An exceptionally simple and efficient method for the preparation of a wide variety of fulvenes
TL;DR: The pyrrolidine is un reactif efficace pour promouvoir la formation de fulvene a partir du cyclopentadiene and d'une serie de composes carbonyles as mentioned in this paper.
Abstract: La pyrrolidine est un reactif efficace pour promouvoir la formation de fulvene a partir du cyclopentadiene et d'une serie de composes carbonyles. On observe d'excellents rendements sauf avec la dimethyl-2,6 cyclohexanone. On etudie les effets du solvant, de la temperature et de la concentration
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TL;DR: In this paper, the power of cycloadditions for ring formation derives from the potential for chemo-, regio-, diastereo-, and enantioselectivity, and three types of conjunctive reagents appear to be promising candidates: (1) selected 4-alky-lidene-4,5-dihydro-3H-pyrazoles, (2) 2-[(trimethylsilyl)methyl]allyl esters and halides, and (3) alkylidenecycloprop
Abstract: The power of cycloadditions for ring formation derives from the potential for chemo-, regio-, diastereo-, and enantioselectivity. Trimethylenemethane (TMM) and its equivalents offer the possibility of extending such benefits to the synthesis of five-membered rings. Three types of conjunctive reagents appear to be promising candidates: (1) selected 4-alky-lidene-4,5-dihydro-3H-pyrazoles, (2) 2-[(trimethylsilyl)methyl]allyl esters and halides, and (3) alkylidenecyclopropanes. Thermal reactions, especially intramolecular ones, effect the cycloaddition of the pyrazoles to olefins–especially electron-poor olefins. The latter two precursors require a catalyst, notably a palladium complex, to unlock the synthetic potential. With the 2-[(trimethylsilyl)methyl]allyl esters, a general chemo-, regio-, and diastereoselective cycloaddition with typical Diels-Alder dienophiles forms methylenecyclopentanes in both inter- and intramolecular fashion. A tin analogue allows extension of this cycloaddition to aldehydes, and, in a related sequence, to ketones and imines to form 3-methylenete-trahydrofurans and 3-methylenepyrrolidines with excellent diastereoselectivity. The 2-[(tri-methylsilyl)methyl]allyl esters also serve to effect net methylenecyclopentane annulation to cyclic enols. Such adducts can further undergo three-carbon intercalation or combined ring contraction-spiroannulation simply by the use of either a nucleophilic or electrophilic trigger. Alkylidenecyclopropanes undergo cycloadditions to both electron-rich and electron-poor olefins when stimulated by metal catalysts, especially palladium. A complementary regiochemistry to the approach based upon silicon conjunctive reagents is observed. The availability of these cycloadditions provides new strategies for the synthesis of natural products.
376 citations
TL;DR: An insight is provided into the synthesis of fulvene-derived titanocenes and their activity in preclinical experiments and it is shown that metal-based anti-cancer drugs may come from this simple and effective synthetic approach.
Abstract: 6-Substituted fulvenes are interesting and easily accessible starting materials for the synthesis of novel substituted titanocenes via reductive dimerisation, carbolithiation or hydridolithiation reactions, which are followed by a transmetallation reaction with titanium tetrachloride in the latter two cases. Depending on the substitution pattern, these titanocenes prove to be bioorganometallic anti-cancer drugs, which have significant potential against advanced or metastatic renal-cell cancer. Patients bearing these stages of kidney cancer have a poor prognosis so far and therefore real progress in the area of metal-based anti-cancer drugs may come from this simple and effective synthetic approach. This tutorial review provides an insight into the synthesis of fulvene-derived titanocenes and their activity in preclinical experiments.
290 citations
TL;DR: In this article, the authors showed that the selectivity for trimerization depends on the presence of a pendant arene group on the cyclopentadienyl ligand and the nature of the bridge between these two ligand moieties.
176 citations
Patent•
22 Feb 2007TL;DR: In this paper, the authors describe a method for the synthesis of a bimodal molecular weight distribution of ethylene polymers with a first Group 4 metallocene compound comprising bridging η 5 -cyclopentadienyl-type ligands.
Abstract: This invention relates to catalyst compositions, methods, and polymers encompassing at least one first Group 4 metallocene compound comprising bridging η 5 -cyclopentadienyl-type ligands, in combination with at least one second Group 4 metallocene with non-bridging η 5 -cyclopentadienyl-type ligands, typically in combination with at least one cocatalyst, and at least one activator. The compositions and methods disclosed herein provide ethylene polymers with a bimodal molecular weight distribution.
171 citations
TL;DR: The molecular structure of the methylene-bridged titanocene dichloride, CH2(C5H4)2TiCl2, and that of the novel, ethylene-branched derivative, (CH2)2-(C 5H4)-2TiX2 have been determined by X-ray diffraction methods as discussed by the authors.
137 citations