tions. When the cycloaddition of 1a with methyl acrylate
was performed in C6H6, 6a and 7a were obtained in 73%
overall yield. On the basis of 1H NMR analysis, the
regioselectivity (6a/7a ) 3:1) and stereoselectivities [exo/
endo ratio ) 4:1 (6a) and 5:1 (7a)] were found to be identical
to the corresponding values when CH2Cl2 was used as the
solvent.
was probably formed via 1,4-hydrogen shift of the carbonyl
ylide intermediate.
The CdO bond of benzaldehyde is also an effective
dipolarophile. Treatment of 1a with benzaldehyde (5 equiv)
and [RuII(TTP)(CO)] (1 mol %) in CH2Cl2 at room temper-
ature afforded the 1:1 cycloadduct exo-13 exclusively in 73%
yield (Scheme 6). Unlike the related Rh-catalyzed reaction,11
A similar reaction of 1b with methyl acrylate produced
four diastereomeric cycloadducts exo-/endo-6b and exo-/
endo-7b (Scheme 4), which were isolated in 78% overall
yield. 1H NMR analysis of the reaction mixture revealed the
regioisomeric (6b/7b) ratio ) 5:1 and the exo/endo ratios
being 15:1 (6b) and 5:1 (7b). The observed product yields
and selectivities for the Ru-catalyzed cycloadditions are
similar to that reported for the analogous Rh-catalyzed
reactions.11
Scheme 6
Dropwise addition of 1b to a CH2Cl2 solution of styrene
(5 equiv) and [RuII(TTP)(CO)] (1 mol %) resulted in
cyclopropanation predominantly, and cyclopropane 10 was
isolated in 55% yield with the anti/syn ratio ) 8.5:1. Yet,
cycloadducts 8 and 9 were obtained in 28% overall yield
(Scheme 5) and characterized spectroscopically.11 The re-
formation of the [2:1] cycloadduct was not observed in this
work. With p-quinone as dipolarophile,3d cycloaddition to
the CdO bond occurred preferentially to give 14 in 72%
1
isolated yield. By H NMR analysis, the CdC cycloadduct
was detected in <10% yield. A similar finding was observed
for the analogous [Rh2(CH3CO2)4]-catalyzed reaction (14:
76% isolated yield).
Scheme 5
Employing 1a and methyl acrylate as substrates, the effect
of the porphyrin structure on the Ru-catalyzed cycloaddition
has been examined. As depicted in Table 1, the regio- and
Table 1. Effect of Ruthenium Porphyrin Catalysts on the
Cyclization of Diazo Compound 1a with Methyl Acrylate
gioselectivity of the cycloaddition (8:9) was determined to
be 7:1 with the exo/endo ratios ) 26:1 (8) and 5:1 (9) based
on H NMR analysis of the reaction mixture. The Ru-
catalyzed reaction of 1b with propargylic bromide afforded
the cycloadduct 11 in only 14% yield by the carbonyl ylide
formation/1,3-dipolar cycloaddition cascade. The enol ether
12 was isolated as the major product (56% yield), which
regio-
% yieldb selectivityc
1
exo/endoc
entry
Ru catalysta
(6a + 7a ) (6a /7a )
6a
7a
1
2
3
4
5
6
[RuII(TTP)(CO)]
85
80
82
83
78
87
2.5:1
2.6:1
3:1
4.8:1
4.5:1
2:1
4:1 5:1
3.8:1 7:1
3.9:1 7:1
3.8:1 3.3:1
3.2:1 3.3:1
3:1 3:1
[RuII(4-OMe-TPP)(CO)]
[RuII(4-F-TPP)(CO)]
[RuII(TMP)(CO)]
(3) Recent examples, see: (a) Hodgson, D. M.; Avery, T. D.; Donohue,
A. C. Org. Lett. 2002, 4, 1809. (b) Wood, J. L.; Thompson, B. D.; Yusuff,
N.; Pflum, D. A.; Mattha¨us, M. S. P. J. Am. Chem. Soc. 2001, 123, 2097.
(c) Chiu, P.; Chen, B.; Cheng, K.-F. Org. Lett. 2001, 3, 1721. (d) Pirrung,
M. C.; Kaliappan, K. P. Org. Lett. 2000, 2, 353.
(4) (a) Ibata, T.; Jitsuhiro, K.; Tsubokura, Y. Bull. Chem. Soc. Jpn. 1981,
54, 240. (b) Ibata, T.; Jitsuhiro, K. Bull. Chem. Soc. Jpn. 1979, 52, 3582.
(5) (a) Zhang, R.; Yu, W.-Y.; Sun, H.-Z.; Liu, W.-S.; Che, C.-M. Chem.
Eur. J. 2002, 8, 2495. (b) Liang, J.-L.; Huang, J.-S.; Yu, X.-Q.; Zhu, N.-
Y.; Che, C.-M. Chem. Eur. J. 2002, 8, 1563. (c) Zhang, R.; Yu, W.-Y.;
Wong, K.-Y.; Che, C.-M. J. Org. Chem. 2001, 66, 8145. (d) Yu, X.-Q.;
Huang, J.-S.; Zhou, X.-G.; Che, C.-M. Org. Lett. 2000, 2, 2233. (e) Zhang,
R.; Yu, W.-Y.; Lai, T.-S.; Che, C.-M. Chem. Commun. 1999, 409. (f) Au,
S.-M.; Huang, J.-S.; Yu, W.-Y.; Fung, W.-H.; Che, C.-M. J. Am. Chem.
Soc. 1999, 121, 9120. (g) Lai, T.-S.; Zhang, R.; Cheung, K.-K.; Kwong,
H.-L.; Che, C.-M. Chem. Commun. 1998, 1583.
[RuII(TDCPP)(CO)]
[Rh2(CH3CO2)4]
a [H2TTP] ) meso-tetrakis(4-tolyl)porphyrin; [H2-4-OMe-TPP] ) meso-
tetrakis(4-methoxyphenyl)porphyrin; [H2-4-F-TPP] ) meso-tetrakis(4-fluo-
rophenyl)porphyrin; [H2TMP] ) meso-tetrakis(mesityl)porphyrin; [H2TDCPP]
) meso-tetrakis(2,6-dichlorophenyl)porphyrin. b Isolated yield. c Based on
1H NMR analysis of the reaction mixture.
stereoselectivities show modest variation with the porphyrin
structure. The sterically bulky [RuII(TMP)(CO)] and [RuII-
(TDCPP)(CO)] were found to exhibit comparable activities
to [RuII(TTP)(CO)] and [Rh2(CH3CO2)4].
When 1-diazo-9-decene-2,5-dione (Scheme 7)12 containing
a tethered terminal CdC bond was added slowly to a CH2-
Cl2 solution of [RuII(TTP)(CO)] (1 mol %), hexahydro-1H-
(6) (a) Gross, Z.; Ini, S. Org. Lett. 1999, 1, 2077. (b) Berkessel, A.;
Frauenkron, M. J. Chem. Soc., Perkin Trans. 1 1997, 2265. (c) Groves, J.
T.; Roman, J. S. J. Am. Chem. Soc. 1995, 117, 5594. (d) Higuchi, T.; Ohtake,
H.; Hirobe, M. Tetrahedron Lett. 1989, 30, 6545. (e) Groves, J. T.; Quinn,
R. J. Am. Chem. Soc. 1985, 107, 5790.
Org. Lett., Vol. 4, No. 19, 2002
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