyclobutane 9.
Keywords: C C activation · carbon monoxide · cycloaddition ·
transition metals
.
[1] For reviews see: a) C.-H. Jun, Chem. Soc. Rev. 2004, 33, 610 –
618; b) M. E. van der Boom, D. Milstein, Chem. Rev. 2003, 103,
1759 – 1792; c) M. Murakami, Y. Ito in Topic in Organometallic
Chemistry, Vol. 3 (Ed.: S. Murai), Springer, Berlin, 1999, pp. 97 –
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[2] a) R. Noyori, Y. Kumagai, I. Umeda, H. Takaya, J. Am. Chem.
Soc. 1972, 94, 4018 – 4020; b) P. Binger, M. J. Doyle, R. Benn,
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[3] For reviews see: a) A. Brandi, S. Cicchi, F. M. Cordero, A. Goti,
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Klute, W. Tam, Chem. Rev. 1996, 96, 49 – 92; d) ”Carbocyclic
Three-Membered Ring Compounds” in Methods of Organic
Chemistry (Houben-Weyl), Vol. E17 (Ed.: A. de Meijere),
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pp. 77 – 151.
[4] For reviews concerning cobalt complexes in organic synthesis
see: M. E. Welker, Current Org. Chem. 2001, 5, 785 – 807, and
references therein.
Subsequent
(cyclopropylmethyl)metal-to-homoallylmetal
rearrangement[10] of 7 or migratory CO insertion in 9 leads
to an alkylidenecobaltacyclopentanone 6, which undergoes
reductive elimination to give the alkylidenecyclobutanone 2
(Scheme 2).
[5] a) D. T. Shay, G. P. A. Yap, L. N. Zakharov, A. L. Rheingold,
K. H. Theopold, Angew. Chem. 2005, 117, 1532– 1534; Angew.
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danli, R. Beck, D. Leukel, U. Flörke, Angew. Chem. 2005, 117,
997 – 999; Angew. Chem. Int. Ed. 2005, 44, 975 – 977; c) T. L.
Dzwiniel, J. M. Stryker, J. Am. Chem. Soc. 2004, 126, 9184 –
9185; d) T. L. Dzwiniel, N. Etkin, J. M. Stryker, J. Am. Chem.
Soc. 1999, 121, 10640 – 10641.
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Chem. 2002, 114, 2905 – 2908; Angew. Chem. Int. Ed. 2002, 41,
2781 – 2784; b) Y. D. Y. L. Getzler, V. Mahadevan, E. B. Lob-
kovsky, G. W. Coates, J. Am. Chem. Soc. 2002, 124, 1174 – 1175;
c) J. T. Lee, P. J. Thomas, H. Alper, J. Org. Chem. 2001, 66, 5424 –
5426; d) P. Davoli, I. Moretti, F. Prati, H. Alper, J. Org. Chem.
1999, 64, 518 – 521; e) M. E. Piotti, H. Alper, J. Am. Chem. Soc.
1996, 118, 111 – 116; f) D. Robert, H. Alper, Organometallics
1984, 3, 1767 – 1769.
[7] T. Kurahashi, A. de Meijere, Synlett 2005, 2619 – 2622.
[8] Representative procedure: In an oven-dried Schlenk flask
(2508C) were placed [Co2(CO)8] (17 mg, 0.05 mmol) and freshly
distilled anhydrous THF (10 mL) under an argon atmosphere.
To the resulting dark red solution was added 1a (138 mg,
1 mmol), and the mixture was stirred at 608C under an
atmosphere of CO provided by a balloon attached to the flask.
The progress of the reaction was monitored by TLC. Upon
completion, the initially dark green solution turned pale brown.
The cooled reaction mixture was diluted with diethyl ether
(20 mL) and stirred under air for 1 h. Filtration through a pad of
Celite and purification by Kugelrohr distillation gave 2a
(146 mg, 0.88 mmol, 88%) as a pale yellow oil. Rf = 0.29
(hexane/diethyl ether 10:1). 1H NMR (CDCl3, 500 MHz): d =
6.26 (tt, J = 7.6, 2.8 Hz, 1H; CH), 2.91 (t, J = 8.2Hz, 2H;
CH2CO), 2.58 (m, 2H; CH2), 2.07 (m, 2H; CH2), 1.47–1.39 (m,
2H; CH2), 1.35–1.25 (m, 6H; 3 CH2), 0.88 ppm (t, J = 6.9 Hz,
3H; CH3); 13C NMR (CDCl3, 125 MHz): d = 199.4 (CO), 147.8
(C), 131.1 (CH), 43.3 (CH2CO), 31.6 (CH2), 29.0 (CH2), 28.8
(CH2), 28.2 (CH2), 22.5 (CH2), 20.2 (CH2), 14.0 ppm (CH3). IR
(neat): n˜ = 2929, 2857, 1757, 1670, 1457, 1394, 1222, 1098, 1006,
893, 727, 668 cmÀ1; MS (EI): m/z: 166 ([M]+, 2), 151 ([MÀMe]+,
1), 109 ([MÀBu]+, 48), 81 (52), 68 (58), 55 (39), 43 (76), 41 (100);
elemental analysis calcd (%) for C11H18O: C 79.46, H 10.91;
found: C 79.16, H 10.68. Spectroscopic data of the minor
Scheme 2. Mechanistic rationalization of the cobalt-catalyzed [3+1]
cocyclization of methylenecyclopropanes with carbon monoxide.
