- Cyclobutylidenecyclopropane: New synthesis and use in 1,3-dipolar cycloadditions - A direct route to spirocyclopropane-annulated azepinone derivatives
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Cyclobutylidenecyclopropane (7) was prepared in multigram quantities by a new three-step sequence starting from ethyl cyclobutanecarboxylate (4) (39% overall yield). 1,3-Dipolar cycloadditions of phenyl- (9), pyridyl- (10), and the newly prepared (four st
- De Meijere, Armin,Von Seebach, Malte,Kozhushkov, Sergei I.,Boese, Roland,Blaeser, Dieter,Cicchi, Stefano,Dimoulas, Tula,Brandi, Alberto
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p. 3789 - 3795
(2007/10/03)
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- REACTIONS OF CYCLOPROPENES WITH DIAZOMETHANE IN THE PRESENCE OF PALLADIUM COMPOUNDS
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The reaction of cyclopropenes with diazomethane in the presence of palladium acetate leads to bicyclobutane isomerization products, to olefins containing 1,4-pentadiene fragments, and to the oligomers of cyclopropenes.The predominating reaction path is determined by the degree of substitution of the double bond.
- Lukin, K. A.,Zefirov, N. S.
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p. 242 - 246
(2007/10/02)
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- Chemistry of Dicyclopropylcarbene and Related Intermediates in Dimethyl Sulfoxide
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The potassium salts of the anions of (phenylsulfonyl)hydrazones of diisopropyl, isopropyl cyclopropyl, and dicyclopropyl ketone were decomposed in dimethyl sulfoxide in the temperature range of 110-130 deg C.The diisopropyl phenylsulfonyl anion decomposes to form 2,4-dimethyl-2-pentene and diisopropyl ketone.Similar decomposition of the isopropyl cyclopropyl substrate forms 1-cyclopropyl-2-methylpropene, 1-isopropylcyclobutene, and isopropyl cyclopropyl ketone, while thermal decomposition of the dicyclopropyl ketone (phenylsulfonyl)-hydrazone anion forms cyclopropylcyclobutene and dicyclopropyl ketone.The rate constants for the first and second steps of the consecutive first-order decomposition of the (phenylsulfonyl)hydrazone anions were determined over the temperature range of 110-130 deg C.The activation parameters ΔH* (kcal/mol), ΔS* (eu), and ΔG* (kcal/mol) were calculated for the diazo compound to carbene step (k2) for the diisopropyl (15.6 +/- 1.1, -30.9 +/- 2.8, and 27.7 +/- 1.6), the isopropyl cyclopropyl (27.7 +/- 2.0, 3.3 +/- 5.1, and 26.4 +/- 2.8), and the dicyclopropyl (36.8 +/- 1.8, 28.4 +/- 4.6, 25.6 +/- 2.5).These results are discussed in terms of two factors: interaction of the cyclopropane ring with the functional group and orientation of the polar solvent.
- Freeman, Peter K.,Wuerch, Stephen E.,Clapp, Gary E.
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p. 2587 - 2590
(2007/10/02)
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- Generation and Chemical Properties of Dicyclopropylcarbene. Ring Expansion, Chlorine Abstraction, C-H Insertion, and Alkene Addition Reactions
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Thermolysis of 5,5-dicyclopropyl-2-methoxy-2-methyl-Δ3-1,3,4-oxadiazoline in solution at 80 deg C affords dicycloproylcarbene and methyl acetate in high yields.Dicyclopropylcarbene undergoes a variety of reactions including ring expansion to 1-cyclopropylcyclobutene, chlorine atom abstraction from carbon tetrachloride, and efficient insertion into the CH bond of chloroform.A rationale for the very different reactions of the carbene with CCl4 and CHCl3 is suggested.Carbene trapping by addition to tetrachloroethylene, using the oxadiazoline as the carbene source, is illustrated with the preparation of an adduct.
- Bekhazi, Michel,Risbood, Prabhakar A.,Warkentin, John
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p. 5675 - 5679
(2007/10/02)
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