Categories: C-C Bond Formation > Cyclic compounds > Cyclic enones
Synthesis of cyclopentenones
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Recent Literature
A highly efficient catalytic, intermolecular synthesis of the cyclopentane
skeleton from simple starting products is reported. Allyl halides, alkynes, and
carbon monoxide react under very mild reaction conditions by means of a
substoichiometric amount of iron, acetone, and a catalytic amount of Ni(II)
iodide.
M. L. Nadal, J. Bosch, J. M. Vila, G. Klein, S. Ricart, J. M. Moretó, J. Am.
Chem. Soc., 2005, 127, 10476-10477.
Indanones and 2-cyclopentenones have been successfully prepared in good to
excellent yields by the palladium-catalyzed carbonylative cyclization of
unsaturated aryl iodides and dienyl triflates, iodides, and bromides,
respectively. The mechanism is discussed.
S. V. Gagnier, R. C. Larock, J. Am. Chem. Soc., 2003, 125,
4804-4807.
Conjugated addition of primary nitroalkanes to α,β-unsaturated ketones or
α,β-unsaturated esters, in the presence of two equivalents of DBU, allows the
one-pot prepration of γ-diketones or γ-keto esters, respectively. The reaction
of 2-aryl-1-nitroethane derivatives with α,β-unsaturated ketones gives
cyclopentenones.
R. Ballini, L . Barboni, G. Bosica, D. Fiorini, Synthesis, 2002,
2725-2728.
Cyclization of electron-rich 2-alkyl-1-ethynylbenzene derivatives was catalyzed
by TpRuPPh3(CH3CN)2PF6 in hot
toluene to form 1-substituted-1H-indene and 1-indanone products. The
cyclization mechanism involves a 1,5-hydrogen shift of an initial
metal-vinylidene intermediate.
A. Odedra, S. Datta, R.-S. Liu, J. Org. Chem., 2007,
72, 3289-3292.
Stirring α,β-unsaturated α-diketones in the presence of activated silica gel
results in cyclization to α-hydroxycyclopentenones in good yield. The reaction
is sensitive to the mode of stirring and proceeds more rapidly in the presence
of triethylamine consistent with a Nazarov reaction proceeding through the enol
tautomer.
E. A. Uhrich, W. A. Batson, M. A. Tius, Synthesis, 2006,
2139-2142.
The acid-catalyzed Nazarov reaction of easily accessible β-alkoxy divinyl
ketones provides 5-oxycyclopent-2-enones. The effects of the β-alkoxy group on
the catalyst efficiency and the regioselectivity are based on the stabilization
of the intermediates and the spontaneous elimination of the group followed by
trapping.
M. Shindo, K. Yaji, T. Kita, K. Shishido, Synlett, 2007,
1096-1100.
A chiral iridium diphosphine complex catalyzes an enantioselective
intramolecular Pauson-Khand-type reaction to give various chiral bicyclic
cyclopentenones. A low partial pressure of carbon monoxide is important to
achieve excellent enantioselectivity.
T. Shibata, N. Toshida, M. Yamasaki, S. Maekawa, K. Takagi, Tetrahedron,
2005, 61, 9974-9979.
The Rh(I)-catalyzed [3 + 2] cycloaddition of cyclopropenones and alkynes
provides a highly efficient and regioselective route to cyclopentadienones (CPDs)
that would be otherwise difficult to obtain. The versatility of the method is
explored with a wide range of alkynes and diaryl- as well as
arylalkylcyclopropenones.
P. A. Wender, T. J. Paxton, T. J. Williams, J. Am. Chem. Soc., 2006,
128, 14814-14815.
An entrapped Rh catalyst derived by a sol-gel process (see article for method),
has been used in a Pauson-Khand reaction under mild conditions. The catalyst can
be reused at least 10 times without losing activity. This catalytic system is
not effective for intermolecular reactions.
K. H. Park, S. U. Song, Y. K. Chung, Tetrahedron Lett., 2003,
44, 2827-2830.