In conclusion, a new cobalt-mediated and -catalyzed
[3+1] carbonylative cocyclization of methylenecyclopropanes
to give 2-alkylidenecyclobutanones under mild conditions has
been developed. Thus, for the first time cobalt has been
demonstrated to be an efficient transition metal for the
activation of strained carbon–carbon s bonds.[12] In compar-
ison with rhodium, ruthenium, and nickel complexes, which
are usually used for the activation of carbon–carbon bonds,
octacarbonyldicobalt is significantly less expensive.
Received: July 25, 2005
Published online: November 15, 2005
1
diastereomer (Rf = 0.41): H NMR (CDCl3, 500 MHz): d = 5.58
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Communications
(tt, J = 7.8, 2.2 Hz, 1H; CH), 2.85 (t, J = 8.3 Hz, 2H; CH2CO),
2.56 (m, 2H; CH2), 2.46 (m, 2H; CH2), 1.41–1.23 (m, 8H; 4 CH2),
0.87 ppm (t, J = 6.6 Hz, 3H; CH3). 13C NMR (CDCl3, 125 MHz):
d =020.3 (CO), 146.2(C), 136.2(CH), 43.2(
CH2CO), 31.6
(CH2), 29.6 (CH2), 29.1 (CH2), 28.8 (CH2), 22.5 (CH2), 20.9
(CH2), 14.0 ppm (CH3). IR (neat): n˜ = 2926, 2856, 1752, 1663,
1559, 1457, 1394, 1072, 706, 668 cmÀ1. MS (EI): m/z: 166 ([M]+,
2), 151 ([MÀMe]+, 1), 109 ([MÀBu]+, 51), 81 (56), 68 (67), 55
(41), 43 (75), 41 (100). The diastereomer ratio was determined
according to the integrals of distinguishable signals in the
1H NMR spectrum of the crude product mixture: major isomer
d = 6.26 ppm (tt, J = 7.6, 2.8 Hz, 1H; CH); minor isomer d =
5.58 ppm (tt, J = 7.8, 2.2 Hz, 1H; CH).
[9] Among the various cobalt complexes which, according to
literature reports, are active in the Pauson–Khand reaction,
the best one [Co(acac)2]/NaBH4 (better than [CpCo(CO)2],
CoCl2, and [CoCl(PPh3)3]) did not show any catalytic activity in
the current transformation. Cf. N. Y. Lee, Y. K. Chung, Tetrahe-
dron Lett. 1996, 37, 3145 – 3148.
[10] a) T. Sugihara, M. Yamaguchi, M. Nishizawa, Chem. Eur. J. 2001,
7, 1589 – 1595; b) J. Foerstner, S. Kozhushkov, P. Binger, P.
Wedemann, M. Noltemeyer, A. de Meijere, H. Butenschön,
Chem. Commun. 1998, 239 – 240.
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metals see: a) R. C. Larock, S. Varaprath, J. Org. Chem. 1984,
49, 3432– 3435; b) P. A. Wender, C. O. Husfeld, E. Langkopf,
J. A. Love, N. Pleuss, Tetrahedron 1998, 54, 7203 – 7220; c) A.
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Brꢀse, Angew. Chem. 1999, 111, 3881 – 3884; Angew. Chem. Int.
Ed. 1999, 38, 3669 – 3672; d) B. M. Trost, F. D. Toste, H. Shen, J.
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Wender, T. J. Williams, Angew. Chem. 2002, 114, 4732– 4735;
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Saito, Y. Yamamoto, J. Org. Chem. 2002, 67, 4911 – 4915; h) S.
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10540 – 10541.
[12] One of the referees proposed that the previously reported
reaction of 1H-cyclopropa[b]arenes with tris(acetonitrile)tricar-
bonylchromium to afford cyclobutaarene-1-ones should be cited
as a precedent: P. Müller, G. Bernadinelli, Y. Jacquier, A. Ricca,
Helv. Chim. Acta 1989, 72, 1618 – 1626.
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